THE ANALYST. APRIL, 1891. ON THE COMPOSITION OF MILE AND MILK PRODUCTS. (Read at Meethg, Pdruary, 189 1 .) FOR a number of years I have been in the habit of laying before you annual re- ports on the work done in the laboratory which is under my charge ; the report for the yeax 1890 forms the subject matter of my present paper. (For former reports see TEE ANALYST, vii. pb 53; viii. p. 33; ix. p. 56; x, p. 67; xi. p. 66; x5. p. 39; a. p. 46 ; xiv. p, 69 j and xvb p. 44). BY DR. P. VIETH.62 THE ANALYST. The total number of samples analysed in 1890 is 22,670, viz. :- 20,6 3 5 samples of milk, 1,188 ,, cream, 586 ,, skim milk, 40 ,7 butter milk, 3 7, whey, 165 ,, butter and butter-fat, 29 ,, water, 24 ), sundry articles, Of the milk sample 11,816 were taken from the railway churns in which the milk arrived from thecountry.While part of this milk is kept back for the production of cream, the bulk of it is distributed with the least possible delay. In order to keep a constant control over the men entrusted with delivering the milk to the customers, 7,104 further samples were taken before, during, and after delivery, and submitted to analysis. The following table contains the monthly averages of the results referring to all these samples :- 1890. January, . .. February .. March . . . . April . . ... May . . .. June .. . . July .. ~ . . August . . .. September . . October . . .. November . . December . . Yearly Average AVERAGE COMPOSITION OF MJLK. Samples taken Zpec.Gravit 1.0323 1.0324 1.0323 1.0322 1.0324 1.0323 1.0320 1.0319 1.0319 1.0322 1.0321 1.0322 On arrival.Tot, Sol. 12.95 12.84 12-76 12.66 12.63 12.64 12.81 12.86 12.81 13.04 13.07 ' 13.02 1.0322 1 12.84 I Fat. 3-80 3.70 3.63 3.57 3.53 3.55 3.75 3.81 3-7 7 3.89 3.94 3.89 3-74 Soh. Fct, 9 15 9.14 9-13 9.09 9-10 9.09 9.06 9.05 9-04 9.15 9.13 9.13 Before 1 During 1 After sent out. delivery. return. Tot. Sol. 12.88 12.75 12-69 12-57 12-58 12.54 12-75 12.83 12.86 12-94 12.92 12.86 Tot Sol. 12-96 12-90 12.84 12.70 12.74 12.68 12.82 12.87 12.83 13.03 13.08 13.07 9*10, 1 12-16 I 12.88 I I Tot. Sol. 13.02 12.86 12.93 12-74 12.74 12-77 12.84 12.90 12-90 13.13 13.18 13.10 18-92 The results obtained in the year 1890 are in close concordance with those of former years, not only with regard to the yearly average composition, but also with regard to the variations which the quality of milk undergoes in the course of the year.The lowest percentages of total solids and fat was found, as usual, in the second, the highest in the fourth quarter of the year. Considering that the circumstances under which the samples are taken can by no means be called very favourable, the agreement between the results referring to the severalseries of samples will, I think, be found satisfactory. Such differences as doTHE ANALYST. 63 exist might be easily explained, but to do so on this occasion seems to me to be rather beyond the limit of this paper. Cream samples were taken for analyais before the cream was sent out, and also while it was delivered to the customers. The total number of such samples was 1,010 and the average results of their analysis were as follows :- AVERAGE PERCENTAGE OF FAT IN CREAM.1890. ~~ January February March April June July August September October November December May * . .. . . .. .. .. .. .. . . .. ... .. .. .. . . .. . . . . . . * . .. . . .. Samples taken I Before sent out. 1 During delivery. I 46.0 4716 48.7 49.9 49.6 48.3 47.7 49.0 49 5 50.5 46.5 46.8 45.3 47.5 48.6 50.0 49 *3 48.6 47.3 49.2 50.3 50.4 47.0 46.9 Pearly average . . I 48.3 1 48.4 I I Clotted cream, of which 51 samples were analysed, was of the following average composition :- Water . . L 1 L . b . 35.16 per cent. Fat .. .. .. . . 