Comparisons Between Model Predictions and Measured Values for Available Lysine Losses in a Model Food System

Abstract

A mathematical model, developed to predict available-lysine losses in a model food system which had undergone an isothermal-nonstirred process, was tested under different process conditions. The model predictions were compared to measured available-lysine losses in both jacketed-mixer processing and extrusion processing. Statistical analysis using a paired t-test analysis indicated a significant correlation between predicted and actual results for the jacket-mixer process. In the extrusion experiment a statistically significant correlation (0.7) occurred when the predicted values were plotted against observed. However, variation due to product backmixing and inaccurate temperature measurement prevented a rigorous test of the model. The reaction order of available lysine loss in casein, single-cell protein and a soy protein isolate were determined at an elevated temperature. The casein and singlecell protein followed fust-order reaction kinetics. The soy isolate initially follows first-order loss but after an approximate loss of 40-50% available lysine, the loss abruptly stops and a no-loss phase occurs.

Kinetics of chemical marker M-1 formation in whey protein gels for developing sterilization processes based on dielectric heating

“…Wolf, Thompson, and Reineccius (1978) monitored the change in lysine concentrations at elevated temperatures (80-130°C) in Maillard reaction. After a loss of about 40-50% of available lysine the concentration of lysine remained constant even though glucose concentration continued to decrease with heating time.…”

Kinetics of Protein Quality Change in an Extruded Cowpea‐Corn Flour Blend under Varied Steady‐State Storage Conditions

“…(Labuza, 1980). Wolf et al (1978) found initial lysine losses (40-50%) in a soy isolate, glucose and microcrystalline cellulose system were best described by a first-order model, but after this initial phase, a significant increase in reactive lysine occurred followed by a phase where no further loss with heating was found. In the present study, the linear component of time was significant (p 5 0.001) whereas the nonlinear component, which may be important if the data were best described by zero or second-order models, was not significant (Table 2).…”

“…Jokinen et al (1976) observed more rapid loss of lysine (E, = 28.5) during heating of a soy isolate and glucose model system. Wolf et al (1978) found that soy isolate produced much different lysine loss reaction kinetics when compared to casein and single-cell protein. This difference suggests that legume proteins may react much differently than do other proteins during Maillard browning.…”

Browning and Amino Acid Loss in Model Total Parenteral Nutrition Solutions

“…Rate constants, k,, for initial amino acid losses using times up to approximately 35 days were calculated using a first-order model (Wolf et al, 1978). Generally only two or three data points beyond zero time were available since it was not expected that a no loss period would occur.…”