Flour

FLOUR. Contents: Types of milling ................... 259 Types of flour and commercial grades ........... 260 Sanitary evaluation of flour ............... 264 Chemical composition, food, and nutritional value of flour . . 272 Research methods for flour ............. 274 Flour is a product obtained by milling cereal grains. Wheat and rye are of the greatest importance for the production of flour, and corn, oats, barley, as well as buckwheat and legume seeds (peas, beans, and recently soy) are of significantly lesser importance. Cereal grain consists of the starchy kernel, envelopes, and germ. The wheat germ occupies 2–3% of the grain weight, the envelopes together with the aleurone layer (see Aleuronate) 13–15%, and thus the starchy kernel, or otherwise the endosperm, accounts for 82–85% of the total grain weight. The envelopes are subdivided into fruit and seed coats: the former (three of them—epidermis, or epicarp, mesocarp, and endocarp) make up 4–4.5% of the grain weight and are relatively easily separated from the rest of it; the latter (two of them—episperm, or testa, and endopleura, or hyaline layer), thinner, make up only 1.2–2% of the grain weight and are tightly fused with its inner part; the seed coats include pigment and therefore influence the appearance of the flour. "Husked" grains, i.e., oats, barley, rice, and emmer, are furthermore covered by a chaff or floral envelope, the weight of which in oats is on average 27% of the grain weight, in barley—12%, in rice and emmer—18–20%. The chemical composition of individual parts of the grain is given in Tables 1 and 2 (according to Aimé Girard). Table 1. Chemical composition of grain envelopes (in percent). Composition: Fruit envelopes, Seed envelopes, Aleurone layer, Total. Cellulose ..... 3.51, 2.41, 1.25, 7.12. Nitrogenous substances 24.41, 0.65, 4.44, 29.89. Fat ......... 3.56, 0.92, 11.55, 15.31. Mineral substances ... 5.06, 3.38, 5.60, 14.04. Total: 30.98, 7.67, 61.30, 99.95. Table 2. Chemical composition of individual parts of the grain (in percent). Composition: Envelopes and aleurone layer, Germ, Endosperm. Water ....... 11.55, 11.55, 13.4. Cellulose . . . 59.36, 21.1, 0.3. Carbohydrates .... 18.97, 9.6, 74.7. Nitrogenous substances: 5.60, 39.2, 10.2. Fat ....... 4.47, 12.5, 0.9. Mineral substances: 5.3, 0.5. It can be seen from the tables that the fruit and seed envelopes contain few nutrients; they are rich in crude fiber, which is indigestible by the human body; the aleurone layer, although containing a significant amount of nitrogenous substances and fat, is also rich in indigestible fiber, which accounts for more than half of its weight; the germ is very nutritious—it contains many nitrogenous substances and fat, but at the same time a significant amount of fiber. It must be added to this that the fat of the germ and the aleurone layer has the property of turning rancid relatively quickly, and therefore, in order to obtain flour that is stable during storage, one has to beat off the envelopes, germ, and most of the aleurone layer during grain milling and send them to bran. Commercial grain always contains a certain amount of foreign impurities (refuse), among which are so-called dead refuse (earth, sand, fragments of stem and ear, husks, flour dust, etc.), weed seeds, and so-called harmful impurities, resulting mainly from the disease of the grain by fungi (smut, ergot, etc.). In addition, the grain may contain so-called grain impurities—grains of other, usually less valuable crops (e.g., rye and barley in wheat), as well as damaged (broken), darkened from self-heating and strong drying, sprouted, and strongly underdeveloped grains (e.g., caught by frost, which is often observed in Siberia). All these impurities, on the one hand, worsen the appearance of the flour and affect some of its qualities (e.g., with a significant content of sprouted grains, the diastatic activity of the flour increases, the presence of earthy impurities and sand causes a crunch on the teeth when chewing the flour and bread made from it), and on the other hand, some of the impurities have a harmful effect on the human body (weeds—corn cockle, intoxicating darnel; plant parasites—fungi of ergot and smut, etc.). This circumstance makes it necessary to subject the grain to careful cleaning from foreign impurities before milling. Small mills usually do not do such cleaning, whereas commercial mills have grain cleaning installations. Types of milling. Low and high milling are distinguished. In low milling, the grain is immediately crushed into flour in one or several passes, while in high milling, the grain is crushed on grooved rollers into large pieces, doing this in several passes through the rollers (break passages). After each pass, the product is sorted by size on sieves; the largest part—break groats (oversize from the top sieve)—is sent to the next break pass, the smallest part (undersize from the bottom sieve)—flour—is usually obtained of a dark color from dust (from the beard of the grain) and crushed grain envelopes falling into it, and therefore they strive to conduct the crushing process so that the flour obtained is as small as possible (in the first break pass usually less than 1%, and in all passes together—about 10% of the grain weight). Intermediate products in terms of coarseness between break groats and flour, so-called middlings and semolina, are higher in quality than break groats and break flour, and from them subsequently, after some additional cleaning, the bulk of the flour is obtained by grinding on smooth rollers. Ultimately, after all break passes, middlings and semolina of various numbers by coarseness and quality (in general about 60–65% of the grain weight) and break flour (in general 10–12%) are obtained, while the rest of the grain is sent to bran and waste from preliminary grain cleaning. Middlings and semolina are first subjected to cleaning (winnowed on purifiers, scoured on rollers, sifted on sieves), then intermediate products of equal quality are mixed, subjected to grinding on smooth rollers and again sifting on sieves; this produces flour of varying quality depending on the quality of the middlings. From the highest quality middlings, semolina is sometimes 'extracted' (in the USSR 2% of the grain weight). Thus, with this milling method, one can obtain a different number of flour grades. In pre-war times, some mills produced up to 12 grades of wheat flour, and each large mill had its own milling scheme and its own assortment of flour. At present, both in the USSR and abroad, wheat milling is carried out for the most part only into 2–3 grades; so-called single-grade flour is also often produced, i.e., all flour goes into a single grade. Types of flour and commercial grades. During high milling, middlings and semolina of various quality are collected in the process of breaking, from which flour of various grades can be obtained; if we select, for example, 30% of the best flour, and from what remains, take 30% of the best as well, and then collect the last 15% of flour separately, and send the rest to bran, then we will be dealing with a three-grade milling, and it is customary to depict these grades as follows: 1st grade 0–30%, 2nd grade—30–60% and 3rd grade—60–75%. If all three grades of this milling were combined together and the flour released as single-grade, then such flour is usually depicted as 0–75%. If, for example, flour was released in the form of two grades: 1st grade—50% and 2nd grade—25%, then such milling is depicted as follows: 1st grade—0–50%, 2nd grade—50–75%. Commercial grades of flour of different countries have very different names and designations, but they can all be reduced to a small number of types. Thus, for wheat flour, the types of flour are characteristic: three-grade millings: 0–30%, 30–60%, 60–75%; two-grade millings: a) 0–50%, 50–75%; b) 0–65%, 65–75%; single-grade millings: a) 0–75%; b) 0–80%; c) 0–85%; d) 0–95%. For rye, the types of flour are characteristic: two-grade millings: a) 0–50%, 50–75% (or 0–45% and 45–72%) and b) 0–65%, 65–75%; single-grade millings: a) 0–75%, b) 0–85% and c) 0–95%. Of course, various variations are possible around these types, especially on the private market. 1) Wheat flour, depending on the coarseness of the flour milling, can be soft or granular (when felt, graininess is felt by the fingers). All commercial milling of the USSR is currently concentrated in the All-Union Association "Soyuzkhleb". Flour produced by the mills of the USSR is regulated by standards approved annually by the People's Commissariats of Foreign and Internal Trade. For the 1930/31 year, the following grades (standards) of flour have been established: 1) single-grade wheat flour of 75% extraction, 2) the same of 85% extraction, 3) rye wallpaper flour of 95% extraction, 4) peeled flour of 87% extraction, 5) corn flour of 75% extraction. In previous years we had two-grade, three-grade, and even four-grade millings for wheat and a large number of grades for rye flour. Thus, in 1926, the largest milling trust "Khleboprodukt" produced grades of wheat flour: 1st red yield 0–10%; 2nd red yield 10–45%; 3rd red yield 45–65%; 4th red yield 65–75%; 1st blue—0–15%; 2nd blue—15–45%; 3rd blue 45–65%; 4th blue—65–75%. Red flour had a red brand on the sacks and was prepared from soft wheat varieties, blue flour was marked with a blue stamp and was prepared from a mixture of soft and hard wheat varieties in approximately a ratio of 3:1; the 1st red and 1st blue grades were granular, while the rest were soft.