58.35 ,, Ash .. .. .. Proteids and Milk Sugar . . * * 5.97 ,, .. -52 7, Skim milk, resulting when cream was separated from milk by means of centrifugal cream separators, contained, as a rule, from *2 to 04 per cent.of fat. I do not think it necessary to give the flgures relating to the analysis of 103 samples of butter, as these results, with the excsption of those obtained in December, were included in a paper which .I read before this Society two months ago (THE ANALYST, xvi. p. 1). On that occasion, however, I did not refer to the examination of the clarified butter-fat. The volatile acids- Wollny figures-found in the several classes of butter in 1890 mere as follows :-- English butter 25.3 - 30.0 average 27.6 C.C. French ,, 25.6 - 3 0 8 ,, 28 7 ,, Kid ,, 21.3 - 30.7 ,, 27.7 ,, Danish ,, 27.3 - 29.9 9, 28.8 ,, The figures fall below what is considered the limit in four cases of Eiel butter derived from two large well-known and managed dairies in Holstein-I will call them A and B-the tmme which turned out butter with low volatile acids in 1889.There were64 THE ANALYST. three abnormal samples from dairy A, the results being 24.2, 22.0, and 21.3, and one abnormal sample from dairy B, the result being 23.7. The low results were found during the time from July to October, i e . , at the same period of the year at which low volatile acids were observed in 1889. When speaking on this matter last year a good ileal of incredulity or, at any rate, suspicion was displayed with regard to the genuineness of the butter in question. Among others the question was asked, whether it was not a fact, that the volatile acids were found to be low at a time when butter prices were high.This was not the case either in 1889, or in 1890. In the former year butter prices were below the average for the year, from beginning of April to end of September, and in the latter again from beginning of April to end of August, while in both years the highest prices mere paid in March and in December. There is, then, no coincidence whatever between low volatile acids and high butter prices, and vice versa, and even if there had been, I should never have held that tho latter stood in any connection with, or explained the former in the cases in question. The matter seemed to me of sufficient interest and importance to cause my friend, Dr. Schrodt, principal of the Dairy Experimental Station at Kid, to follow it up. The proprietor of dairy A willingly agreed to send a sample of butter to Kiel for examina- tion once a week, and he has done so since beginning of May.Dr. Schrodt informs me, that with the progress of the period of lactation the volatile acids decreased reaching their lowest point in October, and that with the beginning of calving season in November they at once increased and quickly rose above 25. I will here put together all my results referring to butter from this particular dairy and add, with Dr. Schrodt’s permission, those of his results which he has com- municated to me in corroboration of my own. Results obtained in London :- 1889. *June, 27.6 ; July, 25.9, 24.7 ; August, 24.2 ; Octobsr, 22.8 ; November, 1890. July, 24.2 ; October, 22’0, 21.3 ; Nov., 2 6 9 1890. July, 24.6, 24.7, 24-0, 24.0 ; October, 23.0, 21.6, 22.2, 23.1 ; November, I may remark that results obtained in London ought to be compared with those obtained in Kiel about a fortnight previous.I once more express my firm conviction that in this instance we have to deal with a decrease in volatile acids below the usual limit, which has to be put down entirely to natural causes. I have mentioned on several previous occasions another case of naturally low volatile acids ; I refer to butter-fat derived from the milk of cows kept at the Aylesbury Dairy Company’s farm near Horsham. Of such butter-fat thirty-two samples were examined during the past year with the result, that the Wollny figures were found to be below 25 from January to middle of April, and again from August t o November. During the remaining parts of the year they varied from 25 to 26. The observed extremes were 22.1 and 26.2.In butter-fat which had been exposed to the action of air and light for eighteen 21.1; Dee., 29-2, 29.3. Results obtained in IGe1:- 2602,26*6, 27.0, 27.1 ; December, 27.3.THE ANALYST. 