Section C. Dairy chemistry and physics: Part I. Chemistry and physical chemistry

Abstract

nitrogen decreased; chloride percentage was high, and lactose percentage low; and there was a significant fall in yield. Schmid & Zollikofer(35) observed that the strain of a 30 km. journey of six cows to higher altitudes of the Alps caused an immediate decline in milk yield, fat and lactose percentages, while the chloride concentration increased. Data for bulk milk received in Norwegian dairies for the three periods 1927-30, 1937-40 and 1944-5 show but little variation(36), the levels of protein being 3-11, 3-19 and 3-11%, those of lactose 4-64, 4-87 and 4-83%, and those of fat 3-72, 3-80 and 3-69% respectively. Ash remained steady at 0-72%. The milk of six Sindhi cows and five buffaloes was examined for cholesterol by Gulvady, Kannan & Basu(37). Variations from 10 to 50p.p.m. were noted in the former and from 10 to 80 p.p.m. in the latter. In both species there was a sharp rise at the end of lactation. Evidence of proteolysis during the souring of the milk of cows and buffaloes is presented by Khambatta & Dastur(38). Variations in non-protein nitrogenous constituents of the milk of cows, buffaloes, goats and sheep were examined by Venkatappaiah & Basu(39). All the non-protein nitrogen constituents except creatinine were 2-5 times higher in the first colostrum of cows and buffaloes. The averages were respectively 258-2, 276-0, 323-9 and 432-9 p.p.m., of which urea was 44-8, 41-2, 64-9 and 32-9 p.p.m., uric acid 2-1, 0-9, 0-6 and 0-4 p.p.m. and amino-acids 15-7,18-6,16-6 and 22-2 p.p.m. Bakalor(40) found that the mean composition of 1608 samples of milk from forty-six producers taken on arrival at a Pretoria milk plant was: total solids 12-12%, fat 3-51 %, solids-not-fat 8-61%, ash 0-737%, protein 3-19% and lactose 4-69%. Fat and ash showed greatest variation. During the 12-month period 2-8% of the total number of samples fell below 3-0% fat, and 35-4% fell below 8-5% non-fatty solids. The milk from 25% of the producers contained less than 8-5% yearly average non-fatty solids. The author concludes that mastitis and poor feeding during the dry winter months are largely responsible for low non-fatty solid content. The Capetown city milk supply was shown by Bakalor(41) to have declined steadily in both fat percentage and solids-not-fat over the years 1934-46. In this period the fat varied between 3-51% in December to 3-79% in May, while solids-not-fat rose to 8-74% in July to September after reaching a minimum of 8-62% in January. The same author examined the milk supply of nine South African cities (42) during the period October 1949 to September 1950, and again noticed a frequent failure to reach the 8-5 % limit. In some cities all samples failed in this respect for one or more months in the year. Deficiencies in fat were much less frequent. Milk of 138 cows in the Parma region of Italy showed a decline in fat percentages from 3-86 to 3-52 % during the period 1939-43(43). The bulked milk of 30,000 cows in the province of Milan during the period 1930-9 was found by Fabris(44) to contain 3-49 % fat and 8-87 % solids...