One of the most important problems in storing
apples is skin browning (scald). Apples brown after 2–
4 months of storage. Thus, it is not possible to predict
the intensity of scald and its dependence on the date of
harvest. To prevent scald development, fruits are
treated with chemicals. Previously, diphenylamine was
used for this purpose. Apples were dipped in a solution
of this element. Later, 1methylcyclopropene gas was
applied in order to inhibit ethylene synthesis in fruit
[1]. As a result, apples were kept from ripening, which
also reduced the risk of scald.
Currently, very few studies have investigated possi
ble nonchemical control of scald during storage. It is
known that scald development depends on the harvest
date. Apples harvested too early are particularly prone
to scald. However, even when harvesting fruit on the
recommended date, it is not always possible to avoid
scald. Thus, indicators should be worked out for pre
dicting scald development that would show whether
chemical treatment is needed during harvesting. Max
imum treatment is often unnecessary, because scald
susceptibility is extremely variable. For 20 years after
the approval of antioxidant chemicals, little further
attention was given to this problem. Currently, the
interest is renewed due to the need to reduce the use of
chemicals wherever possible. It has been previously
demonstrated [3] that heat treatment of 38°C for
2 days slowed the development of scald in fruit stored
for 3 months, although by 6 months of storage it
reached the same levels as in control apples. Heating
for 4 days was effective in preventing scald for the first
3 months of storage. However, after 6 months of stor
age, scald incidence averaged 50%. It was also revealed
that fruit harvested on other days and heated for 4 days
were not fully protected from scald. Depending on har
vest dates, this type of treatment is not effective in inhib
iting scald. Therefore, it can substitute for chemical
treatment of scald for only shortterm fruit storage.
The purpose of the present study was to work out
new nonchemical control of scald during storage.
METHODS
The experiments were performed with Antonovka
obyknovennaya fruit during the period of ripening
prior to harvest. The fruit placed in storage were taken
from different harvests and varied in the content of
chlorophyll. The content of chlorophyll in the apple
skin was measured using the ratio of reflectance at
R750/R700 [2]. Apples (15 kg) were picked and placed in
a box. The fruit in storage were subjected to the cyclic
effect of heat and light to imitate a natural orchard
environment. For this purpose, apples were stored in
15–25°C air during the daytime and put in a refriger
ator (3–4°C) at night. After 4–5 months of storage,
the fruit were analyzed for scald.
RESULTS AND DISCUSSION
The year 2009 was marked by favorable weather
conditions: deviation in the sum of active tempera
tures from its long term average for the first decade of
September was 123°C; precipitation from the middle
of April to September 10 amounted to 254 mm; hydro
thermal index equaled 1.03. The content of chloro
phylls in the apple skin was measured from August 28
to September 21 using the ratio of reflectance at
R750/R700. It can be seen from Fig. 1 that the content
of chlorophylls in the apple skin was minimum on
August 31, September 11, and September 21. It
reached maximum values during September 4–9.
Heat and light treatment was applied to the fruit har
vested on the days as shown in Fig. 2. Simultaneously,
Heat Treat