Prof. S. V. Lebedev

Dissolution of Pentosans in Relation to the Cooking Process in Fermentation Technology

In the present state of milling, the usual waste of this production is bran. Under the market product called bran, a rather heterogeneous material is encountered in trade, not fully corresponding to what is meant by this name from the standpoint of milling practice. In this sense, bran is understood to be a mixture of the various parts of the milled grain that do not pass into flour. Under ideal conditions this mixture should consist exclusively of the hulls of the grain and of the germ part; generally speaking, bran should consist of everything that constitutes the grain proper as such, apart from its starchy part, which is converted into flour during milling. In work concerned with the study of the chemical composition and nutritive value of the individual morphological parts [[unclear: of the grain]] [[unclear: by Girard]]¹) the following distribution is given:

Thus, bran should account for about 16% of the substance of the grain being milled. However, the amount of bran obtained in reality usually does not correspond to this ratio for flour and bran, which is determined by calculation. [[unclear: The reason for]] this lies chiefly in the impossibility of a perfect separation of the individual parts of the grain, some of which pass into flour, whereas others pass into bran. Owing to this, during milling either part of the mealy mass of the grain passes into bran, or the reverse is observed. In addition, the adopted method of milling is of importance, being determined to a considerable extent by the nature and perfection of the equipment of the flour mill, and also by the individual properties and peculiarities of the grain being milled. Besides this, a very important factor proves to be the desire to place on the market flour of one or another quality, which, in turn, is connected with the practically established standards of purity for this product; these standards are not identically understood in different countries. Thus, the quantitative ratio of flour and bran obtained during milling is substantially affected by the degree of cleaning of the grain being milled. All of the above explains why the amount of bran in individual cases is not the same and, depending on the milling, may fluctuate within wide limits from 12–15%²) by weight of the grain, rising to 20–25% and even higher.

One of the tasks of removing bran is to increase the strength and the nutritive value of the flour obtained, as compared with the original grain being milled. The former is achieved chiefly—

¹) Annales de chimie et de physique, 6th series, III, 1884, p. 297.
²) Kozmin, Flour-Milling Production, 1912, pp. 513 and 586–589.

with enrichment of the germinal part of the grain, which is closely connected with the removal from the flour of indigestible or poorly digestible parts of the grain, concentrated chiefly in its husks.

Thus, during milling, the part of the grain that is not removed into bran and enters the final products can, with respect to wheat that is ground into flour, be represented from the data of Table I, compiled on the basis of Girard’s investigation.

TABLE I

The figures in Table I indicate the amount of parts of the grain passing into bran together with substances, such as fiber, that are relatively poor in nutritional value. However, not all the substances entering the bran can be classified as indigestible: in addition to indigestible fiber, they also include the protein of the aleurone layer, and the germ of the grain, which is considerably enriched in protein and fat and which also contains easily oxidized substances that, with time, impart a darker coloration to the flour. In view of this, together with the coats of the grain, the germ and the aleurone layer are directed into the bran; a greater or lesser amount of starch from the floury portion of the grain also enters there, depending on the nature of the milling and the degree of grinding of the grain. In repeated milling, the total mass of substances passing into the bran is usually divided into several fractions, which differ from one another in their composition; therefore, the substances that have entered one of these fractions may be absent from the others. The mixture of such bran fractions in the most varied combinations determines that, when bran is used, the nutritional value of the latter may be very unequal in individual cases. The composition of bran is also very strongly affected by such accidental impurities. Such impurities may result from incomplete cleaning of the grain when it is prepared for milling, or accidentally during the milling itself. Thus, for example, sand, soil particles, small parts of weeds, flax fibers, and much else enter the bran.

How complex, in this sense, the composition of commercial bran may be is shown by comparisons made by Petrov with respect to [[unclear: continuation on next page]].

