Fate of vitamin C in commercial fruit juices

摘要: Vitamin C occurs in relatively high concentrations fresh and processed fruits vegetables but is found to a lesser extent animal tissues animal-derived products. Nearly 90 % of vitamin the human diet obtained from this can be indirect by way commercially prepared fruit juices. These juices are often enriched with which has been synthetically prepared. There wide range such on New Zealand market, they significant source dietary for many population. The focus research Keri juice present study monitors fate during storage up best-before date, under other consumption situations. Two methods were adopted determining ascorbic acid (AA, chemical identity C). titrimetric method, based upon reduction dye 2,6-dichlorophenolindophenol AA acidic solution, liquid chromatography, used separate its immediate oxidation product dehydroascorbic acid. In latter method these two analytes measured independently. chromatography was less successful than simpler so most work done titration. However, concentration acid, activity vivo, remained uncertain. Moreover, could not applied purple anthocyanin concentrations, like blackcurrant, because colour change at titration end point detected. pH adjustment ineffective, decolourisation charcoal led rapid complete destruction AA. time manufacture always much higher claimed labels. Storage nine months room temperature resulted loss between 37 68 %, depending exposure fluorescent light. more dominant factor light exposure. kinetics loss, straight lines, easily explained an aerobic model degradation oxygen diffusing across polyethylene tetraphthalate bottle wall. Overall, label claims made defensible terms it took least 100 days before susceptible fell below value. This drinks fast moving consumer goods