65 months and become bleached, the volatile acid figures had increased from 29.2 in the original to 30.4 in the bleached sample. A decrease of volatile acids was observed in butter which had been kept for more than ten years. A glass and a stoneware jar filled with such butter were accidentally found and their contents examined. In both jars the bottom layers of butter appeared fairly well preserved. I n the glass jar the top layer was extremely rancid, but contained no visible fungi; in the stoneware jar the butter had no particular smell, but was covered with a thick green fungous growth, and red fungi had penetrated the upper layer to a depth of about two inches.The results of the examination were as follows :- Glass jar, bottom layer .. . . 26.2 C.C. fi alkali. 9 ) 9 , t'?P j, .. . . 35.6 ,, Stoneware jar, bottom layer . . . . 25.7 ,, N 9 , 9 , top 9 , - - . . 21-2 ,) These results fully agree with similar ones which I submitted to you five years ago (THE ANALYST, xi. p. 70). Turning once more to the subject of milk, I wish t o relate some experiments which I have made with regard t o freezing milk. Two gallons of milk were put into an oblong tin vessel, ten inches in height, a tight-fitting lid screwed on, the vessel put in tl refrigerated salt solution, and kept therein at a temperature of 14OF.for three hours. Preliminary experiments had shown that after that length of time the mas9 of ice formed did, apparently, not further increase. On examination it was found that ice was formed at the bottom and sides of the vessel, and that a funnel-shaped cave in the centre was filled with liquid. This liquid was poured 06 and a sample of it analysed, as mere also samples of ice taken from the top and bottom layer. The results were as follows :- Ice. Liquid Cream. Skim milk, Part. Total solids ... 25.30 7-86 19.58 per cent. Fat ,.. ... 18.94 *68 5.44 ,, Ash ... ... -53 *62 1.11 ,, Sol. n. fat . ... 6.36 7-18 14.14 ,, The experiment was repeated, care being taken to drain off the part which remained liquid as completely as possible, and to carefully separate the frozen cream from the frozen skim milk.The following were the results of the examination :- Proportion . . . Spec. Gravity ... Composition : Water ... Fat ... Proteids ... Milk Sugar . . . Ash ... Ice. Cream. 8.8 1-0100 74.44 19.23 2.64 3.33 -52 Skim milk, 64.7 1.0275 92.10 *68 %SO 3.95 *60 Liquid Pait. 26.5 per cent. 1.0525 80.54 per cent. 5.17 ,, 5.3s ,, 7.77 ,, 1.18 ,, --- --- -- 100.16 100.13 100.04 These figures prove what has been shown on previous occasions, that frozen milk contains a much higher proportion of water than the original milk in which the ice wm formed, and that the part remaining liquid is a concentrated milk.66 THE ANALYST. The ice is by no means a solid mass, but a conglomerate of crystalline plate$ The fact that the latter, when examined singly, are found to be quite clear, proves tha fat globules do not enter into the crystals. The component parts of the ‘‘ Solids no fat ” seem t o participate in the formation of the crystals in about the same relativ proportion in which they. are present in the milk.This was so, at least, in the case t which my remarks refer, the relative proportions of proteids, sugar, and ash being foun as follows :- Ice. Liquid Cream. Skim milk. Part. Proteide ... 40.68 38-10 37.55 sugar ... 51.31 53-74 54.23 Ash .. ... 8-01 8.16 8.22 The behaviour of milk, when exposed to low temperatures, is not without interes in itself, but apart from this it is also of some practical importance. People who ar ignorant of what is actually taking place when milk freezes would naturally see no harr in melting milk ice and using the liquid obtained as milk.I f a milk vendor woul proceed in this way he might easily get into trouble. DISCUSSION. The PRESIDENT said that Dr. Vieth had added to the debt they already owed hin: His papers were not only welcome to this Society, but were looked forward to wit interest by all interested in dairy matters in England and abroad. Dr. MUTER said he quite confirmed Dr. Vieth’s results about frozen milk. During th long frost in January he had occasion to examine the contents of a frozen churn a delivered at the railway station. The following were the results :- (1) Milk passing through strainer :- Total solids . . . . . . . . 