The investigation of bentonite and gelatin effects on purification indexes of raw sugar beet juice to production of liquid sugar

The present study deals with modeling the effects of bentonite (1.5-5 g/lit) and gelatin concentrations (0.02-0.08 g/lit) along with time (30-80 min) at constant temperature and pH on color, turbidity, adjusted purity, ash and invert sugar content of purified raw sugar-beet juice through face-centered central composite design of response surface methodology and to optimize these key parameters of the process. Our main goal was focused around the possibility to produce invert sugar directly from raw sugar-beet juice in conjunction with an alternate purification process in comparison with the conventional lime process used industrially. In this connection, second-order polynomial models were developed for dependent responses using least-square fit of regression analysis. The correlation coefficients of the developed response surface models were determined to be 0.90, 0.84, 0.90, 0.92, and 0.99 respectively for color, turbidity, ash content, adjusted purity, and invert sugar value of purified juice. The results of analysis of variance (ANOVA) revealed that all three independent parameters investigated have significant influence on raw beet-juice purity indexes. The optimum conditions were based on minimization of color, turbidity and ash content and maximization of invert sugar and adjusted purity at a constant temperature (75˚C) and pH (4.5) and it was found to be at bentonite concentration of 1.55g/lit, gelatin concentration of 0/04g/lit and reaction time of 68.6 min. At this optimum point, color, turbidity, ash, adjusted purity and invert sugar content were found to be 1973 ICU₄₂₀, 1.06 NTU, 0.54 %, 91.4 %, and 1.95 %, respectively.