Preserved vegetables

Article index

		Pretreatment, peeling and washing
		Possible cutting
		Blanching
		Pot/tin
		Packing
		Pasteurising/sterilising
		Deep freeze
		Freezing
		Packing
		Deep freezing

Pretreatment, peeling and washing

The pretreatment of vegetables that are to become preserved vegetables happens the same way as with fresh vegetables and fruit. See what is written under salad in the left menu.

Possible cutting

The vegetables are cut dependent on the kind of vegetable. The cutting process can happen manually as well as mechanically. In the mechanical process the vegetables are transported through rotating knives.

Blanching

The vegetables are blanched to reduce the initial germ count, to shorten the process time and to inactivate the enzymes. Blanching means that the vegetables are strongly heated (98°C) for a short time (several minutes at most).

Pot/tin

Packing

After the vegetables have been blanched they are packed. Preserved vegetables are packed in either a pot or a tin. In filling a brine is added to the vegetables. The brine gives extra flavor and may consist of the boiling water of the vegetables themselves or for example acid.

Pasteurising/sterilising

In order to increase the storage life of the vegetables they are pasteurised or sterilised. Pasteurisation is a mild heat treatment which kills only vegetative microorganisms. This heat treatment is only applied to vegetables when they are packed with acid. By the low pH the acid prevents the growth of spores of microorganisms so that they become vegetative cells. If the vegetables are not packed with acid they are sterilised. Sterilisation kills besides the vegetative cells also the spores.

Deep freeze

Freezing

The pieces of vegetable are de-watered and are frozen separately. This means that they are frozen apart from each other on a large plate or conveyor. Freezing can be done in batch or in a continuous process. By rapidly freezing the individual pieces the structure is better preserved and they do not stick to each other. In this phase of freezing the pieces are frozen lightly to a temperature of about 5°C below zero.

Packing

The lightly frozen pieces of vegetable are normally put in plastic bags, which are sealed.

Deep freezing

The pieces of vegetable are deep frozen in the packing. Because the vegetables are already lightly frozen this phase does not have to happen rapidly. However, the quality remains better if this phase freezing process happens rapidly. Non-blanched deeply frozen vegetables have a storage life of several months. Blanched deeply frozen vegetables have a storage life of several years.