Effect of modified okara insoluble dietary fibre on the quality of yoghurt

Abstract

The aim of this study was to investigate the potential of adding soya bean dregs insoluble dietary fibre (IDF) modified by jet cavitation combined with cellulase to yoghurt to improve its functional properties (Yoghurt was prepared by adding 10 μL of yoghurt fermenter to 100 mL of milk, fermented to pH 4.5 in a constant temperature incubator at 42 °C, and then stored in a refrigerator at 4 °C after adding IDF separately). The results showed that the modified IDF had a rough structure with high water-holding capacity and sodium cholate adsorption capacity. The addition of modified IDF improved the pH, hardness, and elasticity of the yoghurt. During the entire storage period, the titratable acidity and whey precipitation rate of the modified IDF yoghurt gradually increased, and antioxidant activity gradually decreased, and its titratable acidity, whey precipitation rate, and antioxidant activity had a significant advantage compared with those of the blank group yoghurt. In conclusion, the modified soya bean dregs IDF-added yoghurt prepared by jet cavitation combined with the cellulase method has the potential for sodium cholate adsorption capacity and antioxidant activity, which can confer unique functional properties and improve the pH, texture, and reduce whey precipitation of yoghurt. This study provides a scientific basis for the application of soya bean dregs IDF as a fibre fortifier in yoghurt production and suggests innovative ideas for the design of functional dairy products.

Keywords: Functional yoghurt; Modification; Okara insoluble dietary fibre; Stability.

Fig. 1

(A) FTIR spectra of F-IDF and M−IDF, (B) WHC, OHC, and SC of F-IDF and M−IDF, (C) SAC of F-IDF and M−IDF, (D) colour parameters of IDF and IDF-added yoghurt: L* (brightness) a* (red) and b* (yellow). Rheological properties of yoghurt with IDF: (E) Effect of shear rate (0 ∼ 1000 s⁻¹) on viscosity; (F) Relationship between storage modulus G′ and angular frequency (0.1 ∼ 100 rad/s); (G) Relationship between loss modulus G“ and angular frequency (0.1 ∼ 100 rad/s); (H) Sensory evaluation. Histogram and scatter plot represent mean ± SD (standard deviation), and the difference between different letters was statistically significant (P < 0.05, n = 3). FY: add 0.5 % F-IDF yoghurt; MY 0.1 %: add 0.1 % M−IDF yoghurt; MY 0.5 %: add 0.5 % M−IDF yoghurt; MY 1.0 %: add 1.0 % M−IDF yoghurt. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

SEM micrographs of different IDF: F-IDF (A), M−IDF (B) and yoghurt with IDF: Control (C), FY (D), MY 0.1 % (E), MY 0.5 % (F), MY 1.0 % (G). FY: add 0.5 % F-IDF yoghurt; MY 0.1 %: add 0.1 % M−IDF yoghurt; MY 0.5 %: add 0.5 % M−IDF yoghurt; MY 1.0 %: add 1.0 % M−IDF yoghurt.