Effect on total phenolic content
Phenolic compounds are beneficial compounds mainly found in
fruits and vegetables. They have been implicated in the reduction of degenerative diseases in human beings primarily because of their antioxidant potential. The initial phenolic content of the fresh sample
(untreated) was 33.6 mg GAE/100 mL. At 200, 300 and 400 MPa, the
TP (total phenols) content of the samples were well retained as in the
untreated samples (Fig. 2). High pressure treatment at 30 and 40 °C resulted in a significant increase in TP content (p b 0.05). This could be attributed to the enhanced extractability and solubility of the phenolic
compounds under pressurization (Kaushik et al., 2014). The pressure induced extraction effect on TP led to the increase in the TP content ranging from 3 to 24%; this could be the result of plant cell disruption caused
by instantaneous pressurization, leading to a higher extractability of
these compounds (Van Eylen et al., 2009). The pressure induced extraction effect on TP was also observed after single pulse. For instance, at
400 MPa/40 °C/1 s, the TP content showed an increase of 18%, in comparison to an increase of 3% at 20 min under the same pressure–temperature conditions. This trend was prominent at all temperatures, except
at 70 °C. On the other hand, TP content in the beverage reduced significantly (p b 0.05) at 60 and 70 °C for extended pressure hold period
(≥10 min). For example, at 400 MPa/70 °C/5 min, the total phenol contents was 35.3 GAE/100 mL of beverage, but prolonged processing