In the pre-war period, granular flour of various grades and names was widely used, as well as diverse grades of soft flour (first-best soft flour of several grades, vyboynaya—also soft flour, but darker than the first, mezheumok—the best of the vyboynaya, etc.). Rye flour also came in quite diverse grades, namely: a) ordinary flour or simple-milled flour; b) brown (oboynaya) flour—before milling, the grain was cleaned of debris and passed through machines (oboyki) to remove part of the upper seed coats and ends (yielding about 94% of the grain weight); c) peeled (obdirnaya) flour—with partial sifting of bran (yielding about 85% of the grain weight); d) sifted-out flour—with almost complete sifting of bran (yielding about 75% of the grain weight); e) bolted (seyanaya) flour—cleaner and finer; usually of two grades: first grade with a yield of about 60–62% of the grain weight and second grade with a yield of the subsequent 12% of the grain weight, i.e., with a total yield of 72–74%; f) pestered (peklevannaya) flour—the finest and whitest of all grades of rye flour; it was on sale in several grades, the best with a yield of about 27% and a darker one with an approximate yield of 45% of the grain weight. Foreign flour. In the USA, the most characteristic grades of wheat flour are straight, patent, clear, and low-grade, with patent and clear flour each having two types: first and second. In America and England, there is a distinct method of designating types. On average, about 73% of graded flour is obtained from grain; if the flour is not separated into grades but produced as a single grade, this is straight flour, and it is referred to as 100% flour (in our country and in Europe this is 0–73% flour). If the flour is separated into grades, patent, clear, and low-grade flours are obtained, and their quantities are expressed as a percentage of the total amount of flour (rather than grain, as in our country). For rye flour, the main grades in the USA are white rye flour (average yield 60% of the grain weight), medium rye flour (average yield 70%), and dark rye flour (with a yield of 92.5%—corresponding to our brown flour). In England, there are flour grades similar to the American ones. In both countries, so-called whole wheat flour or Graham flour is also sold—a single-grade flour without the removal of bran. There is also granular flour (semolina) for special purposes, e.g., for macaroni and special bakery products. In Germany, known wheat flour grades include Auszugsmehl 1st and 2nd grades, types 0–30% and 0–50%, Helles Semmelmehl (light flour for small rolls), types 0–65% and 0–75% (1st grade), as well as 30–50% and 30–70% (2nd grade), Brotmehl (bread flour) types 0–80% and 30–75%, Schrotmehl or Grahammehl (whole-meal flour) types 0–94% and 0–100%. Rye flour is found in the following grades: Vordermehl or Feinmehl (fine flour) type 0–50%, Brotmehl (bread flour) types 0–65% and 0–75%, Graubrotmehl (grey bread flour), otherwise Kommissmehl type 0–82%, and Schwarzbrotmehl (for black bread), otherwise Schrotmehl, type 0–94% and 0–100%. In France in recent years, only a single grade of wheat flour has been regulated—farine entière (whole flour) with a yield of approximately 75–77%, depending on the nature of the grain. Flour of other cereals. From other cereals, corn, barley, less frequently oats, as well as legume seeds and buckwheat are ground into flour. Corn flour. Corn (maize) is characterized by a strongly developed germ rich in fat (the germ accounts for 10–12% of the weight of the entire grain, and its average fat content is about 30%); corn fat has the property of going rancid relatively quickly, especially under unfavorable storage conditions, and therefore in the production of corn flour for food purposes, efforts are made to separate the germ as completely as possible, especially since this also makes economic sense, as edible vegetable oil is obtained from the germ. Corn is milled in specially adapted mills using the granular milling method. In some mills of the North Caucasus, a method of combined milling of corn with wheat was used (75% wheat and 25% corn): grain cleaning, breaking, and middlings cleaning proceeded along two parallel schemes for wheat and corn separately, while the mixture of wheat and corn middlings was directed to the reduction systems, resulting in a well-blended wheat-corn flour. Corn flour is consumed in pure form in the places of production, and in consuming regions as an admixture to wheat flour for the manufacture of baked bread and confectionery products. In 1929/30, at USSR mills during corn milling, 15% middlings (of semolina type) and 62% flour were extracted, while waste products obtained were 9% germ, 10% bran, 3% cleaning and hulling waste, and 1% dust loss; the oil content of the germ was 14–20%; sometimes flour was also produced without extracting middlings, with a yield of 77%; the fat content in such flour was 3–3.5%, mineral content (ash content) 1.0%; high-grade corn flour, well cleaned of germ and husks, contains about 1.5% fat. Corn flour contains no washable gluten (see below), and therefore in bread baking, its admixture to wheat flour somewhat lowers the rising capacity of the dough; the bread turns out less fluffy and usually goes stale somewhat faster compared to pure wheat flour, which becomes quite noticeable with the addition of 10–15% corn flour; for confectionery biscuits, flour not rich in gluten is used, and therefore in this case the admixture of corn flour has little effect on the appearance of the biscuit and in small amounts (up to 10%) is even favorable. Barley flour. Barley grain, with the exception of a few varieties (e.g., Himalayan barley), is covered by a chaffy husk (hull) tightly fused to the grain (averaging 12% by weight of the grain); in producing flour from barley, it is necessary to remove this husk from the grain; at our mills, this is usually done by passing through emery scouring machines; in 1929/30, barley milling yielded 68% flour, alongside 14.5% bran, 15% scouring waste (husks), 1.5% preliminary cleaning waste, and 1% dust loss; in addition, joint milling of wheat and barley (combined milling) was also performed in graded wheat mills—in this case, only 66% of barley flour was extracted. Barley flour in pure form is suitable only for obtaining flatbreads and flat cakes, as it lacks gluten; dough made from barley flour has the ability to acquire a bluish-gray color, and wheat bread with an admixture of barley flour, compared to bread made from wheat flour alone, is denser, rougher to the touch, and has a certain characteristic odor and aftertaste. These changes become quite noticeable when adding more than 15% barley flour. Oat flour is produced in relatively small quantities (it is no longer produced in the USSR) for special grades of bread and biscuits. Like barley, oat grain is covered with hulls, but the latter separate from the grain relatively easily (averaging 27% by weight); the naked oat grain is entirely covered with fine hairs, unlike the grains of other cereals, which have only a tuft at the upper end of the grain. During oat milling, these fine hairs get into the flour and are characteristic of oat flour. Oat milling typically yields 50–55% flour; compared to wheat flour, this flour contains an increased amount of fat (3–4%) and therefore must be dry (10–11% moisture), otherwise it rapidly goes rancid; wheat bread with the addition of oats has a characteristic aftertaste, is harder to bake, and turns out less fluffy. Buckwheat flour in the pre-war period was on sale in two types: a) granular and b) soft; in small quantities (of low quality), it is obtained at present in the production of buckwheat groats. The chemical composition of buckwheat flour, according to König: water 13.84%, nitrogenous substances 8.28%, fat 1.49%, starch and nitrogen-free extractive substances 74.58%, fiber 0.76%, ash 1.11%. Soya flour. Recently, flour made from soybeans has been attracting great attention. Characteristic of soybeans is their high content of fat (17–20%), proteins (30–35%), and a relatively low content of carbohydrates in general (about 30%) and in particular the almost complete absence of starch. Soya flour obtained directly by milling soybeans has a peculiar aftertaste resembling peas, and its high fat content makes it very unstable during storage. Recently, a method for producing soya flour patented by Dr. Berzeller (Hungary) has been spreading in foreign practice, according to which the flour is obtained odorless (deodorized), free from any aftertaste, and stable in storage (the method apparently consists in steaming the soya flour for a short time, about 12–15 minutes, under vacuum). This flour is recommended by the patent author as an improver of the baking properties of wheat flour, as well as for all kinds of sauces and dishes. Since soybeans are rich in lecithin (1.5%) compared to other cereals, soya flour is sometimes added instead of a portion of eggs to wheat flour in the manufacture of "egg" macaroni for adulteration purposes (the presence of eggs in pasta products, as is known, is controlled by the lecithin-phosphoric acid content). There is also a desire to utilize soya press cake remaining at oil extraction plants for food.

