Relative Importance of Food Composition in Free Lysine and Methionine Losses During Elevated Temperature Processing

Free lysine and methionine loss were monitored as a function of food composition (independent variables) utilizing fortified model food systems. The food systems were composed of varying quantities of protein, sugar, oil, salt, cellulose, and water, and were isothermally processed for varying time intervals at 65 or 115°C. The arnino acid losses were best modeled by first order reaction kinetics. Protein, sugar, and water activity (a w ) had the predominant influence on the loss rate. The rate coefficient increased when protein or sugar levels were increased, but decreased when water activity was increased. Salt and oil had only a minor influence on the rate coefficient when compared with other variables. Interactions among food components also influenced the loss rate coefficient.