Agriculture Reference
In-Depth Information
United States) indicated that most impact bruising damage
occurs during the packinghouse operation and long trans-
portation from orchard to packinghouse. Critical impact
bruising thresholds (the minimum fruit firmness measured
at the weakest point to tolerate impact abuse) have been
developed for many of the commercially important peach
and nectarine cultivars.
Abrasion damage can occur at any time during post-
harvest handling. Protection against abrasion damage
involves procedures to reduce vibrations during transport
and handling by immobilizing the fruit. These procedures
include: installing air suspension systems on axles of field
and highway trucks, using plastic film liners inside field
bins, using plastic bins, installing special bin top pads
before transport, avoiding abrasion on the packing line and
using packing procedures that immobilize the fruit within
the shipping container before they are transported to
market. In situations when abrasion damage occurs during
harvesting on fruit that have heavy metal contaminants,
such as iron, copper and/or aluminium, on their skin, a dark
discolouration (inking or peach skin discolouration) is
formed on the surface of peaches and nectarines. These
dark or brown spots or stripes on the fruit are a cosmetic
problem and a reason for discard. Heavy metal contami-
nants on the surface of the fruit can occur as a consequence
of foliar nutrients and/or fungicides sprayed within 15 days
or 7 days before harvest, respectively. Pre-harvest intervals
that have been developed for several approved fungicides in
California should be followed. Light brown spots or stripes
are also produced on the surface of white flesh peaches and
nectarines as a consequence of abrasion occurring mainly
during harvesting and hauling operations.
were thoroughly cooled in the bins will warm substantially
during packing and should be thoroughly re-cooled after
packing. A new technique to delay IB symptoms and
pre-ripen fruit has been successfully introduced to the
California and Chilean industries. This technique consisted
of a ≈48-hour controlled cooling delay. Forced-air cooling
is normally indicated after packing.
Stone fruit storage and overseas shipments should be at
or below 0°C. Maintaining these low pulp temperatures
requires knowledge of the freezing point of the fruit, of
the temperature fluctuations in the storage system and
equipment performance. Holding stone fruits at these low
temperatures minimizes both the losses associated with
rotting organisms, excessive softening, water losses and
the deterioration resulting from CI in susceptible cultivars.
Horticultural maturity indices
The maturity at which stone fruits are harvested greatly
influences their visual quality, ultimate flavour and market
life (Crisosto 1994). Harvest maturity affects the fruit's
flavour components, physiological deterioration problems,
susceptibility to mechanical injuries, resistance to moisture
loss, susceptibility to invasion by rot organisms, market
life and ability to ripen. Peaches and nectarines that are
harvested too soon (immature) may fail to ripen properly
or may ripen abnormally. Immature fruit typically soften
slowly and irregularly, never reaching the desired melting
texture of fully matured fruit. The green ground colour of
fruit picked immature may never fully disappear. Because
immature fruit lack a fully developed surface cuticle, they
are more susceptible to water loss than properly matured
fruit. Immature and low-maturity fruit have lower soluble
solids concentrations and higher acids than properly
matured fruit, all of which contribute to inadequate flavour
development. Low-maturity fruit are more susceptible to
both abrasion and the development of flesh browning
symptoms than properly matured fruit. Over mature fruit
have a shortened post-harvest life, primarily because of
rapid softening and they are already approaching a senes-
cent stage at harvest and developing a mealy texture. Such
fruit have partially ripened, and the resulting flesh softening
renders them highly susceptible to mechanical injury and
fungus invasion. By the time such fruit reach the consumer,
they may have become overripe, with poor eating quality
including off-flavours and mealy texture.
In several countries, harvest date is determined by skin
ground colour changes from green to yellow in most culti-
vars. A colour chip guide is used to determine maturity of
each cultivar, except for white flesh cultivars. A three-tier
maturity system is used in California and a similar system
Temperature management and optimum
storage conditions
Optimum temperature is -1°C to 0°C. The freezing point
varies, depending on SSC, from -3°C to -1.5°C (Table 10.3).
Relative humidity (RH) should be 90-95% with a low air
velocity during storage (Thompson
et al
. 1998). Fruit can be
cooled in field bins using forced-air cooling or hydro-
cooling. Hydro-cooling is normally done by a conveyor-
type hydro-cooler or
in situ
. Fruit in field bins can be cooled
to intermediate temperatures of 5-10°C provided packing
will occur the next day or pack immediately. If packing is
to be delayed beyond the next day, then fruit should be
thoroughly cooled in the bins to near 0°C. In IB-susceptible
cultivars, fast cooling within 8 hours and maintaining fruit
temperature near 0°C are traditionally recommended.
Peaches and nectarines in packed containers should be
cooled by forced-air cooling to near 0°C. Even peaches that
