Food browning is undesirable as it causes deterioration in food quality and appearance. This phenomenon was related to polyphenol oxidase (PPO), which catalyzes conversion of phenolic compounds into -quinones. The present work evaluated the use of chemical and natural anti-browning agents to prevent the browning of ginger PPO. Sodium metabisulfite (5 mM) is a better chemical inhibitor compared to l-cysteine and sodium chloride as 55.00% of ginger PPO inhibition was achieved. The percentage of inhibition increased as the concentration of anti-browning agents increases. The addition of heated onion, chili pepper and pineapple extracts exhibited a stronger inhibitory effect on ginger PPO than unheated extracts. Heated chili pepper extract was the best natural inhibitor found in this study and it inhibited the ginger PPO (47.97%) mixed-competitively. Natural anti-browning agents have potential to be used to control the browning of ginger as well as other vegetables and fruits.

Honey, pineapple, chilli pepper, and onion extracts were investigated for their ability to inhibit enzymatic browning in sweet potatoes. Honey had the highest inhibition (41.39%–48.0%), comparable with l‐ascorbic acid. Heated onion extract increased polyphenol oxidase (PPO) inhibition by 2.5‐fold when 4‐methylcatechol was used as substrate. However, percentage inhibition decreased drastically (7.42%–19.67%) when heated pineapple extract was used. Fresh chilli pepper extract showed a higher PPO inhibition (45.97%) than that of heated extract. These natural inhibitors were also compared to synthetic inhibitors that ranked: l‐cysteine > l‐ascorbic acid > sodium chloride. l‐cysteine was the most effective chemical inhibitor which inhibited up to 70.4% PPO activity. It was found that natural inhibitors extracted from common food items are able to control the enzymatic browning of sweet potato. These natural inhibitors extracts are safe to human and would also be potentially replaced chemical inhibitors for the preservation of other fruits as well as vegetables. Practical applicationsFruits and vegetables are prone to enzymatic browning. This is caused by the oxidation reaction of endogenous phenolic compounds, catalyzed by PPO. PPO oxidizes o‐diphenols to o‐quinones, which will turn into brown pigments as the o‐quinones polymerize immediately. Enzymatic browning of fruits and vegetables always take places after harvest, during the post‐harvest processing as well as storage. Thus, identification of suitable and acceptable inhibitors is important in order to prevent food browning and to increase the food marketability for food industry. This study indicated that sweet potato PPO was successfully inhibited by extracts from common food items such as honey, chilli pepper, pineapple, and onion which are safe for human consumption. Thus, these natural inhibitors could also be applied to similar food materials such as apples, star‐fruit, and normal potatoes. We expect that the inhibitors examined in this study can be isolated and identified as lead molecules for the development of natural anti‐browning food additives.

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