Agriculture Reference
In-Depth Information
may come from several others as well - farms that are too small to have a packing shed of
their own or that simply don't want the bother. Here all the fruit is combined into one lot,
sorted only by variety.
Women workers line both sides of the belt, culling any fruit that is obviously damaged.
Rejected nectarines will be used for animal feed or fertilizer. The fruit that is left runs un-
der an electric eye that sorts it by size. As each nectarine reaches the gate for its size, it
is shunted through into the hands of one of the waiting women, who carefully places it
in a packing case. Peaches and nectarines are typically packed into a two-layer cardboard
tray container to a total weight of roughly twenty-two pounds. These containers are then
stacked on wooden pallets and toted by forklift to be cooled.
This cooling stage is critical. At harvest the internal temperature of nectarines can be in
the 90s. If left unattended, they would spoil in less than a day. The ideal storage temper-
ature for peaches and nectarines is right at freezing - 32 degrees (because they contain so
much sugar, peaches don't freeze until they get between 27 and 30 degrees). Much warmer
than that, and the fruit enters the perilous "chilling injury" zone - roughly 35 to 45 degrees.
The reasons behind the harmful effects of cold storage within this temperature range have
not been fully explained, but the symptoms are well known: a cottony, dry texture and an
absence of flavor. As little as a day spent at these temperatures can be enough to ruin a
piece of fruit.
Different sheds cool their fruit in different ways. Probably the most common method is
forced-air cooling, basically putting the fruit in a refrigerator the size of a handball court.
The next most popular is hydrocooling, streaming ice-cold water over the bins, like put-
ting the fruit under a giant cold shower. The Rolls-Royce of chilling techniques is vacuum
cooling, but this is so expensive that it is used only for extremely perishable items such
as herbs and leaf lettuces. The fruit is placed in a sealed container, and all of the air is
pumped out. When the atmospheric pressure gets low enough, some of the moisture from
the fruit begins to evaporate and cool the fruit.
Some shippers have begun using a new cooling process called "preconditioning,"
which shows promise in eliminating chill injury. Developed by the University of Califor-
nia at Davis, it calls for the fruit to be cooled only to between 68 and 77 degrees and then
to be held for twelve to thirty-six hours to allow the fruit to begin the ripening process.
The fruit is then chilled to below 34 degrees for storing and shipping. The fruit is held in
giant refrigerated rooms, with pallets stacked fifteen to eighteen feet high, until it is ready
to be shipped.
