Triggering mechanisms for oxygen-scavenging function of ascorbic acid-incorporated whey protein isolate films


Correspondence to: Theeranun Janjarasskul, Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand. E-mail:



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.


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.


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