Kinetic and Thermodynamic of Thermal Inactivation of the Peroxidase,Polyphenoloxidase and Inulinase Activities during Blanching of Yacon (Smallanthus sonchifolius) Juice |
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Authors: | Camila Carvalho Lago Caciano Pelayo Zapata Noreña |
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Affiliation: | 1. Institute of Food Science and Technology, Federal University of Rio Grande do Sul, Av. Bento Gon?alves 9500, Campus do Vale 91501-970, Porto Alegre, RS, Brazil
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Abstract: | The present study evaluated the kinetics and thermodynamic parameters for the thermal inactivation of peroxidase (POD), polyphenoloxidase (PPO) and inulinase (INU) from yacon juice. The yacon juice was acidified with 1 % citric acid prior to blanching at different time-temperature combinations in the range of 0–10 min, and 80–100 °C. All enzymes showed a biphasic kinetic behavior. The velocity constants increased and D values decreased with temperature for both the labile and the heat resistant fractions. The activation energy of the heat-labile (E aL ) and heat-resistant fractions (E aR ) were 38.19, 16.05, 30.08 kJ/mol, and 30.65, 71.94, 41.86 kJ/mol for POD, PPO and INU, respectively. Thermodynamic studies indicated a non-spontaneous (ΔG?>?0) and endothermic (positive enthalpy values) process, and the enzyme aggregation step is the rate determining of the reaction (negative entropy values). |
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