MASc Oral Exam|Development and Characterization of Soymilk Okara Gels Modified by Citric Acid by Minh Xuan Nguyen

Monday, November 20, 2023 9:30 am - 10:30 am EST

In a closed session Minh Xuan Nguyen will discuss her research.


The present study aimed to explore the effects of CA modified okara materials on the characterization of soymilk okara gels as well as gain understanding of the underlying mechanisms of okara modification and gelation. After the modification with CA, the fiber in okara is hypothesized to be hydrolyzed, along with the release of soluble polysaccharides such as pectic substances, ultimately enhancing the compatibility of the CA modified okara with the soymilk protein matrix. The impacts of the physical state of CA (liquid or

solid) and the drying time during the okara modifications to textural characterization of the soymilk gels were first examined. The sample preparations of the soymilk okara gels for the measurements of the rheological and mechanical properties to improve reproducibility, as well as the development of a methodology to evaluate protein – protein interactions were examined. Subsequently, the changes in CA modified okara and the characteristics of soymilk okara gels were examined. To maintain uniform soymilk quality across experiments, the solid content of soymilk was measured by drying method at 60 °C for 3 h in the oven and kept constant at the level of 15 to 16 % (w:w).

In the final formulation, okara was modified with CA solutions at concentrations ranging from 2.5 to 10 % (w:w), and then dried at 60 °C for

20 h. Soymilk okara gels were subsequently prepared using heat treatment at

95 °C for 45 min. Higher CA concentrations induced more significant degradation of okara fibers and release of pectin, as evidenced by TGA and FTIR, leading to changes in the texture and protein-protein interactions of soymilk okara gels. As the CA concentration increased, the soymilk okara gels exhibited increased homogeneity, as indicated by lower porosity in optical images. This was accompanied by reduced viscoelasticity and a decrease in hydrophobic protein-protein interactions. Notably, water holding capacity and mechanical properties remained constant and were unaffected by the CA level.

Additionally, the unreacted CA on modified okara materials had an impact on gelation, resulting in a particulate structure, different from the fine-stranded structure of soymilk okara gels without CA observed in CLSM images. The fabrication of soymilk okara gels with improved homogeneity through the modifications of okara with CA was confirmed. The alternations in the textural profiles and protein – protein interactions when varying the concentration of CA solution examined in this study could be further applied in the development of desired textural profiles matching commercial products.

Supervisor: Professor Christine Moresoli