Inhibition of lipid oxidation in soybean oil-in-water emulsions and bulk oil using acid hydrolyzed extracts of sugar beet leaves

This research investigated the effects of acid hydrolysis (AH) on phenolic extracts of sugar beet greens (SBG). SBG extracts were acid hydrolyzed using 0.6 M HCl at 80 ℃, and their total phenolic content (TPC), antioxidant activity, metal chelating activity, chlorophyll content and phenolic profile were monitored. The cupric chelating activity, TPC, and DPPH radical scavenging activity of extracts were significantly improved (p ≤ 0.05) after AH. The chlorophyll content decreased significantly after AH. Moreover, AH disrupted the glycosidic link of phenolic compounds, causing concentrations of individual polyphenols to rise or the appearance of new phenolics such as catechin, myricetin, etc. The extracts were added to soybean oil-in-water emulsions and bulk oil to inhibit lipid oxidation. The emulsion was prepared by adding 2% (w/v) stripped soybean oil and 0.2% (w/v) Tween 20 as a surfactant to a sodium acetate-imidazole buffer (10 mM, pH 7.0). The physical properties of the emulsions were examined by assessing the distribution of droplet sizes and the zeta potential using a Zetasizer Nano-ZS apparatus. The oxidation stability of the emulsion was monitored by measuring the primary (hydroperoxide) and secondary (hexanal) oxidation products. The Rancimat method was used to measure the oxidative stability of bulk soybean oil. The emulsion containing 400 μM TPC of the control extract had the longest lag phase in oxidative stability. However, the bulk oil containing 400 μM TPC of the acid-hydrolyzed extract had the highest oxidative stability. Figure 1 shows the design of experiment of the project. The better effectiveness of acidhydrolyzed extract in the bulk suggests that the modified phenolic composition had a more favorable impact in this lipid environment.