IX. OCCURRENCE IN FOOD 455 



because in the animal organism the thiamine is easily phosphoiylatcd (by 

 an adenosinetriphosphate-containing enzyme) and dephosphorylated by a 

 powerful phosphatase. 



Thiamine is present as such in blood plasma, but as pyrophosphate in 

 the corpuscles. In human blood only about 10 % of the thiamine is present 

 as such in the plasma; the rest is in the corpuscles. Normal blood of a well- 

 fed person contains about 6 to 12 7 of thiamine per 100 milliliters. The mean 

 values of the thiamine pyrophosphate content of well-nourished men were : 

 1.5 7 per 10" red cells; 290 7 per 10" leucocytes; for women: 1.3 7 per 10" 

 red cells; 270 7 per 10" leucocytes.-' ' 



As thiamine is fairly resistant to high temperature and O2 in a weakly 

 acid milieu, it is clear that most processed foods contain thiamine. However, 

 in alkaline and even in the neutral state the resistance to heat is not great. 

 Therefore, if processing of neutral foodstuffs includes treatment at or 

 above 100°, a substantial loss of thiamine takes place, dependant upon the 

 duration of the heating. Furthermore, in the cereal grains thiamine is found 

 especially in the outer grain layers, and therefore machine-milled rice is 

 very poor in thiamine. Thus it is obvious that beriberi is a disease of rice 

 and cassava (manioc) -eating countries,^' ^ as here a great deal of the popula- 

 tion depends on rice or cassava as their main source of calories. 



For the thiamine content of the different foods we may refer to tables 

 as published elsewhere.® Special consideration will here be given to those 

 foods that are either particularly rich in thiamine or that forming the main 

 food item for many people. 



a. Cereals 



(1) Wheat. The thiamine content of wheat depends especiallj'' on the 

 variety and to a lesser extent on the conditions under which it is grown, 

 i.e., the quality of the soil, the use of fertilizers, etc. Usually the content is 

 between 500 and 800 7 of thiamine per 100 g. of whole wheat. 



Thiamine is very unevenly distributed in the kernel. The content of 

 the inner layer, the endosperm, is the lowest, about 30 7 per 100 g. The 

 aleuron layer and the germ are much richer in thiamine; by far the richest 

 part is the scutellum, the small layer between the germ and the rest of 

 the kernel. This .small layer alone, consisting approximately of 1.5% of 

 the whole kernel, contains 60 % of its thiamine (Hinton^). The scutellum of 

 rye, corn, and barley has a similar high content of thiamine (Hinton^). 



^ O. Smits and E. Florijn, Biochim. et Biophys. Acta 3, 44 (1949). 



^ II. G. K. Westenljrink and J. Goudsmit, Arch. need, phijsiol. 23, 79 (1938). 



•* .\. Dubois and G. Corin, Bull. soc. pathol. exotique 7, 402 (1914). 



* B. C. P. Jansen, Repts. Didch-Iniiian Med. Service I, 1 (1923). 



« B. K. Watt and A. L. Merrill, U. S. Dept. Agr., Handhook 8. 



"■ J. J. ('. Hinton, /. Soc. Chem. Ind. 61, 143 (1942). 



8 J. J. C. Hinton, Biochem. J. 38, 214 (1944). 



