FRUIT JUICE PROCESSING
PREPARED BY:ŞEMSİ PULAT
Fruit juice comes from squeezed or pressed fruit. Fruit juices and concentrates used in Frucor’s products are chosen for their flavour and quality. Citrus, berry and tropical fruit juices come from all over the world including New Zealand
What does the term Brix (°Brix, °Bx) refer to?
Brix is a measure of the concentration of soluble solids in a solution and is based upon the relationship between the specific gravity and %w/w soluble solids of a pure sucrose solution, i.e.
1° Brix = 1% sugar w/w (weight by weight)
Whilst this relationship is only strictly applicable to sucrose solutions, the Brix provides a useful indication of the soluble solids of a fruit juice. The range of extracted orange juice and grapefruit juice is 9 -12° and for lemon and lime juice 7° Brix.
Measurement of either specific gravity or refractive index is widely used in the fruit juice and soft drink industry to provide a quick, empirical measure of soluble solids in solution.
Why is the Brix value relevant to the production of fruit juice?
The soluble solids to acid ratio is the best criterion to determine citrus quality. The Brix/acid ratio also known as the Maturity Index alters according to the growing regions and the effect of early and late season fruit.
An international code of practice is also available which sets out recognised Brix levels for fruit juices produced from various fruits in order to ensure the high standard expected.
Fruit juice can be adulterated by the addition of various ingredients. Why does this happen and how can it be detected?
The Brix and acid levels of juices are two of the most important parameters which determine the organoleptic (taste) quality of juices. These can be used to help to detect when fraudsters are attempting to import adulterated product into the market place. They do this in order to take advantage of higher prices which tend to occur during times of shortage.
Take for example, apple juice. High acid apple juices are preferred to sweet apple juices by a majority of consumers. In times of shortage, the prices of the high acid apple juice tends to be higher, therefore increasing the potential risks of possible adulteration by people who want to take advantage of the higher prices.
In the past the industry has discovered synthetic D-malic acid in adulterated juice. D-malic acid is not naturally present in apple juice. Apple juice contains only L-malic acid (L stands for Levogyre and D for Dextrogyre). Techniques can be used to detect both D and L forms in apple juice, hence determining whether a juice has been tampered with.
What is ‘Juice from Concentrate’?
This term may be found on packs of pure fruit juice. In this case the fruit has been picked, squeezed and concentrated (through the evaporation of a large quantity of the natural water present in the juice by continuous evaporators) in the country of origin. The ‘concentrated juice’ is then frozen and shipped to the country of use for packing. Fruit juice packers then reconstitute the juice restoring it to its original strength by adding the same amount of water. They use brix and acid ratios to ensure that this meets the internationally recognised standards
So what’s the difference between “Not from concentrate” and “Freshly squeezed juice”?
Not from concentrate juice is taken from fruit which is squeezed in the country of origin and then lightly pasteurised and frozen or aseptically packed for shipment to the country where it will be sold. Freshly squeezed juice is taken from fruit which is shipped to the country of use and squeezed there for immediate use. It may be unpasteurised or lightly pasteurised.
What are the main ingredients in a soft drink?
The basic ingredients of a soft drink are always water, a sweetener, an acid and a flavour. Optional extra ingredients often include fruit and / or fruit juice, carbon dioxide, preservative and colour. Water is always the major ingredient and represents approximately 86% of a carbonated drink, 90% of a fruit juice and 100% of bottled waters
How much acid is used in a soft drink?
The amount of acid used in soft drinks depends on the individual product recipe and the type of acid used; the stronger the acid the less is required to make the final drink. For example very little phosphoric acid needs to be added to a cola drink as it is a very strong acid.
B: Fruit Juices% acidpH levelOrange0.75 – 1%3.4 – 3.6Apple 0.4 – 0.7%3.4 – 3.8Grapefruit1.1 – 1.6%3.2 – 3.4Pineapple0.4 – 1%3.3 – 3.7Lemon4.6 – 6.4%3.0 – 3.2Tomato 0.3 – 0.45%4.0 – 4.5Sweetened
Why do soft drinks contain sugar?
A number of soft drinks, such as pure fruit juices, dilutables, squashes and juice drinks, contain natural fruit sugars (sucrose, fructose and glucose). It is also a fact that humans have a preference for products which taste sweet. So sugars are normally added to assist taste
Water is the major ingredient in all soft drinks. It represents at 90% of a fruit juice
Which vitamins can be found in soft drinks?
In general, any soft drink which contains a quantity of fruit juice as an ingredient will contain some amount of vitamins. In addition it is becoming increasingly popular for manufacturers to add a variety of vitamins to the final product.
