Bioactive compounds and enzymatic activity of red vegetable smoothies during storage

Abstract

Changes in the polyphenoloxidase (PPO), peroxidase (POD), pectinmethylesterase (PME) and phenylalanine ammonia-lyase (PAL) activities, total phenolics content (TPC) and total antioxidant capacity (TAC) on two red fresh vegetable smoothies (R1 and R2) based on tomato, red pepper, broccoli and carrot stored at 5 and 20 °C were monitored. A conventional thermal treatment of 3 min at 80 °C was applied to extend shelf life. The initial PPO, POD, and PME activities of R1/R2 smoothies (58/83, 0.023/0.020, and 1.50/0.38 kg−1 fresh weight (fw)) were 100 % reduced after thermal treatment and maintained at zero levels during storage up to 40 and 58 days at 20 and 5 °C, respectively. Initial PAL activities of R1/R2 smoothies of 7.3/11.5 μmol cinnamic acid formed kg−1 h−1 were reduced in a 65–70 % after thermal treatment. The initial TPC of R1/R2 smoothies were 404/462 mg GAE kg−1 fw, and it was not significantly affected after the thermal treatment. No great TPC degradation during storage was observed either at 5 or 20 °C. The initial TAC of R1/R2 smoothies were 301/373 mg Trolox equivalent kg−1 fw which was increased 62/77 % after the thermal treatment. The TAC showed a similar behavior to TPC during storage being those two parameters satisfactorily correlated (r 2 = 0.69–0.88). In conclusion, the thermal treatment inactivated the studied quality-degrading enzymes. Health-promoting compounds were well preserved during 58 days at 5 °C and 40 days at 20 °C in red fresh vegetable smoothies.