Tocopherol degradation and lipid oxidation during storage of Chenopodium quinoa

Chenopodium quinoa serves as an essential source of dietary lipids and tocopherols. The current study evaluated the stability of tocopherols and the occurrence of lipid oxidation in quinoa seeds, sprouts, and flakes during storage. Quinoa samples (seed flour, sprout flour, flakes) were stored at different temperatures (0°C, 25°C, 35°C); changes in their tocopherol profile and the progress of lipid oxidation were evaluated for 180 days. Tocopherol concentration was measured using HPLC, and the degradation of major homologues was modeled using first and second order kinetics. γ- tocopherol (107-135 µg g-1 dwb) was present in highest concentration in fresh products, followed by α- tocopherol (19.3- 32.4 µg g-1 dwb) and δ- tocopherol (1.6- 2.3 µg g-1 dwb). Storage at 25°C and 35°C resulted in a drastic reduction of tocopherols; out of the three products, seed flour and flakes retained <50% of γ- and α- tocopherols after 180 days, while sprout flour showed better retention at both temperatures. The investigation of lipid oxidation revealed the presence of 13 volatile compounds that were formed due to oxidation of linoleic, linolenic, and oleic acids. Hexanal, a key indicator of oxidation, significantly increased at 35°C, demonstrating that temperature during storage represents a critical factor to maintain the quality of quinoa products.