Agriculture Reference
In-Depth Information
total soluble solids (TSS), otherwise known as Soluble Solid
Concentration (SSC) or °Brix. For certain specific cultivars
and situations, the titratable acidity (TA) and SSC-TA ratio
are used as maturity indices (Guelfat-Reich & Safran 1971;
Crisosto
et al
. 1994). Cultivars other than 'white' ones also
have minimum colour maturity requirements, based on the
percentage of berries in the cluster that show a certain mini-
mum colour intensity and coverage. Other quality criteria
for table grapes are good appearance, free of decay, thin
skin, large size, good texture and flavour. The rachis should
be fresh and green (i.e. not desiccated and brown). The
bloom is also an important quality factor. It is destroyed by
over-handling and rubbing which causes the berries to
become shiny rather than lustrous.
Minimum maturity requirements vary with cultivar,
growing area and market; however, standards are gradually
being harmonised within the major market places. The
Economic Commission for Europe, for example, has its
own standards for table grapes (UNECE 2003) but work is
underway to align these standards with draft FAO/WHO
Codex Standards on table grapes by the end of 2007. The
EU standards define table grapes as fruits grown from
cultivars of
Vitis vinifera
. L.. Minimum SSC levels are
given as 12° Brix for the Alphonse Lavalleé, Cardinal and
Victoria varieties, 13° Brix for all other seeded varieties,
and 14° Brix for all seedless varieties. By contrast, in
California, United States the minimum SSC is generally
16.5° Brix and in early production areas, an SSC/TA ratio
of 20 or more is used to determine maturity for cultivars
with a minimum required SSC less than 16.5° Brix.
EU standards classify cultivars into greenhouse grown
varieties and field grown varieties. This latter classification
is being further divided into large-berried and small-berried
types. The berries of 'Extra Class' grapes must be evenly
spaced along the rachis and have the bloom virtually intact.
Lower classes (I-III) are determined by the bunch shape
and the presence or absence of colouring defects, bruising
and sun-scorch. In all classes the berries must be firm and
firmly attached to the stalk. The larger the berries, the
higher the class, provided other quality factors are met.
Ethnic background can influence the factors that
determine consumer acceptance as shown in a study of the
acceptability of 'Red Globe'. For example, TA played an
important role in American and Chinese consumer
acceptance (Crisosto & Crisosto 2002).
were shed packed (Crisosto & Mitchell 2000). Recently, a
combination of shed and field ('avenue') packing is
developing in California and Chile.
Before harvesting, irrigation is usually withheld and the
avenues between vines are treated to reduce dust contami-
nation. The picker is trained to select appropriate bunches
on the basis of the maturity indices described above.
Grapes that fail to meet minimum standards are usually
taken to local wineries or for use by other local industries
such as cattle feed. Higher levels of efficiency can be
obtained by training the vines at an appropriate height for
convenient harvesting.
Field packing
The most common field-packing system is the 'avenue
pack' (Figure 9.2a). The picker usually trims the fruit to
remove defective berries and obtain a better bunch shape
and size. The bunches are then placed carefully into field
crates ('lugs') or baskets which are made of wood or plas-
tic. The picking lugs are then transferred a short distance to
the packer, who works at a small, shaded portable stand in
the avenue between vineyard blocks (Figures 9.2b). It is
common for the packer and several pickers to work as a
crew. Packing materials are located at the packing stand,
which also shades the packer (Figure 9.2c). The bunches
may be packed directly into shipping cartons which reduces
damage from repeated handling. With many packing stands
around the vineyard supervision to maintain quality
standards is more difficult than in a packing shed.
Shed packing
Shed-packed fruit is harvested by pickers and placed in
field lugs. These are then moved into the shade of the
vines to await transport to the shed. At the packing shed
the field lugs are distributed to packers who select, trim
and pack the fruit. In some operations, trimming, colour
sorting, and a first quality sorting may have occurred in
the field.
Packaging
Whether field or shed packed, grapes are nearly always
packed on a scale to facilitate packing to a precise net
weight. Generally two grades are packed simultaneously
by each packer. High quality bunches, often destined for
export, will be individually packaged, increasingly either
in 'zip and slide' polyethylene bags, or plastic 'clam
shells'. Both forms of packaging provide consumer-sized
units and reduce the drop of loose berries onto produce
department floors.
The use of the plastic cluster bags greatly reduces fruit
damage during marketing (Luvisi
et al
. 1995). Bags and
Harvesting and packaging
Detailed information on the post-harvest handling of table
grapes is well described by Nelson (1985). Traditionally
most California table grapes have been packed in the field
while a high proportion of grapes in South Africa and Chile
