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Molecules 2018, 23(7), 1743; https://doi.org/10.3390/molecules23071743

Inactivation, Aggregation and Conformational Changes of Polyphenol Oxidase from Quince (Cydonia oblonga Miller) Juice Subjected to Thermal and High-Pressure Carbon Dioxide Treatment

1
Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Ministry of Education, Wuhan 430070, China
2
College of Food Science and Technology, Huazhong Agricultural University, No. 1, Shizishan Road, Wuhan 430070, China
*
Author to whom correspondence should be addressed.
Received: 19 June 2018 / Revised: 11 July 2018 / Accepted: 12 July 2018 / Published: 17 July 2018
(This article belongs to the Special Issue Recent Advances in Studies of Food and Beverages)
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Abstract

Polyphenol oxidase (PPO) causes the browning reaction in fruits and vegetables and deteriorates the quality. Thermal treatment for enzyme inactivation may result in defects as opposed to high pressure CO2 (HPCD) processing. In this study, the changes in activity, dissociation, aggregation and conformation of purified PPO from thermal and HPCD treated juice were investigated. HPCD exhibited inactivation of PPO at 55–65 °C whereas thermal processing alone at the same temperature resulted in PPO still showing activity. Under thermal treatment at 25 and 65 °C, the browning degree was higher (0.39 and 0.24) than for HPCD-treated juice (0.23 and 0.12). Fluorescence and circular dichroism spectral results indicated that HPCD induced large decreases in intensities, revealing a rearrangement of the secondary structure and destruction of the native configuration of the PPO molecule. The particle size distribution (PSD) pattern revealed structural modification leading to initial dissociation and subsequent aggregation of PPO after HPCD treatment. Polyacrylamide gel electrophoresis (PAGE) analysis exhibited that molecular size of protein was 40 kDa. In conclusion, the HPCD method was found to be more effective than thermal treatment to inactivate PPO. Structural modifications provided better insights into the phenomena of activation and inactivation of PPO. View Full-Text
Keywords: polyphenol oxidase; high pressure carbon dioxide; aggregation; λmax; conformation polyphenol oxidase; high pressure carbon dioxide; aggregation; λmax; conformation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Iqbal, A.; Murtaza, A.; Muhammad, Z.; Elkhedir, A.E.; Tao, M.; Xu, X. Inactivation, Aggregation and Conformational Changes of Polyphenol Oxidase from Quince (Cydonia oblonga Miller) Juice Subjected to Thermal and High-Pressure Carbon Dioxide Treatment. Molecules 2018, 23, 1743.

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