Cereal Chem. 73 (5):579-587  |  VIEW ARTICLE

Nonwheat Grains and Products

Sensory and Chemical Studies of Lipid Oxidation in Raw and Heat-Treated Oat Flours.

Eldrid Lein Molteberg (1,2,3), Ellen Merethe Magnus (2), Johanne Margrete Bjørge (1), and Astrid Nilsson (1). (1) MATFORSK - Norwegian Food Research Institute, Osloveien 1, N-1430 ÅS, Norway. (2) Department of Food Science, Agricultural University of Norway, P.O. Box 5036, N-1432 ÅS, Norway. (3) Corresponding author. Fax: +47-64 97 03 33. Accepted June 24, 1996. Copyright 1996 by the American Association of Cereal Chemists, Inc. 

The storage stability of oat flours (Avena sativa L.) was investigated by sensory and chemical methods. Raw and heat-treated flour samples of three cultivars of oats (Kapp, Mustang, and Svea) were stored at 23ºC and 50% relative humidity for 0, 5, 18, and 42 weeks before analyses. Descriptive sensory analysis and analyses of total fatty acids (FA), free fatty acids (FFA) and volatile lipid oxidation products were performed after each storage period. Storage of raw flours for five weeks resulted in 66% FFA but stable levels of flavors and volatile compounds. After 18 weeks, the level of volatiles and FFA was higher, while the samples at 42 weeks had an intense paint flavor, high levels of several volatiles, and reduced levels of FA and FFA. The major volatiles in stored oat flours were hexanal and 2-pentyl-furan. The other carbonyls were mainly aldehydes. For raw oat flours, most correlation coefficients between volatiles and the attributes of paint odor, paint flavor, odor intensity, and flavor intensity were >0.90. The volatiles were negatively correlated to oat odor and flavor and sweetness (r = ­0.80 to ­0.90). Heat-treatment of oat flours reduced the levels of FA, FFA, and most flavors, particularly bitterness and astringency. The levels of hexanal and oat flavor increased, while most volatiles remained constant. Stability against lipid oxidation was greatly increased by heat treatment. The levels of volatiles in heat-treated samples were less well correlated to flavors. Thus, differently heat-treated samples should be assessed separately in future flavor prediction models.