GLYCINE LOSS AND MAILLARD BROWNING AS RELATED TO THE GLASS-TRANSITIONIN A MODEL FOOD SYSTEM

The effects of water activity and the glass transition on the rate con stants for glycine loss and brown pigment formation due to the Maillar d reaction were evaluated in a model food system. Equimolar glucose an d glycine were incorporated into amorphous polyvinylpyrrolidones of va rious molecular weights and moisture contents. Glycine loss and brown pigment formation were quantified during storage at 25 degrees C. At c onstant water activity, rate constants were higher in systems with low er grass transition temperatures. Glycine rate constants decreased upo n matrix collapse, but browning rate constants were not affected by co llapse. Changes associated with the glass transition influence bimolec ular reactions and should be considered during product formulation and shelf-rife testing.