A study was made of the effect of high hydrostatic pressure treatment
(50−500 MPa) combined
with heat treatment (20−60 °C) on peroxidase (POD), polyphenol
oxidase (PPO), and pectin
methylesterase (PME) activities of tomato puree. Assays were
carried out on fresh made tomato
puree, and a 15 min treatment time was selected.
Pressurization/depressurization treatments caused
a continuous denaturation of soluble proteins at room temperature (20
°C). Also, ultrahigh
hydrostatic pressure (UHP)/mild heat treatments produced a significant
reduction (32.5%) of PME
activity when a combination of 150 MPa/30 °C treatment was employed,
while some activation was
observed for treatments carried out at 335−500 MPa and different
temperatures. A reduction of
POD activity (25%) was obtained in tomato purees treated at 350 MPa/20
°C, but a combination of
higher pressures and mild temperatures (30−60 °C) produced an
enhancement of this activity. PPO
activity did not show any significant change due to
UHP/mild-temperature treatments in tomato
product. Only a combination of 200 MPa/20 °C seemed to produce a
significant loss (10%) in PPO
activity.
Keywords: High pressure; tomato; polyphenol oxidase; peroxidase; pectin
methylesterase; proteins
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