幾丁聚醣處理對輕度加工番石榴楔形切塊櫥架品質影響之研究

Abstract

由於工商業的發達，輕度加工蔬果由於其新鮮即食的特點，需求量日益增加。這些輕度加工蔬果在販售前經過一些清洗、去皮、截切和簡單的調理處理，雖保有蔬果之生鮮，卻也因蔬果本身細胞仍具活性，造成質地改變、酵素褐變、以及微生物增殖等問題，而導致品質的劣變。 由於幾丁聚醣具有抑制微生物的作用，同時幾丁聚醣溶液可在蔬果的表面形成半透膜，因此本論文研究之目的在探討使用不同溶劑配製之幾丁聚醣溶液對番石榴楔形切塊品質保存之影響，期望延長輕度加工截切番石榴切塊在市場上之櫥架壽命。 結果發現，若是珍珠拔楔形切塊未經任何處理直接低溫貯藏，在貯藏第3天總生菌數即超過每公克生菌數105，不符衛生署生食水果類之衛生標準。使用1.0%和2.0%幾丁聚醣溶液處理組可分別延長總生菌數之櫥架壽命至6天及7天；幾丁聚醣乳酸溶液處理的抑菌效果則稍差，分別為5天及6天。不論是0.5%和1.0%幾丁聚醣醋酸溶液或乳酸溶液處理，皆有效降低番石榴楔形切塊的失水率至1.1%和1.2%，而2.0%幾丁聚醣溶液處理則和對照組相同，失水率達4%以上。使用幾丁聚醣溶液處理則會抑制番石榴楔形切塊的維生素丙含量隨貯存時間延長而上升之現象。幾丁聚醣溶液處理可以使珍珠拔楔形切塊的軟化率趨緩，以1.0%幾丁聚醣醋酸溶液處理樣品之效果最佳。而1.0%、2.0%幾丁聚醣乳酸溶液之處理對相同樣品之硬度皆有維持之效果。幾丁聚醣溶液為淡黃色，珍珠拔楔形切塊經處理後會輕微影響果肉面的色澤，對果皮面則無明顯影響，肉眼亦不易分辨其色澤差異。溶液濃度愈高，顏色愈深。以幾丁聚醣乳酸溶液的色澤較淡。

The demands of minimally processed fruits and vegetables increased rapidly in recent years due to their “fresh to eat” characteristics. Unit operations of minimally processed fruits and vegetable, such as washing, peeling, and cutting, preserve the freshness of fruits and vegetables, however, the sensory qualities, such as color, texture, flavor, etc, may be deteriorated by physico-chemical reactions and bacterial growths during processing and storage. The antimicrobial function of chitosan has been widely studied by many researchers. The objective of this study is to investigate the effect of chitosan solution pretreatment on the quality characteristics of minimally processed guava wedges and shelf-lives of the respect processed products. ‘Jen-Ju Bar’ guava, the most popular fresh-eat guava cultivar in Taiwan, was used in this study. Fresh-cut guava wedges dipped in 1% and 2% chitoson dissolved in 0.05M acetic acid solution for 10min, then stored at 5±1℃, the total microbial counts of the wedges were be able to control under 105 for 6 and 7 days respectively. Similar treatments of guava wedges using lactic acid instead of acetic acid demonstrates that the control of total microbial count to only 5 and 6 days shelf-life respectively. Nevertheless, both chitosan solution treatments show better microbial control than non-treatment samples (<3 days shelf-life). Higher moisture loss of guava wedges stored at 5±1℃ for 7 days are observed in 2% chitosan solution (both acetic acid and lactic acid solutions) treatments (>4%) as compared to 0.5% and 1% chitosan solution treatment (1.1% and 1.2% moisture loss, respectively). This is due to the higher water sorption characteristics of 2% chitosan film on wedge surface than 0.5% and 1% chitosan, which accelerate the water evaporation rate, and resulted in higher moisture loss of the wedges. Little color change was observed on the guava skins treated with different concentration of chitosan. When analyzed color of the guava wedges with colorimeter, the darkness of guava flesh tend to increase as the chitosan concentration of treated solution increased, however, no visual differences were observed. Chitosan solution treatments also demonstrate the decrease of soften rate in guava wedges. Based on the experiment results of microbial control, moisture loss, and softening rate, 1% chitosan-acetic acid solution treatment was considered to be the ideal pretreatment solution for minimally processed guava wedges with both sensory and safety shelf-life for 6 days.