Eggplant PPO Activity Inhibition by MRPs
J. Agric. Food Chem., Vol. 54, No. 14, 2006 5125
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Figure 7. PPO activity recovery after dialysis of incubation media
containing heated cysteine (115
°C for 3 h 20 min, 0.25 M) and MRPIPmax
in white and gray, respectively. The incubation media consisted of PPO
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°C for 180 min (see the
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As compared to other chemical inhibitors (4-hexylresorcinol
and aromatic carboxylic compounds), MRPIPmax appears to be
much more efficient as an inhibitor of the eggplant PPO activity.
The apparent inhibition constant of these compounds thus
indicates that the addition of less than 2.5 µM (equivalent
cysteine before heating) is sufficient to inhibit the eggplant PPO
activity by 50%. In addition, the inhibition appears almost
irreversible. The strong potency of these MRPs to inhibit the
browning of fresh cut apple, mushroom, and eggplant was
shown even at low concentrations without effects on the color
of the products (36). These results are of great importance for
manufacturers considering shelf life product constraints linked
to fresh fruits and vegetable marketing. Further experiments at
a larger scale could show whether the replacement of sulfite by
MRPs in food processes would prevent the enzymatic browning
leading to the development of ready-to-eat or ready-to-cook
fruits and vegetables. Nevertheless, even if used as aromas or
naturally neoformed in heated foodstuffs, MRPs are suspected
of negative effects on health, suggesting that toxicological
analysis of these compounds should be carefully carried out
prior to their utilization in food industries. The next challenge
of this research will be the fractionation and the identification
of the compounds involved in these antioxidant properties in
order to characterize their toxicological behaviors and anti-
browning effects while widening their potential interest by
testing them on other oxidation phenomena.
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