Part 49

Ten cubic centimeters of the milk are diluted with from three to five times that quantity of water and warmed to a temperature of about 40°. One cubic centimeter of a concentrated solution of potash alum is added, the mixture well stirred and the coagula which are formed allowed to subside. If the coagulation of the casein does not take place promptly, a small addition of the alum solution is made, usually not exceeding half a cubic centimeter, until the precipitation is complete. The temperature during the process should be kept as nearly as possible 40°. After a few minutes, the mixture is poured upon a filter and the filtrate, if not perfectly clear, is poured back until it is secured free of turbidity. In difficult cases the filtration may be promoted by the addition of some common salt or calcium phosphate, the latter acting mechanically in holding back the fine particles of casein. The precipitate is washed with water at a temperature of 40°, and afterwards with alcohol, not allowing the alcohol wash water to flow into the filtrate. When the water has been chiefly removed from the precipitate by washing with alcohol, the fat of the precipitated casein is removed with ether and the residue used for the determination of nitrogen in the usual way. The albumin is removed from the filtrate by a tannin solution in the manner already described (=480=). If it be desired to separate the albumin and globulin, the methods described in paragraph =399= may be used.

=524. Mercurial Method.=—A volumetric method for determining the total proteid matter in milk has lately been proposed by Deniges.[533] It is based upon the observation that in the precipitation of proteid matter by mercury salts, a definite quantity of mercury in proportion to the amount of proteid, is carried down therewith. The precipitation is made with a mercurial salt of known strength and the excess of the mercurial salt in the filtrate is determined by titration. For the details of the manipulation, the paper cited above may be consulted.

=525. Water and Ash.=—From two to five grams of the koumiss are dried to constant weight in a flat platinum dish over ignited sand, asbestos or pumice stone, and the dried residue incinerated.

=526. Composition of Koumiss.=—The composition of koumiss varies with the character of the milk used and the extent of the fermentation. Some of the data obtained by analysts are given below:[534]

COMPOSITION OF KOUMISS.

Carbon Kind Water, Sugar, Alcohol, Fat, Proteid, dioxid, Acidity, of Per Per Per Per Per Per Per milk. cent. cent. cent cent. cent. cent. cent. Cow 89.32 4.38 0.76 2.08 2.56 0.83 0.47 Probably 3.95 1.38 0.88 2.89 0.82 cow skim’d Mare 91.87 0.79 2.89 1.19 1.91 1.04

From the above it is seen that koumiss is made either from whole or skim milk, and that the percentage of alcohol may vary within large limits, its proportion being inverse to that of the milk sugar.

Koumiss is a beverage which is very palatable, easily digested and one which is not appreciated in this country in proportion to its merits, especially for the use of invalids.

AUTHORITIES CITED IN PART SIXTH.

[400] Wiley; Proceedings of the Society for the Promotion of Agricultural Science, 1889, p. 84. (Omit “food” before idiosyncrasy.)

[401] Pharmaceutical Journal and Transactions, Series 3, Vol. 18, p. 479.

[402] The Analyst, 1892, p. 85.

[403] Henkel; Wiener Landwirtschaftliche Zeitung, 1888, S. 401: Bulletin No. 24, Division of Chemistry, U. S. Department of Agriculture, p. 155.

[404] Die Landwirtschaftlichen Versuchs-Stationen, Band 35, S. 351: Bulletin No. 24, Division of Chemistry, U. S. Department of Agriculture, p. 151.

[405] Baumeister; Milch und Molkerei-Producte, S. 16.

[406] Bulletins Nos. 9 and 25 of the Office of Experiment Stations, U. S. Department of Agriculture: Farmers’ Bulletins Nos. 9 and 29, U. S. Department of Agriculture.

[407] Annales de Chimie et de Physique, 3e Série, Tome 64, p. 61.

[408] Bulletin de la Société Chimique de Paris, 3ᵉ Série, Tome 15-16, p. 248.

[409] Vid. op. cit. supra, p. 453.

