Background: Growing interest in sustainable packaging materials, such as recycled polyethylene terephthalate (rPET), raises the question of whether they can effectively replace traditional glass in packaging cold-pressed vegetable oils, which are particularly susceptible to oxidation. Methods: Rapeseed oil and golden flaxseed oil were analyzed after 6 months of storage in glass and rPET bottles at 4 °C and 21 °C. Peroxide value, tocopherol content, sterol and oxyphytosterol profiles, color parameters, and triacylglycerol composition were evaluated using validated ISO/AOCS, HPLC, and GC methods; results were subjected to ANOVA statistical analysis. Results: Temperature was shown to be the main factor determining the rate of degradation, and flaxseed oil exhibited significantly lower oxidative stability compared with rapeseed oil. At 21 °C, a rapid increase in peroxide value, intensive tocopherol degradation, greater sterol losses, and deterioration of color were observed, particularly in samples stored in rPET. At 4 °C, the rate of change was markedly lower, and differences between glass and rPET remained minimal. Conclusions: Glass provides the best protection against oxidation; however, rPET can serve as a suitable packaging material for vegetable oils with higher oxidative stability stored under refrigerated conditions; at room temperature, it promotes a noticeable deterioration in oil quality.
Kilian‐Pięta et al. (Thu,) studied this question.