Effects of Different Processing Temperatures-Time Frame on the Total Soluble Solids and Titratable Acidity of Three Plant-based Liquid Food Products: A Comparative Analysis

The effects of different thermal processing techniques (temperature-time frames) on total soluble solids (TSS) and titratable acidity (TA) of three plant-based liquid food samples (pawpaw juice, tomato juice, soya milk) were compared in this study. The juice samples were extracted with motorized juice extractor and the soya milk was prepared by cold maceration. The samples were divided into two groups: (1) low temperature–long time (LTLT), (2) High temperature-short time (HTST). The LTLT group was further divided into lots (L₁, L₂, and L₃) and was pasteurized at 65 ℃, for 10 minutes (L1), 20 minutes (L2) and 30 minutes (L3).  HTST group was divided into two lots (L₄ and L₅). L₄ was pasteurized at 90 ℃ for 6 seconds and L₅ was pasteurized at ultra-high temperature (UHT), 140 ℃ for 2 seconds. Each lot was cooled down to 4 ℃ in a refrigerator. Biochemical analyses of the samples followed standard methods. Results showed that at LTLT, TSS decreased as the processing time increased for all the foods. At HTST, the highest loss in TSS from 5.43 ^OBRIX to 5.18 ^OBRIX (4.60 %) was recorded in tomato juice at 90 ^oC, 6 seconds. Soy milk increased in TSS from 2.15 ^OBRIX to 2.27 ^OBRIX (5.58 %). TA decreased as the processing time increased in tomato juice. TA in pawpaw increased from 0.63 to 0.66 (4.76 %) at 60 ⁰C, 10 minutes, stable at 65 ^oC, 20 minutes and decreased thereafter. Soy milk recorded increasing TA across the temperature-time frames.