Change in Available Lysine Loss Reaction Rate in Fish Flour Due to an a^w Change Induced by a Temperature Shift

The loss of available lysine was measured in fish flour samples prepared at 25°C and water activities (a^w) of 0.33, 0.44 and 0.65, sealed and then held at 25, 38 and 45°C. The loss rate was compared to the loss rate of product similarly humidified and held at each temperature but stored open at the original relative humidity corrected for temperature. Theoretically, if there is no effect of temperature on a^w, then the rate constants should not differ between the systems. It was found that the sealed systems had a greater loss rate. The results also indicate that the FAO specification of zero available lysine loss after storage at 38°C for 6 months was exceeded.