[410] Central-Blatt für medicinische Wissenschaft, Band 34, S. 145.

[411] Conn; Farmers’ Bulletins 9 and 25, Office of Experiment Stations, U. S. Department of Agriculture: Farmers’ Bulletins 9 and 29, Department of Agriculture: Les Microbes et leur Rôle dans la Laiterie Freudenreich: Langlois, Le Lait, pp. 95 et seq.

[412] The Analyst, Vol. 20, p. 157.

[413] Vid. op. cit. supra, p. 152.

[414] Forschungs-Berichte über Lebensmittel etc., Band 2, S. 368.

[415] Vid. op. cit. supra, Band 1, S. 422.

[416] Vid. op. cit. supra, S. 372.

[417] Hopkins and Powers; Bulletin No. 47, Division of Chemistry, U. S. Department of Agriculture, p. 127.

[418] Bulletin No. 38, Division of Chemistry, U. S. Department of Agriculture, p. 118.

[419] Becke; Die Milchprüfungs-Methoden, S. 45: Rouvier; Le Lait, p. 45.

[420] The Analyst, 1890, Vol. 16, p. 170.

[421] Rouvier; Le Lait, p. 35.

[422] Central-Blatt für Nahrungs und Genussmittel Chemie, Band 13, S. 277.

[423] Bulletin No. 46, Division of Chemistry, U. S. Department of Agriculture, p. 36.

[424] Journal für Landwirtschaft, 1882, S. 293; 1885, S. 251.

[425] Vid. op. cit. supra, 1879, S. 249.

[426] Forschungen auf dem Gebiete der Viehhaltung, 1879, S. 265.

[427] The Analyst, Vol. 7, p. 129.

[428] Vid. op. cit. supra, Vol. 13, p. 26.

[429] Bulletin No. 47, Division of Chemistry, U. S. Department of Agriculture, p. 123.

[430] This work, Vol. 1, page 411.

[431] Bulletin No. 16, Division of Chemistry, U. S. Department of Agriculture, p. 36.

[432] Sixth Annual Report Wisconsin Agricultural Experiment Station, p. 64.

[433] Fourth Annual Report New York (Geneva) Agricultural Experiment Station, p. 298.

[434] Woll; Seventh Annual Report Wisconsin Agricultural Experiment Station, p. 238.

[435] The Analyst, 1885, p. 46: Bulletin No. 13, Part 1, Division of Chemistry, U. S. Department of Agriculture, p. 86.

[436] Haidlen; Die Milchprüfungs-Methoden, S. 12.

[437] Dingler’s polytechnisches Journal, Band 232, S. 461.

[438] Macfarlane; The Analyst, Vol. 18, p. 73.

[439] Duclaux; Le Lait, p. 176.

[440] Abraham; The Analyst, Vol. 9, p. 22.

[441] Gantter; Zeitschrift für analytische Chemie, Band 26, S. 677.

[442] Morse, Piggot and Burton; American Chemical Journal, Vol. 9, pp. 108 and 222.

[443] Chemiker-Zeitung Repertorium, 1889, S. 228.

[444] Journal de Pharmacie et de Chimie, 1890, p. 460.

[445] Richmond; The Analyst, Vol. 17, p. 48: Bulletins 28, 31, 35, 38, 43, and 46, Division of Chemistry, U. S. Department of Agriculture.

[446] Bulletin No. 28, Division of Chemistry, U. S. Department of Agriculture, p. 31.

[447] Zeitschrift für analytische Chemie, Band 27, S. 464.

[448] Chemical News, Nov. 1889.

[449] The Analyst, Vol. 16, p. 67.

[450] Vid. op. cit. supra, Vol. 18, p. 53.

[451] Vid. op. cit. supra, Vol. 17, p. 81.

[452] Chemiker-Zeitung, Band 15, S. 1833.

[453] Journal of Analytical Chemistry, 1888, Vol. 2, p. 371: Fifth Annual Report Wisconsin Agricultural Experiment Station.

