Effect of thermal processing on oxide reductase inactivation and on colour fixing in erva‐mate (Ilex paraguariensis St. Hill) leaves

Abstract

Leaves of erva-mate (Ilex paraguariensis St. Hill) were heat treated with different combinations of time and temperature. Polyphenol oxidase (PPO) and peroxidase (POD) residual activities and colouring (L, a, b and DE) were studied after treatment for 3 weeks. The best results for enzyme inactivation after heat treatment were obtained with the leaves treated at 450°C for 15 s and at 500°C for 10 s, with reductions of 90.6% and 83.4% for PPO and 94.5% and 92.7% for POD. These groups also showed low levels of enzyme activity during the first few days of storage, and a few days later no enzyme activity was detected. The data on the colours, specially -a values (green colour), were in accordance with results for enzyme activity and helped in the research on the changes that occur in the leaves during storage. Data from this work can be suggested for the improvement of the current method of erva-mate processing, which is still performed empirically.

Thermal inactivation of peroxidase and polyphenoloxidase enzymes in mate leaves (Ilex paraguariensis) in a conveyor belt oven

“…There are few studies on thermal inactivation of POD and PPO enzymes in mate leaves (Ceni et al, 2009;Provesi et al, 2010;Xander, Acosta, Scipioni, & Argüello, 2000) and none on the kinetics of the inactivation of these enzymes in the plant matrix of mate, as performed in this study. This raw material has irregularities in its dimensions which should be considered for future industrial projects.…”

“…These results with temperatures lower than those in the traditional industrial processing show that the inactivation of PPO enzymes does not justify the use of excessive heat, commonly adopted in mate factories. Provesi et al (2010) evaluated the thermal treatment of mate leaves in an oven and reported that, after thermal treatment, PPO enzymes showed higher residual activity than POD enzymes. However, only POD showed recovery of enzyme activity after seven days of storage (Whitaker, Voragen, & Wong, 2003).…”

“…The criterion for the selection of the treatment was based on the treatments that showed residual enzyme activity below 10%, which was the value established as the most adequate in order to assure thermal inactivation of the enzymes (Provesi et al, 2010).…”

“…These enzymes are responsible for undesirable changes in the colour of mate, which is consumers' first criterion for choice (Primo et al, 2007;Provesi, Nabechima, Vieira, & Amante, 2010). In Brazil, consumers prefer mate that has a bright green colour.…”

Effect of the Mild Temperature and Traditional Treatments on Residual Peroxidase Activity, Color, and Chlorophyll Content on Storage of Mate (Ilex paraguariensis) Tea

“…Although mate processing is done in factories at a high temperature, the sapeco operation at mild temperature was studied by Provesi and others () and Nabechima (), and it was found that 255 °C was sufficient for the process, and that it inactivated oxidoreductase enzymes.…”