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Raisin Production in India
Ajay Kumar Sharma and P.G. Adsule,
National Research Centre for Grapes, Pune
The world production of grapes is presently 65,486,235 MTs, out of which India
accounts for 1.2 million Mt of grapes making a share of 1.83 percent of the world
production and 3 percent of the total fruit production in the country. Area under this fruit
has been increased by 50% and its production by 71% in the country in the last decade
(1994-2004) due to the economic importance of this fruit. India has achieved the highest
productivity of 20 t/ha in the production of table grapes. Presently in India about 78
percent of grape is used for table purpose, nearly 17-20 percent is dried for raisin
production, while 1.5 percent is used for juice and only 0.5 percent is used in
manufacturing wine. The processing of this fruit in our country is very less as compared to
the traditional grape growing countries in the world where more than 80 percent of the
produce is processed in the form of wine, raisin and juice. The processed products viz.
wine; raisins and grape juice are the most popular products from the grape all over the
world. Raisin is prepared from the sound dried grapes of the varieties conforming to the
characteristics of Vitis vinifera L. The grapes are processed in an appropriate manner into
a form of marketable raisin with or without coating with suitable optional ingredients.
Status of raisin at world level
The raisin trade in international market is increasing day by day. USA is the largest
raisin producer in the world. USA and Turkey together produce almost 80% of the total
raisins of the world. USA, Turkey and South Africa are the largest raisin producers at the
global level besides Greece, Australia, Iran, Afghanistan, China, Russia and others. India
has achieved the production level in the range of 55,000 to 65,000 t of raisins, which is
next to Turkey at world level. Efforts on improvement in quality of the Indian raisins have
been initiated to promote the export of this product in world market. As the overall
investment in raisin grape production is considerably less as compared to table grape
production for export, hence the raisin exporters are expected to accrue better price
realization out of this product in terms of superior cost: benefit ratio. India’s export of
raisins is 314 Mt with the value of 0.473 million US dollars.
Characters of good raisin
The raisins of good quality should have following characteristic features:
Good and uniform appearance of produce in terms of its color (perfectly green or
grey-green), size (round) and smooth texture
A higher pulp content and a pleasing taste without any sugar coat outside
Intact skin and its outer layers, free from injuries, dust and foreign matter.
Important grape varieties for raisin making
Major production of raisin (90 per cent) in the world is from Thompson Seedless.
The Thompson Seedless is a white, thin skinned grape, which produces the best raisins
available today. Its small berries are oval and elongated. It does not contain seeds and has
high sugar content. Besides the other varieties viz. Muscat of Alexandria, Waltham Cross
and other white and colored seeded varieties are also used for raisin production. In India,
Thompson Seedless and its mutants i.e. Sonaka, Tas-A-Ganesh. Manik Chaman are
mainly used for raisin production. NRC for Grapes, Pune, screened a sizeable germplasm
for production of quality raisin production and identified some varieties viz. A 17-3,
E 12/3, Mint Seedless, Superior Seedless, KR White, Manik Chaman, A18-3 (Coloured
seedless) and Cardinal (for manukka) for this purpose.
Technology for Quality raisin production – an Indian perspective
Grape berry has juice / pulp containing sugar, acids, flavonoids, vitamin and
minerals and outer protective skin has different layers. Drying process has to be selective
to remove the water from berry without affecting outer skin structure and arrangement of
wax plates. The quality of waxy layers in terms of wax plates is about 0.1 mg/cm
2
. This
layer only protects the berries from getting dried in fresh form. During storage of berries at
ambient and low temperature, the water moves out from the stalk and rachis and not from
the skin coated with white waxy layer and this result in drying of pedicels in first instant
and then berry drop.
Waxy layer on the green berry skin is the main target of various pretreatment of
grape berries for quickening the drying process. Many treatments have been worked out in
different countries after various research trials and an appropriate and economic treatment
have been listed below for drying of grapes in India.
A water solution containing 2.5% potassium carbonate and 1.5% ethyl oleate for
dipping of berries has been suggested. A dipping time of 3 minutes duration has been
recommended to increase water removal @ of 1.4 mg/cm
2
in comparison to 0.4 mg/cm
2
in
control. However, the cumulative quantity of waxes has been reduced only by 13 per cent
in treated berries and therefore the drying effects is due to loosening of waxy plates on the
outer skin and not removing the wax on the skin. This has been further proved based on
the microscopic studies on skin structure with such treatments and without treatment in
Australia.
