Changes of Aldehyde Levels in Defatted Soybean Extract

ABSTRACT Aldehyde levels in defatted soybean extracts were measured by using aldehyde dehydrogenase. The level increased during incubation of flour‐water suspension and its centrifuged extract at pH 6.5, while it decreased markedly at alkaline pHs. This aldehyde‐eliminating activity was observed in 1:5 flour:water ratio, but was not in 1:20 flour:water ratio. 14 C‐labelled acetaldehyde added to 1:5 flour:water extract was converted into acetic acid. Fractionation of the extract indicated that a heat‐labile protein and a heat‐stable compound with low molecular weight were required for the aldehyde‐eliminating activity.