Processamento de suco de açaí (Euterpe oleracea) por tecnologias não térmicas: efeitos nos compostos bioativos e na atividade das enzimas peroxidase e polifenoloxidase.

Abstract

Non-thermal processing technologies attract attention because they aim to lower the loss of important nutritional components and not causing undesirable changes in food. The aim of this study was to evaluate the effects of ultrasonic, plasma and pulsed light on the phenolic compounds, anthocyanins, antioxidant and enzymatic activity (polyphenoloxidase and peroxidase) of açai juice compared to thermal processing. Stability, application of sequential processes and bioaccessibility of bioactive compounds were also evaluated. The first step of this study consisted of the development of an experimental design to evaluate the effects of these technologies individually in the açai juice. The best processing conditions found were applied again, as well as the sequential application of these technologies (ultrasound and plasma). Finally, bioaccessibility of bioactive compounds was evaluated. The results showed an increase in total phenolics in juices treated by ultrasound (3079,16±25,00 mg gallic acid/L), plasma (1384,37 ±43,75 mg gallic acid/L) and thermal processing (1945,83±58,00 mg gallic acid/L) compared to the control sample. Regarding anthocyanins, an increase was observed only by plasma (149,17 ± 9,95 mg de cyanidine-3-glucoside /L) and pulsed light (124,74 ± 5,50 mg de cyanidine-3-glucoside /L) compared to the control sample. Antioxidant activity increased in all applied processing, since the increase of phenolic and anthocyanin compounds directly influenced antioxidant activity. The enzymes PPO and POD showed resistance to the applied treatments. The largest reduction in residual enzymatic activity was found in cold plasma processing for peroxidase enzyme (55.44 ± 4.61). Furthermore, the stability was evaluated by principal component analysis (PCA). The shorter storage period (0 and 30 days) showed higher amounts of vitamin C, anthocyanins, PPO, POD, DPPH, ABTS and FRAP, which decreased after longer storage periods (45 and 60 days). The samples stored by 45 and 60 days presented the highest amounts of total phenolics. Thermally processed samples, regardless of storage period, decreased the residual activity of the enzymes PPO and POD, as well as the antioxidant activity determined by the DPPH, ABTS and FRAP methods. As for the sequential treatments, these showed an increase in residual activity of POD and PPO enzymes after processing. It was also observed that in sequential processing the order of application had no relevant effect on the composition of acai juices. Regarding bioaccessibility of sequential processing, phenolic and anthocyanin contents were reduced by 20 and 67% respectively after the digestion process. However, non-thermal technologies showing better results when applied individually and the storage period showed important results up to 30 days. In this context, further studies are important to optimize these processing variables in order to maintain the functional characteristics of products such as fruit juices.