246 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



ing. In the process of refining, these parts are largely removed, 

 hence the importance in the diet of whole-grain breads and cereals 

 from the standpoint of vitamin Bi. 



All fruits and vegetables contain some vitamin Bi. Although 

 none of them is a rich source, they should be considered important 

 sources since they comprise a part of all diets and are usually eaten 

 in relatively large amounts. Potatoes should be considered especially 

 in this respect. 



Milk is a good source of vitamin Bj in that it is generally con- 

 sumed without having been subjected to treatment other than pasteur- 

 ization which entails little loss of the vitamin. Eggs are also a 

 good source, the vitamin being in the yolk. 



Meats should probably be rated as good sources of vitamin Bi, 

 although there is considerable destruction during cooking. For 

 reasons not yet determined pork has a vitamin-Bi content two or 

 three times greater than other meats, and the dark meat of chicken 

 may be richer than the light meat. Glandular organs, liver and kid- 

 neys for example, are somewhat richer than muscle meats. 



Fats and oils do not contain vitamin Bi. 



Losses of vitamin B^. — In considering loss of vitamin Bi in foods 

 it is essential to keep certain facts clearly in mind: (1) The vitamin 

 is soluble in water; (2) it exists in foods in different combinations 

 which may have a bearing on the ease of removal and also on its 

 destruction; and (3) inactivation of the vitamin depends upon con- 

 ditions,^ and the quantity destroyed cannot very well be expressed by 

 a definite percentage but is more a matter of rate of destruction. 



When foods are cooked by boiling, the proportion of vitamin Bi 

 destroyed is relatively small up to cooking periods as long as 1 hour, 

 and generally does not exceed 10 to 15 percent unless the food is 

 distinctly alkaline or has been made so by the addition of soda. 

 The loss by solution, on the other hand, may be considerable, de- 

 pending, in addition to other factors noted, upon the proportion of 

 water used. Larger amounts of water remove more of the vitamin. 

 The proportion of vitamin Bi found in water in which food has 

 been cooked has been reported as high as 50 percent of that origi- 

 nally present in the food. If this water is used there will be little 

 loss of the vitamin. 



Baking causes only slight, if any, destruction of vitamin Bi but 

 the higher temperature and longer time required for roasting results 

 in appreciable destruction. 



' Acid solutions containing vitamin Bj liave been heated as long as 1 hour at 120° C. 

 without appreciable deterioration of the vitamin. In slightly alkaline solutions losses ap- 

 proximated 30 percent during 1 hour of heating at the boiling point of water. Dry mix- 

 tures containing vitamin B^ have been heated at 100° C. for as long as 48 hours and have 

 shown no detectable change in their vitamin-Bi content. 



