Technical Bulletin No. 1 Aonla (Emblica oficinalis Gaertn.): Post Harvest Handling and Processing Technology Authors Dr. Sunil Pareek Dr. N. S. Rathore Dr. R.A. Kaushik Department of Horticulture Rajasthan College of Agriculture MPUAT, Udaipur, Rajasthan, India Sponsored by National Agricultural Innovation Project Indian Council of Agricultural Research New Delhi, India
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Technical Bulletin No. 1
Aonla (Emblica oficinalis Gaertn.):
Post Harvest Handling and Processing Technology
Authors Dr. Sunil Pareek
Dr. N. S. Rathore
Dr. R.A. Kaushik
Department of Horticulture
Rajasthan College of Agriculture
MPUAT, Udaipur, Rajasthan, India
Sponsored by
National Agricultural Innovation Project
Indian Council of Agricultural Research
New Delhi, India
INTRODUCTION
Aonla or Indian gooseberry (Emblica officinalis Gaertn) is one of the most
important non-traditional and underutilized fruits of Indian origin, having immense
potentiality of cultivation on marginal or waste lands. It belongs to the family
Euphorbiaceae and sub-family Phyllanthoidae. Aonla tree thrive well throughout the
tropical and sub-tropical parts of India either found growing wild or cultivated. Aonla is
quite hardy, prolific bearer and highly remunerative even without much care. It can be
grown easily on calcareous and slightly saline as well as alkaline soils where common
fruit crops do not thrive.
Aonla is regarded as sacred by Hindus and has great mythological significance.
According to Hindu mythology, one day meal is arranged beneath a aonla tree during
Kartik (October) when trees are laden with fruits. Hindu religion also prescribe that ripe
fruits of aonla be eaten for forty days after fast in order to restore health and vitality
known as Kaya Kalp (Benthal, 1946).
The fruit is highly nutritive and it is the richest source of vitamin 'C' among fruits
after Barbados cherry (Asenji, 1953), which is essentially having antioxidant effect on
human beings. The edible fruit tissues of aonla contain about 3 times more protein and
160 times more vitamin ‘C’ as compared to apple (Barthakur and Arnold, 1991).
Normally, single aonla fruit contains 20 times more vitamin ‘C’ in terms of antiascorbutic
value as two oranges. It contains 500 to 1500 mg of ascorbic acid per 100 g of pulp. This
is much more than vitamin ‘C’ content of guava, citrus and tomato fruits. The fruit
contains a chemical substance called leucoanthocyanin or polyphenols which retards the
oxidation of vitamin ‘C’ and presence of astringency (Sastry et al., 1958; Singh et al.,
1993). Hanif et al. (1966) noted marked antioxidant effect of gallic acid present in aonla
fruits. Thus, vitamin ‘C’ content of aonla is in no way lower than that of Barbados cherry
(Mustard, 1952; Ledin, 1958) from nutritional point of view.
The aonla fruit is valued high among indigenous medicines in India. It has been
recognized as Amritphal in oldest scriptures (Anonymous, 1952; Chopra et al., 1958). It
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is valued as an antiascorbutic, diuretic, laxative (Nadkarni, 1927), antibiotic (Ray and
Majumdar, 1976) and acidic, cooling and refrigerant (Singh et al., 1993). Dried fruit is
useful in hemorrhage, diarrhea, chronic dysentery, diabetes, jaundice, dyspepsia and
cough. Aonla is the main ingredients in chavanprash and triphla.
Aonla may be an important fruits of future due to its high medicinal and
nutritional value, high productivity per unit area and suitability even in the wastelands
particularly in salt affected soils. It has immense scope for processing and value addition
as the fruits are not consumed fresh or in raw state as it is highly acidic and astringent.
For an underutilized species of its economic stature, the genetic improvement
work on aonla is noteworthy. It is a species researched by several research institutions
and universities and this has resulted in the development of a large number of varieties,
standardization of cultivation practices, post harvest technology and processing. The
relevant findings on post harvest management and processing have been used in this
bulletin to meet the requirement of research workers, extension workers, growers and
processors.