This oilcake is very rich in valuable protein substances, and if flour made from it is rendered stable in storage and freed from its bitter taste, then, when mixed into rye bread, it will increase the nutritional value of the latter. Soybean flour has a rather intense yellow color and is commercially available (according to Berczeller's patent) in two forms: soft and granular. In the USSR, only trial millings are currently being produced. Sanit. evaluation of flour. Good-quality flour must possess proper external characteristics corresponding to its grade and purpose: color, odor, taste, and a specific particle size. 1. The color of flour, with its characteristic tint and sheen, depends first of all on the quality and grade of the grain from which the flour is obtained, then on the degree of grinding, i.e., on the shape and size of the flour particles, on the degree of moisture, on the presence of foreign impurities in the flour, and finally on the chemical treatment of the flour, if any took place. (To impart whiteness to flour, it is subjected to artificial bleaching with a mixture of chlorine and air, nitrogen oxides, benzoyl peroxide, etc. In the USSR, flour bleaching is not practiced.) When comparing various flour samples by color, it is necessary to bring them to identical conditions of grinding, dryness, and packing density. Good first-grade wheat flour has a white color with a more or less yellowish (cream) tint and proper sheen; lower grades of flour have a darker color and less sheen. With a decrease in the grade of flour, an increasingly large number of specks (pins) also appears in it. These are small fragments of grain husks, colored brown or dark gray. Flour that has been stored for a long time loses its sheen and becomes dull. Flour that is excessively ground during milling also loses its sheen, acquires a "dead appearance," becomes like chalk, and along with this, its baking qualities are also lowered. High-grade rye flour (pekelvant) also has a white color and differs little in color from wheat flour; whole-grain and plain rye flour has a mottled appearance due to the presence of a large number of crushed husks. Flour from dried grain may have a yellowish tint. Well-cleaned barley flour has a white color. The color of corn flour depends on the color of the grain: white corn produces white flour with a faint yellowish tint, while yellow corn yields bright yellow flour. Buckwheat flour has a white color with a reddish tint. 2. The odor of flour can provide certain indications regarding its freshness, purity, and quality: the flour should not have a musty, pungent, or any foreign odor whatsoever. 3. When chewing flour, no crunching on the teeth should be felt; the taste of good-quality flour is pleasant, slightly sweetish; a bitter taste, as well as a sourish one, indicates either spoilage of the flour or the presence of foreign impurities. 4. To the touch, good soft flour should be dry and tender and contain no lumps; at the same time, in the hand it should easily compress into a lump, which, upon releasing the hand and tapping lightly on the palm, immediately crumbles into powder; the flour should not stick to the fingers. The presence of hard lumps in the flour indicates poor storage of the flour; the formation of strong lumps when compressing the flour in the hand indicates moisture in the flour; the inability to compress into a lump indicates a significant bran content and coarse grinding. Granular flour, when rubbed between the fingers, gives a feeling of graininess. The coarseness of grinding and the uniformity of flour particles are important for the dough-formation process; fine flour absorbs water faster and somewhat more. Coarseness is usually determined by sifting; flour samples (50-100 g) through appropriate sieves. Thus, according to the temporary standards for 1930/31, whole-grain rye flour when sifted through a metal sieve No. 24 should yield no more than 2% residue. Single-grade wheat flour of 85% extraction through silk sieve No. 5 - no more than 5% residue; 75% wheat flour on sieve No. 5 - no more than 2%; sifted rye flour on metal sieve No. 38 - no more than 1.5%. 5. The moisture content of flour varies within fairly significant limits. According to the temporary standards of the People's Commissariat of External and Internal Trade for 1930/31, three moisture states are distinguished for flour: "dry" with a moisture content of up to 14%, "medium-dry" from 14% to 15.5%, and "moist" from 15.5% to 17%. The moisture content of flour is of great importance for its transport and storage: dry flour can be stored and transported at any time of the year, medium-dry in the cool months and not for long periods, moist flour can be transported and stored only in the cold season (raw flour should go only for local consumption). Dry flour gives increased yields during bread baking, and for every reduced percentage of flour moisture, the yield increases by approximately 1.6% or even more. When storing flour with increased moisture in a warm place, respiration processes intensify in it, microorganisms develop, a self-heating process occurs, the temperature rises sharply, and this can lead to complete spoilage of the flour. 6. Ash content characterizes the degree of purification of flour from grain husks; the whiter the flour, the lower its ash content: first-grade wheat flour with an extraction of up to 50% by weight of the grain has an ash content of about 0.5%, flour with a 75% extraction - about 1.0%, bran has an ash content of over 5%. According to temporary standards approved by the People's Commissariat of External and Internal Trade, the following ash content for flour has been established: 95% whole-grain rye - 1.90%, 87% extraction sifted rye - 1.65%, 85% extraction wheat flour - 1.40%, 75% extraction wheat flour - 0.95%. Aside from the increased content of ground husks, high ash content of flour can result from insufficient cleaning of the grain before milling, from earthy impurities and weed seeds, from the abrasion of millstone material during milling, or accidental contamination of the flour with foreign impurities. In America, an ash content of no more than 1.0% is permitted for graded wheat flour; for "whole" flour, the ash norm is not established. 7. Sand, earth, and other mineral impurities (insoluble in 10% HCl) in flour should be allowed to no more than 0.1% (otherwise a crunch on the teeth is felt). The addition to flour of copper compounds (copper sulfate), zinc, alum, gypsum, chalk, and similar mineral substances is not permitted (these substances are sometimes added to flour in small quantities to improve its baking qualities). 8. The acidity of flour is also one of the factors in evaluating flour. It is caused mainly by the content of acid phosphates (predominantly KH₂PO₄) in the flour, and therefore any flour shows an acidic reaction. Lower (dark) grades of flour contain more salts than higher grades, and therefore their acidity is higher, i.e., acidity is to some degree proportional to ash content. In addition, in flour, especially under poor storage conditions, lactic, acetic, propionic, formic acids, fatty acids, amino acids, etc., develop. Thus, it is necessary to distinguish between natural acidity (of fresh flour) and acquired acidity (for stale flour). In practice, total acidity is usually determined. The acidity of flour is customarily expressed in degrees of acidity; this is the number of cm³ of a normal sodium hydroxide solution (40 g per 1 l of water) required to neutralize the aqueous extract from 100 g of flour. [If acidity is determined not in an aqueous extract, but in a "mash" of flour and water, the results obtained are higher (1.5–2 times).] The acidity of light grades of fresh wheat flour usually does not exceed 1–2°, for dark grades 3–4°; fresh whole-grain rye flour exhibits no more than 4–5° of acidity. Acidity increased above these norms already indicates that the flour is not fresh. Sometimes acidity is expressed in grams of lactic acid (America), in grams of sulfuric acid (France), in grams of acid phosphate KH₂PO₄ (England). 9. The content of raw and dry gluten (kleber, gluten) is one of the factors in evaluating wheat flour. Raw gluten is obtained by kneading wheat flour with water (2:1) into dough, letting the latter stand for 30–45 minutes, and then washing out the starch, kneading the dough with fingers under a thin stream of water; the sticky, viscous mass remaining in the hands is called raw gluten; its dry matter consists of 85% nitrogenous substances, it contains 60–70% water, and it is considered that the higher its water-absorption capacity, the better, and therefore, in addition to the raw gluten content, the dry gluten content and the ratio of raw to dry are also usually determined. The average content of raw gluten in flour is 30–35%, dry gluten is 2¹/₂ times less. The raw gluten of good flour is elastic, viscous, and resilient, its color is light cream, pleasant odor. In dark grades of flour, gluten has a dark color and is poorly elastic. Flour having inelastic gluten that breaks quickly upon stretching usually possesses lowered baking qualities. An unpleasant odor of gluten indicates that the flour is not fresh or the presence of foreign impurities in it. Lower grades of wheat flour usually yield more gluten than higher grades from the same grain, but the quality of gluten in the latter is higher, and therefore flour can be compared by gluten content only of identical types. 10. The fiber content in flour is usually small.

