Dual-objective optimization of ultrasound-assisted organic acid extraction of pectin from umbu (Spondias tuberosa L.): a promising Brazilian native fruit from Caatinga biome

Fruit waste and by-products have considerable potential for valorization as a source of value-added compounds of industrial interest, and unconventional substrates, including native fruits, are a promising source of pectins. This study investigated the potential of umbu (Spondias tuberosa L.) peel as a raw material for pectin isolation using high-intensity ultrasound technology and organic acid for the development of an eco-friendly extraction method aiming high yields and adequate degree of esterification. After optimization through central composite design (CCD) with three independent variables (2³) and five levels, a high yield close to 22% of low esterified pectin (DE = 46%) was achieved under ultrasound amplitude of 60%, SLR (solid-to-liquid ratio) of 1:33, and pH 1.5. The extraction process was validated, and the effects of different acids on the yield of pectins and DE were evaluated, demonstrating that the use of citric acid allows yields of around 22% of low methoxyl pectin (LMP) to be achieved, confirming the reproducibility of the process, while using oxalic acid, nitric acid, and hydrochloric acid led to the production of around 13% of high methoxyl pectin (HMP). The quality of pectins, assessed through instrumental color, showed significant differences when compared to commercial citrus pectin CCP, which demonstrated the influence of the type of raw material and extraction method on the quality of the product obtained. Therefore, our study describes for the first time the extraction of pectins from umbu peels using ultrasound technology, proving that this material is a promising source of LMP and HMP pectins and that this approach can considered  an efficient green method to obtain different food grade pectins with higher yield and quality.