| Summary: | 碩士 === 國立嘉義大學 === 食品科學系研究所 === 104 === Excess harvest is one of the problems of persimmon storage because it is kind of seasonal fruit. Dried persimmon is one of the common processed product. In this study, frozen persimmon used as the raw material to increase the use of persimmon. Fresh purée prepared by pre-treatments including washing, de-stalking, peeling, cutting, crushing. Purée was blanched under steam and 4 types of additives (sodium metabisulphite, L-ascorbic acid, sodium erythorbate and L-cysteine) were added respectively. Persimmon purée were stored at room temperature or under refrigeration (4℃) condition for 3 months after being processed with traditional thermal treatment (80℃,10 min) and high hydrostatic pressure process (HPP, 20℃,450 MPa for 3 min) respectively. The effects of different process treatment and additives on quality of persimmon purée were discussed in this study. The result showed that there was no significant differences on the general analysis between fresh and frozen persimmon but frozen persimmon fruit cannot maintain the original hardness and brittleness. However, there was no effect on the texture of manufacture persimmon purée products. Besides, no significant differences in soluble solid content, moisture content, water activity, pH value and titratable acid content after blanching, traditional thermal treatment and high hydrostatic pressure process. In color analysis, purée turned into yellow after traditional thermal treatment, the color of orange was faded (a*, b* value decreased). On the other hands, the L* value of group with L-ascorbic acid (44.4-48.6) were higher than others. There was no microbiology was detected after traditional thermal treatment and high hydrostatic pressure process. However, the total bacterial counts in untreated groups were up to 1.17-2.63 log CFU/g and 1.00-2.06 log CFU/g for yeast counts.
Within 3 months storage, package expansion occurred in untreated groups within 1 week under room temperature but HPP groups only occurred after 8 weeks. The total bacterial counts of HPP groups were up to 3.09 log CFU/g but no yeast was detected at all. No significant difference in general analysis during storage. All groups stored at refrigeration were generally better than room temperature in color analysis and better results obtained fresh purée treated with traditional thermal treatment and stored at low temperature. The groups of adding L-ascorbic acid were the best among them, with browning occurred. There were no significant differences in DPPH free radical scavenging ability after different processes but there was decrement in total phenolic content after traditional thermal processing. DPPH free radical scavenging ability of products decreased rapidly in room temperature. For the reason of adding antioxidants (L-ascorbic acid), DPPH free radical scavenging ability maintain at 95% and total phenolic content were the highest. They were trended to decrease in other groups during storage. Moreover, DPPH free radical scavenging ability of control group reduced to 41%. Traditional thermal treatment groups had the lowest polyphenol oxidase activities and decreased in HHP groups (30%). Sensory analysis showed that overall acceptability, the group of traditional thermal treatment with L-ascorbic acid stored at low temperature had pretty good palatability. In over all, it was found that HPP treatment could not prevent and addition of L-cystein might lead to browning in persimmon purée. It was effective to process persimmon purée by traditional thermal treatment combining addition of L-ascorbic acid as hurdle technology to inhibit browning and maintain color and extend its shelf life under room temperature for 3 months. Moreover, under refrigeration storage could extend the shelf life up to more than 3 months. In future, new products can be developed by this technique to provide more choices to consumers.
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