[454] Molkerei Zeitung, 1892, No. 1; Chemisches Central-Blatt, 1892, Band 2, S. 429.

[455] Chemiker-Zeitung, Band 18, S. 1816; Band 19, S. 348.

[456] Zeitschrift für analytische Chemie, Band 32, S. 168.

[457] Zeitschrift des Landwirtschaftlichen Vereins in Bayern, 1880; Zeitschrift für analytische Chemie, Band 20, S. 452.

[458] Bulletin No. 13, Division of Chemistry, U. S. Department of Agriculture, p. 92.

[459] Instruction sur l’Emploi du Lactobutyrometer, Paris, 1856 et 1878: Becke; Die Milchprüfungs-Methoden, S. 66.

[460] Bulletin No. 8, Iowa Agricultural Experiment Station, p. 295.

[461] Dingler’s polytechnisches Journal, Band 261, S. 219.

[462] Milch Zeitung, Band 21, S. 496.

[463] Op. cit. supra, Band 22, S. 85.

[464] Bulletin No. 24, Wisconsin Agricultural Experiment Station.

[465] Bulletin No. 31, Wisconsin Agricultural Experiment Station.

[466] The Analyst, Vol. 17, p. 83.

[467] Bulletin No. 21, Vermont Agricultural Experiment Station.

[468] Vid. op. cit. 67, Vol. 17, p. 144; Vol. 18, p. 130; Vol. 19, p. 62.

[469] Chemiker-Zeitung, Band 16, S. 1839.

[470] Vid. op. cit. supra, Band 19, S. 348; Band 18, S. 1816.

[471] Vid. op. cit. supra, Band 19, S. 348.

[472] Comptes rendus, Tome 107, p. 772; Hoppe-Seyler’s Handbuch der Physiologisch- und Pathologisch-Chemischen Analyse, S. 479.

[473] Proceedings of the Society for the Promotion of Agricultural Science, 1888, p. 13.

[474] Journal of Physiology, Vol. 11, p. 459.

[475] Die Land wirtschaftlichen Versuchs-Stationen, Band 31, S. 131.

[476] Sixth Annual Report of the Wisconsin Agricultural Experiment Station, p. 64.

[477] Bulletin No. 46, Division of Chemistry, U. S. Department of Agriculture, p. 36.

[478] Zeitschrift für Biologie, Band 33, S. 43.

[479] Journal für praktische Chemie, {2}, Band 15, S. 329.

[480] Vid. op. cit. 79, Band 33, {Neue Folge, 15}, S. 55.

[481] Stenberg; Zeitschrift für physiologische Chemie, Band 13, S. 138.

[482] Vid. op. cit. supra, S. 137.

[483] Vid. op. cit. supra, S. 160.

[484] Journal of the American Chemical Society, Vol. 15, p. 644.

[485] Handbuch der Physiologisch- und Pathologisch-Chemischen Analyse, S. 285. (Read, Makris instead of Makeris.)

[486] Zeitschrift für Biologie, Band 23, S. 64.

[487] Bulletin de la Société Chimique de Paris, 3ᵉ Série, Tome 11, p. 152.

[488] Vid. op. cit. 86, S. 487.

[489] Zeitschrift für Nahrungsmittel-Untersuchung, Band 10, S. 104.

[490] Zeitschrift für physiologische Chemie, Band 9, S. 445.

[491] American Chemical Journal, Vol. 6, p. 289.

[492] Journal of the American Chemical Society, Vol. 18, p. 428.

[493] Journal de Pharmacie et de Chimie, 6e Série, Tome 4, p. 65.

[494] Contribution à l’Étude des Lactoses, Thèse pour le diplôme supérieure de Pharmacie, Paris, 1892. (Read Thibault instead of Thibonet.)

[495] Journal für praktische Chemie, Neue Folge, Band 15, S. 348.

[496] Zeitschrift für angewandte Chemie, 1896, S. 72.

[497] Chemisches Central-Blatt, 1892, Band 2, S. 1028.

