Modification of alpha-farnesene levels in cool-stored `Granny Smith' apples by ventilation
Adam J. Matich, Nigel H. Banks and Daryl D. Rowan
Postharvest Biology and Technology Vol: 14 Issue: 2 Page 159-170
1998
บทคัดย่อ
`Granny Smith' apples (Malus domestica Borkh) were arranged
sequentially in low density polyethylene (LDPE) plastic tubes and ventilated
with humidified air at 1°C to characterise the effect of ventilation on the
accumulation, oxidation and evaporative depletion of -farnesene
from the apple cuticle. Evaporation of
-farnesene
into the air stream produced a vapour phase concentration gradient along the
tubes, with a concomitant decrease in the rate of evaporation of
-farnesene
from the fruit with distance down the tube. The concentration of
-farnesene
in the apple wax rose 13-fold during the first 5 weeks of cool storage and
decreased thereafter. In contrast, that in the air rose to a maximum value at
between 10 and 15 weeks' storage time and then decreased. Concentrations of
-farnesene
oxidation products (conjugated trienes) in the wax increased steadily with
storage time, but were not markedly affected by ventilation and were not well
correlated with
-farnesene
concentrations. Mass transfer coefficients between 1 and 19 nmol s-1
m-2 Pa-1 were obtained for evaporative loss of
-farnesene
from the apple surface. These coefficients are 10¯200
times greater than those for the permeance of the fruit skin to metabolic gases
which suggests that loss of
-farnesene
occurs by evaporative release from the cuticle wax, rather than diffusion
through the skin. Mass balance calculations for the depletion of
-farnesene
from the apples indicated a high rate of accumulation of
-farnesene
during the first 5 weeks of storage followed by a short period of rapid
depletion and then a longer period of gradual depletion. This suggested that
the rate of loss of
-farnesene
from the surface of the fruit depends more on storage time than on its
concentration in the wax. Comparison between concentrations of
-farnesene
in ventilated and non-ventilated fruit supported these conclusions and
suggested that reduction of superficial scald by ventilation may not be
explicable merely by enhanced evaporative depletion of
-farnesene.