I 



DAIRY FARMING DAIRY IN(J. 87 



The changes of the fat in the ripening of cheese, K. Wimmsch [ArL K. 

 (iemndheilmititr, 17 {1901), p/>. l-ldO; nhs. in (*hem. Cerifld., 73 {1901),. I, No. H, pp. 

 l^S-130). — The changes in the fat in the ripening of chee-se are apparent from the 

 variations in the quality and the amount of the fat. The changen in the quality are 

 ehemical and are especially noted in the formation of soluble fatty acids. The 

 breaking up of the glycerids with the formation of soluble fatty acids ])egins shortly 

 after the manufacture of the cheese, the volatile acids lu-ing in part at least elimi- 

 nate<l. With the changes of fatty acids, there is a gradual reduction of the Keichert- 

 Meissl and the refractometer mnulters, and in a lesser amount the mponification 

 number. The source of the free fatty acid is in the l)reaking up -of the fat, and it is 

 not formed from the milk sugar or albumin. From a studv of the causes of the 

 breaking uj) of the fat, tlie author believes that Ixu-teria play the ]>rincipal role, the 

 work l)eing especially aided by certain enzym-producing species. 



Influence of rennet on cheese ripening, S. M. R.muock, li. J^. Ku.sskll, and 

 A. Vivian {Wiscomin Sta. Rjit. 1900, pp. 10^'-12J, jUj.^. r>). — The views of various 

 authors on the action of rennet in cheese making are given and investigations to 

 <letermine the effect of different (juantities of reiniet in cheese ripening are rejMirted. 



Two, four, eight, and sixteen ounces of rennet extract, respectively, were added to 

 1,000 lbs. of milk, and the iiercentage of solul>le nitrogen in the cheese made in each 

 case was determined at different intervals. An increase in the quantity of rennet 

 extract used was accompanied in each case by an increase in the percentage of soluble 

 nitrogenous products. The average water content of cheese made from 1,000 lbs. of 

 milk to which 3 oz. of rennet extract had been added was 35.23 per cent, and from 

 the same quantity of milk to which 9 oz. of rennet extract had been added was 34.37 

 l»er cent. The hypothesis advanced that an increase in the amount of rennet tends 

 to increase the moisture of cheese and so hasten the ripening process is therefore 

 considered untenal)le. To determine if other ferments than rennin in the rennet 

 extract was the cause of increased digestion where large quantities of the extract were 

 used, an attempt was made to inhibit the action of rennin by heat. Rennet extract 

 heated to 152° F. for 5 minutes was compared with the unheated extract. As heat- 

 ing decreased the proteolytic action as well as the curdling power of the rennet 

 extract, the results of this experiment did not permit of a definite conclusion. 



Studies were made of the soluble decomposition products in cheese made with vary- 

 ing (juantities of rennet. Four series of experiments are reported in detail. Deter- 

 minations of the alljumoses, peptones precipitated by tannin and ))y phosphotungstic 

 acid, amids, and ammonia in cheese made with varying (juantities of rennet at different 

 stages of rijiening are given. The effect of adding varying (juantities oi pejtsin to the 

 rennet extract was also studied, as well as the influence of acidity of curd on rate of 

 peptic digestion. Several different brands of commercial pepsin were compared. 

 The results of the investigations are summarized as follows: 



"The increase in soluble nitrogenous products in cheese and also in milk due to an 

 increase in amount of rennet extract used are also coniined to those by-products that 

 are j)eculiar to pej)sin, thus indicating that the digestive action of rennet extract is 

 attributal)le to the action of the pepsin incor|)orated with the rennet extract. The 

 crucial test of this ccmclusion was made by adding j)urified i)ei)sin to milk and 

 making the same into cheese, where rennet extract was or was not added to curdle 

 the milk. In such cheese digestion has been increased in those cases to which 

 pepsin has been added, and this increase has been confined to th(jse by-products 

 that are characteristic of pepsin, and which also appear in cheese made with high 

 quantities of rennet. 



"The digestion in cheese incident to pepsin is determined mainly by the degree of 

 acidity developed in the nulk and curd. In Cheddar cheese, peptic digestion ])rob- 

 ably does not begin until the acidity of the milk is approximately 0.3 per cent lactic 



