Influence of inulin/oligofructose on the acid-induced cold aggregation and gelation of preheated soy proteins

Background: In recent years inulin-type prebiotics have attracted much attention due to consumers' awareness of the health benefits of functional foods. Currently no information is available about the possible texture-modifying effect of these non-ionizable polar carbohydrates in different soy-based food systems. In this study, the effect of inulin/oligofructose on the cold aggregation and gelation of preheated soy protein isolate (SPI) and its fractions (7S, 11S, and their mixture), induced by glucono-δ-lactone (GDL), were evaluated by turbidity (A₆₀₀) and dynamic rheological measurements. Results: Oligofructose significantly delayed the aggregation of all protein samples and decreased the end-point optical density of 11S fraction and SPI. Inulin, a long-chain fructan, only delayed the aggregation of 7S globulin and reduced the capacity of aggregation (A₆₀₀) of SPI. While oligofructose showed no significant effect, the addition of 5% (w/v) inulin enhanced the gelation of SPI and the 7S/11S mixture, which was demonstrated by the increase in gel storage modulus up to 13.6% and 10.1% (P < 0.05), respectively. Conclusion: Inulin was found to enhance the viscoelastic properties of GDL-induced cold-set soy protein gels. It is expected that 'functional' cold-set gel products with improved texture can be prepared from preheated soy proteins and inulin.