Inhibitory effect and the involved mechanism of furaneol on enzymatic browning of potatoes

Enzymatic browning is an important issue impacting the shelf life of fresh-cut potatoes. Using browning inhibitors is an effective method to solve the issue. This research aimed to identify novel and safe inhibitors of enzymatic browning. The research first investigated the inhibitory role of furan compounds in enzymatic browning, then explored the anti-browning effect of furaneol and the involved mechanism. Among the eight tested furan compounds classified as flavorings in food additives, seven showed anti-browning effects, of which three demonstrated superior efficacy in delaying browning compared to the others. Based on the efficacy and odor, furaneol as one natural flavor composition of fresh fruit was selected to be further investigated. At 4 °C, control potatoes browned on day 1. However, furaneol at concentrations of 4 and 8 mM prevented the fresh-cut potatoes from browning for up to 10 d, and their anti-browning efficacies reached that of sodium bisulfite. Sensory evaluation showed the treated fresh-cut potatoes exhibited a slight and acceptable sweet aroma, which quickly disappeared after heat cooking. Further research revealed furaneol reduced the activity of polyphenol oxidase (PPO), chelated Cu 2+, and acted as a mixed-type inhibitor of PPO with competitive inhibition being the dominant. Circular dichroism analysis indicated furaneol decreased α-helix content, increased the β-fold content, and altered the secondary structure of PPO. Fluorescence quenching data showed furaneol can form complexes with PPO, quench the fluorescence produced by PPO and change its tertiary structure. Molecular docking suggested that furaneol could enter the active center region near copper ions and interact with surrounding amino residues through van der Waals force, pi-alkyl interactions and carbon-hydrogen bonds. Furaneol can also cause the brown pigment colorless to a certain extent. Moreover, furaneol addition also improved the antioxidant capacity of enzymatic browning reaction system. Our study first reported the inhibitory effect of furan compounds on enzymatic browning and furaneol has great potential as an anti-browning inhibitor for fresh-cut produce in future.