1) Mikeshin, Guide to Bakery and Yeast Production, 1912, p. 92.
2) V. A. Petrov, “Bran as a raw material for flour-milling production,” News of the Moscow Agricultural Institute, 1912, vol. XVIII, issue 2.

analyses of wheat bran from one of the large mills of Ufa. The proposed comparative tests, which, as far as I know, were first proposed by the laboratory of general technology at the Moscow Agricultural Institute. In this case, determinations were made for the investigation of bran both in the form in which it arrives at the plant and in the form of the individual constituents or bran fractions obtained by their selection at the mill.

The quantitative ratio of these fractions is represented by Table II, while their qualitative aspect is sketched by the figures of Table III.

TABLE II*)

TABLE III*)

*) Timiryazev, p. 49.

*) Proceedings of the Moscow Agricultural Institute, 1912, XVIII, appendix, p. 53.

According to the data just presented, the composition of the sample being examined, entering the product, includes many completely accidental impurities, which certainly spoil the product and lower its nutritive value. The presence of such impurities, in addition to the other defects indicated above, makes it understandable why it is impossible to give any general chemical composition for the market product called wheat bran. What diversity there may be in the composition of bran can be imagined from the data in Table IV, where the analyses of Wolff, Kanonnikov, and Koenig are averages for a very large number of tests on various samples of bran.

TABLE IV.

With a very great diversity in the composition of bran, all of it has one common distinguishing feature, namely a considerable protein content. This circumstance, together with the high content in it of carbohydrates, fats, and mineral substances, served as the basis for regarding bran as a product of high nutritive value. The most ardent supporters of this view, and at the same time opponents of separating bran from ground grain, were Millon⁶) and Liebig⁷).

The latter proposed preserving in flour the chief mass of the bran, with the exception of 4–6% of it. Bread prepared from such flour was for a time considered especially nutritious.

However, the numerous experiments of Meier⁸), Rubner⁹), Buchinsky¹⁰), and other investigators, carried out on the assimilability of bread and crackers prepared from flour rich in bran, led to results that did not confirm the desirability of leaving bran in flour.

1) Izv. Mosk. S.-Kh. Inst., 1912, XVIII, appendix, p. 51.
2) Kanonnikov, Guide to the Chemical Investigation of Foods and Flavoring Substances, 1891, p. 70.
3) “Trofimovskoe Estate of Kentr,” p. 267.
4) Izv. Mosk. S.-Kh. Inst., 1912, XVIII, appendix, p. 53.
5) Koenig, B-II, p. 826.
6) Compt. rend., vol. 38, p. 12.
7) Chemische Briefe, Bd. [[unclear: volume/page]], p. 169; cited according to Guide to Breadmaking and Yeast Production, Mikini, 1912, p. 321.
8) Zeitschr. f. Biologie, 1871, Bd. VII, p. 1.
9) Zeitschr. f. Biologie, 1879, Bd. XV, p. 150.
10) Buchinsky, Materials for the Dietetics of Bread and Crackers, 1873, dissertation.

The causes of the poor assimilability of bran substances by the animal organism were first touched upon by Bischoff¹) in a particular case relating to experiments whose purpose was to explain the causes of the poor assimilability of black bread. These causes, according to Bischoff, were due to the accumulation of considerable quantities of lactic and other organic acids, formed in starchy bread with bran during its stay in the intestine. These acids, by their presence, irritate the intestinal wall and intensify its peristaltic movement, owing to which the food passes too quickly through the digestive tract, without having time to give up to the organism all its nutritive constituents.

