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ANALYSIS OF THERMAL INACTIVATION KINETICS OF MEMBRANE‐BOUND POLYPHENOL OXIDASES AND PEROXIDASES FROM METROXYLON SAGU
Author(s) -
ONSA GALILA HASSAN,
ABDULHAMID AZIZAH,
SELAMAT JINAP,
BAKAR JAMILAH,
MANAP MOHD YAZID,
BIN SAARI NAZAMID
Publication year - 2011
Publication title -
journal of food biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 47
eISSN - 1745-4514
pISSN - 0145-8884
DOI - 10.1111/j.1745-4514.2010.00419.x
Subject(s) - chemistry , browning , peroxidase , polyphenol , kinetics , polyphenol oxidase , food science , starch , biochemistry , enthalpy , enzyme , antioxidant , physics , quantum mechanics
Thermal inactivation kinetics for the purified membrane‐bound polyphenol oxidases (mPPOs) and peroxidases (mPODs) isolated from Metroxylon sagu were analyzed. Each isoenzyme was treated at different time–temperature combinations in the range of 0–70 min and 20–70C. Thermal inactivation rates constant (k) at 70C for mPOD‐I (72.9 × 10 ‐ 3 /min) and mPOD‐II (97.9 × 10 ‐ 3 /min) were lower than that of mPPO‐I (379.7 × 10 ‐ 3 /min) and mPPO‐II (138.1 × 10 ‐ 3 /min). The activation energy for inactivation of mPPO‐I (32.94 kcal/mol) and mPPO‐II (40.34 kcal/mol) was lower compared with mPOD‐I (45.77 kcal/mol) and mPOD‐II (40.62 kcal/mol). The enthalpy values for mPOD‐I (45.08 kcal/mol) and mPOD‐II (39.94 kcal/mol) were higher than those of mPPOs (mPPO‐I, 32.26 kcal/mol; mPPO‐II, 39.66 kcal/mol). This result implies that both mPOD‐I and mPOD‐II are more thermostable.PRACTICAL APPLICATIONS Sago starch has a great potential for application in various food systems. However, its further development and exploitation was hindered by browning‐associated problems due to polyphenol oxidases and peroxidases. In this work, we have investigated the effect of heat treatment on the stability and inactivation kinetics of membrane‐bound polyphenol oxidases and membrane‐bound peroxidases. The results from this work will enable the food industry to develop optimum process parameters with respect to heating time and temperature during processing and production of sago starch to produce high‐quality starch.