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In this research, response surface based on central composite design (3-factor 5-level) was applied to estimate the efficacy of independed variables on quality indexes (depended variables) of raw beet juice. Hence, the effect of different durations (20-100 min), temperatures (40-55 °C), and at various concentration level of pectinase (0.001-0.02 % v/v) on viscosity, color, turbidity and purity of sugar beet juice were investigated and successfully coordinated by a second-order polynomial model (R² > 0. 85). The experiments indicated that the temperature was the most important variable affecting the characteristics of the raw juice as it exposes a significant effect on the responses. The optimum enzymatic treatment condition from the study was at 0.012 % enzyme concentration at 49 ֯C for 65 min.

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In this research, response surface methodology based on 3-factor 5-level central composite design was used to determine the effect of refining pretreatment variables on quality indexes of beet molasses. Hence, the effect of bentonite concentration (2-10 g/L), gelatin concentration (0.01-0.1 g/L) and pH (3-7) on turbidity, color, concentration of colloids (CCs) and ash of beet molasses were studied and well fitted by a quadratic polynomial model (R² > 0. 85). The results showed that the pH was the main factor affecting the purification indexes as it had a significant effect on all responses. Bentonite and gelatin as two common clarifying agents improved the quality of molasses, although the ability of bentonite was much higher. The optimum condition for purification pretreatment was found as 8.3 g/L for bentonite, 0.08 g/L for gelatin and 4.03 for pH which were determined on minimization of the turbidity, color, concentration of colloids (CCs) and ash. At this condition, the turbidity, color, ash and concentration of colloids were calculated as 12.1 NTU, 2573 IU, 2.7, 0.9 g/L respectively.
 

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In this study, stevia and guar were used as alternatives for sucrose and fat in frozen yogurt formulation, respectively. For this purpose, a completely randomized block design with 0-100% replacement levels for stevia and 0, 0.25 and 0.5 % for guar gum was used. To investigate the effect of applied treatments, the physicochemical properties of frozen yogurt including acidity, viscosity, overrun, firmness, first drop time of melting and amount of melting were measured. The results showed that the viscosity decreased by increasing the level of stevia as a replacement for sucrose, while, overrun increased with increasing levels of sucrose substitution with stevia. All levels of stevia and guar replacement resulted in a significant increase in firmness. Also, with increasing the concentration of stevia and guar gum, the first drop time and stability of the sample increased. The results showed that stevia and guar gum are good alternatives to sucrose and fat, respectively, and samples containing 75-100% stevia and 0.5% guar were identified as the optimal treatment.