INFORM October 2025

BIOTECHNOLOGY

inform October 2025, Vol. 36 (9) • 13

PUFAS: GOOD FOR HEALTH, BAD FOR SOY PROCESSING

of enzymes that catalyze PUFA oxidation. Heat treatment can reduce lipoxygenase activity and produce compounds that can help mask beany or painty compounds. Bathing soybeans in an alkaline solution can also lessen the impact of these enzymes. Bilyeu and her team, however, went right to the source— the genes encoding lipoxygenases, as well as genes encoding fatty acid desaturases that can convert other fatty acids into PUFAs. “My work has been to find non-functional versions of each of those enzymes to try to stop compounds from going through the oxidation pathway,” says Bilyeu. Together with Scaboo, she developed new soybean varieties that have differ ent defects in these two classes of enzymes. “We have been so fortunate to have the USDA-ARS Germplasm Resources Information Network (GRIN, https:// www.ars-grin.gov/), which is a seed bank that provides researchers with over 20,000 different accessions of soybean from all over the world,” says Bilyeu. “It is a treasure.” The team screened GRIN’s naturally diverse collection by pheno type and genotype to discover the best varieties for their work. They also used chemical mutagens to make changes to soy bean plants that they screened for appropriate phenotypes. Because they are not directly changing the genes with molec ular biology techniques, the varieties are not considered to be genetically modified organisms, or GMOs. The first good candidate soybean variety (referred to as HOLL) had high levels of oleic acid and low levels of linolenic acid (the PUFA linked to off-flavors in soybeans). They patented and trademarked this variety as Soyleic® (https://soyleic.com/). Its oil is about 80 percent oleic acid and about 2.5 percent lin olenic acid. The team also developed HOLL varieties with other beneficial attributes, such less raffinose, a carbohydrate with out nutritional value, to make the soybean protein meal more

Soy is an unusual seed oil crop. Unlike canola or sunflower seeds that contain up to 50 percent oil, soybean seeds are only about 18-22 percent oil but about 40 percent protein ( https:// doi.org/10.1186/s12870-019-2199-7, https://doi.org/10.1007/ s00122-022-04222-9). The protein in soybeans is complete, meaning it contains all of the essential amino acids. This is important for consumers who are vegetarians or vegans and avoid eating meat. To unlock the oil and protein, soybean seeds are broken open by mechanical grinding. But that exposes the oil to lipid oxidation reactions since its composition is more than 60 per cent polyunsaturated fatty acids (PUFAs) and 25 percent oleic acid, which is monounsaturated. Consuming PUFAs can reduce the risk of heart disease and is recommended for a healthy diet. However, PUFAs are more susceptible to lipid oxidation. Oxidation reduces shelf life and produces unpleas ant off-flavors and smells from compounds such as alde hydes, ketones, and alcohols (https://doi.org/10.3390/ foods12050923). “The flavor of the oil will change; however, lipid oxidation will also affect the flavor perception of the pro teins,” says Vardhanabhuti. That is because a little bit of the oil carries through some of the processing steps along with the protein as it is modified from flakes to soy protein concentrate and soy protein isolate, making them taste bad as well, she explains. FLAVOR-NULL, NOT FLAVORFUL Oxygen in the air and enzymes in the plant can oxidize PUFAs, resulting in undesirable compounds. Industry has a few tools at its disposal to dampen the effects of lipoxygenases, a family

Soybeans called Super L are high in oleic acid and low in linolenic acid, the fatty acid most likely to be oxidized in a lipid oxidation reaction. Source: Kristin Bilyeu