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< prev - next > Food processing Fruits vegetables and roots KnO 100234_Fruit waste utilisation (Printable PDF)
Processing of fruits produces two types of waste - a solid waste of peel/skin, seeds, stones etc -a
liquid waste of juice and washwaters. In some fruits the discarded portion can be very high (eg
mango 30-50%, banana 20%, pineapple 40-50% and orange 30-50%). Therefore, there is often
a serious waste disposal problem, which can lead to problems with flies and rats around the
processing room, if not correctly dealt with. If there are no plans to use the waste it should be
buried or fed to animals well away from the processing site.
Solid wastes
There are a number of possibilities for use of some types of solid fruit wastes but there is as yet
no evidence that any of these are economic. It is stressed that a full financial evaluation should
be done before attempting to introduce any of the ideas below.
One of the main problems in using fruit wastes is to ensure that the waste has a reasonable
microbiological quality. Only waste produced during the same day should therefore be used - it is
not advisable to store-up wastes to use for example at the end of a week's production. Even with
this precaution the waste is still likely to contain mouldy fruit, discarded during processing,
insects, leaves, stems, soils etc which will contaminate any products made from it.
Therefore, it is necessary to ensure that some preliminary separation takes place during
processing (eg peel and waste pulp into one bin, mouldy parts, leaves, soil etc to another which is
discarded, stones, seeds etc into a third bin).
Possible products
The six main products that can be considered are as follows:
Candied peel
Reformed fruit pieces
Candied peel
Peel from citrus fruits (orange, lemon, grapefruit) can be candied for use either in baked goods or
as a snack food. In addition, shreds of peel are used in marmalades and the process to make
these is similar to candying. In summary, the process involves boiling the slices or shreds of peel
in 20% sugar syrup for 15-20 minutes and then progressively increasing the sugar concentration
in the syrup to 65-70┬░Brix (% sugar by refractometer) as the food is soaked for 4-5 days. It is
then removed, rinsed and given a final drying in the sun or a hot air drier. This can therefore form
a second product for a fruit juice or jam processor especially if larger food companies are
available and willing to buy the candied peel as an ingredient for their foods. In one application,
candied melon skin has been used to substitute for sultanas in baked goods and in another,
candied root vegetables have found a similar market.
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