Thermal inactivation of peroxidase during blanching of butternut squash

The kinetics of thermal inactivation of peroxidase in butternut squash during water blanching was studied. Thin slices of squash were immersed in water Lit 60-90 degrees C for 0-60 min. For treatments below 70 degrees C, a biphasic, first-order kinetics model was proposed for peroxidase inactivation that would correspond to heat-labile and heat-resistant fractions of the enzyme. Parameters of the first-order model for the heat-labile and heat-resistant fractions were k(L,ref) = 24.8733 min(-1), E-aL = 14023 J/mol and k(R,ref) = 0.0729 min(-1), E-aR = 15794 J/mol, respectively. For treatments above 70 degrees C, a monophasic first-order kinetics model was proposed. Parameters were k(ref) = 8.6425 min(-1), E-a = 149900 J/mol. Decreases in ascorbic acid contents due to blanching were analyzed. Blanching processes at high temperature and short time resulted in higher ascorbic acid retention. A linear relationship between ascorbic acid retention and processing temperature was found. (C) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.