[498] Vid. op. cit. supra, Band 21, S. 753.

[499] Vid. op. cit. 90, S. 86.

[500] Bulletin No. 13, Division of Chemistry, U. S. Department of Agriculture, pp. 29 et seq.

[501] Vid. op. cit. supra, pp. 73-75: Bulletin No. 46, Division of Chemistry, U. S. Department of Agriculture, p. 26.

[502] Benedikt and Lewkowitsch; Oils, Fats and Waxes, p. 490.

[503] Forsuchungs-Berichte über Lebensmittel, 1895, Band 2, S. 424; Chemiker-Zeitung Repertorium, 1896, Band 20, S. 15.

[504] Revue Internationale des Falsifications, Mai, 1893, p. 157.

[505] Chemiker-Zeitung, 1893, Band 17, S. 468.

[506] Zeitschrift für angewandte Chemie, 1896, S. 177.

[507] Vid. op. cit. 90, Aug. 26, 1894, S. 219; Le Stazioni Sperimentali Agrarie Italiane, 1893, pp. 25-77.

[508] Farmers’ Bulletin No. 12, U. S. Department of Agriculture.

[509] Bulletin de l’Association Belge des Chimistes, Tome 9, p. 279.

[510] Vid. op. cit. 101, p. 26.

[511] Vid. op. cit. supra, p. 27: Chemical News, Vol. 55, p. 49.

[512] Vid. op. cit. 111, p. 28.

[513] Vid. op. et. loc. cit. supra.

[514] Russell; Dairy Bacteriology.

[515] Woll; Dairy Calendar, p. 223.

[516] Van Slyke; Bulletin 82, New Series, New York Agricultural Experiment Station, p. 654.

[517] Babcock; Twelfth Annual Report Wisconsin Agricultural Experiment Station, p. 133.

[518] Woll; Dairy Calendar, 1895, p. 220.

[519] Bulletin No. 46, Division of Chemistry, U. S. Department of Agriculture, p. 37.

[520] Landwirtschaftliches Jahrbuch, 1872, part 1.

[521] Molkerei Zeitung, 1893, Nos. 20, 22.

[522] This work, Vol. 2, p. 204.

[523] Vid. op. cit. 120, p. 24.

[524] Milch Zeitung, 1895, Band 24, S. 729: Chemiker-Zeitung Repertorium, Band 19, S. 372.

[525] Chemiker-Zeitung, 1895, S. 554.

[526] Zeitschrift für analytische Chemie, Band 35, S. 497.

[527] Vid. op. cit. supra, S. 499.

[528] Vid. op. cit. supra, S. 502.

[529] Bulletin No. 13, Division of Chemistry, U. S. Department of Agriculture, pp. 118, 293.

[530] This work, Vol. 2, p. 204.

[531] Pflüger’s Archiv, Band 56, S. 558.

[532] Hoppe-Seyler’s Zeitschrift für physiologische Chemie, Band 22, S. 213.

[533] Bulletin de la Société Chimique de Paris, Tomes 15-16, p. 1126.

[534] American Chemical Journal, Vol. 8, p. 200: Bulletin 13, Division of Chemistry, U. S. Department of Agriculture, p. 120.

PART SEVENTH.

MISCELLANEOUS AGRICULTURAL PRODUCTS.

=527. Classification.=—In the preceding parts have been set forth the fundamental principles underlying the conduct of agricultural analysis and a résumé of the best practice of the art. The analyst, as a rule, will seldom be required to undertake investigations which are unnoticed in the preceding pages. Cases will arise, however, in which problems are presented which can not be solved by the rules already elucidated. In respect of the great classes of agricultural bodies, it will be observed that dairy products have already received special mention. In respect of foods and fodders in general, it is evident that they are chiefly composed of moisture, ash, carbohydrates, oils and proteid matters. The methods of identifying, separating and estimating these constituents have been fully set forth. It is not necessary, therefore, to study in this part the analytical processes which are applicable to cereals, cattle foods and other food products, further than is necessary to present in the most important cases a working résumé of principles and methods. There remain, however, certain products of importance which require some special modifications of treatment, and it is to these that the present part will be chiefly devoted. Among these are found tobacco, tea and coffee, fruits, fermented and distilled drinks and certain animal products. It is evident that an enumeration of all agricultural products, with a description of their methods of examination, would be impracticable in the available space and undesirable by reason of the repetition which would be required. In each case the analyst, in possession of the methods described, will be able to adapt the means at his disposal to the desired purpose to better advantage than any rigid directions could possibly secure.