In high grades of wheat flour, fiber is usually contained in an amount of less than 0.2%, in medium grades - no higher than 0.5%, in low grades - 1.5%, calculated on dry matter. The fiber content in ordinary rye flour is 2-3%, in wallpaper (whole grain) flour - 1.5-1.2%, in sifted flour - less than 1%, in bolted flour - no more than 0.3%. 11. Pentosan content. Whole wheat and rye grain contains about 6-8% pentosans (pentose anhydrides). High grades of wheat flour contain 2-3% of them, low grades - up to 5%, bran - over 20%. In rye flour, pentosans are usually somewhat more numerous than in wheat flour. 12. Soluble carbohydrate content. In the aqueous extract of flour, there are various types of sugar - glucose, fructose, maltose, sucrose, raffinose, etc., as well as dextrins. The sugar content in grain depends on the growing conditions: in wet years, the grain usually contains more soluble carbohydrates than in dry years; fully ripened grain contains fewer soluble carbohydrates than unripe grain. The sugar content, determined by analysis, depends not only on the grade and quality of the flour, but also on the conditions of its extraction with water. Directly, the sugar content in flour is apparently insignificant, namely 0.15-0.25% of reducing sugars (fructose and glucose) and about 1% of sugar after inversion (mainly from sucrose). If flour is mixed with water, sugar is formed from the flour starch under the influence of enzymes. This sugar formation in dark grades of flour proceeds more intensively than in light grades, and in wheat flour more energetically than in rye flour. A great influence on the sugar content in the aqueous extract of flour is exerted by the water temperature and the duration of infusing the flour in it. Among the soluble carbohydrates of rye flour, sucrose and raffinose occupy the main place, and in wheat flour - glucose (Neumann). Recently, the carbohydrate trifructosan, characteristic of it, has been discovered in rye flour by Tillmans, and this has made it possible to find a method for determining the admixture of rye flour in wheat flour even in finished products. 13. Starch content in flour. High grades of flour contain more starch than low grades. Recently, attention has also been paid to the quality of flour starch, determining the coarseness of its grains, the viscosity of the paste, etc., since apparently the swelling capacity of starch from different grades of flour is not the same, which has an effect on the baking capacity of flour. Determination of the starch content in flour is rarely done; its amount is judged by the difference from 100: starch = 100 - (water + ash + fat + nitrogenous substances + sugars + fiber + pentosans). 14. Fat content in flour and its quality. Wheat and rye flour contain a very small amount of fat: in high grades of flour it is usually less than 1%, and in dark grades - about 2%, in bran - 4-5%. Under unfavorable conditions or long storage, the flour fat becomes rancid, its acidity increases significantly, and this can serve as an indication of the freshness and age of the flour. 15. Enzymes of flour. Flour contains various enzymes, of which the greatest importance are amylase (diastase), proteolytic enzymes, oxidases, and catalase. a) Amylase (see Amylase, amylolytic enzyme) converts starch into a soluble state and then turns it into sugar (maltose). This takes place during dough fermentation and is necessary for the proper progress of this process. However, too high a amylase content in flour leads to the production of liquid, sticky dough and poorly rising bread: gases develop too rapidly in the dough, and the gluten of the latter is unable to retain them. On the other hand, if there is little amylase in flour, this also adversely affects the dough fermentation process, causing weak gas development and partly affecting the color and appearance of the resulting bread. Malt, sprouted grain flour, and bran extract are rich in amylase; dark grades of flour have more amylase than light grades. Drying grain at a high temperature can destroy amylase, and flour from such grain ferments poorly. In view of such importance of amylase, in necessary cases, the determination of the so-called diastatic activity (strength) of flour is performed, i.e., finding out what amount of maltose can be obtained in a certain time, at a known temperature, by acting with an aqueous extract of flour on starch. Several methods for determining the diastatic activity of flour are known; among them, the methods of Lintner, Kolbach-Windisch, and Ramsay are widespread. In the first two methods, an aqueous extract of flour acts on artificially prepared soluble starch, and in the latter - on the flour's own starch under conditions close to dough-formation processes (1 hour at 27°). The normal diastatic strength of high-grade flour according to Lintner is about 20, medium grades about 30, and low grades above 50. According to Ramsay, normal flour forms about 2 g of maltose, calculated per 100 g of flour. Temperature, duration of exposure, and medium acidity have a great influence on the development of diastatic activity. b) Proteolytic enzymes act on proteins, breaking them down into amino acids. In dough making, this process takes place, but under normal conditions, this enzyme effect is apparently very small. c) Oxidases cause poor storability of dark grades of flour, dark color of the dough, rancidity of fats, etc. In low grades of flour, a stronger manifestation of the action of oxidases is detected than in high grades, and in rye flour it is stronger than in wheat flour. Numerical expressions cannot yet be given. d) Catalase (see) is contained in large quantities in grades of flour with a high shell content. Attempts to classify flour by catalase content have been made repeatedly, but so far the results cannot be considered fully consistent. The very determination of catalase should be recognized as very useful in laboratory practice for judging the quality of a given flour. 16. Baking properties of flour. Flour possesses varying water-absorbing capacity, and from the same amount of different grades of flour, an unequal amount and quality of both dough and baked bread are obtained. Dough from flour of good baking qualities becomes elastic and seemingly stiffer upon standing, while dough from flour of weak baking qualities becomes more liquid and sticky; during fermentation, dough from flour of good baking qualities rises evenly and increases in volume by 2.5-3 times, while dough from weak flour ferments strongly, rises quickly, and then quickly falls and does not maintain its volume. Likewise, during the "proofing" of shaped loaves and their baking, in the first case, loaves are obtained that have risen well and maintain their volume, while in the second, loaves spread out and turn out low. To determine all the indicated properties of flour, it is customary to conduct a trial laboratory baking of bread, and the methodology for conducting such baking is not standardized everywhere. In all methods, the ultimate determination is a) the yield of dough and bread from 100 g of flour, b) the quality of the bread (volume per 100 g of flour, structure and quality of the crumb, quality of the crust), and c) the behavior of the dough during processing. It is considered that from 100 g of wheat flour of medium baking qualities, 165 g of dough and 145 g of baked bread are obtained; from 100 g of such flour, a bread volume of 400 cm³ is obtained when baking bread in pans. The methodology for trial laboratory baking of sourdough rye bread is even less developed. Usually, the method set forth in Neumann's book (Brotgetreide u. Brot) is used. 17. Microorganisms of flour. Flour is rich in various microorganisms - yeast and mold fungi, bacteria, and their spores. Microorganisms come predominantly from the grain, but can also come from the air and from objects in contact with the flour during production, storage, and transport. Bran-rich flour is usually richer in microorganisms than flour from the inner part of the grain. Among the bacteria, species of Bacillus lactis acidi, Bacterium coli commune, Bac. mesentericus, and others are found. Among the molds, there are Mucor mucedo of dark brown color, Penicillium glaucum of greenish color, Aspergillus glaucus and fumigatus of green color, Rhizopus nigricans of black color, Oidium auranticum of orange color, Thamnidium elegans of white color, and others. In addition, yeast fungi are found, most often of the species Saccharomycetes. Flour does not tolerate sterilization; its baking capacity suffers greatly from this. Most microorganisms of flour die in an acidic environment at the bread baking temperature, but spores of certain species, e.g., Bac. mesentericus (potato bacteria), survive and under certain conditions can cause a disease of bread known as "ropy bread" or "potato disease" (see). The contamination of flour with microbes is important for flour storage, namely, under unfavorable storage conditions (humidity, heat, lack of ventilation), microorganisms develop and cause flour spoilage, consume its dry substance, give it an odor and taste, etc. 18. Animal pests in flour. During storage, flour is often subjected to the attack of animal pests, which contaminate the flour with their excreta and thereby affect the smell and taste of the flour; the eggs and larvae of certain pests permeate the flour so much that they make the latter not only unpleasant in appearance, but also inedible.

