The effect of inulin addition on rheology and texture of nonfat yogurt (NFY) was studied by the large (texture analyzer) and small (dynamic oscillatory rheometry) deformation tests. Skim milks (12% solids) were supplemented with three commercial chicory inulins with different chain lengths at 4% level and inoculated with mixed cultures of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Textural and rheological tests were conducted after an overnight storage at 4C and during a shelf life of 28 days. A good correlation was observed between the two tests. During storage, all inulin-containing yogurts in comparison with the control NFY were characterized by lower values of firmness, apparent viscosity, yield stress, complex viscosity, storage modulus and loss modulus. NFYs supplemented with long-chain inulin demonstrated a rheological behavior closer to that of control full-fat yogurt.
The use of inulin and oligofructose in the food industry has grown recently because of their interesting nutritional and technological properties. In the work presented here, three commercial inulin products with different chemical composition and functions were added to yogurt milk, and changes in rheological properties of yogurt were investigated in comparison with nonsupplemented control yogurts. According to the manufacturer's specifications, Raftiline HP and Raftiline GR are suitable for fat replacement because of the presence of long-chain inulins, while Raftilose P95, being rich in mono- and disaccharides, is highly recommended for sugar replacement. The knowledge obtained from this study may be applied for the development of nonfat yogurts to satisfy the nutritional expectations of ever-increasing health conscious consumers and at the same time to match the sensory and textural characteristics of full-fat yogurt.