For example in pure fruit juice there are often significant levels of folates (folic acid) present. These aid the development of genetic material and are involved in red blood cell production. A deficiency or low level in the diet can cause gastrointestinal disorders, anaemia and cracking of the lips, particularly for premature infants and pregnant women.
Vitamin C, essential for the structure of bones, cartilage, muscle and blood vessels, and maintenance of capillaries and gums and the absorption of iron is found in citrus fruit juices in particular but also at varying levels in other fruit juices. Vitamin C is very sensitive to oxygen and heat but modern processing and packaging, such as resealable cartons and bottles, reduce the potential losses of vitamin C. For example a 250ml glass of orange juice contains up to 120mg of vitamin C, 200% of the recommended daily amount, and a 250ml glass of blackcurrant squash contains approximately 14 mg of vitamin C, nearly 25% of the recommended daily amount
Which drinks are most likely to include preservatives and why?
Not all soft drinks contain preservatives. The need for a preservative is dependent upon the type of product and the processing used. For example aseptically filled or in-pack pasteurised drinks do not require preservatives. In addition the presence of carbon dioxide prevents mould growth and high levels of acidity and carbonation also help to inhibit the growth of yeasts and lactic acid bacteria.
However the presence of fruit or fruit juice in a product provides additional nutrients which may enable organisms to grow despite the high levels of acidity and/or carbonation. Therefore the soft drinks most likely to ferment are mildly acid types with low carbonation and containing fruit juice. In these cases a preservative must be added to prevent microbiological spoilage
1 Processing the Fruit into Juice
Once the fruit is pressed the juice can be concentrated. The concentration process involves heating the juice to evaporate some of the water contained in the juice, while still maintaining the taste. This removal of water makes the concentrate a lot easier and cheaper to transport – which is particularly important given that some of our exotic juices, like Calamansi, come from far away places!
The concentrates may be blended with other fruit such as guava, mango or orange, depending on the juice variety being produced. The essences or flavours that were recovered during the juice concentration process, are added back at this stage to ensure the distinct aroma of the juice is maintained. Ascorbic acid (Vitamin C) is also added here to replace what has been lost during processing. These natural flavours are declared on the ingredients panel, in line with the requirements of the new food standards.
The blended concentrates are then diluted with water to create a single strength juice, the same strength as the juice was when it was pressed from the fruit. The juice is then ready to be filled into bottles, cans or cartons
2 Bottling Juice
Ever wondered how juice made from concentrate is bottled? The following provides a step-by-step guide to making your own bottling line and producing your own juice
Juices are mixed together.
The juice is transferred
and stored in tanks
The juice is pastuerised
Pasteurisation is a heat treating process that destroys natural micro-organisms and maintains the quality of the juice. A similar process is also used for many milk and food products and has been safely used for decades.
Micro-organisms are always floating in the air around us. These are the same things which cause fruit to “go off” or spoil in your fruit bowl at home. When juice concentrate is diluted during production, it’s exposed to the air and a very low level of micro-organisms. If these organisms are not removed, they will feed on and spoil the juice, causing yeasts and mould to grow.
The way we remove any micro-organisms is to pasteurise or heat treat the juice. Quick heating, then cooling ensures that the juice maintains the best possible flavour.
The trick then is to get the pasteurised juice into an airtight container without any further exposure to micro-organisms
The bottles are hot filled
The bottles are capped then cooled with water spray in a cooling tunnel.
The bottles are then date coded with expiry date (usually 9 months
The bottles are packed into trays and shrink-wrapped on pallets
The pallets are labelled with use by date.
Quality control occurs usually 7 days incubation and testing
COMMON JUICE PRESERVATIVES AND ADDITIVES
Ingredient ( Use)
Sulphur Dioxide (Retards microbial and enzymatic activity )
Benzoates (Antimicrobial @ pH <4.5 )
Sorbates (Antimicrobial @ pH <6.5 )
Carbon Dioxide (pH reduction, anaerobic atmosphere )
Ascorbic Acid (Retards enzymatic browning )
Dimethylpyrocarbonate (Antimicrobial )
Unit operation involved in juice manufacture
Mass transfer Fruit delivered, dry cleaned
Separation Sized, graded
Separation Peeled, cored and deseed
Size reduction Crushed, comminuted
Pressure application Juice extracted
Separation Solids screened
Deaeration Oxygen removed
Centrifugation Solids separated
Fluid flow Juice transferred, pumped
Heat transfer Enzymes inactivated, juice pasteurized and cooled
Concentration/evaporation Volume reduction, stability
Mass transfer Packaging, shipping
( Generalized juice flow Chart
Fruit production6. Yield and quality sampling2. Load weighing and recording7. Segregated storage3. Fruit unloading8. Fruit washing4. Rough grading, debris removal9. Final grading and sizing5. Grading and cull removal10. Extractor surge bin
Flowchart of the process
Preparation of the fruit
Fruit should be washed in clean water, peeled and the stones removed. All fruit should be ripe and free from bruising. Any rotten or bruised fruit should be thrown away as this will spoil the flavour of the juice. Pineapple contains an enzyme that damages the skin.
