Assessment of the Oxidative Stability of Flaxseed-Enriched Lasagna Using the Rancimat Method

Abstract

The oxidative stability of flaxseed-enriched lasagna during thermal processing was quantified using the Rancimat method. Lasagna was processed at high temperatures (120 and 180C) and oxidation was assessed from the electric conductivity of a water solution dissolving volatile secondary oxidation products. The oxidative stability of the lasagna was defined as the time to increase the conductivity by 5 μS/cm. The oxidative stability of the lasagna was higher than pure flaxseed oil, showing the protective effect of the lasagna matrix against the development or diffusion of oxidation products. Rolling the lasagna multiple times in the sheeter and reducing the processing temperature increased resistance to oxidation. The oxidative stability of the lasagna was independent of the extraction of flaxseed oil prior to enrichment. For both flaxseed enrichment levels (10 and 20%), the oxidative stability at 120C was approximately 10 times longer than the time required to dry lasagna at this temperature. Practical Applications The enrichment of lasagna with flaxseed improves its nutritional quality because of flaxseed omega-3 fatty acid, lignan and fiber content. However, the oxidation of flaxseed lipids during enriched lasagna processing is a major concern because of their high degree of unsaturation. This work validates the use of the Rancimat method to determine the processing parameters with a significant impact on flaxseed lipids oxidative stability and indicates that the number of passes in the sheeter, the processing temperature and the flaxseed enrichment level should be carefully considered to limit flaxseed lipids oxidation during processing.