Determination of Oligosaccharides in Fermented Soymilk Products by High-Performance Liquid Chromatography

Abstract

Soybean is one of the most economical and valuable agricultural commodities because of its unique chemical composition. However, soy products have low consumer acceptability owing to the presence of high levels of undigested sugars (e.g., stachyose, raffinose). These oligosaccharides are degraded by the human intestinal bacteria to carbon dioxide, hydrogen, and methane, which produce flatulence and abdominal pain (1). Therefore, processes including fermentation of soymilk with fungi (2,3) or lactic acid bacteria (4–6) have been examined as means to avoid such problems and to improve the acceptability of soybean. Analysis of the carbohydrate contents of soymilk and soymilk products are very important for nutritional evaluations. High-performance liquid chromatography (HPLC) provides a rapid and simple method for assessing the type and quantity of sugar present in these products. The column used in the method applied here, separates compounds using a combination of size exclusion and ligand exchange mechanisms. For the determination of sugars by HPLC, it is necessary to previously remove the potential interferences present in the substrate, such as proteins.