Effects of far-infrared radiation on activity and conformation of polyphenol oxidase of yam

Abstract

Objective: This study aimed to investigate the effect of far infrared radiation heating on the oxidase activity and conformation of polyphenol oxidase (PPO) of yam. Methods: By using different far infrared radiation temperatures, the effects of different far infrared radiation temperatures on yam PPO activity, browning degree, total phenol content and PPO conformation were studied. Results: When the radiation temperature is 260 ℃ PPO enzyme is not deactivated after 11 min. When the radiation temperature is higher than 260 ℃, PPO can be inactivated within 3~7 min. However, the browning degree and total phenol content did not change regularly with the increase of radiation temperature and treatment time. After far-infrared pretreatment, the contents of random curling and α-helix changed slightly with the increase of radiation temperature, while β-angle decreased and β-folding increased, indicating that far-infrared radiation changed the secondary structure of PPO. The ultraviolet spectrum of PPO shifted blue and fluorescence spectrum shifted red, indicating that the tertiary structure of PPO changed. Conclusion: Far-infrared radiation heating can change the conformation of yam PPO and eventually deactivate it.

Keywords

• far-infrared radiation
• yam
• polyphenol oxidase
• enzyme activity
• conformation