Improved Volatile Profiles and Enhanced Storage Stability of Soy Protein Isolate through the Development of Novel Soybeans

Novel soybean lines with improved traits such as high oleic and low linolenic acid (HOLL), ultra-low raffinose and stachyose (ULRFO), and absence of lipoxygenase (LIPOX) have been developed to address the challenge of off-flavors in soy protein isolate (SPI), a major protein ingredient in foods. This study aimed to determine the effects of different soybean seed composition traits on the volatile profile and storage stability of SPIs.

Four soybean lines were investigated: Commodity (Patriot), HOLL, HOLL/ULRFO (Tiger), and HOLL/ULRFO/LIPOX (Super). SPIs were prepared from cold press meals using alkaline extraction, acid precipitation, and freeze-drying. Volatile profiles were determined by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry at time 0 and after 3-month storage at 50°C and 30% or 75% relative humidity (RH). Data were evaluated by ANOVA with means separation.

Soybean line significantly influenced the types and relative concentrations of volatile compounds in SPIs. Patriot exhibited higher concentrations of total volatiles, aldehydes, and alcohols (p< 0.05), while Super showed the lowest concentrations, even lower than HOLL and Tiger (p< 0.05). Major off-flavor compounds such as hexanal, 1-hexanol, 2-pentylfuran, and 1-octen-3-ol were significantly higher in Patriot (p< 0.05), while Super contained the lowest concentrations of hexanal and heptanal (p< 0.05). After storage, Patriot continued to have higher concentrations of total volatiles, aldehydes, and alcohols (p< 0.05), while Super exhibited the lowest concentrations. Larger changes in volatile contents were observed at 30% RH compared to 75% RH, with Super exhibiting the smallest changes, particularly at 75% RH. In conclusion, HOLL, Tiger, and Super showed lower off-flavors compared to Patriot, with Super producing SPI with the lowest concentrations of off-flavor compounds and better storage stability, demonstrating its potential as a protein ingredient with higher consumer acceptability.