Study of effects of D-tagatose and inulin as sugar substitutes on the physical, chemical and rheological properties of milk chocolate.

Chocolate is a popular product for cunsumers in different ages . Chocolate sweetness  is related to the sucrose in its formula , it can be replaced by sweeteners like low digestible carbohydrates (LDCS) .The results would be reduction in calories and glycemic index and prevention of tooth decay. The aim of this study was to replace  the sucrose with the inulin (as dietary fiber) and tagatose (as natural keto hexose  with sweetness similar to sucrose). The ratio of the replacements were 100:0 , 75:25 , 50:50 , 25:75 and 0:100 inulin:tagatose in milk chocolate formula and the chemical and rheological properties of samples were tested. Results indicated that when the amount of inulin reduced and amount of tagatose  increased in chocolate formula, moisture contents reduced but aw values increased . The hardness of samples was related to the percentage of tagatose when tagatose added  to the formula, hardness was increased and the hardness of sample with 100% tagatose and control were comparable. In color parameters the least amounts of l* ,a*,b*,c* and hue° were observed in chocolate with 100% inulin which they went up when amount of tagatose was increased in formula. When inulin reduced in samples,  and  incresed and the lowest real and linear yield stress occurred in the sample with 100% inulin. By reduction of inulin, apparent and plastic viscosity were reduced. The least amount of apparent and plastic viscosity was observed in sample with 25%inulin-75% tagatose and the viscosity in formula with tagatose had no significant difference with control. Flow property index also reduced with reduction of inulin. Results showed that the samples with 50% inuin -50% tagatose and 25% inuin -75% tagatose  and 100% tagatose were the best ratio of the sugars as replacement of sucrose in formula, the two formers formulas are the best formula from nutrition point of view and are considered  as a functional food.