Phenylalanine ammonia lyase inhibitors control browning of cut lettuce
Peiser, G., López-Gálvez, G., Cantwell, M. and Saltveit, M.E.
Postharvest Biology and Technology. Volume 14, Number 2, 1998. Pages 171-177.
1998
บทคัดย่อ
Inhibitors of the first enzyme in the phenylpropanoid pathway, phenylalanine
ammonia lyase (PAL), were used to investigate the role of phenolic metabolism
in browning of lettuce tissue. Excised 4×7-cm midrib segments were
soaked for 1 h at 20°C in aqueous solutions of the PAL inhibitors, 
-aminooxyacetic
acid (AOA; 0.1¯10 mM), 2-aminoindan-2-phosphonic acid (AIP;
50¯100
M),
and -aminooxi-
-phenylpropionic
acid (AOPP; 200 M).
Browning of the cut ends and uncut surfaces was measured using a visual score,
and CIE color values (L*, a*, b*). Overall browning
potential was measured as the absorbance at 340 nm of an aqueous extract of the
tissue. The visual scores were more highly correlated with hue angle than with
the a* and b* values; there was no correlation with the L*
values. Ethylene applied at 5 l
l-1 had no effect upon browning compared with the air treatments.
AIP at 50 M
and AOPP at 200 M
effectively inhibited browning; AOA was less effective requiring 3¯10
mM to reduce browning. These results confirm the view that for browning to
occur in lettuce PAL activity is required to form phenolics that are
subsequently oxidized and polymerized.