Abstract: Headspace solid phase micro-extraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to determine the effect of different drying methods (sun, hot air, microwave, vacuum and vacuum freeze) on the aromatic composition of okara, and the odor thresholds and relative odor activity values (ROAV) were measured to identify major beany flavor compounds in okara. A total of 52 volatile compounds were detected in okara samples dried by five different methods, mainly aldehydes, ketones, esters, alcohols, etc. The predominant aromatic compounds in sun dried okara were 3-hydroxy-2-butanone (18.29%), hexanal (16.30%) and acetone (11.87%) and the most beany flavor compounds with the highest relative content were found in sun dried okara followed by vacuum dried okara. Volatile compounds showed a lower relative content in hot air dried okara, whereas the relative contents of alcohols and ketones were higher in microwave dried okara. Benzaldehyde (11.18%) and 2,3-butanedione (11.27%) were found in vacuum dried okara as dominant aromatic components. The major volatile compounds in vacuum freeze dried okara were ethyl acetate (46.72%) and acetone (22.86%) and the beany flavor compounds accounted for only 1.81%.

Key words: okara, drying, solid phase micro-extraction, gas chromatography-mass spectrometry, volatile compounds, beany flavor, relative odor activity value