keywords: Ozonation, chitosan, fruit juices, yeasts, inactivaion
The major problem of fresh tropical juices is their limited shelf life. Food grade chitosan was investigated for its ability to inactivate both inherent microflora and challenge spoilage yeasts in three tropical fruit juices from orange, pineapple and water melon. Juices were prepared using Binatone juice extractor fitted with a special filter. The natural flora were isolated and enumerated following standard microbiological techniques. The juice was ozonated using an ozone gas generator with a concentration of 3.33 mg/min. Chitosan concentrations of 1000, 1500 and 2000 µg/ml were biocidal on bacteria with number reduced by > 0.5-1.27 log10CFU/ml immediately after addition to orange, pineapple, watermelon, and mixed fruits juices. At a concentration of 2000 µg/ml, non-detectable levels of Saccharomyces cerevisiae, Candida pulcherrima and Pichia fermentans were obtained in all juice samples stored at 28±20C showing the fungicidal nature at this concentration of chitosan. Concentrations of ≥1500 µg/ml were considered fungicidal in tropical fruits juices. The effect thus demonstrated chitosan can delay the spoilage of tropical fruits juices by both bacteria and yeasts at chill or ambient storage temperatures.
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