Method development for sphingolipid quantification in soybeans and soy products

Gutierrez, Elizabeth
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Soybeans are believed to be a relatively rich source of sphingolipids, which are a class of polar lipids with potential cancer-inhibiting activities. Quantitative data for foods are scarce, including soybeans and soy foods. Fewer studies have attempted to investigate the effects of processing, genotype or other factors that may influence sphingolipid contents in soybean products. Glucoslyceramide (GlcCer), the main sphingolipid type in soybean, was extracted and quantified from soybeans and soy products using a novel method developed for this research. After GlcCer was extracted from soybean samples, solvent partition and thin layer chromatography (TLC) methods were used to produce all GlcCer-enriched fractions, which were analyzed by high performance liquid chromatography (HPLC) and an evaporative light scattering detector (ELSD). GlcCer was measured in several soybean genotypes in this study to determine the effect of genotype, stage of seed development, and growth location on GlcCer concentration in soybean. The GlcCer concentration among these soybean types ranged from 142 to 492 nmol/g (dry weight). To determine effect of processing on sphingolipid contents, whole soybeans were processed into full-fat flakes from which crude oil was extracted. Crude oil (84 g) was refined and defatted soy flakes (DSF) were further processed into alcohol-washed and acid-washed soy protein concentrate (SPC) and soy protein isolate (SPI). All processes were conducted on laboratory-scale that simulated typical industrial practices. After oil extraction and production of DSF, 89% of the GlcCer content in the starting full-fat soy flake material was recovered. Most of the recovered GlcCer remained with the DSF (91%) rather than with the oil (9%). Recovery of GlcCer from the DSF through the production of the acid-wash SPC (52%), alcohol-wash SPC (42%), and SPI (26%) products was poor. All protein purification products had a similar GlcCer concentration, which was about 281 nmol/g (dry weight). The minor quantity of GlcCer in the crude oil was almost completely removed by water degumming; therefore lecithin could be a rich source of sphingolipids.

Food science and human nutrition, Food science and technology