Title
Effect of ultrasonic processing on the changes in activity, aggregation and the secondary and tertiary structure of polyphenol oxidase in oriental sweet melon (Cucumis melo var. makuwa Makino)
Author
Siyu Liu, Yan Liu, Xingjian Huang, Wenjin Yang, Wanfeng Hu, Siyi Pan
Year
2016
Journal
Journal of the Science of Food and Agriculture
Abstract
Polyphenol oxidase (PPO) mainly contributes to the browning reaction of fruits and vegetables and causes serious damage to the quality of sweet melon products. However, traditional methods to inactivate browning may induce more unexpected risks than ultrasonic processing. Meanwhile, there are no reports on the effect of ultrasound on PPO directly purified from sweet melon. The PPO in the original juice was less inactivated than the purified form when treated with ultrasound. As for purified PPO, superior to thermal treatment, less heat was needed to inactivate the PPO with ultrasonic treatment. At intensity lower than 200 W, ultrasound did not significantly affect the structure and activity of PPO (P > 0.05), and latent PPO was activated. At intensity higher than 200 W, ultrasound inactivated PPO, induced aggregation and dissociation of PPO particles and significantly decreased the α-helix structure content. Low-frequency high-intensity ultrasound caused an inactivation effect and conformational changes of purified PPO from oriental sweet melons. Changes in the PPO structure induced by ultrasound eventually inactivated the enzyme. Ultrasound may be a potential method to inactivate PPO in oriental sweet melons.
Instrument
J-???
Keywords
Circular dichroism, Secondary structure, Food science, Biochemistry