Buchinsky²) explains the low assimilability of bread or rusks made from flour with bran by the mechanical irritation of the intestinal walls by coarse particles of food of this kind. As a result of this, the peristalsis of the intestines increases, and their contents, leaving the organism earlier than the normal period, do not have time to give the latter all their nutritive constituents. Thus, the imperfection of the grinding of bran, which is much more difficult to comminute than the floury part of the grain, is in this case accepted as one of the main causes of the weak assimilability of bran. The consequence of this was the requirement that bran be carefully ground before use, without which the supposedly complete utilization of its nutritive parts was impossible. On the other hand, wishing to avoid introducing into the organism large quantities of cellulose, which are unsuitable for its nutrition, attempts were made to find means for using bran. For this purpose it was recommended to steep the bran in water, which, after straining and removing everything that together with the cellulose remained undissolved, was added to the dough of the bread being prepared. Such methods were proposed³) by Herpin, Rollet, Fehling, Artus, Mège-Mouriés, Frapoli, Souvant, Gallavardin, and others. However, in all such methods, which had as their purpose the utilization of the valuable nutritive substances of bran, and chiefly their nitrogen-containing substances, this direct task was achieved only very little, since most of the nitrogenous substances, being bound to the cellulose, remained undissolved and therefore not fully utilized.

Later, numerous investigations, both chemical and physiological in character, widely embraced the question of the nutritive value of bran, and the result of all these investigations is the view now firmly established of bran as an excellent feed for domestic animals. At the same time it turns out that the coefficient of digestibility of bran is the higher, the smaller the content in it of fruit and germ coats. In addition, it has been established that, in order to pass into an assimilable state, bran requires a more prolonged action than the remaining floury parts of the crushed cereal grain. Owing to this, different animals differ very considerably in the assimilation of bran; for example, cattle utilize it considerably better than horses; the human organism, however, in most cases leaves bran very little digested.

The chief value of bran consists in the substances containing nitrogen. The quantity of the latter is very considerable, and in any case it is not lower than in the grain from the grinding of which the given bran is obtained.

¹) “Versuche über Die Ernährung mit Brod,” Zeitschr. f. Biologie, Bd. V, 1869. Cited from: Materials on the question of the assimilability of various sorts of black bread, N. Popov, 1890, pp. 131–132.

²) N. Popov, “Materials on the question of the assimilability of various sorts of black bread,” 1890, p. 139.

³) Mitint: “Handbook of Bread Baking and Yeast Production,” p. 322.

…however, the cost of bran in most cases amounts to about one-third of the cost of the corresponding grain. This explains the great demand for bran wherever this product is properly valued because of the high content of proteins in it.

Russian flour-milling production annually yields an enormous quantity of bran—more than 140 million poods. The principal consumer of it is agriculture, whose profitability is ensured, among other things, by the availability of cheap and nutritious feeds, among which bran is also included.

However, in Russia bran is often valued disproportionately low, both in comparison with other feedstuffs and in relation to its actual feed value, determined by the high content in it of digestible proteins.

As a result, Russia annually loses tens of millions of poods of bran that go irretrievably abroad. How rapidly the demand for Russian bran beyond Russia’s borders is increasing may be seen from the fact that over 20 years, beginning with 1890, the export of Russian bran increased fourfold, reaching by 1910 almost 40² million poods; in 1913 the export had already risen to 48.5³ million poods, for a sum of 32.6 million rubles, amounting to 33.6% of the total annual production of bran in Russia.

Under these conditions, according to data from the Review of Russia’s Foreign Trade, it turns out that in international trade Russia occupies first place, supplying the world market with 42.9% of the total quantity of bran delivered.

The valuable constituent parts of bran are digestible proteins and carbohydrates; the former amount to about one-tenth of the weight of bran. Thus, with an export of the latter of more than 40 million poods, Russia loses about 20–25 million poods of feeds extremely valuable for agriculture, receiving for them about 30 million rubles. However, this sum by no means compensates for the loss; for example, in his article on the nutritive value of bran, Petrov⁴ says the following: “if the bran annually exported abroad were fed to our own cattle, it would yield immeasurably greater income in the form of animal products, which are in good demand.” Despite this, in Russia the growth of bran exports was invariably observed from year to year. This is promoted to a considerable degree by reduced tariffs of 0.1 kopeck per pood per verst, as well as by the absence of a duty on exported bran. Meanwhile, the bran leaving Russia could find expedient application within the country itself, and not only as feed, but also as a valuable raw material suitable for certain industries where a cheap starting material rich in nitrogen is required. A case of this kind is provided, for example, by yeast production, since in it the quantity and cost of the final product produced—yeast—are determined chiefly by the content of the corresponding forms of nitrogen in the starting material and by the cost of the latter; in this respect, bran, because of its cheapness and its richness in nitrogen, fully satisfies the indicated requirements. In view of this, the question of the possibility and conditions of using the nitrogen of bran in yeast production is of considerable interest.

