CHEMICAL COMPOSITION, STORAGE STABILITY AND EFFECT OF COLD-PRESSED FLAXSEED OIL CAKE INCLUSION ON BREAD QUALITY

Flaxseed oil cake from a South African factory was screened for proximate composition, mineral content, fatty acid profile and storage stability. The oil cake was included at 10 and 15% levels (w/w) in brown bread and evaluated using a 96-member consumer panel. The oil cake contained between 38.0 and 47.3% protein, 12.8 and 26.1% crude fat and 3.7 and 5.1% ash. The total carbohydrates were mostly dietary fiber. Calcium, magnesium, phosphorus and potassium were in the range of 3.3 to 3.8, 4.8 to 5.9, 6.4 to 8.2 and 9.0 to 10.1 (mg/g), respectively. The oil from the flaxseed oil cake contained 58.5 to 59.7% of C18 omega-3 fatty acids. Peroxide levels of the flaxseed oil cake were below the threshold limits after 6 months storage. Thiobarbituric acid threshold values were exceeded after 5 months aerobic storage at 20C. Bread samples with inclusion levels of 10 and 15% flaxseed oil cake were acceptable to the consumer sensory panel. PRACTICAL APPLICATIONS: This research would have practical applications in the brown bread and flaxseed oil industries in terms of providing added value for an otherwise overlooked by-product of flaxseed oil extraction. The results indicate that flaxseed oil cake is rich in nutrients such as protein, crude fiber and crude fat, containing 58.5 to 59.7% of omega-3 fatty acids. In addition, flaxseed oil cake is stable during storage under various conditions. Acceptable brown bread could be made with up to 15% (w/w) inclusion of flaxseed oil cake. Because of the tendency for the consumer panel to prefer lower levels of inclusion, it is pragmatic therefore to recommend inclusion of 10-15% flaxseed oil cake in commercial standard brown bread.