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POST HARVEST HANDLING
Post harvest management activities start immediately after harvesting of fruits at
proper maturity level. This also includes number of activities such as minimal or primary
processing at field level i.e., removing field heat, sorting, grading and packaging for
transportation, secondary processing for value addition and finally packaging and
marketing. Post harvest management of fruits depends on number of factors such as
cultivation and production practices adopted, quantity and quality of fruits obtained after
harvesting, size of farm and orchard, expected return and value addition near by if any,
etc. Production practices have a tremendous effect on the quality of fruits at harvest and
on post harvest quality and shelf life of products. In addition, environmental factors such
as soil type, temperature, relative humidity, air flow rate, frost and rainy weather also
affect the storage life and quality.
The harvest and post harvest management of aonla fruits includes proper maturity
indices, washing (removing field heat), sorting and grading, pre treatment or other
minimal processing techniques, packaging, storage, transportation and marketing. The
detailed description of these steps involved in post harvest handling is given in this
chapter.
Determination of maturity indices: Harvesting crops at the proper maturity allows
handlers to begin their work with the best possible quality produce. Fruits harvested too
early may lack flavour and may not ripen properly, while produce harvested too late may
be fibrous or overripe ( Kitinoja and Gorny, 1999). It is therefore essential to formulate
harvest indices or criteria for harvesting the fruit at the right stage of maturity. Maturity is
that stage at which a commodity has reached a sufficient stage of development that after
harvesting and post harvest handling, its quality will be at least the minimum acceptable
to the ultimate consumer. Horticultural maturity is the stage of maturity at which plant or
plant part possesses the prerequisites for use by consumers for a particular purpose (Reid,
2002).
Being an underutilized fruit crop, less attention has been given on establishing
reliable maturity indices of aonla. However, several parameters like specific gravity, TSS
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: acid ratio, colour of fruit surface, fiber content, seed colour, heat units, days from
flowering to maturity can be used for determining maturity index of particular cultivar of
aonla in a particular region (Ojha, 1986; Singh, 1997; Singh et al., 2004).
After the fruits have set, the embryo lies in dormant condition and ovary does not
exhibit any symptom of external growth until middle of August. The diameter and
volume of the fruit increase rapidly thereafter, and the maximum growth is achieved by
November after which there is not much increase in size (Bajpai, 1968). Fruits completed
almost 70 per cent growth during last week of August to last week of September.
On the basis of season of maturity in eastern Uttar Pradesh, aonla varieties have
been classified into three groups i.e., early, mid and late season (Pathak et al., 1993). The
maturity season of aonla varieties is given in Table 1.
Table 1: Maturity season of aonla varieties
Early Mid Late
Banarasi Francis Chakaiya
Krishna NA-7
NA -10 Kanchan
NA-6
NA-9
However, maturity period is affected by various factors such as location, climate,
soil types, and other cultivation practices etc. In north Indian arid climatic conditions of
Rajasthan and Gujarat, fruits of Agra Bold, NA-7 and Banarasi matures by the last week
of October; Francis and Krishna matures by first week of November; Gujarat-1 and
Gujarat-2 by middle of November and that of Kanchan and Chakaiya by the last week of
November (Singh et al., 2006).
Specific gravity increases with the advancement of maturity and at the time of
maturity specific gravity should be 1.02 in Chakaiya; 1.03 in NA-7, Krishna and
Kanchan; 1.06 in Gujarat-2; 1.07 in Agra Bold and 1.08 in Banarasi, Francis and Gujarat-
1. Fiber content at maturity is 0.37 per cent in Krishna, 0.38 per cent in Banarasi , 0.54
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per cent in NA-7, 0.58 per cent in Gujarat-1, 0.60 per cent in Gujarat-2, 0.65 per cent in
Agra Bold, 0.72 per cent in Francis, 0.81 per cent in Chakaiya and 0.84 per cent in
Kanchan (Singh et al., 2006).
