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.

Hexane‐Free Green Solvent Extraction of Canola Oil From Microwave‐Pretreated Seeds and of Antioxidant‐Rich Byproducts

“…Canolol exhibited an increase of up to 317% by effect of the microwave pretreatment, indicating the production of this compound with microwave radiation, and of up to 2564% in the H‐EthF phases with respect to the oils obtained by P2, presenting a larger concentration thereof (Table ). These results show that an antioxidant‐rich byproduct was obtained, containing 83% of the canolol of the OF obtained by P1.…”

“…Canolol accounts for 85% of total phenolics in crude canola oil . Several authors studied the effect of microwave pretreatment on oilseed extraction and the tocopherol content of canola oil extracted with hexane, and by cold‐pressing reported an increase in the canolol concentration of canola oils due to a microwave pretreatment. In previous works, a content of 27 mg kg −1 of canolol was reported for canola oil extracted with hexane, and of 168 mg kg −1 for canola oil extracted with hexane from microwave‐pretreated seeds, while a content of up to 532 mg kg −1 was observed in canola oil extracted by pressing from seeds subjected to combined hydrothermal‐microwave pretreatments .…”

Front-Face Fluorescence Spectroscopy and Chemometrics for Quality Control of Cold-Pressed Rapeseed Oil During Storage

“…Rapeseed oil has lower oxidative stability as compared to olive oil [6,7]. Several studies have been performed to assess quality degradation of rapeseed oil during photo-and autooxidation and storage [8][9][10][11][12][13][14]. It was found that the overall quality during storage was influenced by the type of container material (plastics, glass), storage conditions (light, temperature, oxygen availability), and time [13].…”