ITDG 
Interdev Agroalimentaire  

Production of fruit juices

	Type de fiche	Techniques/Technologies
	Mise en œuvre	ITDG(Royaume Uni)
	
	Zone géographique	Global; 
	Mots clés	JUS; PASTEURISATION; FILTRE; FRUIT; PULPE

	Echelle d’action	Groupe
	Public(s) cible(s)	Small- and medium-scale food processors

Contexte
Fruit juices are made from pure filtered fruit with nothing added.  In some places, sodium benzoate is added as a preservative to extend the shelf life after opening, but this is not essential.  Any fruit can be used to produce juice, but common ones include pineapple, orange, grapefruit, passion fruit and mango.

Some fruit juices are not filtered after pulping - these are known as fruit nectars (see fiche).  Guava is commonly used to produce a fruit nectar.  The nectar is made by the same method as the fruit juice, but omitting the filtering stage.

Fruit juices rely on a combination of acidity, pasteurisation and packaging in sealed containers for their preservation. They have to be drunk immediately after opening. If care is taken over the packaging, pasteurised juices can be stored in a cool dark place for up to a year.  It is normal for some sediment to form at the bottom of the bottle as it is left to stand, but if this is excessive, a finer filter can be used.

This fiche gives a general overview of fruit juice processing.  For specific details on different fruit juices, please refer to the relevant fiches - pineapple juice, passion fruit juice, orange juice, guava nectar.

Problématique / Objectifs
It is essential that juices are prepared from good quality ripe fruit that is free from blemishes and mould.

The use of chemical preservatives in fruit juice is tightly regulated. Processors should check local regulations and recommendations. With proper processing and adherence to good hygienic practice, fruit juices do not require chemical preservatives

Description/Mise en oeuvre
Washing and sorting
The fruit should be thoroughly washed and rinsed in clean water.  All rotten fruit should be removed as this will spoil the final product.  Fruit washing machines are available, but their use is determined by the scale of operation and the type of fruit.  Berries and soft fruits such as apricot and tomato are very fragile and should be handled carefully.

Juice extraction
After washing and sorting, fruit is crushed or pulped to extract the juice. Citrus fruits are easily pressed with a hand presser or a revolving citrus 'rose'. Other fruits such as mango and guava require pulping to extract the juice. 

Pulping
After peeling and stone removal, the flesh of the fruit is pushed through a perforated metal plate. The fineness of grinding is important since fruit that is ground too finely becomes difficult to press the juice.  Pulping is commonly used for the production of nectars and squashes since it breaks down and blends the plant cell material rather than purely extracting the juice from the fruit. 

Pressing
If a clear or partly cloudy juice is required, fruit must be pressed rather than pulped.  This entails rupturing the cell walls to allow the juice to be extracted.  Occasionally the fruit may need grinding to increase the juice extraction.  A range of mechanical presses are available.  Often the presses are called filter presses, which indicates that the equipment carries out two processes - pressing followed by filtering to remove fruit particles. 

Preparation
When the juice or pulp has been collected, the batch is prepared according to the chosen recipe.  This is very much a matter of choice and judgement, and must be done carefully to suit local tastes. Juices are sold either pure or sweetened.  Fruit squashes would normally contain about 25% fruit material mixed with a sugar syrup to give a final sugar concentration of about 40%.  These are diluted with water prior to use and as the bottle is opened, partly used and then stored, the addition of a preservative is necessary (for example 800ppm sodium benzoate).  Cordials are simply crystal clear squashes.

Another range of products that has proved popular is fruit nectars which are consumed on a 'one shot' basis.  Essentially, these consist of a 30% mix of fruit pulp and sugar syrup to give a final sugar level of 12-14%. All fruits contain sugar, usually around 8-10%, with variations not only from fruit to fruit but also in the same fruit grown in different parts of the world.  The addition of sugar to give the recommended levels must take into account the sugar already in the juice.  However, the amount of sugar added in practice is finally decided by what the purchasers actually want.

In all cases, sugar syrups should be filtered through muslin cloth prior to mixing to remove particles of dirt which are always present.

Fining, clarification, filtration and separation
Pectic substances and pectic enzymes play a very important role in fruit juice technology.  Pectic enzymes can have both beneficial and detrimental effects, depending upon the type of juice being made. 

