Optimization of Formulation in Dietary Gaz Fortified with Stevioside and Ganoderma locidum using Response Surface Methodology (RSM)

Background and Objectives: Nowadays, production and consumption of functional and dietary foods have increased. Since carbohydrates are one of the most important sources of increasing daily calories, food industries are focused on decreasing use of this important source and replacing it with non-calorie sweeteners. This objective of this study was to decrease sugar quantities in Gaz production, promoting its nutritional values by use of stevia and Ganoderma lucidum.  Materials & Methods: Effects of replacements of stevia (0–100%), Ganoderma (0–1%) and cooking temperature (70–90°C) on Gaz qualitative and textural characteristics were investigated. Optimization of the fortified diet Gaz formulation was carried out using response surface methodology and Design-Expert Software. After determination of the optimum point, results of Gaz physicochemical, texture and sensory characteristics were analyzed using SPSS Software. Results: In general, increases in density and decreases in cohesiveness, springiness and chewiness of the treatments were observed by increasing stevia replacement levels. Increases in Ganoderma levels increased hardness and gumminess and decreased springiness and chewiness. Results of color assessment revealed that increases in stevia and Ganoderma levels decreased indices of L* and b*. The optimum conditions (p < 0.05) included 41% of stevia and 0.14% of Ganoderma at 90 °C of cooking temperature as well as 37% of stevia and 0.12% of Ganoderma at 85 °C of cooking temperature. Comparisons between the optimized and control samples showed that protein, fat, potassium, phosphorus and vitamin D contents of the fortified diet Gaz were higher than those of the control sample. For sensory evaluation, no significant differences were seen between the optimized and control samples (p<0.05). Conclusion: In general, combination of stevia and G. lucidum resulted in decreased sugar contents and improved nutritional aspects of the novel formulated Gaz.