Preservation and evaluation of spiced chayote juice using hurdle technology

Abstract Chayote (Sechium edule) is a perennial climbing plant, belonging to the Cucurbitaceae family and is neglected or underutilized as a food or as a raw material in the food industry because of its bland taste. This bland taste can be overcome by blending with a suitable substrate such as sugarcane juice along with natural flavouring. However, this blending represents a preservation problem for the spiced juice, since both chayote juice and sugarcane juice are prone to microbial attack. Therefore, an attempt was made in the present study to preserve the spiced chayote juice by employing different hurdles i.e. pasteurization temperature (70 °C and 80 °C) and pasteurization time (10 and 20 min) followed by the addition of different concentrations of potassium metabisulphite (KMS) (200, 300 and 400 ppm). The samples so prepared were filled into glass bottles and stored under refrigeration for forty-five days. As the storage period proceeded there were significant decreases in pH, total protein content, total phenolic compounds, antioxidant activity, reducing power, metal chelation, tannin content, ascorbic acid content and overall acceptability, whereas there were significant increases in TSS (total soluble solids), titratable acidity, reducing sugars, total sugar, TPC (total plate count) and MIC (minimum inhibitory concentration). A cluster analysis of the data revealed that the pasteurization temperature exerted the most significant effect on the physicochemical and sensory characteristics of the spiced chayote juice as compared to the pasteurization time and KMS concentration, which failed to fall into the separate and respective clusters. In a nutshell, it was concluded that spiced chayote juice can be successfully preserved using hurdle technology (pasteurizing at 70 °C for 10 min followed by the addition of 400ppm KMS).摘要 佛手瓜（Sechium edule）为多年生攀援植物，隶属于葫芦科（Cucurbitaceae），因风味寡淡常被忽视或未充分用作食品及食品工业原料。可通过与甘蔗汁等适宜基质复配并添加天然风味剂改善其寡淡风味，但该复配调味汁存在保鲜难题：佛手瓜汁与甘蔗汁均易受微生物侵染。为此，本研究尝试采用栅栏技术（hurdle technology）对调味佛手瓜汁进行保鲜，设置两类处理变量：巴氏杀菌温度（70℃与80℃）、巴氏杀菌时长（10 min与20 min），并添加不同浓度的焦亚硫酸钾（KMS，potassium metabisulphite）（200、300及400 ppm）。将制备所得样品灌装于玻璃瓶中，于冷藏条件下贮藏45天。结果显示，随着贮藏期延长，样品的pH值、总蛋白质含量、总酚类物质含量、抗氧化活性、还原能力、金属螯合能力、单宁含量、抗坏血酸含量及综合接受度均显著下降；而总可溶性固形物（total soluble solids, TSS）、可滴定酸度、还原糖、总糖、总平板菌落数（total plate count, TPC）与最低抑菌浓度（minimum inhibitory concentration, MIC）则显著升高。对数据的聚类分析结果表明，相较于杀菌时长与焦亚硫酸钾添加浓度（二者未单独形成各自的聚类簇），巴氏杀菌温度对调味佛手瓜汁的理化与感官特性影响最为显著。总而言之，本研究证实，采用栅栏技术（70℃下巴氏杀菌10 min并添加400 ppm焦亚硫酸钾）可成功实现调味佛手瓜汁的保鲜。