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Role of ascorbic acid in the inhibition of polyphenol oxidase and the prevention of browning in different browning‐sensitive Lactuca sativa var. capitata (L.) and Eruca sativa (Mill.) stored as fresh‐cut produce
Author(s) -
Landi Marco,
Degl'Innocenti Elena,
Guglielminetti Lorenzo,
Guidi Lucia
Publication year - 2013
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.5969
Subject(s) - ascorbic acid , browning , polyphenol oxidase , lactuca , chemistry , food science , eruca , catechol oxidase , peroxidase , polyphenol , point of delivery , biochemistry , botany , antioxidant , enzyme , biology
BACKGROUND Polyphenol oxidase ( PPO ) and, to a minor extent, peroxidase ( POD ) represent the key enzymes involved in enzymatic browning, a negative process induced by cutting fresh‐cut produce such as lettuce ( Lactuca sativa ) and rocket salad ( Eruca sativa ). Although ascorbic acid is frequently utilised as an anti‐browning agent, its mechanism in the prevention of the browning phenomenon is not clearly understood.RESULTS The activity of PPO and POD and their isoforms in lettuce (a high‐browning and low‐ascorbic acid species) and rocket salad (a low‐browning and high‐ascorbic species) was characterised. The kinetic parameters of PPO and in vitro ascorbic acid– PPO inhibition were also investigated. In rocket salad, PPO activity was much lower than that in lettuce and cutting induced an increase in PPO activity only in lettuce. Exogenous ascorbic acid (5 mmol L −1 ) reduced PPO activity by about 90% in lettuce. POD did not appear to be closely related to browning in lettuce.CONCLUSION PPO is the main enzyme involved in the browning phenomenon; POD appears to play a minor role. The concentration of endogenous ascorbic acid in rocket salad was related to its low‐browning sensitivity after cutting. In lettuce, the addition of ascorbic acid directly inhibited PPO activity. The results suggest that the high ascorbic acid content found in rocket salad plays an effective role in reducing PPO activity. © 2012 Society of Chemical Industry