title: Triggering mechanisms for oxygen-scavenging function of ascorbic acid-incorporated whey protein isolate films.
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 (a(w)), 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 a(w) level was found to control the O₂-scavenging rate. At high a(w) 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 a(w) level.
  
  
  CONCLUSIONS
  The desirable activation of oxygen scavenging in AA-WPI film at high a(w) 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.
authors: Department of Food Science and Technology, University of California, Davis, CA 95616, USA.
authors: Theeranun
authors: T
authors: Janjarasskul
authors: Sea C
authors: SC
authors: Min
authors: John M
authors: JM
authors: Krochta
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry; D018857:Food Packaging; D005519:Food Preservation; D005782:Gels; D005990:Glycerol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008894:Milk Proteins / Q000737:chemistry*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010968:Plasticizers / Q000737:chemistry; D014867:Water / Q000032:analysis; D000067816:Whey Proteins
chemical_list: D000975:Antioxidants; D005782:Gels; D008894:Milk Proteins; D010968:Plasticizers; D000067816:Whey Proteins; D014867:Water; D003300:Copper; D005990:Glycerol; D001205:Ascorbic Acid
keywords: ascorbic acid; edible films; kinetics; oxygen scavenger; whey protein