In respect of the analytical methods of determining the nutritive value of foods, they may be divided into chemical and physiological. The chemical methods embrace the thermal and artificial digestion investigations, and the physiological include those which are carried out with the help of the animal organisms. In the latter case the digestive process is checked by the analysis of the foods before ingestion and of the excreta of all kinds during and after digestion.

It is evident that a detailed description of this method should be looked for in works devoted to physiological chemistry.

CEREALS AND CEREAL FOODS.

=528. General Analysis.=—The cereals are prepared for analysis by grinding until the fragments pass a sieve having circular perforations half a millimeter in diameter. The moisture, ash, ether extract, proteids and carbohydrates are determined by some one of the processes already described in detail. In this country the methods of the Association of Official Agricultural Chemists are generally followed.[535] For convenience these methods are summarized below.

_Moisture._—Dry from two to three grams of the fine-ground sample for five hours, at the temperature of boiling water, in a current of dry hydrogen. If the substance be held in a glass vessel, the latter should not be in contact with the boiling water.

_Ash._—Char from two to three grams of the sample and burn to whiteness at the lowest possible red heat. If a white ash can not be obtained in this manner, exhaust the charred mass with water, collect the insoluble residue on a filter, burn it, add this ash to the residue from the evaporation of the aqueous extract and heat the whole to low redness until the ash is white.

_Ether Extract._—Pure ether is prepared by washing the commercial article four or five times with water to free it of the chief part of the alcohol it contains. The residual water is mostly removed by treating the liquid with caustic soda or potash. Any residual alcohol or water is finally removed by the action of metallic sodium. The ether thus prepared is stoppered, after the evolution of hydrogen has ceased, and is kept over metallic sodium. Immediately before use it should be distilled out of contact with moist air.

The residue from the determination of moisture, as described above, is extracted in an appropriate apparatus (=39=) with the pure ether for sixteen hours. The extract is dried to constant weight. The weight may be checked by drying and weighing the extraction tube and its contents before and after the operation.

_Crude Proteids._—Proceed as in the method of determining nitrogen in the absence of nitrates and multiply the weight of nitrogen obtained by 6.25. This factor is a general one, but should not be rigidly applied. In each instance, according to the nature of the cereal, the appropriate factor, pointed out in paragraph =407= should be used, and the factor 6.25 be applied only in those cases where a special factor is not given. The factors for the common cereals are wheat 5.70, rye 5.62, oats 6.06, maize 6.22, barley 5.82 and flaxseed 5.62.

For separating the proteid matters consult paragraphs =392-410=. In the case of wheat the methods of Teller may be consulted.[536]

_Amid Nitrogen._—The albuminoid nitrogen is determined as directed in paragraph =203= of volume II. The difference between this number and that representing the total nitrogen gives the nitrogen as amids.

_Fiber and Carbohydrates._—The methods of analysis are described in detail in Part Third.

=529. Bread.=—In general, the same processes are followed in bread analysis as are used with cereals and flours. In addition to the regular analytical processes, breads are to be examined for adulterants, bleaching and coloring matters, and for the purpose of determining the changes which have taken place in their nutrient constituents in the processes of fermentation and cooking.

_Temperature of Baking._—The interior of a loaf during the process of baking does not attain the high temperature commonly supposed. This temperature is rarely found to be more than one degree above the boiling point of water.[537] In biscuits and other thin cakes, which become practically dry and which by reason of their thinness are the more readily penetrated by heat, the temperature may go as high as 110°.

