354: Transforming Soy Proteins Into Nanoporous Aerogels Using Supercritical Carbon Dioxide Drying

Introduction

Soybean is a widely cultivated legume crop for its high protein (35-40%) and oil (~20%) contents. While soybean oil is widely used in food, the protein-rich defatted meal mostly goes to animal feed (98%), despite being a complete protein source with numerous health benefits. Therefore, the goal of this study was to generate high-value protein-based food ingredients from soy proteins using a green, innovative approach based on SC-CO2 technology.

Methods

First, proteins were extracted from defatted soy meal and used for the aerogel formation at different pH (6-10) at 15% concentration (w/w) using SC-CO2 drying with constant pressure (10 MPa) and temperature (40°C). The formed SPI hydrogels and aerogels were characterized for their rheological properties and textural properties. SPI aerogels were characterized for their morphology, crystallinity, chemical structure, thermal stability, and solubility. Statistical analysis was conducted following Tukey’s test at a significance level of 5%.

Results

The gels formed at pH values of 7.0-10.0 were able to form strong gels, where all the gels showed a shear-thinning behavior. The hardness of the gels increased with the increase in pH from 7.0 to 10.0. The resulting SPI aerogels upon SC-CO2 drying showed outstanding properties, such as surface areas of 222-278 m2/g, pore sizes of 8-11 nm, and pore volumes of 1.88-3.13 cm3/g. Their densities were ~0.21 g/cm3 with high porosities of ~83%. Further, SEM images of aerogels showed three-dimensional open porous structures, where the structures were more heterogeneous at higher pH values, leading to a higher surface area. XRD and FTIR data provided information about the crystallinity and changes in the chemical structure of proteins, respectively. The main thermal degradation peak for aerogels was ~295°C, which was slightly lower than that for SPI powder at 303°C. The water solubility of SPI powder increased with the formation of aerogels from 17-19% to 30-36%.

Significance

The expected outcomes of this research are to (i) create new health-promoting food ingredients for developing functional foods, (ii) generate value-added protein-based aerogels for the delivery of bioactive compounds with enhanced health benefits, and (iii) eliminate the use of petroleum-based solvents.

Authors: Sumanjot Kaur, Ali Ubeyitogullari