The processes involved in the following for fruit and vegetables:


Tunnel driers used for drying fruit and veg in a cube form (diced).

Highest quality dried products are produced by freeze-drying - accelerated freeze-drying AFD.

High cost of process = Higher price of product.

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Juice Extraction (1)

Macerate the porduct before extraction or treate with enzymes (pectolytic enzymes) - increase yield.

Two juices - Low Viscosity and High Viscosity

Low Viscosity Juices eg. Apple Juice

Clear (no suspended matter)

Apples macerated to form a pulp with is pressed in a rack-and-cloth press.

Pectolytic enzymes and amylase are added to clear the juice.

suspened particles removed by filtration.

Juice is pasturised before bottling/canning.

Centrifuges sometimes used in addition to press

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Juice Extraction (2)

High Viscosity Juice e.g. Tomato Juice

Higher the viscosity = better quality

Cold-break method - raw tomatoes are macerated at room temp.

Seeds and skin filtered.

Yeilds a juice of lower viscosity as the pectins and degraded by petolytic enzymes.

Juice has excellendt flavour and colour.

Hot-break method - favoured by industry

tomatoes macerated and heated to 85C to inactivate the pectolytic enzymes.

Viscosity of juice is higher but flavour and colour not as good.

Hydrochloric acid is added during maceration - improves consitency.

Neutralised after extraction with sodium hydroxide solution - forms sodium chloride - saltiness to product.

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Product is preserved and flavoured by solution of salt and edible acid (vinegar).

Acid either added or produced by fermentation.

All veg can be fermented by lactic acid bacteria to yeild a sufficient level or lactic acid.

Preservation by fermentaion depends on:

  • Reduction of the activity of natural enzymes of product
  • Inhibition of oxidative chemical changes
  • Inhibition of the growth of spoilage organisms

Pickles can be preared directly from veg without fermentation by adding salt and vinegar.

Some ferment in weak brine solution (dill picles)

Fermented in high-salt brine and then later converted into mixed pickle

Traditional Method- fill wooden vat 1/3 of a 10% brine into veg filled. Dry salt added to keep salt solution at 10%. Brine added to cover the veg completely to ferment without air. Bacteria multiplys, the brine becomes cloudy. Lavtic acid is produced and with the slat preserves the product.

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Preserve-making (1)

Preserves: Jellies, jams, marmalades, conserves and candied fruit

Gel formation is essential part of preservation,

Underripe fruit, rich in pectin is ideal material (pectin may be added).

Fruit pulp is frozen/canned/stored to be made into jame out of seaons.

Sulphur Dioxide is added to prevent microbial growth and discolouration, but is boiled off during manufacture.

  • Sugar is added to an equal weight of fruit (also depends on acidity, sugar content and ripeness of the fruit).
  • Mixture is boiled - under reduced pressure to reach total soluble solid content of about 68%
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Preserve-making (2)

Marmalades contain fruit pulp and peel - from under-ripe fruit, rich in pectin an dacid. Citrus fruits.

Conserves contain more fruit than jame and are expensive. Chopped nuts added to give texture and flavour.

Crystallized/Candied fruit tradition middle east product.

Strong sugar solution added to prepare slices of fruit - become dehydrates by the osmotic effect.

Glace cherries/citris peels and mixed cake deco produce.

cherries destones, heathed to 60C for up to 20mins

small amount of calcium chloride is added to firm the tissues

Cherries added to boiling syrup and stand for some time.

Prepared, very sensitive to high humiditiy and must be sotred below 50% Relative Humidity and 10C

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