Phytochemicals and antioxidant activity degradation kinetics during long-term storage of rapeseed oil pressed from microwave-treated seeds

Abstract

The present study focuses on the kinetics of degradation of phytochemicals and antioxidant capacity during long-term storage of rapeseed oils prepared from microwave (MV) pre-treated seeds (2-10 min, 800W). A maximum tocochromanols (90.48 mg/100g) and phenolic compounds (mainly canolol, 1692.15 μg/g) concentration was achieved after 10 min of seeds MV pre-treatment, while the highest content of carotenoids (1017.51 μg/100g) was found in the oils pressed from seeds exposed to microwaves for 6 min. During storage, the tocochromanols and carotenoids decreased following zero-order kinetic, the reduction of phenolic compounds displayed pseudo first-order kinetic. Storage stability of tocochromanols in the oils obtained from MV pre-treated seeds was comparable to that of the control oil. Oils produced from 8 min MV pre-treated seeds showed the slowest progress of carotenoids reduction, as the values of degradation rate constant (k) were lower (14.678 μg/100g/month) than that of the control oil (18.168 μg/100g/month). The half-life (t₁/₂) of oils phenolic compounds increased with longer seeds exposition to MV. The decrease of the antioxidant capacity of the oil followed zero-order reaction model, with the reaction rate constant (k) ranging from 6.3×10-2 to 10.2×10⁻² mmol TEAC/l/month.

Practical applications: Numerous studies have shown favourable effect of oilseeds thermal pre-processing on the concentration of phytochemicals in the resulting oil. However, there is lack of information regarding storage stability of oils prepared from microwave pre-treated seeds. As the prediction of shelf-life is a desirable goal in the food industry, evaluation of phytochemicals degradation based on the kinetic models will provide information on cost-effectiveness of the seeds thermal pre-treatment prior to oil cold-pressing.

http://ift.tt/2xBAmL8