4 



The American Public Health Association 



substances which are present in milk, 

 and also on the value of pasteurized 

 milk as a food for infants. The dis- 

 agreement resulted in a very extensive 

 study of the subject by an eminent 

 chemist who established more or less 

 permanently certain points. 



(1) Effect of Heat on Milk. The 

 chemical changes produced in milk 

 solids by heating at different temper- 

 atures for varying lengths of time were 

 determined. North published in 1911 

 a summary of the literature on the 

 subject, together with considerable 

 new work done in his laboratory. This 

 summary appeared in the form of a set 

 of curves, which showed graphically 

 the effect of heating milk on the chem- 

 ical composition of its constituents. 

 This diagram was accepted by the 

 Commission on milk standards of the 

 New York Milk Committee and was 

 published by them in their first and 

 second reports." It points out that 

 the inorganic solids in milk are very 

 little changed by heating to 169 de- 

 grees F. for 40 minutes or less ; that 

 the albumen is much more sensitive 

 than the salts, but will resist a tem- 

 perature of 148 degrees F. for 40 min- 

 utes ; that the enzymes are the most 

 easiljr destroyed constituents of the 

 milk, but are still effective after the 

 milk has been heated to 145 degrees F. 

 for 30 minutes The physical condi- 

 tion of the cream is the most sensitive 

 indicator of over-heating, and the 

 cream line is destroyed before any of 

 the milk solids are chemically affected. 

 In brief, the ordinary temperature and 

 time of heating used in commercial 

 pasteurization, namely, 145 degrees F 

 for from 20 to 30 minutes, seemingly 

 has little, if any, effect on the compo- 

 sition of the milk so far as we are able 

 to determine by chemical analyses. 



(2) Infant Feeding Experiments. 



d) Reports of Commission on Millc Standards ap- 

 pointed by the New Yorl« Mill< Committee. Public 

 Health Reports, Vol. XXVII, No. ]!l. and Vol. 

 XXVITT, No. 34, August 22, Mil 3. 



The results of these chemical tests did 

 not satisfy many of the medical pro- 

 fession, who were familiar with infant 

 feeding. They' still claimed that pas- 

 teurized milk did not produce the same 

 effect on some infants as did clean raw 

 milk. This criticism of pasteurized 

 milk was, to a great extent, tempora- 

 rily quieted by the experience gathered 

 from the immense feeding experiments 

 conducted by the New York Milk 

 Committee in its infant feeding sta- 

 tions, and by similar work done at 

 milk dispensaries in Washington. The 

 results of these experiments seemed 

 very conclusive. Thousands of chil- 

 dren were fed pasteurized milk daily 

 for three years at the New York sta- 

 tions, and the average daily increase 

 in weight of the babies thus fed was 

 ec^ual to the average increase in weight 

 of the babies of like age fed clean 

 raw milk, and no cases of rickets or 

 scurvy developed. The one objection 

 to this evidence seems to be that these 

 children were not always under ob- 

 servation of the station nurses, and 

 other foods may have been given 

 them, which in some way might coun- 

 teract the effect of the heated milk. 



Within the last few years the con- 

 tro\'ersy has been again reopened and 

 much more definite data has been pre- 

 sented. It has been shown that prop- 

 er food substances contain exceedingly 

 small amounts of compounds which 

 are absolutely necessary for the main- 

 tenance of healthy life. These essen- 

 tial compounds have been styled vita- 

 mines. There are several classes of 

 vitamines. One class is responsible 

 for the growth of organisms, and when 

 absent from the diet of the young, 

 growth is not normal. Another class 

 is absolutely essential for the mainte- 

 nance of ordinary metabolism, and 

 without which deficiency diseases such 

 as scurvy and rickets develop. Any 

 process which breaks up or destroys 

 either of these compounds in an arti- 