_Soluble Extract._—The quantity of matters both in flour and bread, soluble in cold water, is determined by extraction in the usual way and drying the extract. Soluble albuminoids, sugars and mineral salts are extracted by this process. When possible, the operation should be conducted both on the bread and the flour from which it is made.

_Color._—In baker’s parlance is found an apparent contradiction of terms, since it speaks of bread with “no color” when the loaf is dark brown, while a white loaf is said to have a high color. An ideal color for the interior of a loaf is a light cream tint, which is more desirable than a pure white.[538] The texture, odor and flavor of the loaf are also to be considered, but these are properties of more importance to the technical expert than to the analyst.

_Quantity of Water._—It is not possible to set a rule of limitation in respect of the quantity of water a bread should hold. For full loaves, perhaps forty per cent is not too high a maximum, while some authors put it as low as thirty-four per cent. Some flours are capable of holding more water than others, and the loaf should have just enough water to impart to the slice of bread the requisite degree of softness and the proper texture. Most breads will have a content of water ranging from thirty to forty per cent. In biscuits and other thin cakes the moisture is much less in quantity.

_Acidity._—The acidity of both bread and flour is determined by shaking ten grams of the sample with 200 cubic centimeters of distilled water for fifteen minutes, pouring the mass on a filter and titrating an aliquot part of the filtrate with tenth-normal alkali. The acidity is reckoned as lactic acid in the case of breads raised by fermentation.

_Nature of Nitrogenous Compounds._—The methods of investigation are described in paragraphs =392-410=.

=530. Determination of Alum in Bread.=—The presence of alum in bread may be detected by means of logwood. Five grams of fresh logwood chips are digested with 100 cubic centimeters of amyl alcohol. One cubic centimeter of this decoction and the same quantity of a saturated solution of ammonium carbonate are mixed with ten grams of flour and an equal quantity of water. With pure flour, a slight pink tint is produced. In the presence of alum the color changes to a lavender or blue, which is persistent on heating.

The test may be varied by diluting five cubic centimeters of the reagents mentioned with ninety cubic centimeters of water and pouring the mixture over ten grams of the crumbled bread. After standing for five minutes, any residual liquid is poured off and the residue, washed once with a little water, is dried in a steam bath, when the blue color is developed if alum be present.[539]

=531. Chemical Changes Produced by Baking.=—Changes of a chemical nature, produced in bread by baking, are found chiefly in modifications of the starch and proteids. The starch is partly converted into dextrin and the albumins are coagulated. The changes in digestion coefficient are determined by the methods which follow. The fermentations which precede the baking are due to the usual decompositions of the carbohydrates under the influence of yeast germs.

FODDERS, GRASSES AND ENSILAGE.

=532. General Principles.=—The analyst, in examining the fibrous foods of cattle, is expected to determine moisture, ash, fiber and other carbohydrates, ether extract and albuminoid and amid nitrogen. If a more exhaustive study be required, the sugar and starch are separated from the other non-nitrogenous matters, the carbohydrate bodies yielding furfuraldehyd separately determined and the ash subjected to a quantitive analysis. The processes are conducted in harmony with the principles and methods of procedure fully set forth in the preceding pages.

Green fodders and grasses are easily dried and sampled by comminution in the shredder described on page 9, and roots by that shown on page 10. The moisture is determined by drying a small sample of the shredded mass, while the rest of it is dried, first at about 60° and finally at 100°, or a little above, ground to a fine powder and subjected to analysis by methods already described. The food values as obtained by analysis should be compared, when possible, with those secured by natural and artificial digestion.

Ensilage is shredded and analyzed in precisely the same way, but in drying, the content of volatile acids formed during fermentation must be considered. In other words, the loss on drying ensilage at 100°, or slightly above, is due not only to the escape of water but also to the volatilization of the acetic acid, which is one of the final products of fermentation which the mass undergoes in the silo.