ZEIN-BASED ENCAPSULATION OF BEET LEAF EXTRACT BY ANTISOLVENT PRECIPITATION: EFFECTS ON TOTAL PHENOLIC COMPOUND AND ANTIOXIDANT ACTIVITY

The industrial production and processing of beets generate byproducts, such as the leafs, which are often discarded despite their high potential for value addition. These leafs are rich in bioactive compounds with antioxidant properties and applications as functional ingredients and nutraceuticals. However, these compounds are susceptible to degradation by environmental factors. In this context, encapsulation stands out as a strategy to increase their stability, and antisolvent precipitation using zein is a promising technique for protecting bioactive compounds and preserving their functional properties. Thus, the objective of this study was to evaluate the total phenolic compound (TPC) content and antioxidant activity of beet leaf extracts (BLE) encapsulated by antisolvents precipitation using zein (ZE), comparing different ratios of extract to encapsulating material. The solvent used for extraction was 70% ethanol, at a ratio of 1:40 (1 g of sample
to 40 mL of solvent), for 2 h. ZE particles were obtained using the antisolvent precipitation technique. Initially, ZE solutions were prepared at concentrations of 1.0, 1.5, and 2.0 mg. mL⁻¹. Next, the BLE was prepared at a concentration of 1.0 mg·mL⁻¹. Subsequently, different ZE/BLE solutions were added under constant stirring, promoting zein precipitation and the formation of encapsulated particles. The final formulations evaluated had the following ZE/BLE ratios: 1:1 (ZEBLE 1), 1.5:1 (ZEBLE 2), and 2:1 (ZEBLE 3). The Folin-Ciocalteu method was used to measure TPC. The antioxidant activity of the microparticles was determined by their ability to inhibit the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical. The results showed that the ZEBLE 3 formulation had the highest TPC content, reaching approximately 28 mg GAE. g BLE⁻¹. This finding indicates that increasing the proportion of zein favored the recovery of phenolic compounds, a trend corroborated by the other formulations evaluated, in which the TPC content increased progressively as the zein-to-extract ratio rose. A similar trend was observed for antioxidant activity, with the ZEBLE 3 formulation exhibiting the highest value, approximately 22 μmol TEAC. g⁻¹. The positive relationship between the zein proportion and antioxidant activity suggests that higher concentrations of the encapsulating material promote better preservation and recovery of the bioactive compounds responsible for antioxidant capacity, as evidenced by the gradual increase in this parameter across all analyzed formulations. Antisolvent precipitation encapsulation using zein proved to be a promising strategy for the preservation of bioactive compounds from beet leaf extract. The ZEBLE 3 formulation exhibited the highest levels of total phenolic compounds and antioxidant activity, indicating that higher proportions of zein enhanced the performance of the formulations.
Funding: FAPESP (2018/14938-4; 2024/10205-3; 2024/17921-6; 2023/10873-3; 2024/06628-6; 2022/14075-1), CAPES (001), and CNPQ (302451/2021-8).