不同温度对超高压处理鲜榨生菜汁贮藏稳定性的影响

Effect of Different Storage Temperatures on Storage Stability of Fresh Lettuce Juice Treated with Ultra-High Pressure

为探究不同冷藏温度(0、4、8℃)下超高压(ultra-high pressure,UHP)(600 MPa、2 min)处理鲜榨生菜汁(fresh lettuce juice,FLJ)的贮藏稳定性,分别在0、5、10、15、20、25、30 d取样,测定微生物指标、理化指标、色泽、叶绿素、物性指标和稳定性指数等,并分析其变化规律。结果表明,UHP处理后FLJ于0、4、8℃贮藏30 d期间总好氧菌数量小于100 CFU/mL,霉菌和酵母菌数量小于10 CFU/mL,均在国家标准(GB 4789.2—2016《食品安全国家标准食品微生物学检验菌落总数测定》和GB 4789.15—2016《品安全国家标准食品微生物学检验霉菌和酵母菌计数》)限量范围内。与初始相比,0、4、8℃贮藏30 d,FLJ色泽由绿色变为棕褐色,总叶绿素含量分别下降18.96%、46.84%、67.07%;4、8℃贮藏30 d FLJ的pH值分别降低至4.66±0.08、4.37±0.08;0、4、8℃贮藏30 d FLJ的总可溶性固形物含量变化不明显;固形物体积、粒径、表观黏度均增大,稳定性和浑浊度降低。随着贮藏温度上升,FLJ各项参数的变化速率加快,其中0℃贮藏变化趋势最为平缓。综合考量FLJ的色泽、理化和稳定性指标,0℃可作为FLJ的最佳贮藏温度,4℃和8℃贮藏货架期分别可达15 d和10 d,本实验可为鲜榨蔬菜汁加工和贮藏提供技术参考。

To investigate the storage stability of fresh lettuce juice treated with ultra-high pressure under different temperatures(0,4 and 8℃),microbial and physicochemical parameters,color,chlorophyll content,physical indicators and turbiscan stability index were determined every five days for 30 days.The results indicated that the total aerobic bacterial count and the total count of yeasts and molds in FLJ remained below less than 100 and 10 CFU/mL during 30 days of storage,respectively,both of which were within the national standard range.After 30 days of storage at 0,4 and 8℃,the color of FLJ changed from green to dark brown,and the total chlorophyll content decreased by 18.96%,46.84%and 67.07%respectively.After 30 days storage at 4 and 8℃,the pH decreased to 4.66±0.08 and 4.37±0.08,respectively.The total soluble solid(TSS)content of FLJ was not significantly changed,but the pellet volume,particle size and apparent viscosity were increased and the stability and turbidity were decreased.As the storage temperature rose,the change rate of all the parameters tested accelerated,while the change was the slowest at 0℃.Considering the color,physicochemical parameters and stability indicator of FLJ,the optimal storage temperature for FLJ is 0℃,and the shelf life of FLJ at 4 and 8℃are 15 and 10 days,respectively.The results of this study can provide a technical reference for the processing and storage of fresh lettuce juice.