When drying occurs fast, the sugar concentration increases in berry in short
possible time and therefore the enzymatic reactions of peroxidase and polyphenolase also
gets reduced and thereby leading less browning of the product. This process also helps in
suppressing the microbial and fungal growth during drying process. A temperature of
25°C and above in dipping emulsion has been recommended for good results. A berry
picks up approximately 35µ mol solution and looses 70 percent during draining and
utilizes only about 10-12 µ mol. A pH of such solution has been suggested always in the
range of 9.5 to 11.00. A pH more than 11.00 breaks the skin and less than 9.5 favours
microbial growth and fermentation. This treatment is more effective when berries attain
the maturity of 20° brix and above and in other cases there is less pick up of dipping
solution and therefore no effect.
In case of higher levels of dipping oil (pickup by skin 7200 ppm); there will be
sucking of moisture in berries from outside this results in unpleasant taste in the product.
Water removal from berries takes place in three stages in treated berries. In first
stage, the moisture removal is highest reducing initial weight to 40 to 50 per cent. When
there is drying of 50 per cent, surface free area of berry is reduced by 28 per cent and as a
result the water removal process is slowed down subsequently.
In second and third stage, the water is removed from pulp to skin and then
removed by evaporation. This process continues till berry is dried to the extent of 13 per
cent moisture. Drying sheds based on covered iron rack system are fabricated where the
number of shelves is kept from six to eleven with interspaces varying from 22.9 cm to 45
cm. The rows of racks are generally spaced apart from a distance of 60 to 150 cm. The
length of the rack could be from 600 to 1800 cm having South-North orientation and flow
of dry air from West to East. This is a modified drying system of Australia, The shelves of
iron rack are netted with nylon mesh and density of fresh grapes on this mat for drying is
maintained from 1.7 to 2.2 g/cm
2
depending upon the height of shelf from 22.9 cm to 45
cm. This Australian method of dipping and rack system for drying has reduced the drying
period to 10-12 days when compared to 20-22 days in conventional method. On the
contrary, in USA, the grapes are dried without any treatment by spreading on graft paper
placed between grapevine rows in vineyard. While in South Africa this is done on concrete
slab. In both the cases the drying is in open sunshine and not in shed as followed in
Australia. In Afghanistan, the drying is done in closed rooms by hanging the grape
bunches on the ropes and it takes about 40 to 45 days for drying. There, the grapes are
grown without following training and pruning and yield is only 1.5 to 2 tons/acre with
T.S.S ranging from 28 to 32
0
B.
The position of bunches can be changed time to time in order to expose the all
berries of the bunch in order to reduce the moisture content up to desire level. If rain
occurs during the process of drying, the berries absorb moisture very rapidly. If moisture
increased in environment it invites the attack of moulds. To decrease the humidity in side
the drying sheds, exhaust fans remain at on position. This practice is also helpful in
maintain the desirable vapour pressure in side the shed. The temperature of drying shed
can be increased by use of hot air blowing fans.
Separation of dried grapes from its stalks and rachis in bunches is done now
using machines designed and fabricated for this purpose locally. However this was being
done manually in the past, while the operation of sorting and grading of dried berries
continued with the manual force for want of appropriate machine for this purpose.
Packing and storage
Raisins are strongly hygroscopic. Contact to moisture may result in mold, rot and
fermentation and if a fermentation process is initiated, it may eventually affect the entire
lot. Under appropriate temperature and humidity conditions, there is a risk of infestation
by maggots, mites, cockroaches, moths, beetles, rats, mice and ants. Mite infestation may
be determined by examination with a magnifying glass: mites may be distinguished from
crystallized glucose because they are whitish, slow moving dots. At temperatures > 25°C
and on exposure to mechanical pressure, there is a risk of candying, agglomeration, syrup
formation and fermentation. Heat generally causes the risk of discoloration and hardening
and the product should thus be stored away from heat sources. At temperatures < 10°C,
mite growth is usually inhibited.
In view of the above, the final packing of produce is done in 400 gauge LDPE film
bags and stored in corrugated boxes of 5 to 15 kg capacity at low temperature (4°C) to
withstand the mechanical, climatic, biotic and chemical stresses to which raisins may be
exposed during transport, storage and cargo handling and preserve the original raisin color
and prevent the attack of pests.
