Preservation of cut pineapples and juices from two varieties using natamycin

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Fresh-cut fruit and juice are increasingly becoming popular with consumers because of its convenience. A major challenge faced by this industry is the appropriate method of preservation to maintain the quality of fresh -cut fruits and juices so that the shelf-life is long enough to ensure efficient marketing. This study was done to evaluate the effects of natamycin on the physiochemical, sensory properties and microbial stability of cut pineapple and juices from MD-2 and Sugar loaf during thirty six days of storage. Natamycin concentration of 10 and 20ppm were used for juices. Optimization of condition for the preservation of cut pineapple was with the help of response surface methodology. The central composite design with 24 experimental combinations was used to optimize the factors and responses. The optimum factors were 1cm thickness of cut pineapple, a time of 2 minutes, natamycin concentration of 30 ppm and a volume of 100 ml. The actual natamycin concentration of 10 ppm which diffused into the cut pineapple after soaking in 30 ppm for 2 minutes was used for the treatment of bulk storage of cut pineapple under refrigeration and ambient conditions. Sensory analysis, determination of pH, titratable acidity, Vitamin C, Brix as well as the enumeration of total moulds and yeasts were carried out on both treated and control samples. The cut pineapple and juices were analysed at 3-day interval of the 36 days storage period. There were significant difference (p≤0.05) in the pH, tittratable acidity, Brix and vitamin C of natamycin treated cut pineapples and juices and their respective controls. However, there were no significant difference in the physiochemical properties of the juices treated with 10 and 20ppm. The natamycin treated cut pineapple and juices were preferred during sensory evaluation, while yeasts and moulds were not detected throughout the storage period. On the other hand, control samples of cut pineapples and juices from the 9th day till storage period were unacceptable by the panellist as they were also highly contaminated with yeast and moulds. Natamycin proved to be suitable and effective antifungal preservative which increases the shelf-life of cut pineapple and juices without changing the characteristics of the product. Comparative analyses showed that there were significant differences (p≤ 0.05) in vitamin C, total soluble sugars and pH of MD2 and sugar loaf varieties of the pineapple whiles differences in the titratable acidity, yeasts and moulds growth of MD-2 and sugar loaf varieties were not significant (p ≥ 0.05).
A thesis submitted to the Department of Food Science and Technology in partial fulfilment of the requirements of Master of Science in Food Science and Technology