Technological improvement of the Sorghum saccharatum syrup production by membrane technologies

Abstract

Easy-to-handle and effective methods of juice clarification and concentration by membrane technologies are still under exploration. The current article presents results of research on the technological development of an alternative natural sweetener of high biological value and improved organoleptic properties. Sorghum saccharatum stem juice is used in research. It is pre-clarified enzymatically with α-amylase and glucoamylase, clarified by ultrafiltration, and concentrated by the direct contact membrane distillation in various temperature ranges. The study shows the efficacy of membrane methods for improving juice purity, total soluble solids (TSS), and total sugar (TS) content in the syrup obtained. Clarification depends on membrane characteristics at the beginning of the process, as there are no differences at the end of it. Juice concentration at high-temperature differences allows to accelerate the process by approx. 60% comparing to low-temperature differences. A lower temperature difference (∆Т = 20–30°С) in the concentration process results in a longer process and syrup acidisation, whereas a higher temperature difference (∆Т = 70°С) affects physicochemical properties of syrup due to local overheating and formation of Maillard reaction products. The juice concentration at ∆Т = 50–60°С allows to obtain high values of total soluble solids without significant degradation of physicochemical and organoleptic properties.