Impact of Inulin Addition on Properties of Natural Yogurt

The influence of the amount of inulin addition (3%, 6%, 9%, 12% or 15% w/w) on the physicochemical properties of natural yogurt was analyzed. The acidity (titration; pH), texture parameters (penetration test), viscosity curves (rotational rheometer), microrheology (macroscopic viscosity index, MVI; elasticity index, EI; solid-liquid balance—SLB; multi-speckle diffusing-wave spectroscopy, MS-DWS) and physical stability (syneresis; LUMiSizer test) of yogurts were investigated. All samples were non-Newtonian pseudoplastic liquids. The sample with 15% inulin content presented an approx. 4% higher pH value (4.34), 3-fold greater MVI and almost 5-fold higher penetration force, compared to the control sample (0% of inulin). In turn, the use of inulin addition in the range of 3–15% w/w resulted in a reduction of syneresis (p < 0.05). A linear decrease in the values of instability indexes and sedimentation velocities was noted in the function of inulin content increase (LUMiSizer test). The application of inulin (in the range of 3–15% w/w) as a functional additive to yogurts significantly contributed to enhancement of their physical stability. Summing up, the possibility of obtaining natural yogurts with a high content of this prebiotic has been demonstrated, thus such products can be classified as functional foods and a health claim can be put on the label.