As was indicated above, the suitability of bran for yeast production is determined by the presence in it of forms of nitrogen compounds that are assimilated by yeast either directly or after appropriate treatment; the practical value of bran in this respect is also determined by the quantity and quality of its other constituent parts. Some of these are necessary and even indispensable for yeast; others, in the best case, prove useless. Among the latter belong fiber, a considerable portion of the ash substances of bran, and pentosans. Table IV gives an idea of the amount of fiber and ash in bran. As for pentosans, as well as hemicelluloses, their content either has not been given any attention at all, or else it has remained hidden under the general heading of carbohydrates, which, besides the isolated fiber, of course also included starch, dextrins, monosaccharides, and hemicelluloses.

All these compounds belong to one group—to carbohydrates—and therefore, from the chemical point of view, nothing can be objected to in such a combination; but in evaluating bran with respect to the possibility of using it in yeast production, such a grouping of the data of chemical analysis of bran would be inexpedient, since pentosans and their derivatives differ from starch and the products of its hydrolysis by their slight suitability for yeast nutrition, and by the fact that these compounds cannot be used for producing potable alcohol. In view of this, the determination of pentosans would be highly desirable for obtaining more precise data on the amount of assimilable carbohydrates present. Meanwhile, not only in the investigation of bran, but even in analyses of grain, pentosans are usually not determined, and the amount of starch present is in most cases calculated indirectly, by subtracting from 100 the sum of the numbers giving the percentage content in the grain under investigation of water, ash, fat, proteins, and fiber.

Thus, besides the impermissible identification of pentosans with starch, the determination of the latter is based on an obviously incorrect assumption that the sum of all the numbers giving the determined constituent parts of the grain is equal as though to 100; in reality the indicated sum is considerably less, as has repeatedly been noted in the literature.²) The reason for this phenomenon lies not only in the inaccuracy of the methods used for quantitative determination, but also in the fact that plants contain still unstudied substances which so far cannot be taken into account by the accepted methods of investigation.

All such substances are customarily called “undetermined substances.” To this same heading, as Frankfurt points out, must also be assigned those already known substances which, by the methods of investigation employed, are not quantitatively taken into account; such, first of all, may be organic bases, amino acids, and also hemicelluloses, if fiber is determined by the generally accepted Henneberg method. The amount of undetermined substances in analyses of plants sometimes reaches, as Frankfurt indicates, 15–20%. In cereal grains the amount of undetermined substances is considerably smaller. It is not the same for different cereals: for example, there is more in rye than in wheat. Obviously, in bran there must be considerably more undetermined substances than in the corresponding grain that gives this bran.

¹) Czapek, Biochemie der Pflanzen, vol. I, p. 246.
²) Frankfurt, “Methods of Chemical Investigation of Substances of Plant Origin,” p. 207.

...which indicates that, in the indirect determination of starch, an exaggerated content of the latter is obtained. And this exaggeration will be especially significant when pentosans, as such, are not determined by analysis, as a result of which they are logically included either in the amount of undetermined substances, or, together with them, are attributed to what is erroneously taken as the starch content.

Very few investigations have been carried out concerning the content of pentosans in cereal grains in general, and they relate chiefly to barley. It has been established that, on average, calculated for the dry matter of barley, there are 8–9%¹ pentosans.

