DEVELOPMENT of KINETIC MODELS FOR METHIONINE DEGRADATION IN FORTIFIED SOYBEAN MODEL SYSTEMS

Abstract

Successful methionine fortification of soy protein may enhance its nutritional value. Methionine, however, is highly sensitive to processing conditions, hence the need for kinetic studies to optimize its retention. Kinetic models describing the effect of major compositional and processing parameters, such as moisture, protein and initial methionine content as well as temperature were developed in this investigation. Methionine degradation in these soy protein‐containing systems appeared to follow a pseudo‐first order reaction. Mathematical models clearly showed that all the parameters studied had a significant effect on the rate of methionine degradation. Statistical analysis of the kinetic data indicated that empirical equations can accurately describe methionine degradation as a function of the aforementioned parameters.

PREDICTION of METHIONINE RETENTION DURING EXTRUSION PROCESSING of FORTIFIED SOYBEAN MODEL SYSTEMS

“…Methionine Retention conducted to examine the deviation between experimental data and predicted values (Table 5). Although there was some disagreement, the effect of temperature on methionine degradation seemed to be described reasonably well by the Arrhenius equation, showing a similar trend between predicted and experimental values (Choi and Villota 1989). Effect of Protein Content.…”

“…Three milliliters of the extract, 0.5 mL of phosphate buffer and 1 mL of dansyl chloride solution were mixed and heated for one hour at 40°C. Dansyl derivatives of methionine were then analyzed by HPLC (Choi and Villota 1989).…”

“…Methionine degradation rates have been previously determined to be strongly affected by temperature (Choi and Villota 1989). Since temperature changes with time and location within the extruder, a mathematical model describing temperature of the sample as a function of process temperature at any given location was found necessary in heat transfer analyses.…”

“…Mathematical models describing the kinetics of methionine degradation (Choi and Villota 1989) and extrusion behavior (temperature profiles of the sample and residence time distributions) were combined to determine the retention of methionine during extrusion through simulation carried out by a computer according to the flow chart presented in Fig. 2. A new reaction rate for methionine degradation was determined according to the temperature profile of the sample in every section along the length of the extruder.…”

“…Kinetic studies demonstrated that the addition of protein showed a catalytic-like effect on the degradation of methionine for concentrations up to 25%. However, any increase in protein above 25% reduced the reaction rate (Choi and Villota 1989). Hence, a kinetic model for the degradation of methionine was evaluated as a function of protein content.…”