Among the pests, the most frequently encountered are: 1) the flour mite (Acarus farinae), an insect about 1 mm long, colorless and almost transparent; its broad oval body bears 4 pairs of legs covered with tiny hairs; they reproduce by eggs, and generally enter the flour from grain. In damp and warm flour, it multiplies rapidly, contaminating it with eggs, waste products, and its own corpses; flour heavily infested with mites acquires a characteristic odor. Under favorable conditions, the complete development cycle of the mite takes about 3 weeks. 2) The mealworm, the larva of the beetle Tenebrio molitor. The female beetle lays eggs singly and in groups in the flour; the eggs are covered with a sticky mucus and therefore are always caked with flour. In about 10-14 days, yellowish larvae emerge from the eggs, reaching comparatively large sizes (25-30 mm in length and 4 mm in thickness); they are easily removed from flour by sifting. 3) The Mediterranean flour moth (Ephestia kuhniella), a butterfly frequently found in mill premises; it lays 150-200 eggs, usually in clusters of 2-6, in the cracks of bins, pipes, spouts, on sacks, sifters, etc. The caterpillar of the moth is white with a creamy tint, with a reddish-brown head, and reaches a length of up to 20 mm. It entangles the flour with webs, turning the latter into solid lumps, so that sometimes the movement of flour through pipes and sleeves even stops. It prefers granular flour and middlings, heavily contaminating the product with eggs, cocoons, and butterfly corpses. Heating to 50° and a frost of -15° are fatal to the larvae. 4) The meal snout moth (Pyralis farinalis) and the confused flour beetle (Tribolium confusum), among others, are less frequently found in flour. Foreign impurities in flour can be divided into two groups: 1) natural impurities, i.e., those not intentionally added to the flour, but remaining in it due to weed contamination of the grain and its poor cleaning before milling, and 2) impurities intentionally added to flour either to improve its qualities or to increase its weight. The first group of impurities includes primarily weed seeds, many of which impart a dark color to the flour, increase the mineral content (ash content) and crude fiber in the flour—such as wild buckwheat (Polygonum convolvulus L.), various species of vetch (Vicia), rye brome (Bromus secalinus), and other weeds—while some impart an unpleasant odor or taste to the flour and the bread made from it, e.g., wild garlic (Allium vineale), wormwood (Artemisia Absinthium L.), knapweed (Acroptilon picris C.A.M.), and others. Some weeds impart poisonous properties to flour and bread: such are the corn cockle (Agrostemma githago), containing the alkaloids gitagin and agrostemmin, and darnel (Lolium temulentum), found in winter crops, the toxicity of which some explain by the development of special types of fungi under the husk of this weed. The toxicity of the corn cockle significantly decreases during the bread-making processes (the action of acids during fermentation and the high temperature of the oven), but nevertheless does not disappear completely. The corn cockle content in flour should not exceed 0.25%. By properly passing the grain through separators, trieurs, and similar machines at the mill, the grain can be almost completely separated from weed seeds; therefore, the utmost serious attention must be paid to this work of mills and elevators, and the fullest possible cleaning of the grain must be required of them. As already mentioned above, plant parasites frequently develop on cereal grains. These include the ergot fungus (Secale cornutum), various types of smut—loose, covered, or stinking (Ustilago carbo, Tilletia caries, and Tilletia laevis), etc.; then various species of rust fungi or simply rust (Puccinia graminis); and finally, mention should also be made of "seed black mold", which causes a phenomenon in bread known as "drunken bread", caused by the presence of fungi (Cladosporium herbarum and Fusarium roseum). Other seed diseases are also known. The content of ergot and smut in flour is permitted to be no more than 0.06% each individually or both together. Flour contaminated with fungi that cause the phenomena of "drunken bread" is not permitted for circulation. To this same group of accidental impurities should be added the accidental admixture of flour from other cereals. Modern grain-cleaning schemes prior to milling make it possible to reduce these impurities to insignificant amounts; therefore, the presence in flour of over 10% of flour from other types must be stated on the packaging, otherwise it is regarded as an intentional admixture (adulteration). For signs of adulteration of wheat flour by the addition of barley, oat, or corn flour, see above. The addition of legume flour to wheat flour noticeably makes the crumb denser. To the group of impurities intentionally added to flour should be assigned various "improvers" of the baking qualities of flour in the form of individual salts or patented preparations. Among them are substances of plant origin (malt, malt extract, potato, corn, and rice starch, etc.), against the use of which it is difficult to object if they genuinely improve the quality of the bread. Besides these substances, in foreign practice, and partly in the USSR, various salts are sometimes added to flour, such as: acid calcium phosphates, calcium peroxide, potassium and ammonium persulfates, perborates, potassium iodate and bromate, benzoyl peroxide, etc. Powders are also used: "Arcady" (in the USSR, a mixture of 27% table salt, 10% ammonium chloride, and 2% calcium peroxide, with the remaining 61% being flour; Neumann gives the following composition for the "Arcady" powder of a German firm: 25% calcium sulfate, 10% ammonium chloride, 0.3% potassium bromate, 25% table salt, 40% flour; this mixture is usually added at 0.4-0.5% to the flour); "Novadelox" (a mixture of acid calcium phosphate with benzoyl peroxide); "Salox" (a mixture of acid calcium phosphate with ammonium persulfate); "Multaglut" (also acid calcium phosphate and ammonium persulfate), and others. The addition of these preparations must be carried out only with the permission of the Academic Medical Council of the People's Commissariat of Health. In baking practice, cases of adding copper sulfate, alum, lime, etc., to flour are known. The addition of such substances is unacceptable. Any addition of weight-increasing substances to flour—chalk, gypsum, ash, etc.—should be regarded as gross adulteration. Likewise, the intentional addition of bran, ground wood, straw, or similar substances to flour must be considered gross adulteration of flour. Based on the accounting of all the listed factors, a sanitary evaluation of flour is performed, and it may be recognized as substandard and unfit for food, adulterated, and of reduced value. 1. Flour is recognized as substandard and unfit for food 1) if it has a musty or generally bad odor and shows signs of spoilage and decomposition; 2) if it contains an admixture of copper, zinc, lead, or any other heavy metals that act harmfully on the human body, as well as alum, etc., substances serving to mask its poor qualities; 3) if the content of ergot, corn cockle, and smut in it exceeds the permitted norms, and also if it contains in significant quantities other impurities that are not indifferent to the body, such as darnel, brome, etc.; 4) if it is so heavily infected with microorganisms that upon baking it produces diseased bread (potato bacteria, Fusarium, etc.); 5) if it is so infested with pests that after sifting an extraneous aftertaste and odor are felt in it. 2. Flour is recognized as adulterated 1) if it contains an admixture of flour from other cereals exceeding the permitted norm; 2) if the content of sand and earthy impurities in it exceeds the established norm. 3. Flour is recognized as being of reduced value 1) if it has undergone chemical treatment for the purpose of improving its external qualities (e.g., flour bleached with chlorine or nitrogen oxides); 2) if it is made from grain with a high content of sprouted grains, as well as from grain killed by excessive drying or strongly crushed on rollers, if this affects its baking qualities to such an extent that it makes it impossible to obtain satisfactory bread by ordinary means. Chemical composition, nutritional, and dietary value of flour. The chemical composition of flour depends on the composition of the grain and the degree of extraction of the latter. Tables 3 and 4 show the approximate chemical composition of wheat and rye flour of various types. From the tables, it can be seen that flour of a higher extraction rate, compared to flour of light grades from the same grain, is richer in nitrogenous substances, fat, sugar, crude fiber, and mineral substances. According to calculations, the theoretical caloric value of dark flour surpasses the caloric value of light flour. Table 3. Change in the chemical composition of flour depending on the degree of grain extraction (according to Neumann). Wheat and rye: Extraction in % Ash Fat Nitrogenous substances Nx6.25 Carbohydrates Sugar Starch Crude fiber Pentosans Undetermined. Wheat, wheat grain. 1st grade flour. 2nd grade flour. 3rd grade flour. Feed flour. Fine bran. Coarse bran. Hulling wastes. Germ. Rye grain. 1st grade flour. 2nd grade flour. 3rd grade flour. Feed flour. Bran. Hulling wastes 1.

