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Keywords:

  • edible films;
  • whey protein;
  • ascorbic acid;
  • oxygen scavenger;
  • kinetics

Abstract

BACKGROUND

Incorporation of ascorbic acid (AA) into whey protein isolate (WPI) films has been shown to increase the film's ability to protect foods from oxidation. The O2-scavenging function of AA-WPI films could be triggered upon being placed in contact with food products. Several food-related factors hypothesized to act as triggering mechanisms for activating the O2-scavenging function of AA-WPI films were investigated, including change of water activity (aw), pH and/or metal catalyst presence.

RESULTS

Rate of O2 scavenging of AA-WPI films was observed to most closely follow first-order kinetics. The film aw level was found to control the O2-scavenging rate. At high aw levels, O2 scavenging occurred at a desirably rapid rate. Food models with pH 7.4 produced the fastest O2-scavenging rate. The slowest rate at pH 3.0 was due to the lower concentration of O2-sensitive ascorbate monoanion. The presence of Cu2+ accelerated AA oxidation at high aw level.

CONCLUSION

The desirable activation of oxygen scavenging in AA-WPI film at high aw and neutral pH in the presence of metal catalyst suggests that such AA-WPI films can be used to protect foods that have the highest vulnerability to oxidation. © 2013 Society of Chemical Industry