If the pentosan content in barley is taken as 100, then according to Rupp² their amount for rye is expressed by the figure 110, for wheat—47, for oats—48, and for buckwheat—45.

These ratios apparently apply to the conditions of Western Europe. Judging from many analyses carried out during the period 1908–1915 in the Laboratory of Nutrients of the Tomsk Technological Institute, the average amount of pentosans, calculated for dry matter, for the ryes of Tomsk and Tobolsk provinces and in wheats corresponds to 8.5%, in rye to 10.8%, while in wheats fluctuations were observed that were considerably greater than in rye.

An idea of the content of pentosans in bran is given by Table V, which presents the composition of wheat bran taken in 1914–1915 from several Siberian flour mills in Tomsk and Altai provinces.

Analysis of wheat bran from the 1914 harvest

TABLE V

TABLE V

Calculated on dry matter, in percent

From the data of Table V, and also from Table IV, it is evident that the mass of bran consists mainly of nitrogen-containing substances, starch, pentosans, fiber, and ash.

It is obvious that they constitute a mass of various substances, some of which are unnecessary in production, while others, at best, are only assimilated with difficulty by the yeast. Proteins, starch, and part of the free pentosans belong to the first category; to the second—fiber, and, to a considerable degree, cellulose and pentosans. However, little is known about the latter in this respect. Windisch¹ indicates that during the fermentation of beer wort the quantity of pentosans changes almost not at all from the beginning to the end of fermentation. According to C. Lintner, Jr.², the presence of a certain kind of pentosans accounts for the viscosity of fermentation media. Such a property is possessed, for example, by galactoxylan, which is found in barley, and by metalaban, contained in barley and rye. Its toughness, stickiness, and slight mobility in rye mash, according to Delbrück⁴, are caused by gum, which on hydrolysis gives pentose, chiefly arabinose, with a small quantity of hexoses.

The evident uselessness and the very high content of pentosans, reaching more than 20%, make it necessary, for the possibility of processing bran in alcohol-production technology, to set forth special requirements of its own. These requirements logically follow from the necessity of eliminating from the material being processed its useless parts, namely—

1) Wochenschr. f. Brauer, 1909, p. 688 ff.
2) Thäusing, Die Theorie und Praxis d. Malzberei u. Bierfabrik, 5th ed., p. 190.
3) Lippmann, Chemie der Zuckerarten, vol. I, p. 57 ff.
4) Maercker–Delbrück, Spiritusfabrikation, 8th ed., p. 107 ff.

… and, depending on the degree of importance of the initial factory operations, the work of the plant is rendered unproductive and useless.

Various books contain relatively few data on pentosans, for example, on the cooking of the fiber- and cellulose-containing material that has long been used in fermentation production. For this purpose, the cooking of the starch-containing material being processed was employed under one or another pressure, during which the non-starch constituents of this material pass into solution.

The completeness of dissolution is promoted to a considerable degree by the subsequent operations associated with the enzymatic action of the malt. As a result, the cellulose and other substances that have not gone into solution are separated and leave the sphere of factory operation, passing into the draff.

The practice of individual fermentation industries has worked out its own definite norms with respect to the temperature, duration, and other conditions of cooking. These conditions, adapted to starch-rich material such as grain, potatoes, etc., took into account chiefly the dissolution of starch and, in part, the possibility of removing cellulose; as for pentosans, they were, of course, given no consideration at all, if only because those who developed these methods either knew nothing about pentosans or did not assume their presence in the material being processed. When, however, they became somewhat acquainted with these compounds and with their significance, there was again no reason, because of the presence of pentosans in the material being cooked, to change the already established method of cooking. The content of these substances was too small, and moreover they had no noticeable adverse influence on the principal processes of production.

A different situation arises with draff. The greatest value of the latter lies in the proteins, while the chief mass of its useless ballast consists of pentosans, which are present in amounts exceeding 20%. Accordingly, the cooking of draff must be conducted with the aim of dissolving the maximum quantity of proteins while dissolving the minimum of pentosans.

