106 THE VITAMINS 



aeration as well as temperature may be a factor in the destruction of 

 vitamin B in fluid milk. 



The effect of heating vitamin B in tomato juice at its natural acidity, 

 approximately pH 4.3, at 100°, 110°, 120°, and 130° C. for 4 hours 

 was studied by Sherman and Grose (1923), by finding how much of 

 the juice heated at each temperature as compared with untreated juice 

 was necessary to maintain weight in carefully matched groups of rats 

 during a similar eight-week experimental period. From their results the 

 rate of destruction of vitamin B was calculated to be as follows: at 100° 

 C, 20 per cent; at 110° C, 33 per cent; at 120° C, 45 per cent; at 

 130° C, 58 per cent. These figures establish a low temperature coeffi- 

 cient of destruction for vitamin B, under such conditions. For an 

 increase of 10° C. in the range 100° to 130° C, the rate of destruction 

 under the conditions described was increased about 1.4- fold as com- 

 pared with the about 2-fold increase in most chemical reactions. 



The successive increases in the rate of destruction at 100° C. of 

 vitamin B in tomato juice resulting from definite changes in hydrogen- 

 ion concentration, shifting the natural reaction of pH 4.28 to pH 5.2, 

 pH 7.9, pH 9.2 and pH 10.9, was investigated by Sherman and Burton 

 (1926). Comparisons were made in solutions (filtered tomato juice) 

 heated at the natural acidity, and in parallel portions unheated ; and 

 between portions heated at natural acidity (pH 4.28) and portions 

 heated after shifting the pH by graded additions of alkali (pH de- 

 termined electrometrically). Hence their results may be stated both 

 in terms of the approximate percentage of vitamin B destroyed at 

 each pH studied, and in terms of the increased destruction due 

 to lowering the concentration of hydrogen ions during the process of 

 heating. 



The increased destruction of vitamin B over that at pH 4.28 (natu- 

 ral acidity of clear filtered tomato juice), on heating for 1 hour at 

 100° C. at pH 7.9 was 20 to 30 per cent, at pH 9.2, 60 to 70 per cent ; 

 at pH 10.9, 90 to 100 per cent. On heating for 4 hours at the same 

 temperature, the increased destruction over that occurring at pH 4.28 

 was 10 to 20 per cent at pH 5.2 ; 60 to 70 per cent at pH 7.9. 



Of the total initial amount of vitamin B the percentages destroyed 

 by 1 hour of heating at 100° C. were as follows : at pH 5.2, about 10 

 per cent; at pH 7.9, 30 to 40 per cent; at pH 9.2, 60 to 70 per cent; 

 at pH 10.9, 90 to 100 per cent ; while the corresponding percentages 

 destroyed by 4 hours of heating at 100° C. were: at pH 4.28, about 

 20 per cent ; at pH 5.2, about 30 per cent ; at pH 7.9 about 70 per 

 cent. 



