A Strategy to Minimize the Chlorophyll Content in the Phenolic Extract of Sugar Beet Leaves: Can this Extract Work as a Natural Antioxidant in Vegetable Oils?

Abstract The presence of chlorophylls in phenolic extracts may limit their use in food products due to undesirable coloration. This project seeks to minimize the co-extraction of chlorophylls during the ultrasonic-assisted extraction (UAE) of polyphenols from sugar beet leaves (SBLs) by optimizing the extraction condition using response surface methodology (RSM). Optimization aimed to minimize the chlorophyll yield (CY) of the extraction while maximizing the total phenolic content (TPC) and total flavonoid content (TFC) with the lowest possible amount of sample. Optimized extraction parameters were 25% ethanol as solvent, 8 min extraction time, and 3.98% (w/v) solid:liquid ratio. The experimental values at optimized condition were 11.49 ± 0.66 mmol gallic acid equivalent (GAE)/L TPC, 2.09 ± 0.06 mmol quercetin equivalent/L TFC, and 0.05 ± 0.01 mg/g CY. In the optimized extract, the ferric reducing antioxidant power (FRAP) was 3.16 ± 0.25 mmol trolox equivalent/L, and trans -ferulic acid had the highest concentration (123.39 ± 4.13 µmol/L) among the detected phenolic compounds. The optimized extract, at a phenolic concentration of 300 µmol GAE/L, chelated cupric and ferrous ions by 48.95 ± 1.06%, and 66.18 ± 1.31%, respectively. Adding the optimized extract to vegetable oils increased their oxidative stability significantly ( p < 0.05). The antioxidant activity index of the optimized extract in all the cases was comparable to butylated hydroxytoluene (BHT), confirming that the obtained extract could be a reliable substitute for synthetic antioxidants. The results of this study are important in enhancing the utilization of extracts recovered from food by-products in the food industry. Graphical Abstract