Abstract
There has been considerable interest in using natural polyphenol oxidase (PPO) inhibitors to control browning in fruit and vegetable products. p-Coumaric acid (pCA), a common secondary metabolite of plants, has been studied as an inhibitor of PPOs/tyrosinases from several foods (e.g., mushroom, apple, and potato). However, studies on the use of pCA for the inhibition of PPO-initiated browning in actual food systems are limited. Therefore, a study was carried out to ascertain the efficacy of using pCA to limit PPO-initiated browning in fresh potato juice. The extent of browning inhibition by pCA was shown to be reaction system-dependent. Browning in potato juice was unexpectedly enhanced by the addition of pCA. This was interpreted as pCA acting as an alternative substrate with significantly higher browning efficiency; extent of browning under this condition was higher than that observed in the native potato juice. The addition of pCA to any of the model reaction mixtures (i.e., those containing semi-purified enzymes and substrates) significantly inhibited browning. The discrepancy in pCA effects on browning inhibition in different reaction systems is postulated to be mainly due to non-enzyme and non-substrate components in potato juice that participate in the post-PPO reaction sequences, which ultimately lead to brown color formation.
Highlights
Enzymatic browning leading to unwanted tissue discoloration is a significant concern in the food industry because it negatively affects food quality and lowers consumer acceptability
Initial experiments were aimed at characterizing color development in the model system, which is based on potato polyphenol oxidase (PPO) and substrates endogenous to the potato
The present study evaluated the efficacy of using p-Coumaric acid (pCA) to limit PPO-initiated browning in fresh potato juice
Summary
Enzymatic browning leading to unwanted tissue discoloration is a significant concern in the food industry because it negatively affects food quality ( appearance) and lowers consumer acceptability. Unwanted enzymatic browning results in large amounts of food waste. This browning (production of melanin pigments) is a consequence of a series of reactions initiated by the polyphenol oxidase (PPO)-catalyzed phenolic compound oxidation to quinones [1]. Sulfites were among the most widely used anti-browning agents for fresh fruit and vegetable products, but their use was banned by the FDA in 1986 due to health concerns. Ascorbic acid is probably the most widely used anti-browning agent in the food industry. Ascorbic acid works by reducing quinones back to the corresponding di-phenols and it only temporarily controls browning [2].
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