Effect of high hydrostatic pressure on the polyphenols and antioxidant activity of plantain pulp (Musa paradisiaca AAB).

BACKGROUND: The impact of high-pressure processing (HPP) on the polyphenol (PP) content and antioxidant activity (AOX) of plantain pulp was evaluated. Pressures of 400, 500 and 600 MPa were applied to plantain pulp for 90 and 180 s at room temperature (25 °C). Polyphenoloxidase activity, extractable (EPP) and non-extractable PP (NEPP) contents, flavonoid content and AOX (FRAP, ABTS•+ ) were evaluated. In addition, PP identification was performed using high-performance liquid chromatography. RESULTS: Polyphenoloxidase activity was inhibited after HPP under all of the conditions studied. Increases of 110.80% and 137.40% in EPP content under conditions of 500 MPa/180 s and 600 MPa/90 s were observed with a simultaneous improvement in the AOX with increments of up to 128.71%. The treatment under conditions of 500 MPa/90 s had the highest total PP content, including the highest content of flavonoids (0.22 g ellagic acid equivalents kg-1 dry weight) and the proportion of NEPP that contained hydrolysable PPs (91.12 g gallic acid equivalents kg-1 dry weight with high AOX. The identified PPs included catechin, quercetin, gallic and hydroxybenzoic acids. CONCLUSION: HPP performed at a room temperature can be used for improving the total content of PP compounds in plantain pulp under specific pressure and time conditions. © 2016 Society of Chemical Industry.

Effect of stevia and citric acid on the stability of phenolic compounds and in vitro antioxidant and antidiabetic capacity of a roselle (Hibiscus sabdariffa L.) beverage.

Plant infusions are consumed due to their beneficial effects on health, which is attributed to their bioactive compounds content. However, these compounds are susceptible to degradation during processing and storage. The objective of this research was to evaluate the effect of stevia and citric acid on the stability of phenolic compounds, antioxidant capacity and carbohydrate-hydrolysing enzyme inhibitory activity of roselle beverages during storage. The optimum extraction conditions of roselle polyphenolic compounds was of 95 °C/60 min, which was obtained by a second order experimental design. The incorporation of stevia increased the stability of colour and some polyphenols, such as quercetin, gallic acid and rosmarinic acid, during storage. In addition, stevia decreased the loss of ABTS, DPPH scavenging activity and α-amylase inhibitory capacity, whereas the incorporation of citric acid showed no effect. These results may contribute to the improvement of technological processes for the elaboration of hypocaloric and functional beverages.