For the manufacture of clear, filtered juice it is necessary to break down pectin. Thus, pectic enzymes (that break down pectin) are added to clear the juice.  In cloudy juices or fruit nectars it is essential that the original content of pectic substances of the freshly pressed juice are retained throughout the production and shelf life of the juice.  This can be achieved by inactivating the naturally occurring pectic enzymes during processing.  

To obtain clear bright juice it is necessary to filter the juice to remove fine suspended fruit particles.  Juices are either filtered by pressure (Kieselguhr or pad filter filtration) or by vacuum.

Filtered juices are filled into pre-sterilised bottles and sealed.  The filled bottles are pasteurised by heating in a boiling water bath for up to 10 minutes depending upon the size of the bottle.  After heating they are rapidly cooled to room temperature by immersing in cold water.

Pasteurisation
All the products mentioned above must be pasteurised at 80-95°C for 1-10 minutes prior to filling hot into the bottles.  At the simplest level, this may be carried out in a stainless steel, enamelled or aluminium saucepan over a gas flame, but this can result in localised overheating at the base of the pan, with consequent flavour changes.

To avoid the use of large expensive, stainless steel pans, a large aluminium pan can be used to boil sugar syrup.  A given amount of the syrup is then mixed with fruit juice in a small stainless steel pan and this increases the temperature to 60-70°C.  The juice/syrup mixture is then quickly heated to pasteurising temperature.

Filling and bottling
In all cases, the products should be hot-filled into clean, sterile bottles.  A stainless steel bucket, drilled to accept a small outlet tap, makes a very successful bottle filler.  The output can be doubled by fitting a second tap on the other side of the bucket.  This system can fill up to 500-600 bottles per day.

After filling hot, the bottles are capped and laid on their sides to cool prior to labelling.

Addition of chemical preservatives

The use of chemical preservatives in fruit juices is regulated by the laws in individual countries.  It is not essential to add chemical preservatives to juices since the acidity of the juice, combined with pasteurisation will prevent the growth of micro-organisms.  However, if the juices are consumed some time after opening the bottle, it may be advisable to add some preservative.  

Sodium benzoate is widely used as a preservative in fruit juices.  The addition of citric acid also increases the anti-septic effect of benzoate to yeasts.  Sodium benzoate is most suitable for foods and beverages which are in the range below pH 4.0.  It has the advantage of being a low cost preservative, but when it is added in high concentrations, it may taint the fruit juice.  The recommended levels are 0.05 to0.1%, however when sodium benzoate is used at the higher level, it gives the product an astringent off-taste.  Therefore, it is recommended not to exceed 0.05% in a carbonated drink.  Fruit juices and squashes that are diluted before drinking can tolerate slightly higher levels.

Résultats/Eléments chiffrés
The following equipment is required;
  Peeler, knives (stainless steel), cutting boards
  Juice extractor
  Pulper
  Filter
  Thermometer
  Analytical balance
  Stainless steel saucepan
  10kg scales
  Measuring cylinder
  Capping machine
  Wooden spoons
  Plastic funnels
  Plastic buckets
  Strainers

Enseignements
  Only fresh, fully ripe fruit should be used; mouldy or insect damaged fruit should be thrown away.  All unwanted parts (dirt, skins, stones etc) should be removed.
  All equipment, surfaces and floors should be thoroughly cleaned after each day's production.
  Water quality is critical, if in doubt use boiled water or add one tablespoon of bleach to each gallon of water to sterilise it.  If water is cloudy, a water filter should be used.
  Pay particular attention to the quality of re-usable bottles, check for cracks, chips etc and wash thoroughly before using.  Always use new caps or lids.
  The concentration of preservative should be carefully controlled for correct preservation of squashes and cordials, and may be subject to local laws.  Check first and use accurate scales to measure the preservative.
  Chemical preservatives cannot be used to cover up for poor hygiene or in-sanitary conditions.  It is imperative that all equipment is thoroughly cleaned before and after use and the juices are filled into sterile containers.  Chemical preservatives are only meant to add extra protection after the products are opened when the juice may become contaminated.
  The temperature AND time of heating are critical for achieving both the correct shelf life of the drink and retaining a good colour and flavour.  A thermometer and clock are therefore needed.
  The correct weight should be filled into the bottles each time.

Auteur : Sue Azam Ali
Saisie le : 05/12/2001
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