91E-11 |
Effect of combined pressure and temperature in soymilk trypsin inhibitors |
Y. ESTRADA-GIRON and G. V. Barbosa-Cánovas. Biological Systems Engineering, Washington State University, Pullman, WA 99164 Soymilk is a suspension of soybeans and water that contains several nutritional and anti-nutritional factors such as Trypsin Inhibitors (TI). During soybean processing heat is used to inactivate these inhibitors without affecting the quality of the product. As an alternative for food processing, non-thermal technologies like High Pressure (HP), have demonstrated to inactivate enzymes and undesirable factors retaining food quality properties. The purpose of this work was to determine the inactivation kinetics of soybean Trypsin Inhibitors when exposed to high pressure and thermal combined treatments. Raw soymilk was subjected to treatments at two pressures (275 and 550 MPa) and two temperatures (50 and 80 °C) at processing times of 5-30 minutes. The kinetic of TI was followed spectrophotometrically before and after thermal-HP treatments. This assay was based on the inhibition of soybean-TI activity at pH 8.2 and 37 °C, using N-benzoyl-DL-arginine-p-nitroanilide hydrochloride (BAPNA) as substrate. The inactivation rate constants were obtained from semilogarithmic plots of the activity retention as a function of time. Under the conditions studied, minimal inactivation rate constants (8x10-4 s-1) were observed in those treatments at 80 °C, 550 MPa, for 15 min (r2=0.9851), and 50 °C, 550 MPa, for 30 min (r2=0.9716), with a residual concentration of about 40%, in comparison with non-treated soymilk. At 80 °C, 275 MPa, and 25 min (r2=0.9526), the inactivation rate constant was fairly similar to that obtained for raw soymilk, 1.8x10-3, and 1.7x10-3 s-1, respectively; noticing that pressure influences the rate of reaction rather than temperature by itself, regardless of the temperature and processing time. These results suggest that adequate conditions of HP and temperature could inactivate soybeans-TI without using high thermal conditions, and that the application of pressure may be an important alternative in soymilk processing.
Session 91E, Nonthermal Processing: Nonthermal processing of foods
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