Investigation of the possibility of using fructooligosaccharides as a sugar substitute in soluble coffee blends

In this thesis, the potential use of inulin and fructooligosaccharides as alternatives to refined sugar and coffee whitener in soluble coffee formulations was investigated. For this purpose, formulations consisting of coffee (9%), coffee whitener (15.97–35%), inulin (0–15%), fructooligosaccharides (40.97–60%), and stevia (0–0.03%) were modeled using response surface methodology based on a D-optimal mixture design, and an optimum formulation was determined considering eight response variables, including solubility, hygroscopicity, color, odor, taste, structure–consistency, astringency, and overall acceptability. The optimum formulation consisted of 9% coffee, 28.18% coffee whitener, 9.62% inulin, 53.18% fructooligosaccharides and 0.02% stevia. The optimized sample was evaluated through physicochemical and sensory analyses and compared with commercial soluble coffee products. Although the moisture content of the optimized sample (1.79%) was higher than that of commercial products, its dry matter (98.20%) and ash (1.19%) contents were lower; however, all parameters were within acceptable quality ranges. Solubility (96.8%), °Brix (3.8), wettability (257.73 s), and pH (6.01) values were comparable to those of commercial samples. The lower hygroscopicity of the optimized sample indicates greater resistance to moisture adsorption under storage conditions. In color analysis, L* and a* values were consistent with commercial products, whereas the higher b* value indicated a more pronounced yellow hue. The larger particle size of the optimized sample suggested a coarser granular structure associated with the freeze-drying technique. Bulk density, tapped density, and Hausner ratio values were lower, while the Carr index was higher; nevertheless, all samples were classified within the same flowability category. Sensory evaluation revealed that the optimized sample exhibited similar scores to commercial products in terms of color, odor, and taste, while achieving higher scores for structure–consistency. The astringency attribute was evaluated as relatively higher. Overall, the findings demonstrate that the optimized formulation is a feasible alternative to commercial soluble coffee products.