Avaliação do efeito da temperatura de secagem nos compostos bioativos de extratos da casca de pitaia

Abstract

The present study investigates the effects of drying on bioactive compounds present in dragon fruit peel, such as antioxidants, highlighting their importance in preserving the quality of food and pharmaceutical products. The aim is to understand the degradation mechanisms of these compounds during the drying process and identify optimal conditions for their preservation. The results will contribute to the development of drying strategies that minimize losses and maximize the effectiveness of bioactive compound preservation. These compounds include flavonoids, phenolics, anthocyanins, yellow flavonoids, and carotenoids. Tests were conducted to verify whether the water content in the samples would impact antioxidant activity analyses. In this regard, no significant difference was observed between the means of phenolics, flavonoids, and DPPH for fresh and freeze-dried samples at a 5% significance level. A central composite rotational design with two factors (extraction time and solvent percentage) was conducted to optimize the extraction of bioactive compounds for methanolic and ethanolic extracts from fresh peels using ultrasound-assisted extraction. The optimal extraction conditions were found to be 50% methanol in 30 minutes and 92.3% ethanol in 51.12 minutes. To evaluate the antioxidant capacity of the extracts under the best extraction conditions, tests were performed for DPPH free radical scavenging, total phenolic content, total flavonoid content, carotenoids, and anthocyanins. The drying modeling indicated that all evaluated models fit well to the experimental data, with the Logarithmic model standing out at 40°C, the Midilli model at 60°C, and the Fractional Order model at 80°C. The extraction kinetics proved to be faster and more efficient with ethanol compared to methanol, especially in DPPH readings, with the highest antioxidant activity observed at 40 minutes for ethanol and 60 minutes for methanol. The mathematical models that best represented the extraction kinetics for gallic acid yield using methanol were So and McDonald’s and Fractional Order, while for ethanol, So and McDonald’s and Elovich were the most suitable. The quantification of bioactive compounds by UHPLC/MS-MS revealed good thermal stability for gallic acid, quercetin, and ellagic acid at temperatures of 40°C, 60°C, and 80°C, while other compounds showed degradation (p-coumaric acid and rutin) or an increase in their concentrations (chlorogenic acid and ferulic acid) compared to the fresh dragon fruit peel extracts. In this regard, there was evidence that drying interferes with the composition of bioactive compounds in dragon fruit peel extracts. The study revealed that the drying process impacts the stability of the bioactive compounds in dragon fruit peels. Compounds such as gallic acid and quercetin showed high thermal resistance, while others, such as p-coumaric acid, exhibited greater degradation. Moderate temperatures and controlled drying times are essential to preserve these compounds, highlighting the potential of dragon fruit peels as a source of natural antioxidants.