% 0-94 o/ /o 0.80 1.15 1.80 1.90 13.00 13.00 4.60 4.85 75.92 74.00 0.28 0.53 3.33 3.95 0.35 0.62 1.87 2.25 13.50 5.19 67.45 2.10 7.25 0.39 Rye Constituents Ash........ Fat ......... Nitrogenous substances Sugar ....... Starch ..... Cellulose..... Pentosans .... Undetermined Flour types 0-50 % 0-701 0-82 % I % 0.60 0.85 6.80 5.00 0.95 1.25 8.10 6.53 78.05; 72.50 0.30 4.00 4.40 0.45 5.20 5.04 1.30 1.65 9.30 7.30 66.45 1.10 7.40 5.50 0-94 1.85 1.80 10.15 8.75 61.20 1.91 8.45 5.89 However, bread made from light grades of flour is more fully assimilated than bread from dark grades, and therefore the former is higher in useful calories than the latter. In scientific literature, there are indications that simple-milled flour is preferable for nutrition compared to light grades of flour, because it is richer in vitamins, phosphates, and mineral salts in general. It must be noted, however, that this can only matter in the case of a diet consisting predominantly of bread alone; under normal conditions, the vitamins contained in flour are easily obtained by the organism from other food products (vegetables, fruits, etc.); likewise, in very rare cases does a person experience a deficiency in the mineral salts contained in flour, especially since the mineral substances of coarse flour bread are assimilated relatively poorly. Methods of flour research. I. Sampling for research. For laboratory testing of flour, it is necessary to have at least 500 g of it, and if trial laboratory baking is also required, at least 2 kg of flour must be sampled. To ensure that the sampled flour truly corresponds to the average qualities of the entire batch of flour, serious attention should be paid to the correct sampling of flour, for which the following procedure is recommended. First of all, a so-called general sample must be taken from the tested batch of flour, which will then serve for the selection of a laboratory sample (average sample) from it in the above-mentioned quantities. The general sample is made up of samples taken depending on the visible homogeneity of the flour and the size of the entire batch: either from each bag, if for example there are no more than 5 bags in the batch, or from every fifth, tenth, hundredth, etc. bag if the batch is large. (Bags that are water-damaged or sharply differ in their qualities are not counted—separate samples are taken from them.) The sample should be taken from different places in the bag using a sampler, bearing in mind that flour from the central part of the bag and from the peripheral parts may be dissimilar in composition and properties. From premises where flour is stored in bulk, it is convenient to take samples during the loading or unloading of the grain, taking samples from the moving flour at regular intervals. To select a laboratory sample, the general sample of flour should be thoroughly mixed, laid out in an even layer, and the necessary amount of flour should be taken from at least 20 places (e.g. in a checkerboard pattern). The well-known method of dividing the leveled layer of flour diagonally into 4 parts and repeatedly taking two opposite parts can also be applied. The selected samples must be placed in glass jars with ground-glass stoppers or in tin cans with tightly closing lids, closed, and sealed. Such samples should be stored in a cool, dry place. If it is intended to determine moisture from a separate sample, flour samples can also be sent in cotton or linen bags; for the determination of moisture in this case, separate samples are taken in an amount of only 50–100 g and placed in glass jars with ground-glass stoppers. II. Research of flour. The research of flour breaks down into 1) research using the senses (organoleptic testing), 2) microscopic research, 3) testing using physical methods, 4) chemical research, qualitative and quantitative, and 5) in some cases, a trial laboratory baking is also performed. II. Testing with the help of the senses determines the color, gloss, purity of milling, granularity, odor, and taste of the flour. Clearly noticeable admixtures, contamination with smut, animal pests, etc., are also noted. When determining the color of flour, the tested flour is usually compared with some close normal sample. For ease of observation, the Pekar apparatus is usually used, testing the flour in both dry and wet forms. It is impossible to compare flour samples that differ sharply from each other in grinding coarseness and moisture. 2. Microscopic research has the main purpose of determining the nature of the flour and the absence of foreign impurities in it, such as: a) admixtures of other types of flour, b) harmful impurities—smut, ergot, corn cockle, animal pests, etc.; c) in some special cases, microscopic research also determines the genus and quality of microorganisms in flour that cause bread diseases or make it inedible. Microscopic research usually breaks down into two processes: 1) research of a flour sample mixed with water, mainly to recognize the type of starch granules in order to determine from which cereal the flour is made and whether it contains admixtures of other types of flour; 2) research of the non-starchy part of flour, which includes fragments of tissues, grain films, fruit and seed coats, the aleurone layer, mold fungus spores, ergot, corn cockle, etc. To study this part, the starch must be removed. It is usually converted into a soluble state by hydrolysis, for which 5–10 g of flour is mixed with 200 cm³ of distilled water to which 10 cm³ of concentrated hydrochloric acid has been added, and the mixture is boiled for ¹/₂ hour. The evaporating water should be replenished with hot water all the time, for which it is recommended to make a mark of the constant liquid level on the beaker or dish and maintain this level by adding water. Upon completion of boiling, the particles suspended in the liquid are allowed to settle (which takes about 30 minutes), the liquid is carefully (by siphon) decanted from the sediment; the latter is poured over with hot water, boiled for some time, the suspended particles are allowed to settle again, and the liquid is decanted by siphon. From the sediment, samples are taken with a dissecting needle to prepare microscopic preparations. (After boiling the flour with acid and removing the liquid, the sediment can also be carefully treated with a weak alkali, for which it is poured over with 200 cm³ of a 5% sodium hydroxide solution and boiled for ¹/₂ hour, allowed to settle, the liquid decanted, poured over with hot water, boiled, allowed to settle again, and the liquid decanted. It must be borne in mind, however, that although the sediment from such treatment becomes denser and cleaner, the membranes sometimes swell from the alkali and may lose their characteristic appearance.) 3. Research using physical methods. 1) Coarseness of grinding. 50.0 g of flour and 10 g of dry wheat are poured onto sieves of the required numbers and sieved for 5 minutes using a laboratory sifter (the Zhuravlev system sifter is adopted in the USSR); upon completion of sieving, the residues on the sieves are poured onto glossy paper and from it into a weighed beaker and weighed. Weighing is carried out on technical scales with an accuracy of up to 0.1 g; subtracting the weight of the wheat (10 g) from the total weight of the residue, the weight of the residue alone is found. 2) Testing of rye flour according to Rakovich's method. For a quick and approximate test of rye flour, Dr. Rakovich's apparatus is often used, which consists of a) several (4–12) graduated test tubes with 36 or 44 divisions of 0.25 cm³ each, b) a copper measure for flour, with a capacity of 2.5 cm³, c) a bone spoon for pouring flour, d) three bottles (one for chloroform of specific gravity 1.43–1.48, another for 95° alcohol, and the third for sulfuric acid 1:5); e) a hydrometer to check the specific gravity of chloroform and an alcoholometer to check the strength of the alcohol; f) a brush for cleaning test tubes; g) cork stoppers for closing the test tubes. All this is packed in a special box and adapted for carrying. Rakovich's method is based on the fact that flour, when shaken with chloroform of specific gravity 1.48 (or with another liquid of the same specific gravity, e.g., a solution of potassium carbonate), separates into layers upon settling; the upper layer contains bran, the middle layer contains the floury part (starch and gluten), and foreign mineral impurities (sand, earth, etc.) gather at the bottom. By Rakovich's method, one can approximately determine 1) the amount of bran in the flour, 2) the relative coarseness of grinding, 3) the relative content of foreign mineral impurities in the flour, 4) to some extent the freshness or spoilage of the flour, 5) qualitatively the presence of ergot and corn cockle, 6) the relative dryness of the flour, and 7) with some skill, the presence of other types of flour. Course of testing. Using a bone spoon, flour is poured into the copper measure flush with the edges, freely without pressing; chloroform is poured into a dry test tube up to the 24th division; flour is poured from the measure into the chloroform, the test tube is closed with a stopper, the flour is shaken in the chloroform by gently rocking the test tube, and the mixture is poured back and forth from end to end of the test tube about two times, trying not to leave particles of flour on the glass in the upper part of the test tube. Carefully bring the test tube into a vertical position, let it stand for 10 minutes, and make the observation.

At present, instead of testing flour by volume (a small measure holds about 0.7 g), it is recommended to take a 1 g sample, and instead of Rakovich's apparatus, a modification of it, the "Novus" apparatus, is proposed. a) Amount of bran in flour. Each division of the test tube occupied by bran corresponds approximately to a content of 1 kg of bran per 16 kg of flour, or 6.25%. (A division of the test tube occupied by bran only approximately corresponds to 6.25% when the bran is fine, uniform, and dark brown. If the bran has a mottled appearance, a brownish-yellow color with white inclusions, this indicates that the floury part has not been rubbed off from the bran sufficiently completely, and the branny layer is abnormally increased by risen middlings. In such a case, to determine the actual amount of bran, it is necessary to grind about 10 g of flour in a porcelain mortar for approximately 15 minutes and carry out the determination of bran in the ground flour using Rakovich's apparatus.) b) Quality of milling. The quality of milling can be judged by the appearance of the branny layer (the upper layer of the chloroform mixture). A mottled color (brownish-yellow with white) of the branny layer and particles of uneven size characterize milling with a high content of middlings and a floury part poorly rubbed off from the bran. In this case, the branny layer is usually located two or more divisions below the mark of the 24th division. A uniform dark brown color of the bran and a location above the 24th division indicate sufficient rubbing of the floury part from the bran, c) Content of sand and other extraneous mineral impurities. A ring is outlined at the bottom of the test tube; if the sand fills the outlined space, this indicates that the flour contains no more than 0.78% (128 g per 16 kg) of sand and earthy impurities. This amount of sand in rye flour is considered permissible with us, d) Freshness of flour. Spoiled flour colors chloroform a brownish or greenish color, whereas from fresh flour, chloroform acquires a milky appearance; fresh but damp flour is characterized by the fact that the chloroform soon settles and becomes transparent, e) Moisture of flour. The greater the moisture of flour, the smaller its specific gravity; therefore, by adding 95-degree spirit to the mixture of flour and chloroform, the specific gravity of the chloroform can be reduced so much that the flour will settle to the bottom of the test tube in it. This will happen the sooner, the drier the flour is. If it is required to pour no more than 3¹/₂ divisions of spirit, the flour is dry (up to 13% moisture), from 3¹/₂ to 5 divisions—flour of medium moisture, and above 5 divisions—damp flour (above 15% moisture), f) Presence of ergot and corn cockle. Shake a sample of flour with 24 parts of chloroform and 7 parts of 95-degree spirit; particles of ergot (black in color) float to the surface of the liquid and can be counted using a magnifying glass: 14-20 black particles correspond to a content of approximately 0.5% ergot in flour. Corn cockle particles settle to the bottom of the test tube during such a test, but since fragments of other weeds also settle at the same time, the true nature of the precipitate should be verified by taking a sample from it with a needle for examination under a microscope. If 2-3 drops of sulfuric acid (1:5) are added to the chloroform sample after pouring the spirit and placed in warm water, a pink coloration of the upper layer of the liquid is obtained in the presence of ergot. The reaction is not very reliable. More reliable is the test proposed by Hoffmann: 10 g of flour is mixed with 20 cm³ of ether and 2 cm³ of diluted sulfuric acid (1:5). After shaking, it is left to stand for several hours, filtered, and the filters are washed with ether so as to obtain 25 cm³ of filtrate. Add 0.5 cm³ of a saturated solution of sodium bicarbonate (NaHCO₃) to it. In the presence of ergot, a violet coloration is obtained, and with a small content, a yellowish-brown one, g) Admixture of flour of other cereals. The admixture of barley and oats can be detected by needle-shaped plates which become noticeable after pouring 8-10 divisions of spirit into the chloroform sample of flour; admixture of buckwheat—by dark red husk particles, admixture of pea flour—by the coloration of the chloroform, etc. The determination requires great skill. 