Browsing by Subject "hapettumistuotteet"

Oats is one of the most cultivated grains in the world. Oat contains 5 to 8 % of lipids, which is a lot compared to many other cereals. Most of the oat lipids are triacylglycerols and about 80 % of its fatty acids are nutritionally significant unsaturated fatty acids. Due to high fat content and high amount of unsaturated fatty acids both the processing of oats and the development of new oat products are challenging. Oat lipids and their reactions during the processing and storage are a significant reason for the changes in oat quality and the unpleasant flavour. It is possible to either decrease or increase the stability of lipids with different processing methods. The objective of this study was to examine oat lipid reactions and stability during the storage. Ravintoraisio Oy gave all the samples for the research. There were seven oat products, which all were differently processed. Samples of different ages of these products were analysed. Short-term storage test was made for four samples, over 16 weeks at 40 °C. At first, all the oat samples were milled to small particles and then total lipids of these products were extracted by accelerated-solvent-extraction. Neutral lipid classes, volatile compounds and tocols were measured from the samples. Neutral lipid classes were analysed by the high performance liquid chromatography method with evaporative light scattering detector. Volatile compounds were measured by a solid phase microextraction method with GC-MS. Tocols were measured by the high performance liquid chromatography method with fluorescence detector. All the oat samples contained about 5 % of lipids. Most of the lipids were still triacylglycerols after a long-term storage. Free fatty acids were detected only from non-heat-treated samples. Content of tocols decreased significantly in oat samples during storage. Tocol content decreased when degree of processing rose. The content of oxidation products of oat lipids, like hexanal, also rose during the storage. Hexanal and 2-pentylfuran were the most abundant volatiles in the samples. The highest amount of oxidation products were found in extrudates which were stored for 16 weeks at 40 °C. Based on the results, storing oat products for 16 weeks at 40°C, corresponds with over one year storage at natural storage temperature. The effects of extrusion and heat treatment have strong influence on reactions of oat lipids and storage stability. The lipids of unprocessed oat grains were the most stable. More information is required to identify the exact reason for off-odors and off-flavours.