Thus, pentosans and proteins are the principal factors, and by properly taking them into account it is possible to determine the most expedient conditions for cooking draff. In view of this, it is necessary to examine each of these factors in detail.

With regard to pentosans, very little is known in this respect. There are only general indications that pentosans contained in the mass of intercellular substance of potato tubers dissolve well under the action of high-pressure steam¹, whereas at normal pressure and in boiling water their dissolution proceeds only partly. What influence the duration of cooking has, how solubility changes as a function of the temperature at which cooking is carried out, and much else still remains very little touched upon. Yet all this is of very substantial importance, especially when one is interested not in the very possibility of dissolution, but in the quantitative side of the results of this phenomenon, in the sense of liberation from pentosans.

To elucidate this aspect of the cooking process, laboratory experiments were carried out. Proceeding from the abundance of pentosans in rye and the definiteness of the composition of the latter, a series of experiments was set up with the aim of tracing the conditions of transition—

Into a Solution of Rye Pentosans Depending on the Cooking Temperature, the Duration of Cooking, and the Amount of Water Taken in the Materials Being Cooked

It should be noted that in the present case the aim of the work was not to elucidate the chemistry of the possible transformations of pentosans in plant material. The task consisted only in establishing what portion of the pentosans present passes into solution when rye is cooked. In accordance with this, in what follows, by the word “pentosans” is meant the sum of all substances that yield furfural under definite conditions of distillation with hydrochloric acid.

For these experiments, rye from Tomsk Province, Kuznetsk District, harvest of 1908, of the following composition was taken:

The cooking of finely ground rye was carried out in an autoclave, with 5.00 grams of flour taken for each separate sample. The duration of cooking was measured by the interval of time between the moment the pressure rose to the height corresponding to the required temperature and the moment at which heating of the autoclave was stopped.

Each cooked sample was quantitatively transferred into a 200 cubic centimeter volumetric flask.

After cooling and adding water up to the mark, the contents of the volumetric flasks, after thorough mixing, were filtered through a double paper dry filter to separate the filtrate. In 100 cubic centimeters of the filtrate, the pentosans were determined quantitatively by Tollens’ and Krüger’s method,¹ used by König as well and in all subsequent cases when it was necessary to determine the pentosan content.

According to this method, as is known, the substance under test is distilled with hydrochloric acid, and in the distillate the furfural is determined by precipitating it with phloroglucin. From the weight of the phloroglucide obtained, the required amount of pentosans is found by the corresponding calculation.

In some experiments the pentosans were determined not only in solution, but also in the insoluble residue of the cooked mass, which made it possible to draw up a pentosan balance for the whole sample. In the experiments, the cooking temperature, its duration, and the amount of water taken into the mass being cooked were varied successively. Table VI gives the figures indicating the amount of dissolved pentosans, expressed as percentages of their initial content in the rye being cooked; in this group of experiments, for one part by weight (5 g) of rye flour, 17 parts by weight (50 cubic centimeters) of water at \(20^\circ\mathrm{C}\) were taken, i.e., Reinke’s conditions for determining starch by the cooking method were adopted.

¹ König, Die Untersuch. d. landwirtschaftl. u. gewerb. wicht. Stoffe, 1906, p. 243.

TABLE VI

The data of Table VI indicate that both an increase in temperature and an increase in the duration of cooking promote the formation of pentosans, but temperature is again a considerably stronger factor than time.

After the maximum corresponding to a certain temperature and duration of cooking is reached, a gradual decrease is observed in the quantity of pentosans present in solution, which apparently indicates their destruction.

It is possible that the latter occurs earlier than the moments indicated by Table VI; the loss of the cooked mass increases only because it is replenished by newly formed quantities of pentosans from the residue of the grain.

