DPA treatment alters alpha-farnesene metabolism in peel of `Empire' apples stored in air or 1.5% O2 atmosphere
Bruce D. Whitaker
Postharvest Biology and Technology Vol: 18 Issue: 2 Pages: 91-97
2000
บทคัดย่อ
Treatment with diphenylamine (DPA), sometimes in combination with storage
under low (
1.5%)
O2 atmosphere, is the major commercial means of limiting superficial
scald in apple fruit. Synthesis and oxidation of the sesquiterpene 
-farnesene
are thought to be directly involved in induction of this storage disorder. Control
of scald by DPA has been ascribed to its ability to block both in vitro and in
vivo oxidation of -farnesene
to conjugated trienes (CTs), but a number of reports have indicated that DPA
has multiple effects, including reduction of -farnesene
synthesis, ethylene production, and respiration. The time course and levels of -farnesene
and CT accumulation in peel tissue were compared in `Empire' apples that were
either DPA-treated or untreated and stored for up to 28 weeks at 0°C
in air or under 1.5% O2 atmosphere. Also, it was found that the
HPLC-UV method previously developed to quantify -farnesene
and CTs could be used to simultaneously measure the concentration of DPA
residue. In air-stored fruit, DPA treatment protracted rather than diminished -farnesene
synthesis; a similar maximum level of -farnesene
was reached at 15 and 28 weeks in untreated and DPA-treated fruit,
respectively. DPA treatment delayed the onset of CT production by ~5 weeks and
reduced CT accumulation more than 2.5-fold. The low O2 atmosphere
was overall more effective than DPA treatment in reducing synthesis and
oxidation of -farnesene.
In combination, however, DPA and low O2 had a synergistic effect,
resulting in a ninefold reduction in -farnesene
and virtual elimination of CT production over 28 weeks. In both air and 1.5% O2,
DPA residue in the peel tissue declined rapidly during the first 15 weeks of
storage and more gradually thereafter, with an overall drop from ~11 to 1.1 
g g-1.