Enzymatic oxidation of hexanal by oat

The fate of hexanal added to flours of five different grain varieties was studied. All the flours appeared to be capable in decreasing hexanal concentration, but the abilities of oat flours were clearly the best. Depending on the oat flour used, the rate of hexanal decrease was 2.45-2.73 μg hexanal min^-1 g^{- 1} flour when 100 μg of hexanal was added to 1 g flour. This ability was highest amongst oat flour fractions rich in protein and fiber, which originated from the aleurone layers. The time course of hexanal decrease followed typical first order kinetics and the reaction was susceptible to heat inactivation. Hexanoic acid was identified as the predominant product correlating with hexanal decrease. These observations suggested the presence of aldehyde dehydrogenase type activity in oat. Hexanal was also absorbed to oat matrix to some extent, but it became saturated relatively quicky. It was concluded that the aldehyde dehydrogenase type activity present in oat efficiently prevents the accumulation of short chain aldehydes that lead to off odours in oat products.