4. Chemical investigation. 1) Determination of moisture content. To obtain fully comparable results, it is necessary to always perform the determination of flour moisture under identical conditions; weigh 2 g of flour in a weighed glass weighing bottle of dimensions d = 4.0 cm, h = 2.5 cm, or 5 g of flour in a tared special metal dish (d = 6 cm, h = 3 cm) with a lid; dry for half an hour at a temperature of about 60° and then for 6 hours at a temperature of 100-105°, with the result given only in whole numbers with one decimal place. Weighing should be done after complete cooling in a desiccator and as quickly as possible, keeping in mind the strong hygroscopicity of flour. The lid of the weighing bottle should be closed during weighing and cooling in the desiccator. Drying, however, is carried out with the lid open. As a faster method, although less accurate, heating 5 g of flour at 130° for 40 minutes is recommended. The accuracy of the result expression is 0.5%. In America, the official method is considered to be drying to constant weight (about 5 hours) in a vacuum apparatus at 98-105° with a vacuum of 25 mm. This method yields elevated results compared to the method of drying at 105° in a steam oven. The method of drying at 130° for one hour is also adopted. 2) Determination of mineral substance content. In view of the insignificant mineral substance content in flour, the flour sample must not be taken as 279

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280 less than 3 g for light grades of flour and 2 g for dark grades. Weigh the flour in a porcelain crucible with a capacity of 30 cm³, previously calcined, cooled in a desiccator, and weighed. Incineration should be carried out carefully, gradually increasing the burner flame to a red-heat temperature (approximately 650°); avoid melting the ash. To accelerate incineration, it is useful after removing volatile substances and forming coke to remove the burner from the crucible, let the mass cool, moisten with a few drops of distilled water, carefully evaporate the water, and continue incineration until the carbonaceous part is completely burned and an ash of white or slightly grayish color is formed. Instead of water, some use nitric acid. For mass ash content tests, it is recommended to have a muffle furnace. 3) Determination of sand content (more precisely, mineral substances insoluble in 10% hydrochloric acid). The ash obtained by the previous method is heated slightly for 15 minutes with 20 cm³ of 10% hydrochloric acid, the liquid is poured through a weighed filter, the residue is washed with distilled water, the filter with the residue is dried, incinerated in a crucible, and the weight of the obtained ash is calculated as a percentage. Roughly, the content of sand, earthy impurities, and impurities such as chalk, gypsum, and talc can be detected by shaking a flour sample with chloroform in a cylinder (in a ratio of approximately 1:10)—mineral impurities settle to the bottom. 4) Determination of the content of heavy metal salts. About 20 g of flour is incinerated, the resulting ash from the previous step is heated with 10% hydrochloric acid and filtered. A stream of hydrogen sulfide is passed through the filtrate—most heavy metals precipitate as a black precipitate. 5) Acidity of flour. There is a diverse methodology for determining the acidity of flour. It must be borne in mind that when mixing flour with water, an increase in acidity occurs under the influence of flour enzymes and microorganisms; this process depends on the duration of exposure and the temperature of the water. For practical purposes, the following method can be adopted. Pour 200 cm³ of distilled water (freshly boiled and cooled to room temperature) over 10 g of flour, shake (by tilting the flask) for uniform mixing, and let stand for 1 hour. Filter 100 cm³, add phenolphthalein, and titrate with n/₂₀ NaOH solution until a pink coloration appears that does not disappear for at least half a minute. Recalculate per 100 g of flour in cm³ of alkali solution. The American Association of Cereal Chemists recommends the following method for determining the acidity of flour. Pour 18 g of flour into a 500 cm³ conical flask, add 200 cm³ of water (previously boiled and cooled to remove carbon dioxide), close loosely with a stopper, place for 10 minutes in a water bath heated to 40°, and periodically shake the flask. Remove from the bath and let stand at room temperature for one hour. Filter through a dry filter, discard the first 10 cm³ of the filtrate, and then collect 100 cm³ of the liquid in a measuring flask. Titrate with n/₂₀ NaOH solution, adding 2 cm³ of a 1% alcoholic solution of phenolphthalein (previously neutralized). Each cm³ of n/₂₀ NaOH corresponds to 0.005 g of lactic acid or 0.05% acidity. (In America, acidity is more often expressed as a percentage of lactic acid.) Acidity expressed in lactic acid can be expressed in sulfuric acid, for which the amount of lactic acid must be multiplied by the coefficient 0.54448. Similarly, acidity expressed in sulfuric acid can be converted to lactic acid by multiplying the amount of sulfuric acid by the coefficient 1.83659. 6) Fat content (ether extract). The determination of fat content is usually carried out in a Soxhlet apparatus. Dry 5–10 g of flour for about two hours at 100° (the sample in which moisture content was determined can be used), place it in the apparatus cartridge, cover with degreased cotton, and extract with ether (free of water and alcohol) for 12–16 hours. (It is recommended to pour ether over the sample and leave it overnight, and extract for 3–4 hours the next day.) The ethereal liquid should then be filtered into a weighed flask, the ether distilled off through a condenser, the ether residues removed by evaporation on a boiling water bath for one and a half to two hours, cooled in a desiccator, and weighed. Very coarse flour should be ground beforehand—it should pass through a sieve with 1 mm openings. 7) Nitrogenous substances content. The total nitrogenous substances content in flour is usually determined by the Kjeldahl method. A flour sample of 1–1.5 g is taken. The coefficient for converting nitrogen to nitrogenous substances is taken as 6.25 in our country, and 5.7 in America for wheat flour. 8) Content of soluble nitrogenous substances. 40 g of flour is poured with 800 cm³ of water and shaken by tilting until all the flour is evenly distributed in the water and no lumps remain; the mixture is allowed to stand for 2 hours, shaking from time to time. Then it is filtered through a dense filter. 200 cm³ of the filtrate is taken in a Kjeldahl flask, 12.5 cm³ of concentrated sulfuric acid is added to it, several pieces of pumice are added, and it is evaporated on a sand bath until sulfuric acid vapors begin to appear. After this, another 12.5 cm³ of concentrated sulfuric acid and one drop of mercury are added, and the Kjeldahl determination is completed in the usual way. Also in this determination, it should be noted that to obtain comparable results, the extraction of nitrogenous substances by water must be carried out each time under identical conditions (the influence of proteolytic enzymes) both in terms of the duration and temperature of flour extraction and the concentration of the extract. 9) Determination of the quantity and quality of gluten. a) To determine the amount of crude gluten in flour, 25 g of flour is mixed in a porcelain mortar or enamel dish (diam. 12–15 cm) using a horn or porcelain spatula with 12–15 cm³ of tap water to the consistency of dough; the latter is taken in the hands and thoroughly kneaded with the fingers. When the dough is ready, it is placed back in the dish and left to swell completely for 30 minutes. Then the dough is taken in the hands and washed with a thin stream of tap water of normal hardness, i.e., about 15° of hardness (with distilled water the results are somewhat lower, with very hard water—higher) and room temperature (in the cold season, it is useful to have a supply of water for this purpose in a large bottle with a tubulus at the bottom or with a siphon). During washing, the dough is continuously kneaded with the fingers: starch is washed away from the dough by the water, and gluten remains. Washing ends when the draining water is completely colorless, i.e., free of starch. Washing continues for approximately 10–12 minutes; it is recommended to test the wash water with iodine for the presence of starch. Washing should be carried out over a small silk or metal sieve so that breaking off lumps of gluten are not carried away by the water and can be collected and added to the total mass of gluten. The washed gluten should be thoroughly squeezed with the fingers, placed in a tared dish (nickel or porcelain), and weighed on technical scales with an accuracy of 0.1 g. b) Determination of the amount of dry gluten. Having stretched the crude gluten (using the thumb) as fully as possible over a dish (or glass plate), it is placed in a drying cabinet and dried for 2 1/2 hours at 120–125°; upon cooling, it is weighed and the weight of dry gluten is found; for control, it is better to place it for another 1 hour at the same temperature (at a temperature of 105°, gluten has to be dried for at least 12 hours). c) Determination of gluten quality. The color and odor of the crude gluten, its ability to stretch (good gluten stretches into a ribbon up to 25 cm long and more), and its behavior during drying (poor gluten becomes sticky at the beginning of drying, "runs," and after drying gives a poor-looking flat cake (dark, poorly risen)) are usually noted. 10) Determination of the content of "crude" fiber is usually carried out according to the Henhenberg method. 3 g of flour is thoroughly mixed in a porcelain dish or beaker with a capacity of 400 cm³ with 50 cm³ of 5% sulfuric acid, 150 cm³ of distilled water is added, and boiled for half an hour. Marks for volumes of 200 and 400 cm³ should be made on the beaker or dish. Evaporating water is constantly replenished with hot water. The burner flame should be adjusted so that the liquid boils calmly; excessive heating can cause the substance to char on the walls of the dish. Then distilled water at room temperature is poured up to the 400 cm³ mark, allowed to settle for half an hour, and using a water-jet pump and a funnel (d = 6 cm) covered with a silk fabric (e.g., mill silk sieve No. 17–22), the liquid is suctioned off to the mark. The liquid can also be separated using a siphon. The rest is filtered through a fluted filter, trying to leave the residue in the dish or beaker.

