FOOD AND DRTTGS ANALYSIS 377 ABSTRACTS Progressive OF PAPERS PUBLISHED IN OTHER JOURNALS. FOOD AND DRUGS ANALYSIS. Oxidation of Cold-Storage Butter. D. C. Dyer. ( J . Agric. Research, 1916, 6, 927-951.)-Since approximately 10 per cent. of the volume of butter is air, it was considered that an examination of the air in packages of butter and of butter-fat might furnish data as to whether the undesirable chemical changes (development of unpleasant flavour) occurring in stored butter are caused by a progressive oxidation of the fat itself or in some one or other of the non-fatty in- gredients.The air contained in various cold-storage butters was, therefore, sepa- rated and analysed. The composition of the air confined within a package of pas- teurised sweet-cream butter known to contain bacteria and made from cream having an acidity of 0.11 per cent. (calculated as lactic acid) showed little or no variation from its original composition after storing for six months at 0" F.; when stored under like conditions, the butter-milk from the same cream did not affect the composition of the air in the vessel containing the milk. When the butter was kept at 32" F., the composition of the enclosed air underwent a decided change, and this change wars increased when the butter remzincd f ~ r z, short time at ordinary teiiiperatiire, the oxygen content decreasing and the carbon dioxide content increasing. The butter itself possessed no unpleasant flavour after six months' storage a t 0" F.The composition of the air enclosed in a butter made from sweet cream and churned immediately after the addition of 15 per cent.of a commercial starter showed but little change after storage for six months at 0" F., and the butter kept well; the air from butter made from cream to which lactic acid had been added underwent con- siderable change during storage, the oxygen and carbon dioxide decreasing in quan- tity. The flavour of this butter became unpleasant after three months.A small quantity of butter-milk from butter prepared with the addition of lactic acid was exposed to the action of a very large and confined surface of air at 0" F.; after one month the whole of the oxygen had disappeared. The carbon dioxide content, originally 2.37 psr cent., had increased to 34 per cent.; it then decreased.Further experiments with pure butter-fat and the same mixed with varying quantities of protein, lactose, etc., showed that after storage a t 0' F. the quantity of carbon dioxide in the enclosed air was directly proportional to the amount of non-fatty ingredient present, and that the oxygen content showed a relative decrease. The pure butter-fat was not oxidised t o any appreciable extent, but when the fat was spread on pumice and exposed to the action of a large volume of air at 32" F., a slight oxidation was noticed.The results of the investigation may be summed up as follows : The unpleasant flavours which develop in butter during cold storage are not produced by the oxidation of the fat itself, but by' some chemical change which takes place in one or more of the non-fatty ingredients.The exteqt of this chemical change is proportional to the quantity of acid present in the cream from378 ABSTRACTS OF CHEMICAL PAPERS which the butter was prepared. The quantity of carbon dioxide present in cold- storage butter probably depends on the amount of butter-milk in the butter, and may increase to a maximum, followed by a progressive decrease.w. P. s. Estimation of Citric Acid in Milk. R. Kunz. ( A r c h . Chem. Microsk., 1915, 8, 120-133; through Int. Rev. Sci. and Prac. of Agriculture, 1916, 7, 739.)- Stahre's method for the estimation of citric acid in wine (ANALYST, 1915, 40, 464) may be used for the estimation of this acid in milk. Fifty C.C. of the milk are treated with 20 C.C. of 50 per cent.sulphuric acid, 2 C.C. of 40 per cent. potassium bromide solution, and 20 C.C. of phosphotungstic acid solution; the mixture is diluted with water to 200 c.c., shaken and filtered. To 150 C.C. of the filtrate are added 25 C.C. of freshly prepared saturated hydrobromic acid solution; the mixture is heated at 50" C. for five minutes, and then treated with 10 C.C. of 50 per cent. potassium permanganate solution, the latter solution being added gradually while the mixture is stirred.The remaining part of the process is then carried out as described in the case of wine. Fresh milk contains aboht 0.19 grm. of citric acid per 100 c.c.; the quantity is slightly larger in the first milk drawn than in that obtained at the end of the milking. In ordinary milk the citric acid content diminishes progres- sively as the milk sours; curdled milk is free from citric acid, but " Yoghurt " contains about 0.16 grm.per 100 c.c., and this quantity does not decrease when the preparation is kept. w. P. s. Estimation of the Fat Content of Dried WholeMilk. K.Mohs. (Zeitsch. ges. Getreidew., 1916, 8,37-41; through J. Xoc. Chem. Ind., 1916,35, 1127.)-Samples of dried whole milk which have been kept for some time show an apparent reduction of fat content as determined by extraction with ether.This appears to be due to adsorption of the fat by the coagulated protein of the milk. The adsorbed fat is not removed by simple extraction with ether. The following procedure, based on a method described by Neumann (Zeitsch. ges. Getreidew. , 1912, 4, 8) is recommended for the determination of the fat: 1.5 grms.of the finely divided milk powder are heated with 50 C.C. of water and 6 C.C. of hydrochloric acid of sp. gr. 1.125 for one and a half hours in a boiling water bath. After cooling, the solution is made neutral to methyl orange by addition of concentrated sodium hydroxide solution, then acidified with dilute hydrochloric acid, and filtered.The filter with its contents is dried for two hours at 105" C., and then extracted with ether for six hours in a Soxhlet apparatus. Valuation of Nitrogenous Compounds in Feeding-Stuff s. N. Passerini. (Annali Chim. Applic., 1916, 6,162-164.)