幾丁聚醣與添加抗壞血酸處理對截切‘紅龍’楊桃櫥架壽命與品質之影響

Effects of Chitosan Coating and Ascorbic Acid on the Shelf Life and Quality of Fresh-cut 'Honglong' Carambola Fruit

楊桃（Averrhoa carambola L.）果實具有五個稜角，橫切片呈星形，具有發展為截切水果的潛力。褐變與微生物滋生為截切楊桃劣變的主要因子。本試驗目的為探討幾丁聚醣被膜與添加抗壞血酸處理對截切‘紅龍’楊桃保鮮及延長櫥架壽命之效果。2%幾丁聚醣被膜顯著抑制截切‘紅龍’楊桃總生菌數之增加，於5°C貯藏12天內皆不超過10^5 CFU．g^(-1)之食品安全門檻，且亦顯著延緩主要汙染源的酵母及黴菌類之滋生。2%幾丁聚醣被膜添加1%或2%抗壞血酸處理可以延緩截切‘紅龍’楊桃褐化，其效果可由官能品評辨識；以數位影像技術（digital imaging method）鎖定外果皮褐化發生部位，測定亮度（L*）值，只有幾丁聚醣未添加抗壞血酸之對照組於5℃貯藏12天，L*值下降至33，而只添加1%抗壞血酸之L*值維持在36，添加2%抗壞血酸效果最佳，L*值維持在38，由整體接受度評分來評斷櫥架壽命，只用2%幾丁聚醣被膜之對照組櫥架壽命為2天，添加1%及2%抗壞血酸則延長至8天，且不影響楊桃切片之失重率、硬度、可溶性固形物、可滴定酸，可同時改善截切楊桃褐化及微生物滋生兩大品質劣變問題。 Carambola (Averrhoa carambola L.) fruit, characterized by five ribs and formed a star-shape slice after a cross-section cut, is considered of great potential for utilization in fresh-cut production. Browning and microbial contamination are the two main causes of deterioration in fresh-cut carambola. The objective of this research was to investigate the effects of chitosan coating and incoperation of ascorbic acid on freshness retention and shelf life extension. Results show that fresh-cut 'Hong-Long' carambola coated with 2% chitosan significantly suppressed the increase in the total bacterial count (＜10^5 CFU．g^(-1), the safety threshold of fresh fruit) throughout the 12 days storage at 5°C. Furthermore, chitosan coating also retarded the proliferation of yeasts and molds as the two main categories of microbial spoilage on fresh-cut carambola. Using 1% or 2% ascorbic acid incorporated with 2% chitosan coating delayed the browning of fresh-cut fruits, based on the assessment of sensory evaluation or L*a*b* system analysis of digital imagings on the cutting edge of the exocarp. The control slice coated with 2% chitosan and without ascorbic acid exhibited severe browning and reduced L* value to 33 after storage for 12 days, as compared with L* values of 36 and 38 in fruits with additional 1% and 2% ascorbic acid, respectively. Shelf life was 2 days for those coated with 2% chitosan. An additional of 2% ascorbic acid extended shelf life to 8 days, had no negative impact on weight loss, firmness, total soluble solids, and titratable acidity, and could delay discoloration and microbial proliferation in fresh-cut carambola.