Aplicação de tecnologias não térmicas no processamento do açaí (Euterpe oleracea Mart.)

Abstract

The main process to which açaí is submitted is to obtain its frozen edible part, known as "açaí pulp" or just "açaí". The Brazilian legislation recommends that the pulp be pasteurized in order to reduce the enzymatic activity and the microbial load. However, pasteurization causes a reduction of some nutrients, bioactive compounds, and changes in sensory characteristics. Thus, studies with the application of non-thermal technologies have been proposed to reduce these losses. Thus, the objective of this work was to evaluate the effects of the application of atmospheric cold plasma (ACP) and continuous ultrasound (US) on the enzymatic activity, color, antioxidant activity, anthocyanin content, phenolic compounds and their bioaccessibility in açaí pulp. In the treatment with ACP the variables excitation frequency (50, 500 and 750 Hz) and time (5, 10 and 15 min) were studied, and in the treatment with continuous US the variables power (100, 120 and 150 W) and passage cycles (1, 2, 3 and 5 cycles) were studied, in both technologies studied the variables responses were enzymatic activity, color, antioxidant activity, and total content of phenolics and total monomeric anthocyanins. The processing at 50 Hz/15 min showed greater reduction in polyphenoloxidase (82.4%) and peroxidase (42.3%) activity (p < 0.05), while in the 50 Hz/10 min condition there was an increase in the bioaccessibility of catechin (194.70%), epicatechin (383, 44%), epigallocatechin gallate (68.84%), procyanidin B1 (130.71%), rutin (16.84%), caffeic acid (341.48%) and chlorogenic acid (57.63%), contributing to the increase in antioxidant activity of the bioaccessible fraction evaluated by DPPH and ORAC assays. The continuous US technology increased the intensity of the purple color and the phenolic content and reduced the activity of polyphenoloxidase by 62.24% (100 W/2 cycles) and peroxidase by 41.91% (150 W/1 cycles). Furthermore, the treatments 100 W/2 cycles and 150 W/1 cycle increased the bioaccessibility of catechin (131.05% and 107.12%), epicatechin (183.57% and 356.19), epigallocatechin gallate (77.54% and 303.54%), procyanidin B1 (115.49% and 99.72%) and procyanidin A2 (124.40% and 128.18%) with consequent elevation of antioxidant activity. The results indicate that PFA and continuous US contribute to reduction of polyphenoloxidase and peroxidase activity, as well as to quality and bioaccessibility of phenolic compounds in açaí pulp. However, optimization protocols should be studied to achieve the best product quality.