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Changes in volatile profile of soybean residue (okara) upon solid‐state fermentation by yeasts
Author(s) -
Vong Weng Chan,
Liu ShaoQuan
Publication year - 2016
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.7700
Subject(s) - food science , torulaspora delbrueckii , debaryomyces hansenii , fermentation , chemistry , kluyveromyces lactis , yeast , solid state fermentation , flavour , yarrowia , hexanal , wine , bioconversion , saccharomyces , biochemistry , saccharomyces cerevisiae
Background Soybean residue (okara), a by‐product of soymilk, is produced in large volumes by the soy food industry and is often discarded due to its undesirable flavour. As it contains a considerable amount of protein and fats, biotransformation of okara to improve its flavour presents an opportunity for alternative utilisation. This paper evaluated 10 yeasts in the solid‐state fermentation of okara based on their volatile profiles as analysed with HS‐SPME GC‐MS / FID . Four ‘dairy yeasts’ ( Geotrichum candidum , Yarrowia lipolytica , Debaryomyces hansenii and Kluyveromyces lactis ) and six ‘wine yeasts’ ( Saccharomyces cerevisiae , Lachancea thermotolerans , Metschnikowia pulcherrima , Pichia kluyveri , Torulaspora delbrueckii , and Williopsis saturnus ) were studied. Results The main off‐odourants in okara, hexanal and trans ‐2‐hexenal, significantly decreased after fermentation due to their bioconversion into methyl ketones and/or esters. The okara fermented by dairy yeasts contained greater proportions of methyl ketones, while that by wine yeasts contained more ethyl and acetyl esters. Notably, the okara fermented by W. saturnus contained 13 esters and the total GC‐FID peak area of esters was about 380 times that in fresh okara, leading to a perceptible fruity note. Conclusion Okara can be exploited as an inexpensive substrate for bioflavour extraction and/or a more pleasant food ingredient via yeast fermentation. © 2016 Society of Chemical Industry