title: Okara (soybean residue) biotransformation by yeast Yarrowia lipolytica.
abstract: Okara, or soybean residue, is a soy food processing by-product from the manufacture of soymilk and soybean curd (tofu). In this study, solid-state fermentation of okara was conducted over 5days using yeast Yarrowia lipolytica, and the changes in proximate composition, antioxidant capacity, non-volatiles and volatiles were investigated. Yeast metabolism of okara significantly increased the amounts of lipid, succinate and free amino acids and enhanced the antioxidant capacity. In particular, there was a marked increase in important umami tastants after fermentation, with 3-fold increase in succinate and a 20-fold increase in glutamate. The final fermented okara contained 3.37g succinate and 335mg glutamate/100g dry matter. Aldehydes and their derived acids in the fresh okara were catabolised by Y. lipolytica mainly to methyl ketones, leading to a reduced grassy off-odour and a slightly pungent, musty and cheese-like odour in the fermented okara. Amino acid-derived volatiles, such as 3-methylbutanal and 2-phenylethanol, were also produced. Overall, the okara fermented by Y. lipolytica had a greater amount of umami-tasting substances, a cheese-like odour, improved digestibility and enhanced antioxidant capacity. These changes highlight the potential of Yarrowia-fermented okara as a more nutritious, savoury food product or ingredient. Y. lipolytica was thus demonstrated to be suitable for the biovalorisation of this soy food processing by-product.
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Weng Chan
authors.initials: WC
authors.lastname: Vong
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Kai Ling Corrine
authors.initials: KL
authors.lastname: Au Yang
authors.affiliation: Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore; National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu 215123, China. Electronic address: chmLsq@nus.edu.sg.
authors.forename: Shao-Quan
authors.initials: SQ
authors.lastname: Liu
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis; D000975:Antioxidants / Q000737:chemistry; D019149:Bioreactors; D001711:Biotransformation / Q000502:physiology*; D005285:Fermentation; D005511:Food Handling / Q000379:methods*; D005971:Glutamates / Q000032:analysis; D007659:Ketones / Q000378:metabolism; D008055:Lipids / Q000032:analysis; D009812:Odorants / Q000032:analysis; D010626:Phenylethyl Alcohol / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism*; D045730:Soy Foods; D041942:Soy Milk; D013025:Glycine max / Q000737:chemistry / Q000378:metabolism*; D019802:Succinic Acid / Q000032:analysis; D025062:Yarrowia / Q000378:metabolism*; D015002:Yeast, Dried
chemical_list: D000447:Aldehydes; D000596:Amino Acids; D000975:Antioxidants; D005971:Glutamates; D007659:Ketones; D008055:Lipids; D010940:Plant Proteins; D011134:Polysaccharides; C412882:okara, Glycine max; C032251:isovalerylaldehyde; D019802:Succinic Acid; D010626:Phenylethyl Alcohol
keywords: Fermentation; Flavour; Okara; Soybean residue; Yarrowia lipolytica; Yeast