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Laboratory Studies on the Chemistry of Soft Curd Milk

1933; Elsevier BV; Volume: 16; Issue: 3 Linguagem: Inglês

10.3168/jds.s0022-0302(33)93334-2

1529-9066

Samuel M. Weisberg, Arnold H. Johnson, E. V. McCollum,

Milk Quality and Mastitis in Dairy Cows

Much interest in soft curd milk has developed since Hill (1) showed how to differentiate the milks of individual cows witt~ respect to curd character and indicated the potential value .ofsoft curd milk for infant feeding.Hill (2) (3) has since devoted most of his attention to studies on the distribution of curd character in herds, environmental and hereditary factors, and 4o the clinical aspects of his findings.Espe (4) (5) has made an excellent experimental study of the digestibility of milk in relation to curd character and has ,given some attention to the chemistry .ofsoft curd miik.Our work carried on independently of the above workers consists primarily of analytical and physieo-ehemical studies on the constitution of soft curd milk. PART I. THE QUANTITATIVE CO1VIPOSITIOlXl OF SOFT AND HARD CURD 1V[ILKS II~ I:~ELATION TO CURD CHARACTERA fairly thorough study was made of the concentration of casein, fat, whey proteins, calcium, phosphorus, citric acid, and lactose in relation to curd character.These constituents will be dealt with both individually and, as far as possible, collectively, in this portion of the paper.The curd character was determined by means of the Hill test.This test affords a fairly quantitative measure of the compactness of the milk curd upon peptic digestion.It is fully described by Hill (1) in one of his bulletins.Briefly, it consists of adding a standard reagent consisting of 3 parts .ofan 0.6 per cent pepsin solution and i part of calcium chloride solution (378 grams made up to one liter) to 100 cc. of milk brought to body temperature.The milk coagulates rapidly about a set of radial knives which are drawn up through the curd and resistance offered is read off on a spring balance in grams.The readings are most readily reproducible for milks that give a loose curd (soft curd milks) so that one may check on duplicate determinations exactly or within 5 grams.With milks that give a relatively stiff curd the accuracy of reproduction is lower, duplicate readings may vary approximately 10 grams.When the milk is extremely hard curded the variations may be considerably greater.