Effects of D-Tagatose, inulin and stevia as sugar substitutes on the physical, chemical, rheological and sensory properties of dark chocolate

Chocolate is very popular among consumers of all ages. However, its consumption is limited for the obese and diabetic people due to its high energy and sucrose contents. Replacing sucrose by low digestible carbohydrates (LDCS) will result in lowering its energy content and glycemic index, as well as in preventing tooth decay. The objective of the present study was to investigate the effects of replacing sucrose with 2 sugar substitutes, namely, D-tagatose and inulin, on the physical, chemical, rheological and sensory properties of dark chocolate Inulin, a dietary fiber, and D-tagatose, a natural keto-hexose with a degree of sweetness similar to that of sucrose, were used as sucrose substitutes in dark chocolate formulas. The inulin:tagatose ratios in the mixtures were 100:0, 75:25, 50:50, 25:75, and 0:100. The physical, chemical, rheological, and sensory properties of chocolate samples prepared with the mixtures were determined. With a reduction in the inulin content and an increase in the tagatose content, the moisture contents of the chocolate samples decreased, while their aw increased. Increased D-tagatose resulted in increased hardness of the samples, the sample with 100% being the hardest, comparable to the control (sucrose) value. With regard to color indices, the least amounts of L*,a*,b*,c* and hue° were observed in chocolate samples with 100% inulin. Increasing D-tagatose led to increases in the color indices. The data also showed that reductions in inulin resulted in decreases in apparent and plastic viscosity and increases in τ0 and τ1. Thus, the lowest real and linear yield stresses were found to be in the sample with 100% inulin. The least apparent viscosity and the lowest plastic viscosity were observed in samples with 25% inulin-75% tagatose and 100% tagatose, respectively, with no significant difference with the control value. Overall acceptability of the chocolate samples increased with increasing the D-tagatose level. It can be concluded that in chocolate formula samples an inulin-tagatose ratio of 25%-75% and 100% tagatose are the best sucrose substitutes. As inulin is a dietetic fiber and tagatose and inulin have prebiotic properties, chocolate samples prepared using them are also desirable from a nutritional point of view and can be considered as functional foods. Keywords: Dark chocolate, Inulin, Tagatose, Stevia, Rheology