Recent advances in technology for raisin production
The traditional method of producing raisins requires a substantial amount of
seasonal labor. Over the years, several methods have been developed which would
mechanize at least a portion of the raisin production process. In traditionally raisin
producing countries, the raisin industry is moving forward with a transition from a
conventionally labour-intensive operation to highly mechanized production system. A
major reason for this is ever-increasing labour cost and non-availability of labours to
perform different steps of grape drying from fresh produce to the final product. A direct
implication of such a transition is reflected in adoption of drying-on-vine as the
technology of choice, which involves severing the fruiting canes when sufficiently mature,
then allowing them to hang on the vines until they dry into raisins and finally harvesting
with mechanical harvester. A major researchable issue is to develop suitable trellis system
that can consistently produce at least 4 to 5 tons of high quality raisins per acre and can be
harvested with a grape harvester. The desired trellis system should separate the vine
canopy into distinct fruiting and renewal zones, which facilitates harvest cane severing and
promotes a good environment for the growth of renewal canes. The fruiting zone, which
later becomes the drying zone, is oriented in a fashion towards sun to enhance the drying
rate, thereby making it possible to dry Thompson Seedless grapes on the vine without oils
or other aids in most seasons.
Drying on vines has at least three potential economic advantages when compared
to traditional production systems. First, mechanical pruning and harvesting will
substantially reduce the costs and uncertainties associated with hand pruning and
harvesting. Harvesting of as high as 160 acres land area can be harvested with only 6 to 8
employees in contrast to the requirement of at least 20 to 40 workers in case of
conventional practices. A second potential advantage is that the grapes dry on the vine
rather than on the ground. This makes the raisins much less susceptible to rain damage,
which is always a concern for raisin growers. Grapes drying on the vine can apparently
withstand substantial rainfall without damage. Further, the quality of the raisins produced
by this technique is usually high, as the produce never touches the ground. This reduces
problems of contamination with physical components like dirt, sand and mold. However,
one potential drawback of this system is that it normally takes 6 to 7 weeks after the canes
are severed for the grapes to dry completely. This means that the drying grapes are
exposed to inclement weather for a longer period of time, although they are likely to
withstand rain better than grapes drying on the ground.
Prospects of raisin industry in India and quality compliance
In India, raisin is mostly produced in Sangli, Solapur and Nasik districts of
Maharashtra and Bijapur district in Karnataka. The technique of raisin production in India
is mostly based on the dipping of the berries in Australian dip emulsion, which contains
2.5% potassium carbonate and 1.5% ethyl oleate and subsequent drying in shade in open
tier system. The place, Junoni, in Sangola taluk of Solapur district in Maharashtra has been
selected for the establishment and promotion of grape drying units on large scale based on
its appropriate geological and weather data and proved the place most suitable in terms of
latitude, longitude, rainfall, temperature, humidity, air velocity, etc. for drying the grape in
natural way. ‘Junoni’ - a barren land is presently leading the raisin activities in the country
and has now turned into industrial urban town.
The conventional technique of cleaning of Indian raisins after drying the grapes is
not efficient to comply with the Codex standard and therefore, improvement has to be
made in respect of cleaning of raisins preferably by adopting mechanical means. In fact,
some mechanization has to be introduced in each unit operation during the journey from
harvesting of fresh grapes to raisin making to avoid any non-compliance to the Codex
standards. Moisture levels in Indian raisins are generally low and thereby their texture and
mouth feel is hard and therefore, this needs to be increased to 15 - 16.5% to have a better
mouth feel and soft texture. To have Indian raisin as a product of international quality
standard, the cleaning has to be done by mechanical means and the drying has to be
completed at moisture level of 15 - 16.5%.
The packaging and labeling has also to be improved so that our product complies
with the international quality standards in this regard. Different packing materials of food
grade quality should be tested for their suitability with regards to easy availability,
convenience, environmental profile and overall economics. There is urgent need to
develop technology for storage of the raisins under ambient condition to save the huge
expenditure incurred towards electricity in cold storage. Further this storage technology
should protect the raisins from browning or discoloration while on storage.
Thus there is a big potential of raisin industry in India in terms of the marketing of
this product in domestic and international market for import substitution and better
utilization. Besides, there is possibility of diversification of raisin industry by promoting
the production of flavoured and coloured raisins and promoting raisins as neutraceuticals
in public health care.
Harvesting Dipping oil
(at proper TSS level) (water solution containing 2.5% potassium
carbonate and 1.5% ethyl oleate for 3 min., pH 9.5-11)
Separation of dried grapes Drying
(under drying shed up to13% moisture content)
Washing Drying Grading
(with luke warm water) (to remove moisture adhering to surface) (based on size and colour)
Storage Packing
(at 4°C temperature) ( in 400 gauge LDPE polythene film bags)
Fig.1: Flow chart of raisin making
