Optimization of sodium metabisulphite addition and vacuum evaporation temperature on production of sweet sorghum juice (Sorghum bicolor L. Moench) concentrate using response surface methodology

Sweet sorghum (Sorghum bicolor L. Moench) is one of the sugar source plants. The purpose of sorghum juice evaporation is to raise total soluble solid content (°Brix). The process produces a dark-brown color concentrate. The aim of this study was to optimise the addition of sodium metabisulphite and the temperature of evaporation to enlighten the color of sweet sorghum concentrate. This current study employed Respond Surface Methodology (RSM) using Central Composite Design (CCD) with 2 factors include the addition of sodium metabisulphite and evaporation temperature. The major responses in this research were the value of Total Soluble Solid (TSS) (°Brix) and the lightness value (L∗). The result showed that the optimum treatment was a combination of 0.50 g/L sodium metabisulphite and 83.71°C vacuum evaporation temperature. The optimum condition resulted sweet sorghum concentrate with pH value of 6.01, TSS of 42.40°Brix, lightness of 36.13, redness of +0.08, yellowness of +17.08, turbidity of 1227 NTU, viscosity of 10.33 cP, density of 1.182 gr/mL and yield of 28.64%, respectively.