Thiamin Stability in Solids as Affected by the Glass Transition

The stability of thiamin was evaluated in solid polyvinylpyrrolidone model systems as a function of water activity (a w ) and the glass transition. In the glassy state, thiamin degradation rate constants correlated with the glass transition temperature (T g ), decreasing as T g increased. Above a w 0.4, rate constants correlated better with a w rather than T g . However, rate constants decreased in the rubbery state above a w 0.4, which could be attributed to glass transition‐induced structural collapse. Glass transition effects (mobility considerations, collapse) have a larger effect on thiamin stability than a w , which should be recognized during the development of fortified food products.