Therefore, gloves should be worn when handling pineapple. The juice must be heated to a higher temperature for a longer time to destroy the enzyme (it must be boiled for 20 minutes). Soft fruit, such as berries and apricots, are delicate and should be handled carefully to avoid bruising
Pure fruit juices have no added ingredients, but sometimes preservatives such as sodium benzoate or citric acid are added. Fruit squashes have sugar added to preserve the squash after opening
Sugar is added to fruit juice to make a fruit squash or cordial. It is added to give a final concentration of 12-14% sugar. The amount of sugar present in the fruit has to be taken into account when calculating the amount of sugar to add. The amount of sugar added to a fruit squash is also determined by consumer taste and demand for sweetness. The amount of sugar syrup to be added to the juice to give a final concentration of 12-14% can be calculated by using the Pearson Square. Sugar syrups should be filtered through a muslin cloth to remove particles of dirt that are present in the sugar.
Juice is extracted in a number of different ways – steaming, reaming, pressing and pulping. Fruit can be pulped in a liquidiser. A range of fruit presses are available to extract the juice. Some machines combine pressing with filtration to remove the fine particles. To make fruit squash or cordial, the extracted fruit juice is mixed with sugar syrup to give a final sugar concentration of 12-14%. See added ingredients.
To make clear bright juice, the juice should be filtered to remove the fine suspended particles. The juice can be strained in a muslin cloth bag, or filtered using a steel filter. Pectic enzymes are sometimes added to the juice to break down the pectin which is naturally present and which gives the juice a cloudy appearance
Fill and seal
At the small-scale, containers can be filled simply using a funnel and a jug. For larger scale operations a range of filling machines are available. The juice containers should be thoroughly washed and sterilised before filling. Bottles that are recycled should be checked for cracks and chips. Only new caps should be used for sealing the bottles
At the small-scale, the filled bottles of juice can be pateurised in a stainless steel, enamelled or aluminium pan over a gas flame.
Care should be taken to avoid localised overheating.
A range of small-scale pasteurising units are available. To make fruit squash, the sugar syrup is heated to boiling in a large pan.
A measured amount of syrup is mixed with the fruit juice in a stainless steel pan, which increases the temperature of the juice to 60-70deg C.
The juice/syrup mixture is quickly heated to pasteurising temperature and hot filled into sterilised bottles and sealed. Fruit juice is pasteurised after it has been bottled.
The filled bottles are heated in boiling water for 5-10 minutes depending on the size of the bottle.
Both the time and temperature of pasteurisation are critical to achieve the correct shelf life and to retain the colour and flavour of the juice
After heating, the bottles are cooled to room temperature by immersing them in clean cold water. If the bottles are cooled too quickly they will crack and break
All equipment must be thoroughly cleaned each day to prevent contamination by insects and micro-organisms
Preservatives – permitted levels in fruit products
The use of chemical preservatives is regulated by maximum permitted levels. These amounts vary between countries. Processors should check with their local authorities for the local regulations and for the regulations in the country of sale.
Chemical preservatives cannot be used to cover up for poor quality raw materials. They are only added as a precaution to extend the shelf life of products by inhibiting microbial spoilage.
Some chemical preservatives can taint the flavour of fruit juices if the recommended level is exceeded. Some consumers prefer to consume fruit juices with no chemical additives. They may be prepared to pay a premium for these products
Recommended additives to inhibit micro-organisms
Both potassium sorbate and sorbic acid are used to inhibit microbial growth. Potassium sorbate is more water soluble than sorbic acid, but about 25% more of the sorbate is needed to acheive the same level of protection. Potassium sorbate is made into a concentrate for dipping and spraying fruit and vegetable products. Sorbates are effective at retarding the growth of many food spoilage organisms. They have many uses because of their milder taste, greater effectiveness and broader pH range (up to 6.5) when compared to either benzoate or proprionate. In foods with a very low pH, sorbate levels as low as 200ppm may give adequate protection. The solubility of potassium sorbate is 139g per 100ml at 20deg C. It can be used in beverages, syrups, fruit juices, wines, jams, jellies, pickles
Sodium benzoate is used as a preservative in acidic foods, where it is mainly used to prevent the growth of yeasts and moulds. Most yeasts and moulds are inhibited by levels of 0.05-0.1%. Benzoates are used in fruit juices, candied fruit peel, pie fillings, pickled vegetables, relishes and cheeses. Sodium benzoate is most effective in foods with a pH of 4.0 or lower.