12.80 Fat ... . .. .. 3-80 Solids-not-fat . . .. .. . . 9-00 _I - (2) Contents of strainer :- Total solids . . .. 6 . . . 9.28 Fat .. .. . . .. .. 2-63 Solids-not-fat . . ,. .. .. 6 6 5 (3) Ice off churn lid :- Total solids . . .. . . , . 4.94 Fat . . * . .. . . . . 1-70 Solids-not-fat . . .. .. ,. 3.24 - It was evident, therefore, that unless very carefully thawed and mixed frozen mil might present moat anomalous results. Mr. FABER inquired if Dr. Vieth had any information about the way the COWS hr been kept,and whether the feeding of them had anything to do with the analysis of tl butter-fat, and as to the cows having recently calved or otherwise. Dr. DUPRE asked if Dr. Vieth had ever compared the volatile acid with the tot soluble acids; whether there was anything in the shape of compensation going o whether when the one increased the other diminished, or vice veraa.THE ANALYST.67 -~ Mr. YOUNQ said he had always taken the estimation of the ash, which he considered of great importance, and a large number of ash estimations would make Dr. Vieth’s figures very valuable indeed. Mr. Young also mentioned that large quantities of milk were frozen into blocks for the large shipping companies who used them as required for their passengers. It was evident from Dr. Vieth’s experiments that if these blocks were used in portions the milk supply on board ship must vary much in quality. The PRESIDENT remarked that presumably Dr. Vieth’s fat determinations were made by the plaster mathod ; he asked what number of cows had yielded the abnormal samples of milk referred to 1 I n his experince there was a direct connection between the price of butter and the proportion of volatile acids.He found that when butter prices went up the number of samples that yielded an abnormally low proportion of volatile acid at once went up, that is to say, that the practice of adulteration was closely connected with the market price. It was a most striking circumstance that when butter was dear whole series of samples analysed by him fell either just upon or slightly below the Reichert limit, and he could not but conclide that foreign shippers sometimes let their produce down ~ t 8 low as they could without much risk of prosecution. Of course, there could not be any connection between price and the proportion of volatile acids in undoubtedly genuine samples. DR.VEITH, in reply, said the butter showing the low results was made at a large farm where about 200 cows were kept. At the time when the abnormal results were observed the cows were fed on pasture land which was reclaimed from the sea. Dr. Schroot was under the impression that the abnormal results had nothing to do with the feed. With regard to the connection between low volatile acids and butter prices hinted at by Mr. Hehner last year, he did not think it was meant seriously, but he now saw it was as Mr. Hehner said he found it so. His (Dr. Vieth’s) experience went the other way. He had during the last three years analysed a great number of samples chiefly from France, Holstein, Denmark, and Sweden, and had never found any definite connection between the prices of butter and the quantity of volatile acids. The compo- sition of frozen milk was certainly of considerable interest. As to frozen milk being used on board ship, he knew of that long ago, but he could not understand how milk could be frozen in blocks. He had never seen milk entirely frozen ; there was always a certain quantity of liquid left which would not freeze, just a5 it was the mse with sugar and salt solutions. With regard to the ash, he must say that it was not determined in the samples referred to in the paper in which sp. gr. and solids were determined and the fat calculated. He made, of course, a great number of ash determinations, but could not see much use in bring them forward because they simply proved what he had Rtated on previous cccasions, viz., that the ash of normal milk was as near as possible 8 per cent. of the solids-not-fat.