The Fruit colour range from dull greenish yellow to translucent in various
cultivars. The fruit skin colour of various cultivars is given in Table 2.
Table 2: Fruit skin colour of aonla at maturity
Cultivar Fruit skin colour
Banarasi Thin, smooth, semi translucent, whitish green to straw yellow
Krishna Smooth, whitish green to apricot yellow in colour with red spots on
exposed surface
Francis Smooth, thick at upper side and thin at basin, light green in colour
Kanchan Smooth, light green, strips deep red at pea stage which disappear later
on
NA-6 Smooth, semi translucent, light green in colour
NA-7 Smooth, semi translucent, yellowish green
NA-8 Slightly rough, thick and light green in colour
NA-9 Smooth, semi translucent, light green in colour
NA -10 Rough, yellowish green with pink tinge
Growing Degree Days (GDD) can also be taken in consideration for
determination of maturity. GDD or heat unit summation is determined using daily
maximum and minimum temperature considering base temperature of 10oC.
Harvesting Method
The goals of harvesting are to gather a commodity from the field at the proper
level of maturity with a minimum of damage in quality and loss in quantity, as rapidly as
possible, and at a minimum cost. Careful harvesting is special consideration in aonla fruit
because damaged and spotted fruits are not useful for fresh consumption as well as
processed products such as preserve and candy. Fully developed fruits, which show sign
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of maturity, are harvested at right time. This helps in size gain of remaining fruit. Delay
in harvesting results in heavy dropping of fruits particularly in varieties like Banarasi and
Francis. It also adversely affects the following year bearing. The method of harvesting is
hand plucking of individual fruits by bending the smaller twigs or shaking of twigs but
the fruits get damaged in later method while dropping on the ground. These dropped
fruits are the source of micro-organisms causing rots during storage to other fruits in lot
also. Therefore, aonla should never be dropped from the tree by using tree climber or
small stairs. Fruit harvester should have long climb and cotton or jute bags or pads for
collecting the fruits. Fruits should be harvested early in the morning or in the evening to
avoid the damage due to field heat. Harvested fruits should immediately be stored under
shade.
Sorting
Sorting should be done just after arrival of fruits in the packing house. Sorting of
aonla is usually done to eliminate injured, decayed, blemished, over or under sized fruits,
or otherwise defective produce before cooling or further handling. These un-marketable
fruits are called ‘culls’. Sorting will save energy and money because culls will not be
handled, cooled, packed or transported. Removing decaying produce items is especially
important since this will limit the spread of infection to other units during handling.
Sorting is generally done by manual picking over a running plateform.
Washing
Aonla fruits require washing immediately after sorting for removing field heat
and making suitable for secondary processing. Water remaining on the surface of produce
must be removed using an air flow and / or sponge rollers in automated units because
residual water may encourage fungal growth. For washing of fruits constant flow of clean
water in required quantity is essential. This tank for washing produce is made from
galvanized sheet metal, a baffle made of perforated sheet metal is positioned near the
drain pipe and helps to circulate water through the produce. Fresh water is added under
pressure through a perforated pipe, which helps move floating produce toward the drain
end of the tank for removal after cleaning. This removed water can be used for other
unproductive work including irrigation.
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Grading
Grading is essential to meet the standards for produce packed for sale through
traditional wholesale markets. Although, more primitive market may not use written
grade standards. But the products are sorted and sized to some extent. Aonla may be
graded according to weight or diameter. So far proper grading have not been standardized
in aonla. Aonla fruits should be graded into three grades as given in Table 3 (Singh et al.,
1993).
Table 3: Grades of aonla fruits
Grade Description
A Large sized fruit according to the variety. Banarasi diameter 4.5 cm and
above, free from blemishes.
B Small sized fruit having diameter less than 4 cm and free from
blemishes.
C Defective fruits i.e., blemished scaring and necrotic fruits.
