Flaxseed use in foods has increased during the last decade due to the presence of functional compounds such as alpha-linolenic acid, lignans and fiber. Due to the high level of polyunsaturated fatty acids, flaxseed is susceptible to lipid oxidation. Thus enhancing stability of the oil is important for prolonging shelf-life. Roasting has been applied to oilseeds to improve aroma, flavor, and shelf life stability.

The objectives of this study were to determine the physical and chemical properties of roasted flaxseed in relation to lipid oxidation.

Omega flaxseed was roasted at 140, 160 and 180C in an air impingement oven (4, 8, 16 and 24 min.). Total lipid extraction (dry basis), peroxide value and free fatty acid content were determined in the roasted flaxseed. Fatty acid composition (palmitic, stearic, oleic, linoleic and linolenic acids) was analyzed by gas chromatography and color quality was determined by Minolta colorimeter.

Flaxseed brightness (L value) (r=-0.52, P<0.01) and yellowness (b value) (r=-0.49, P<0.01) were significantly correlated with free fatty acid content. Roasting significantly (P<0.05) decreased the peroxide value. All roasted flaxseed samples (excluding 180C, 24 min.) were significantly (P<0.05) lower than control in terms of free fatty acid. Total lipid extraction increased with temperature. At 160 and 180C, roasted flaxseed had the highest oil yield. Generally, fatty acid profile of flaxseed showed low variation. Linolenic acid decreased when subjected to high temperatures and long processing times, however roasted flaxseed was higher in linoleic acid than control at each processing temperature.

Processing for 4 and 8 minutes at 140 and 160C showed superior quality flaxseed. Considering the reduction in peroxide value and free fatty acid content, roasting might potentially be used as a means of extending shelf life. 

Session 14B, Food Chemistry: Physicochemical properties
8:30 AM - 12:00 PM, Sunday AM

2003 IFT Annual Meeting - Chicago,