What remains on the filter is washed with a stream of hot water, transferred from the wash bottle back into the beaker, a few drops of methyl orange are added, and the mixture is neutralized with a solution of sodium hydroxide (20 g per 100 cm³ of water). Then 50 cm³ of a 5% sodium hydroxide solution are added, water is added to the mark, and the mixture is boiled for 30 minutes, replenishing the evaporating water as before. Again, as after the acid treatment, distilled water at room temperature is added to the 400 cm³ mark, the mixture is allowed to settle for 10 minutes, the liquid is suctioned off to the mark, the remainder is poured through a folded filter, and so on, as described above. Then it is neutralized with dilute sulfuric acid using methyl orange, washed with hot water, and the precipitate is collected on a pre-dried (two hours at 105°) and weighed filter (11.5 cm in diameter), washed with water until the complete removal of sulfates (the test with BaCl₂ must produce no turbidity), then with alcohol and ether, dried in a weighing bottle to constant weight (about 6 hours at 105°), and weighed. Next, the filter with the precipitate is incinerated in a weighed crucible, and the resulting ash is subtracted from the weight of the "raw" fiber to yield the weight of "pure" fiber. 11) The determination of pentosan content is usually carried out according to Tollens' method using phloroglucinol. 12) Determination of soluble carbohydrates in flour.* A 25 g sample of flour is placed into a 1-liter volumetric flask, slightly more than half the volume of distilled water is added, and the mixture is shaken several times. Then it is brought to the mark with water, shaken again, and filtered through a dry filter into a dry vessel until a completely transparent filtrate is obtained. Reducing substances are determined in the filtrate (calculated as glucose or maltose) using Fehling's solution: a certain amount of Fehling's solution is brought to a boil in a porcelain dish, a precisely determined amount (by pipette) of the flour extract is added into it, and it is boiled for a strictly defined time (2 minutes), filtered through an asbestos filter (an Allihn tube and a suction flask are used for this purpose), taking care to transfer the precipitate as completely as possible onto the filter (using a glass rod with a rubber tip and warm water). The precipitate is washed several times with warm water until Fehling's solution is completely removed, then twice with alcohol, and finally with ether. The tube with the precipitate is dried at 110° (for about half an hour), secured in a stand, connected to a Kipp apparatus, and hydrogen is passed through. When all the air has been displaced from the tube by hydrogen (usually after about 10 minutes; verified by a test: collecting the outgoing gas in a test tube and testing for explosiveness), the part of the tube containing the asbestos with the cuprous oxide precipitate is heated with a weak flame, then the tube is allowed to cool and is weighed. To determine the weight of the Allihn tube itself, it is inserted back into the suction flask and * This determination is performed only in special cases.

284t the copper is dissolved with hot nitric acid (sp. gr. 1.2) under weak suction until the filtrate runs colorless. After this, the filter is thoroughly washed with hot water, then twice with alcohol, and finally with ether, and dried (for half an hour) at 110°. Tables are used to calculate the sugar content from the amount of reduced copper. (Instead of the gravimetric determination of copper, Bertrand's volumetric method can be conveniently used.) 13) Usually, the sugar content in the aqueous extract is determined before inversion and after inversion; the latter is carried out by boiling 100 cm³ of the liquid with 30 cm³ of 0.1 N hydrochloric acid on a boiling water bath for 5 minutes; the liquid is then neutralized with 0.1 N sodium hydroxide, brought to the mark with water, and a 50 cm³ aliquot is taken with a pipette for sugar determination. 14) Diastatic activity of flour. The two most widespread methods of determination are: 1) the old Lintner method and 2) the new Ramsey method. a) Lintner's method. 25 g of flour is treated with 300 cm³ of water and allowed to stand at room temperature for 6 hours (or half an hour at 50°), frequently shaking the contents of the flask by swirling. Then the liquid is brought to the mark with water and filtered through a dry filter into a dry vessel (discarding the first 10-15 cm³). A buret is filled with the filtered liquid. 10 cm³ of a 2% starch solution are poured into a series of identical test tubes, and the filtered flour liquid is added to them from the buret in the following order: 0.1 cm³ to the 1st, 0.2 cm³ to the 2nd, and so on; the mixture is shaken and allowed to stand for 1 hour. Then 5 cm³ of Fehling's solution are added to each, mixed with a rod, and placed in a boiling water bath for exactly 10 minutes; the bath must be of sufficient size and deep enough so that the test tube is almost entirely immersed in water (a saucepan or Reisshauer's maltose determination bath is suitable for this purpose). Note is taken of which test tube exhibits complete decolorization of Fehling's solution. If this occurs in the first tube, the activity is taken as 100; if in the second, 100:2; if in the third, 100:3, and so on. When greater accuracy is required, the flour extract is diluted 10 times and the determination is repeated. Necessary solutions. 1) CuSO₄·5H₂O is recrystallized from water with a small addition of concentrated HNO₃, the crystals are pressed between filter paper, allowed to stand in the room for 12 hours, 34.63 g are weighed out and dissolved in 500 cm³ of water. 2) Dissolve 258 g of NaOH in 500 cm³ of water. 3) Dissolve 173 g of Rochelle salt, add 100 cm³ of sodium hydroxide solution, and bring to 500 cm³ with water. To prepare Fehling's solution, equal volumes of the 1st and 2nd solutions must be mixed on the very day of the work. 4) Soluble starch: potato starch is treated with 7% hydrochloric acid and allowed to stand for a week, the liquid is decanted, washed thoroughly several times with distilled water, allowed to settle, poured onto paper, the water is squeezed out, and dried first at 50° and then at 100-115°. Weigh out 2 g, mix into a paste with water, add 100 cm³ of boiling water, and allow to cool. A fresh solution must be prepared each time. b) Ramsey's method. 10 g of flour is placed into a 250-300 cm³ conical flask, and the temperature is adjusted precisely to 27° in a thermostat; a bottle of distilled water is also placed there to have water of the same temperature. Then 100 cm³ of water is added to the flour, the flour and water are mixed by swirling (taking care that no flour remains on the walls of the flask, for which purpose a little water can be left out of the 100 cm³ and used to wash down the flour particles along the walls). The flask is placed back into the thermostat, loosely stoppered, and allowed to stand for exactly 60 minutes (a few minutes after the flask is placed, its contents should be mixed by swirling to equalize the temperature and better distribute the flour; such swirling should be repeated every 15 minutes). At the end of 60 minutes, the contents of the flask are quickly poured into a 200 cm³ volumetric flask, distilled water is added up to approximately 175 cm³, and for clarification and enzyme destruction (the solution must be neutral or slightly alkaline to thymol blue), 3 cm³ of 15% sodium tungstate (Na₂WO₄·2H₂O) are added, thoroughly mixed, and concentrated H₂SO₄ is added from a buret until the indicator turns pink (usually 0.4 cm³ is sufficient). Then the volume is brought to the mark (200 cm³) with water, shaken, filtered, and maltose is determined in a portion of the solution (50 cm³) by one of the known methods. The same determination of maltose is performed on an aqueous extract of flour (10 g per 100 cm³ of water at 27°) without holding in a thermostat. The difference between the two determinations gives the amount of maltose produced by the action of the enzymes.