Rheological Optimization of Reduced-Sugar Ice Cream Enriched with Inulin and Carob Flour

Sugar reduction is technologically challenging in ice cream because sugars contribute not only to sweetness but also to rheological properties. A D-optimal mixture design was applied to optimize the formulation of reduced-sugar ice cream using inulin and carob flour as functional ingredients. The effects of sucrose, dextrose, inulin, and carob flour on viscosity, consistency index, flow behavior index, and thixotropy were investigated. All formulations exhibited pseudoplastic behavior, although marked differences in rheological properties were observed within the experimental domain. Sucrose increased viscosity and consistency, whereas dextrose reduced both parameters. Inulin and carob flour exerted a pronounced thickening effect due to their water-binding capacity. Based on the rheological targets defined using a commercial reference ice cream, an optimized formulation was identified and experimentally validated. The optimized sample showed a broadly comparable rheological profile to the commercial reference, although some discrepancies between predicted and experimental values were observed. Compared with both the experimental and commercial controls, the optimized formulation showed lower sucrose and glucose contents, corresponding a reduction of approximately 71% in glucose and sucrose. Total dietary fiber (calculated value) reached 11.59 g 100 g^-1, allowing the product to be potentially classified as "high in fiber" with a lower energy value. Sensory evaluation revealed a significant reduction in perceived sweetness (-25%) compared to the control formulation. Inulin and carob flour can be effectively used to develop reduced-sugar ice cream with improved nutritional quality while maintaining properties in agreement with the formulation targets.