Kinetic Parameters for the Thermal Inactivation of Peroxidase and Lipoxygenase in Precooked Frozen Brassica Species |
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Authors: | John Pérez‐Calderón Alicia Califano María Victoria Santos Noemí Zaritzky |
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Affiliation: | 1. Centro de Investigación y Desarrollo en Criotecnología de Alimentos CIDCA (UNLP‐CONICET‐CIC), La Plata, Argentina, Argentina;2. Facultad de Ciencias Exactas, Univ. Nacional de La Plata, La Plata, Argentina, Argentina;3. Depto. de Ingeniería Química, Facultad de Ingeniería, Univ. Nacional de La Plata, La Plata, Argentina, Argentina |
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Abstract: | Thermal inactivation of peroxidase (POD) and lipoxygenase (LOX), both enzymes present in broccoli and Brussels sprouts, is required before freezing, to obtain high‐quality precooked frozen vegetables. Rate constants of a 1st‐order biphasic model for the heat‐labile and heat‐resistant POD and LOX isoenzymes were determined at different temperatures (75, 80, and 90 °C) and the corresponding activation energies were estimated using nonlinear regressions. In the case of Brussels sprouts, the activation energies for the resistant and labile fractions were 56.3 and 62.5 kJ/mol for POD and 63.7 and 65.8 kJ/mol for LOX, respectively. For Brussels sprouts, different precooking times were tested to analyze the effect of residual enzyme activity on quality parameters and sensory attributes, after a frozen storage of 4 mo at ?20 °C. A significant reactivation of enzyme activity after frozen storage was observed (especially in the case of POD) for short precooking times (<6 min) leading to low‐quality parameters at the interior zone of the vegetable. A precooking time of 6 min at 90 °C allowed an adequate inactivation of LOX and POD obtaining a high‐quality final frozen vegetable. A sensory analysis confirmed the global acceptability of the product. The obtained results are relevant to define the precooking stage conditions in the production of frozen cruciferous vegetables. |
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Keywords: | lipoxygenase peroxidase precooked frozen Brassicas quality attributes thermal inactivation kinetics |
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