Characterization of key off-flavor compounds in soybean and their dynamic changes during progressive processing

Area of Science:

• Food Chemistry
• Analytical Chemistry
• Sensory Science

Background:

• Soybean-based products are vital food sources.
• Off-flavors in soybean flour (SF) can negatively impact product quality.
• Understanding the volatile compounds responsible for off-flavors is crucial for improving soybean product palatability.

Purpose of the Study:

• To systematically identify key off-flavor compounds in normal soybean flour (NOR-SF).
• To profile the dynamic changes of these off-flavors in products derived from normal and high oleic acid (HOA) soybeans.
• To provide a theoretical basis for controlling off-flavors in soybean-based products.

Main Methods:

• Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) for volatile compound detection.
• Gas chromatography-olfactometry (GC-O) to identify odor-active compounds.
• Stable isotope dilution analysis (SIDA) for precise quantification of key odorants.
• Odor recombination and omission experiments to confirm contributions.
• Orthogonal partial least-squares discriminant analysis (OPLS-DA) for sample comparison.

Main Results:

• 10 key off-flavor odorants were identified in NOR-SF with significant contributions (OAVs > 1).
• Products from HOA soybeans generally contained lower concentrations of off-flavor compounds compared to those from NOR soybeans, with exceptions like heptanal, nonanal, and octanal.
• Off-flavor compound concentrations varied across different product types (soybean meal, soy protein isolate, textured soy protein), with extrusion influencing levels.
• Soybean variety was identified as a significant factor influencing off-flavor compound formation and evolution.

Conclusions:

• The study successfully identified and quantified key off-flavor compounds in soybean flour.
• High oleic acid soybean varieties show potential for reducing off-flavors in derived products.
• Processing methods like extrusion can dynamically alter off-flavor profiles.
• Findings offer a scientific foundation for developing strategies to mitigate off-flavors in various soybean-based food products.