Rheological properties, melting behaviours and physical quality characteristics of sugar-free chocolates processed using inulin/polydextrose bulking mixtures sweetened with stevia and thaumatin extracts

•Sucrose was replaced with Inulin/polydextrose mixture as bulking agent.•Sugar-free dark chocolates with natural sweeteners Stevia and thaumatin produced.•Casson viscosities higher for sugar-free dark chocolates.•Similar melting behaviour for conventional and sugar-free dark chocolates.•Sugar-free product with reduced calories and improved health benefit produced.

Demand for use of natural sweeteners and prebiotic compounds for manufacture of sugar-free chocolates has dramatically increased over the past decennium. However, their applicability in product formulation and how these will affect the flow (rheological) and physical quality characteristics still remains a big challenge. This study investigated the rheological properties, melting behaviours and other physical quality characteristics of sugar-free chocolates processed from inulin and polydextrose mixtures as bulking agents sweetened with stevia and thaumatin extracts. Standard reference chocolate was developed using sucrose and the effects of the inulin/polydextrose and stevia/thaumatin ingredients on the rheological properties, melting profiles, colour and hardness of the derived products measured using standard methods. Generally, the sugar-free chocolates showed similar flow (rheological) and melting properties as compared to the reference chocolate. Sucrose replacement with the inulin/polydextrose and stevia/thaumatin extracts resulted in significantly higher Casson viscosity. There were however no significant differences in the melting behaviour and texture of the sugar-free chocolates and the reference. Chocolates containing the sugar substitutes recorded lower onset temperatures and higher peak widths than the reference sample. Inulin and polydextrose mixtures could be used for sugar-free chocolate manufacture with satisfactory physicochemical properties when sweetened with stevia or thaumatin extracts.