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, 800 W). A maximum tocochromanols (90.48 mg/100 g) and phenolic compounds (mainly canolol, 1692.15 μg g−1) concentration is achieved after 10 min of seeds MV pre‐treatment, while the highest content of carotenoids (1017.51 μg/100 g) is found in the oils pressed from seeds exposed to microwaves for 6 min. During storage, the tocochromanols and carotenoids decrease following zero‐order kinetic, the reduction of phenolic compounds display pseudo first‐order kinetic. Storage stability of tocochromanols in the oils obtained from MV pre‐treated seeds is comparable to that of the control oil. Oils produced from 8 min MV pre‐treated seeds show the slowest progress of carotenoids reduction, as the values of degradation rate constant (k) are lower (14.678 μg/100 g/month) than that of the control oil (18.168 μg/100 g/month). The half‐life (t1/2) of oils phenolic compounds increases with longer seeds exposition to MV.Practical Applications: Numerous studies have shown favorable 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.The present study focuses on the kinetics of degradation of phytochemicals during long‐term storage of rapeseed oils prepared from microwave pre‐treated seeds. The study includes a comparative study of kinetics of tocochromanols, carotenoids, and phenolic compounds in correlation with changes in the antioxidant capacity. It is shown that the content of phytochemicals in the oil and their storage stability is significantly affected by the time of seeds microwave pre‐treatment prior to pressing.