ITDG 
Interdev Agroalimentaire  

The potential for small-scale processing of fruit waste

	Type de fiche	Techniques/Technologies
	Mise en œuvre	ITDG(Royaume Uni)
	
	Zone géographique	Global; 
	Mots clés	FRUIT; ENZYME; VINAIGRE

	Echelle d’action	Groupe

Contexte
Fruit processing is one of the most popular acitivites carried out by small-scale food processors.  This inevitably produces large quantitiies of waste material such as peel, stones and liquid waste. In some fruits the discarded portion can be very high (for example mango 30-35%, banana 20%, pineapple, 40-50% and orange 30-50%).  This can often result in a serious waste disposl aprblem, which can lead to problems with flies and rats around the processing room, if not correctly dealt with.  Some of the waste material can be utilised to produce a number of additional products.

This fiche gives a general overview of the various types of products that can be made from fruit waste.  It gives a very brief description of the method of production. For more details, please refer to the relevant technological fiches.

Problématique / Objectifs
Processing of fruits produces two types of waste - a solid waste of peel or skin, seeds, stones etc and a liquid waste of juice and wash waters.  The solid waste can be utilised for a number of products.

1. Candied peels -for example peels from citrus fruits can be candied to use in baked goods or as a snack food.  Shreds of orange or grapefruit peel are also used in the production of marmalade.
2. Oils - the stones of some fruits (eg mango, apricot, peach) contain appreciable quantities of oil or fat, some of which have markets for culinary or perfumery/toiletry applications.  In addition some seeds (eg grape, papaya and passion fruit) contain oil which has a very specialised market.
3. Pectin - pectin is extracted from citrus peel and apple pomace (the residue left after apple juice has been removed).  Passion fruit also contains high levels of pectin.
4. Reformed fruit pieces - fruit pulp can be recovered from any fruit and formed into synthetic fruit pieces.
5. Enzymes - the three most important enzymes are bromelin from pineapple, papain from papaya and ficin from figs.
6. Vinegar or wine

While there are a number of possibilities for use of some types of solid fruit waste, as yet there is no evidence that any of these are economically viable.  It is stressed that a full financial evaluation should be done before attempting to introduce any of the ideas discussed.

Production of any of these products cannot be based on the availability of fruit wastes alone. Each of the above uses for fruit waste requires the following:

  a good knowledge of the potential market for products and the quality standard required
  a careful assessment of the economics of production
  a certain amount of additional production knowledge
  a certain amount of additional capital investment in equipment
  a fairly large amount of waste to make utilisation worthwhile.

Description/Mise en oeuvre
Candied peel
Slices or shreds of peel are boiled in a solution of 20% sugar for 15-20 minutes.  The shreds are soaked in the syrup solution for about 4-5 days.  During this time more sugar is added to the syrup until the concentration of sugar in the syrup reaches 65-700Brix (percentage sugar measured by refractometer).  The peel shreds are removed, rinsed and dried in the sun or a hot air drier.  
This process can form a secondary 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.  (See separate fiche for more details of production).

Oils
The process involves grinding the seeds/nuts to release the oil without a significant rise in temperature which would spoil their delicate flavours.  Generally, a powered hammer mill is needed for nut kernels.  A press is required to extract the oil but to our knowledge the existing manual presses have not been tried in this application and a certain amount of experimentation is needed to establish oil yields and suitability of the equipment.  Solvent extraction is not recommended for small-scale applications.  However, steam distillation of citrus peel essential oils is well established at a small-scale (see separate fiche for more details of stream distillation of oils).
The crude oil may be sold for refining elsewhere, but it is likely that at least preliminary (or part) refining would need to be carried out by the producer. It is also possible that the sale of seeds or stones to larger oil processors could generate additional income for small-scale fruit processors.

Pectin 
A detailed knowledge of pectin and its properties is needed to ensure that a producer is supplying the right product.  However, in essence the process of pectin extraction is not too complex.  The shredded fruit peel or de-juiced pulp is soaked in hot water (60-700C), or the hot water is re-circulated through the material, and the pectin is extracted into the water.  This is continued, often passing the same water through several batches of material, until the pectin concentration increases to around 5%.  The pectin is then precipitated from the solution using one of a number of chemicals. The most common are hexane or spirit alcohol which are then recovered by distillation and reused. The pectin gel is then washed and re-dissolved in water to produce a concentrated pectin solution.  It is then standardised or modified to give the specific properties required.  On a large-scale it is usually dried to a powder, but on a small-scale it is possible to add sodium benzoate preservative and sell the concentrated liquid in bottles.

Reformed fruit pieces
Fruit pulp is boiled to concentrate and sterilise it.  Sugar may also be added depending on the fruit used and taste.  A gelling agent, sodium alginate is then mixed with the cooled pulp, which is then mixed with a strong solution of calcium chloride.  All ingredients are safe to eat and are permitted food additives in most countries.  The calcium and the alginate combine to form a solid gel structure and the pulp can then be re-formed into fruit pieces.  The most common way is to pour the mixture into fruit-shaped moulds and allow it to set, but it is also possible to allow drops of the fruit/alginate mixture to fall into a bath of calcium chloride solution where they form small grains of reformed fruit which can be used in baked goods.  The most common product of this type is glace cherries.

Enzymes
It is unlikely to be economical to obtain these from waste fruit.  Even the more efficient collection from fresh whole fruit is no longer economical and changes in both large-scale production (higher quality standards and use of biotechnology to produce 'synthetic' enzymes) mean that small-scale producers will be unlikely to compete effectively.  In addition, there are moves to phase out the use of these enzymes in food products in Europe and USA and their market is therefore declining.

Vinegar
Vinegar should be produced from fresh, high quality fruit juices, but it is also possible to produce it from liquid and solid fruit wastes. Solid waste is shredded and then boiled for 20-30 minutes to extract the sugars from the fruit and to sterilise the liquid.  The liquid is then filtered through boiled cloth to remove the solids and cooled ready for inoculation with yeast.

Liquid waste should be separated during production to ensure that the fruit juice is kept separate from washwater (eg the juice could be drained from a peeling/skin table into a separate drum).  The juice is then boiled for10-15 minutes and treated as above. 

The liquid is then inoculated with a wine yeast (not a bread or a beer yeast) and fermented in the normal way for wine production.  This can then undergo the normal second fermentation to produce fruit vinegar (see the fiche for pineapple peel vinegar).

Résultats/Eléments chiffrés
Most of the products mentioned (with the exception of enzymes) can be carried out by the small and medium food processor, without the need for highly sophisticated equipment or skilled staff.

Pectin production and steam distillation of oils require a certain level of technical knowledge and, for oil production, specialist equipment.

With each of these products, it is essential to remember that there is no economic sense in producing them if there is no market for the products.  It is not sufficient to produce them just to utilise waste material.  In this case it is more cost-effective to dispose of the fruit waste in an environmentally sound manner.

Enseignements
  One of the main problems in using fruit waste is to ensure that the waste has a reasonably good microbiological quality.  Only waste produced during the same day should be used - for example it is not advisable to store up waste to use 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.

  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).

  At the very small scale of operation, where pollution or waster disposal are more important than process economics, the most likely solution is to use the waste as animal feeds.

  With oils, the main problems are to identify the import/export agents who would buy such products, production of the oil in sufficient quantities to meet demand, meeting the very stringent quality standards and finally, obtaining the equipment needed to produce the oils at low cost.

Auteur : Sue Azam Ali
Saisie le : 14/01/2002
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