VITAMINS — MUNSELL 253 



Losses of riboflavin. — There is not a great deal of information 

 available on losses of riboflavin in foods. From the fact that the 

 vitamin is soluble in water it might be anticipated that there would 

 be loss during boiling or any process where food is kept in contact 

 with water for any length of time. It will be remembered, however, 

 that in foods riboflavin is combined with other substances. The 

 difficulty experienced in removing the vitamin from foods by those 

 who have undertaken quantitative estimation by chemical tests indi- 

 cates that probably no great amount would be removed during 

 boiling, blanching, or soaking. 



Riboflavin is described as heat-stable, which again might lead one 

 to think that losses during cooking would be small. Milk whey, 

 having an acidity comparable to that of tomato juice, was found to 

 lose only 10 percent of its riboflavin value when heated at the boiling 

 point of water for 1 hour, and 4 hours of heating was required to 

 reduce the original value by 30 percent. When the mixture was 

 made only slightly alkaline, the rate of destruction reached 30 to 40 

 percent for 1 hour of heating. This is a clear indication that con- 

 ditions within the medium influence inactivation of riboflavin as they 

 do inactivation of vitamin Bi. Under similar conditions, in a liquid 

 medium the rate of destruction of riboflavin was found to be slightly 

 less than the rate of destruction of vitamin Bi. This relieves the 

 situation relative to lack of specific information on loss of riboflavin 

 in foods, since any measures designed to reduce losses of vitamin Bi 

 during boiling apparently would also operate to protect against losses 

 of riboflavin. 



In contrast to vitamin Bi, riboflavin is less stable when heated in 

 a dry mixture than in one that is watery or even only moist. This 

 may afford partial explanation of the fact that the most extensive 

 losses noted have been in the baking, roasting, and frying of meats. 

 These ranged from 30 to 60 percent. 



There is no indication that storage causes loss of riboflavin irre- 

 spective of whether foods are fresh, canned, or dried. Canning per 

 se does not seem to reduce the riboflavin content of foods or at least 

 not significantly. Information on the effect of drying is not 

 available. 



NICOTINIC ACID (PELLAGRA-PREVENTING FACTOR) 



Properties. — Nicotinic acid is a white crystalline substance soluble 

 in water and fairly resistant to heat. The amide, nicotinamide, is 

 also effective as a pellagra preventive. Like some of the other vita- 

 mins discussed, nicotinic acid as present in foods is combined with 

 other substances and is not easily removed until these complex 

 compounds are broken up. 