In order to elucidate the question of the destruction of pentosans, it is necessary to calculate their presence after the experiment in the solution and in the solid residue of the cooked mass. If their sum is less than the total content of these compounds in the original material, then this definitely indicates the destruction of pentosans during cooking, and the degree of destruction will be determined by the magnitude of the loss.

The results of the corresponding experiments are given in the table below.

TABLE VII

Table VII shows that the decomposition of pentosans takes place even at low pressure with prolonged cooking, just as, with an increase in the duration of cooking, the decomposition increases. The duration of steaming with little swelling of the mash has little effect on the degree of decomposition of the pentosans.

Comparing the quantities of pentosans and their subsequent dissolution when the cooking temperature is increased, one may think that the resultant value is the result of two opposite influences. One of them is connected with the destruction of pentosans, the other with their formation, or rather with the formation of furfural and its derivatives, recalculated in this case as pentosans. This formation, moreover, generally proceeds considerably more weakly than the destruction and shows itself clearly and distinctly only at low pressure, at three atmospheres, when the destructive processes are still manifested relatively weakly. Owing to this, under such conditions, instead of the usual decrease in pentosans toward the end of the experiment, an increase of 1.2% is observed. The same phenomenon is seen, although not to the same extent, in other cases of those experiments in which, with an increase in pressure, the pentosans do not increase but decrease.

The possibility of an increase in the amount of pentosans after cooking, when the usual method of determination and calculation of these chemical compounds is used, is confirmed by the work of van Ekenstein and Blanksmа¹), who found, with [[unclear: treatment/boiling]] and with the formation of furfural, [[unclear: comparable phenomenon]]; when working under a pressure of three atmospheres on [[unclear: malt/mash]], they note a very small amount of pentosans dissolved from the [[unclear: mash]].

The data of Tables VI and VII illuminate the conditions of dissolution of the pentosans of rye from the standpoint of the temperature and duration of cooking. The influence of the amount of water is indicated by the figures in Table VIII. Here are compared the results of experiments in which one part by weight of rye flour was taken with 1, 2, 4, 8, or finally 17 parts by weight of water; in all other respects the conditions of the experiments were identical with those considered earlier. The figures of Table VIII show the amounts of pentosans dissolved during cooking, expressed as percentages by weight of the total content of these compounds in the rye flour.

TABLE XIII

¹) Ber. Deutsch. Chem. Ges. 1910, p. 2855.

From Experiment VII it is clear that even the smallest amount of water taken for cooking promotes a good transition of pentosans into solution; the effect of increasing amounts of water, however, grows with a rise in temperature, or, what is the same thing, in cooking pressure.

The results of experiments with the cooking of rye indicate that the least dissolution of pentosans occurs when cooking is carried out at a lower temperature and with a minimum quantity of water. Under these conditions the influence of the duration of cooking on the increase in the quantity of dissolved pentosans proves to be very small. The above gives grounds for assuming that the liberation of wheat bran from pentosans requires similar cooking conditions; but for the final resolution of this question experiments must be carried out directly with wheat bran, and, moreover, in connection with the question of the advisability of using bran in alcohol-fermentation conditions, for example in yeast production. In view of the limited scope of the present brief communication, discussion of this question will take place in one of the author’s subsequent communications.

A. [[unclear: author’s surname]]

[[unclear: title of the following article]]

[[unclear: several lines of heavily degraded text from the beginning of the next article are visible but not legible enough to translate reliably.]]

1. Maercker–Delbrück, Spiritusfabrikation, 8th ed., p. 315. ↩↩

2. Rupp, Die Untersuchung Nahrungsmittel, Genussmittel und Gegenständen, p. 242. ↩↩

3. Russian Miller, 1915, p. 268. ↩

4. Proceedings of the Moscow Agricultural Institute, 1912, XVIII appendix. Petrov, “Bran as a Waste Product of Flour-Milling Production, Its Nutritive Value and Utilization,” p. 45. ↩