-The method is based on the fact that the proteins of ordinary feeding-stuffs are rapidly hydrolysed by 25 per cent.sulphuric acid into soluble dialysable substances (peptones, etc.). After three hours' boiling the amount of ammoniacal nitrogen in the hydrolysed liquid, derived largely from the amines and amino-acids, remains constant. For example, 5 grms. of the sample hydrolysed with the acid yielded the following amounts of ammoniacal nitrogen : After one hour, 0.347 grm.; after three hours, 0.397 grm.; and after four hours,FOOD AND DRUGS ANALYSIS 379 0 397 grm.For the analysis 1 grm. of the finely divided material is taken for the esti- mation of the total nitrogen (a). The amines are then separated in 2 grms. of the sample by Kellner’s method of precipitating the proteins with copper oxide, and the protein nitrogen ( b ) is estimated in the copper precipitate.Kellner’s method is repeated on 5 grms. of the sample, and the copper precipitate is boiled for four hours on a sand-bath beneath a reflux condenser with 100 C.C. of 25 per cent. sul- phuric acid. The liquid is treated with hydrogen sulphide to eliminate the copper, made up to 500 C.C. and filtered. The excess of hydrogen sulphide is expelled by boiling from an aliquot part (200 c.c.) of the filtrate, and the ammoniacal nitrogen ( c ) is distilled.In the residue left on the filter the non-hydrolysable nitrogen (d) is estimated, and is to be regarded as nucleiizic nitrogen. The amounts thus obtained may be assigned as follows: (1) Nitrogen of free amines (asparagin, etc.) = a - b ; (2) nitrogen of amino-acids =b - (c+ d ) . The following results obtained with a vetch flour illustrate the method.Total nitrogen, 3.66; nucleinic nitrogen, 0.14; nitrogen of amino-acids, 1.79 ; ammoniacal nitrogen in hydrolysed liquid, 0.42 ; and preformed amino-nitrogen, 1.30 per cent. C. A. M. Presence of Copper in Tomatoes and Tomato Preserves. G. Liberi, A. Cusmano, T. Marsiglia, and C. Zay. (Ann. Stax. chim.-agrur. sperim. Roma, 1916, 8, 163-303; through Int.Rev. Sci. and Prac. of Agriculture, 1916, 7, 662-664.) -Numerous samples of tomatoes grown at the experimental farm belonging to the Stajtion of Agricultural Chemistry, Rome, and other samples obtained from various districts in Italy, were all found to contain copper in quantities varying from 0.14 mgrm. to 2.1 mgrms. per kilo of juice and pulp, or from 388 mp;rms.to 19-45 mgrms. per kilo of dry substance. All the soils on which the tomatoes had been grown contained copper, the maximum quantity found being 110.74 mgrms. per kilo of dry soil. The amount of copper in the fruits was not affected when the plants had been sprayed with Bordeaux mixture. Preserved tomatoes contained corresponding quantities of copper. w. 9. s. Analysis of Rhamnus Barks.0. Tunmann. (A/noth.-Zeit., 1915, 30, 642; through J . Chem. Soc., 1916,110, ii., 504.)-The red-coloured foam which is obtained when drugs containing anthraquinones are shaken with sodium hydroxide solution is probably due to the presence of chrysophanol; the latter is present, therefore, in Rhamnus carniolicus as well as in R. catharticus, and the reaction simply’ serves to distinguish these from the American rhamnus bark, R.purshiana. Tschirch’s colorimetric method indicates that the quantities of anthraquinone derivatives in R. frartgulus and in R. purshiana have a ratio of 4 : 1, ’whilst according to the author’s gravimetric method the ratio between the two respective quantities is 3 or 2.5 : 1. Use of the Iodic Acid-Starch Reaction in the Examination of Wine and Vinegar.J. Jaenpretre. (Chem. Zeit., 1916, 40, 833.)-A mixture of sblphurous acid, iodic acid, and starch develops a blue colour after some length of time-a reaction which was first pointed out by Landolt (Be?., 1886,19,1317). Investigation380 ABSTRACTS O F CHEMICAL PAPERS of this reaction showed that the development of the blue coloration deyeiids on the kind and concentration of the acid, the temperature, etc.The reagent used consists of a mixture of 10 C.C. of 0.2 per cent. scdium iodate solution, 10 C.C. of 0.2 per cent. sodium sulphite solution, 5 C.C. of 0.5 per cent. starch solution, and 75 C.C. of water. When 10 C.C. of this reagent are mixed with 10 C.C. of $; acid solutions, the time which elapses before the coloration appears is as follows: Acetic acid, 438 sees.; succinic acid, 320 sees.; malic acid, 52 sees.; citric acid, 45 sees.; tartaric acid, 26 sees.; oxalic acid and mineral acids, immediately.As the time required for the development of the coloration is considerably diminished by the presence of a trace of free mineral acid, the reaction may be used for the detection of mineral acids in wine and vinegar.If, when mixed with the reagent, 10 C.C. of the sample give a blue coloration in less time than do 10 C.C. of citric acid of equal strength, an abnormal amount of free mineral acid is present. As a rule, a non-sulphured, non- plastered wine reacts as slowly as does a succinic acid solution. w. P. s. Detection of Artificial Colours in Wines. H. Kreis. (Chew,. Zeit., 1916, 40, 832.)-Certain dark red wines, even when diluted, contain colouring matter which fixes on wool and cannot be removed by washiiig the wool with boiling water; con- sequently, this test may indicate the presence of aniline dye although this may be absent. If the wine dyes wool, the latter should be heated on a water-bath with a small quantity of 1 per cent. ammonia solution which destroys the natural colouring matter derived from the wine, whilst aniline dyes, for the most part. go into solution. The ammoniacal solution is then acidified with sulphuric acid and heated with a fresh thread of wool. The latter remains white if aniline dyes are absent. w. P. s.