Available lysine losses in water soluble protein of mackerel meat by heating.

Abstract

Losses of available lysine in water soluble protein of mackerel meat by heating at 80°C, 100°C and 120°C were determined in the presence of D-glucose or D-glucose-6-phosphate (G6P). Effects of moisture content and pH level on the retention of available lysine were also examined. Loss of available lysine by heating was accelerated by the addition of reducing sugars and their reactions followed the first order kinetics. Rates of available lysine losses increased with increasing temperature and pH value. However, it was observed that there was no significant difference in the retention of available lysine were 16.5-17.5 kcal/mole in the presence of glucose and 18.3-19.0 kcal/mole in the presence of G6P. The degradation of added reducing sugar by heating was first order reaction for up to approximately 90% loss. The activation energy for reducing sugar losses was fairly close to that for available lysine losses. The available lysine loss rate constant was found to increase as the added glucose to lysine molar raito (G/L) increased. On the other hand, the loss of glucose became larger as the G/L ratio decreased.