Recommended additives to reduce PH
Organic acids, which are both naturally present in foods during fermentation or which are added to foods during processing, have been used for many years for food preservation. The most commonly used organic acids include citric, succinic, malic, tartaric, benzoic, lactic and propionic acids.
Citric acid is found in citrus fruits. This acid is more effective than acetic and lactic acids at inhibiting the growth of thermophilic bacteria.
Malic acid is widely found in fruit and vegetables. It inhibits the growth of yeasts and some bacteria due to a decrease in pH.
Tartaric acid is present in grapes and pineapples.
Benzoic acid is the oldest and most widely used preservative. It occurs naturally in cranberries, raspberries, plums, prunes, cinnamon and cloves.
Benzoic acid is primarily used as an antifungal agent in fruit-based and fruit beverages, fruit products, bakery products and margarine. Lactic acid is not naturally present in foods, but is formed during fermentation of sugar by lactic acid bacteria. Lactic acid inhibits the growth of spore forming bacteria at pH 5.0 but does not affect the growth of yeast and moulds.
Propionic acid occurs in foods by natural processing. It is found in Swiss cheese at concentrations of up to 1%. It is effective against moulds and bacteria.
Sulphuring or sulphiting
Sulphur dioxide is used to preserve the colour and increase the shelf life of dried foods. There are two main methods of adding sulphur to foods – sulphuring and sulphiting. Sulphuring is more common for fruits and sulphiting for vegetables. Sulphuring uses rock sulphur which may be more readily available than sodium or potassium metabisulphite. One of the disadvantages of sulphiting is that it wets the fruit (the fruit is dipped into a solution of metabisulphite). This prolongs the drying period required
Sulphuring involves burning elemental sulphur in an enclosed chamber. Sulphur dioxide gas is given off, which is absorbed by the food. The sulphur chamber is either a cabinet or tent in which perforated trays are stacked on top of each other. Food is placed on the trays inside the cabinet. The sulphur is placed in a box close to the trays and allowed to burn for 1-3 hours. A simple sulphur tent can be made from a rack of shelves that are covered with an airtight polythene sheet. It is essential that the cover does not have holes and that it is firmly anchored down at the ground to prevent sulphur dioxide gas from escaping. The amount of sulphur used and the time of exposure depends on the commodity, its moisture content, the sizes of the pieces and the permitted final levels in the product. For most fruits, 5-6g of sulphur per kg of food is adequate. For most vegetables, 10-12g sulphur per kg food is sufficient. Sulphuring should always be carried out in a well-ventilated place – preferably outdoors – as the fumes of burning sulphur are unpleasant and can be dangerous if inhaled. Sulphur dioxide gas is corrosive, therefore the cabinet used for sulphuring should not be made of metal. Wooden or plastic-coated metal shelves should be used within a wooden cabinet or a polythene tent.
Sulphiting uses sulphite salts such as sodium or potassium sulphite or metabisulphite. The fruit or vegetable is either soaked in a sulphite solution or, if the commodity is being blanched in water, sulphite can be added to the blanching water.
Adding sulphite to the blanching water is attractive since it combines two operations into one. However, if the vegetables are steam blanched, or if they are not blanched at all, they need to be dipped into a sulphite solution.
The strength of the sulphite solution and the dipping, spraying or blanching times depend on the type, size and composition of fruit or vegetable.
Dipping and spraying sulphite are not generally recommended for small-scale processors. Immersion blanching in a sodium metabisulphite solution is the most appropriate method, provided that the chemicals are available locally.
Sulphiting must be controlled accurately to obtain the correct levels of SO2 in the food. Too much SO2 gives the food an unpleasant smell and may be illegal according to local permitted levels. The strength of sodium metabisulphite solution is expressed as parts per million (ppm) or mg per kg. As a conversion, 10,000ppm SO2 is equivalent to a 1% solution. 1.5g of sodium metabisulphite dissolved in 1 litre of water will give 1000ppm (0.1%) SO2. The most practical way to make a sulphite solution is to prepare a stock solution of 8,000ppm (0.8%). This is done by dissolving 12g (2.5 level teaspoons) sodium metabisulphite in 1 litre of water. The stock solution can be diluted by adding extra water to give weaker solutions