The fruits may also be graded on the weight basis (A grade = 50 ± 5 g, B grade =
40 ± 5 g and C grade = 30 ± 5 g). Highest physiological loss in weight (PLW) was
observed in C grade fruits followed by B and least in A grade fruits during 8 days of
storage period at ambient temperatures. PLW in Francis cultivar was 12.50, 16.00 and
20.50 per cent in A, B and C grade fruits, respectively on 8th day of storage (Table 4),
however, it was 6.50, 11.30 and 14.50 per cent in Chakaiya (Table 5).
Table 4: Physiological loss in weight (%) during storage of aonla cv. Francis fruits
in different size grades
Grades Days after harvest
2 4 6 8
A 3.20 7.50 11.30 12.50
B 4.50 8.75 14.50 16.00
C 6.00 13.80 16.00 20.50
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Table 5: Physiological loss in weight (%) during storage of aonla cv. Chakaiya
fruits in different size grades
Grades Days after harvest
2 4 6 8
A 1.50 3.50 5.20 6.50
B 2.80 7.25 9.50 11.30
C 4.75 9.00 12.50 14.50
The final destination or utilization of aonla fruits is based on the size, weight and
fiber content of fruits. Large sized fruits with 45 ± 5 g weight and low in fibers should be
used for preserve, candy and pickle making, while small size fruits with medium to high
fiber contents is used in making of medicinal produce i.e., chavanprash. Small fruits with
necrosis and blemishes can be used in making trifla and for drying or powder making.
Packaging
The packaging protect the fruits from injury and water lose, and be convenient for
handling and marketing. Packages should also provide information about the product,
including the grade, handling instructions, and appropriate storage temperatures when the
product is on display. The cost of packaging is important, including whether the container
can be recycled or reused. Packaging provides protection from physical damage during
storage, transportation and marketing. Packaging also decides cost of transportation and
storage of fruits for later use. At present proper packaging is inadequate in case of aonla.
Aonla fruits are packed in gunny bags of 50 to 100 kg capacity. These fruits got impact,
vibration and compression injuries during transportation in these gunny bags. The
corrugated fiber boxes are better as this provides appropriate atmosphere and ventilation
inside the box, printable information at low cost and recyclable also. Newspaper lining
should be provided inside the CFB cartons. The appropriate size of boxes for 20 kg
capacity should be used. Minimum spoilage (16.0 %) was noticed in corrugated fiber
board boxes with newspaper liner package followed by CFB boxes with polythene liner
(17.0 %), where as it was highest in gunny bag without any liner (30.19 %) after 13 days
of storage (Singh et al., 2005a). Singh et al. (1993) conducted an experiment on different
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package containers of 40 kg capacity during distant rail transpotation, and found that
wooden crate with polythene liner is most suitable for packing and long distance
transportation of aonla fruits. Per cent weight loss and bruising were minimum in this
container as compared to gunny bag.
Storage
The fruit availability period of aonla is very short hardly 2 to 3 months and during
November to mid January aonla fruits available in glut. Therefore, storage of fruits at
appropriate temperature is essential to extend the availability period and to stabilize the
price in the market. Being an underutilized fruit crop, very little study has been done on
low temperature, modified atmosphere and controlled atmosphere storages of this
valuable fruit.
The shelf life is very short at ambient temperatures and it is differ with various
cultivars. Singh and Kumar (1997) stored fully mature aonla fruits at room temperature,
modified storage condition, zero energy cool chamber and zero energy plusmodified
storage condition. It was found that decay loss was minimum (26.56 %) in modified
storage condition on 24th day of storage, whereas it was maximum (48.70 %) in zero
energy cool chamber. The fruits may be kept in clod storage for 7-8 days at 0-2oC and 85-
90 per cent relative humidity.
Nath et al. (1992) studied the effect of post harvest treatments on shelf life of
aonla fruits with calcium nitrate (1%), GA3 50 ppm and borax (4%) and found that the
physiological loss in weight and pathological loss increased with the length of storage
period. Calcium nitrate (1%) minimized the weight loss during the storage period and no
pathological loss was observed with borax up to 9 days of storage.
To enhance the shelf life of aonla fruits of local cultivar, Patel and Sachan (1995)