Edible flowers as a new source of natural antioxidants for oxidative protection of cold-pressed oils rich in omega-3 fatty acids

This study aimed to evaluate and compare the effect of methanolic extracts from 23 lyophilized Polish edible flowers on the oxidative stability of two cold-pressed oils rich in omega-3 fatty acids. Two popular oils (flax and chia seed oils) were used in the study and characterized for their chemical composition, quality and oxidative stability. Hydro- and lipophilic components, and antioxidant activity were determined in the flower extracts. The effectiveness of the edible flower extracts in oxidative protection of cold-pressed oils was evaluated in the Rancimat test. The edible flower extracts differed significantly in their composition and antioxidant activity. Among the extracts, the richest source of phenolic compounds were those obtained from red begonia (996.80 ppm), red geranium (1028.16 ppm), and small leaved lime (1003.62 ppm) flowers; whereas red begonia and red geranium flower extracts were also found to be valuable sources of flavonoids, 343.70 and 307.34 ppm, respectively. The extracts from lyophilized edible flowers had a low content of lipophilic pigments (0.97-9.01 ppm for chlorophylls and 0.03-12.34 ppm for carotenoids), while the content of tocopherols varied greatly (0.70-193.34 ppm). Most of the analyzed extracts were characterized by a high DPPH radical inhibition value (>10 µM TE/mL). Almost all studied edible flower extracts improved oxidative stability of the cold-pressed flax and chia seed oils. More favorable effects were observed in chia seed oil, in particular after the addition of extracts from nasturtium, marigold scattered, dog rose, and daylilies flowers (the changes were more than 50% higher compared to the control sample).

Keywords: Chia seed oil; DPPH radical inhibition; Edible flowers; Flavonoids; Flax seed oil; Induction time; Phenolic compounds.