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).
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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. © 2016 Society of Chemical Industry.
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.|Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, China.
authors.forename: Siyu
authors.initials: S
authors.lastname: Liu
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.|Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.|Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, China.
authors.forename: Xingjian
authors.initials: X
authors.lastname: Huang
authors.affiliation: College of Architecture and Materials Engineering, Hubei University of Education, Wuhan 430205, China.
authors.forename: Wenjin
authors.initials: W
authors.lastname: Yang
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.|Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, China.
authors.forename: Wanfeng
authors.initials: W
authors.lastname: Hu
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.|Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, China.
authors.forename: Siyi
authors.initials: S
authors.lastname: Pan
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry* / Q000302:isolation & purification; D028463:Cucumis melo / Q000737:chemistry*; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000737:chemistry*; D006358:Hot Temperature; D006801:Humans; D015416:Maillard Reaction; D010940:Plant Proteins / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D000069453:Ultrasonic Waves
chemical_list: D010940:Plant Proteins; D004156:Catechol Oxidase
keywords: activity; oriental sweet melon; polyphenol oxidase (PPO); structural change; ultrasound