Efficacy of canolol and guaiacol in the protection of cold-pressed oils being a dietary source linoleic acid against oxidative deterioration.

Oils high in linoleic acid are the main sources of polyunsaturated fatty acids in the human diet. The study attempted to increase the oxidative stability of 11 cold-pressed oils with various linoleic acid percentages by adding phenolic acid derivatives (canolol, guaiacol) at concentrations of 20-100 ppm. The oils were characterized by acid, peroxide and anisidine values, diene, triene, and water contents, fatty acid composition, and bioactive compounds. Their oxidative stability was evaluated before and after the addition of phenolic acid derivatives in the Rancimat test. The results indicate that both additives can be deployed as antioxidants in linoleic acid-rich oils, but canolol elicits a stronger protective effect (over fourfold). 100 ppm of canolol caused a significant increase in the oxidative stability of most oils (31-79%). The guaiacol effectiveness was greater (13-19% increase) at higher concentrations in hemp and poppy oils, but its lower amounts were more relevant for other oils.

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).

Impact of the addition of 4-vinyl-derivatives of ferulic and sinapic acids on retention of fatty acids and terpenoids in cold-pressed rapeseed and flaxseed oils during the induction period of oxidation.

In the western diet there is an oversupply of n-6 fatty acids. This adverse trend can be balanced by the consumption of rapeseed and flaxseed oils rich in α-linolenic acid (n-3). However, the high share of this fatty acid contributes to low oxidative stability of oil. Oxidation decreases n-3 fatty acid and other bioactive compounds contents, which adversely affects oil nutritional value. In this study, the impact of ferulic and sinapic acids vinyl derivatives on the fatty acids and oil terpenoids (sterols, tocols, carotenoids, squalene) retention at the end of induction period during accelerated oxidation of rapeseed and flaxseed cold-pressed oils was investigated. It was found that the use of 4-vinylsyringol (4-VS) or 4-vinylquaiacol (4-VQ) increased the retention of intact sterols and carotenoids (at least 2-fold) and squalene (at least 4-fold). The 4-VQ addition also inhibited the α-linolenic acid loss. Unfortunately, both phenolic derivatives favoured α-tocopherol decay in rapeseed oil.

Comparison of the effect of sinapic and ferulic acids derivatives (4-vinylsyringol vs. 4-vinylguaiacol) as antioxidants of rapeseed, flaxseed, and extra virgin olive oils.

The aim of the work is to compare the antioxidant activity of 4-vinylguaiacol (4-VQ) and 4-vinylsyringol (4-VS) added to stabilize three (flaxseed, olive and rapeseed) commercial oils. The phenolics were added at concentration of 20, 40 and 80mg per 100g of oil. The oils were oxidized in a Rancimat test at 110°C. The linear dependences between the concentrations of each of these compounds and the induction period (IP) were found. Generally, 4-VQ was more effective, since the determined IP increase after its addition was from 5 to 25-fold higher than for the same addition of 4-VS. The highest increase was noted for flaxseed oil, for which 80mg 4-VQ addition per 100g of oil resulted in 50% IP increase. The highest absolute values of IP were reached by extra virgin olive oil, naturally abundant in phenolic compounds and with the lowest fatty acids oxidation index.