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Differences Between Sensory Profiles and Development of Rancidity During Long-Term Storage of Native and Processed Oat

¹VTT Biotechnology, P.O. Box 1500, FIN-02044 VTT, Finland. ²Corresponding author. E-mail: raija-liisa.heinio@vtt.fi Phone: + 358-9-456 5178. Fax: +358-9-455 2103. ³Helsinki University of Technology, P.O. Box 1000, FIN-02015 TKK Finland.

Changes in the sensory attributes, lipid composition, and amounts of volatile and phenolic compounds of native and processed (germinated and dried) crushed oat were followed during a 12-month storage period. The influence of the chemical attributes on the sensory profiles of oats was analyzed by statistical multivariate techniques (PLS regression). During the storage period, significant changes in the sensory profiles of the native and processed oat groats were observed. The stability of oat groats was significantly increased through germination and subsequent drying because the chemical changes causing rancidity and bitterness developed more slowly in the processed oat when compared with the native oat. In native oat, the most intensive changes due to deteriorat ion had already occurred after one month of storage, whereas in processed oat, these changes were perceived considerably later. Stored oat that had deteriorated was evaluated as being musty and earthy in odor and bitter and rancid in flavor. The accumulation of free fatty acids and volatile compounds related to lipid oxidation were closely correlated with the development of the undesired sensory attributes described above. The total amount of phenolic compounds, as well as the volatile aromatic and branched chain compounds derived mainly from protein degradation, showed a significant relationship with favorable sensory attributes such as roasted odor and flavor. Lipid oxidation occurred during the storage and was observed both in the polar and in the nonpolar lipid classes of native oat, whereas in the processed oat, these changes were nonsignificant. Photo-oxidation of acylated fatty acids may significantly contribute to the development of volatile lipid oxidation products during storage.