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

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.