Food or edible material: processes – compositions – and products – Direct application of electrical or wave energy to food... – Involving dielectric heating or passage of electric current...
Patent
1997-01-21
1998-08-04
Yeung, George
Food or edible material: processes, compositions, and products
Direct application of electrical or wave energy to food...
Involving dielectric heating or passage of electric current...
426520, 426524, A23L 300
Patent
active
057890064
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to a method for food processing. More particularly the invention relates to a method of processing a solid plant foodstuff during the preparation of an ambient stable food product.
BACKGROUND TO THE INVENTION
A number of food processing methods comprise the steps of heating to an elevated temperature to effect cooking and/or sterilisation and then cooling prior to aseptic packaging. For any particular foodstuff, the maximum target temperature to be attained by heating, and generally held for a short period to achieve sterilisation, is quite critical, as it affects the quality of the finished product.
It is therefore necessary to be able to heat large pieces of foodstuff (for example broccoli) evenly and also to be able to cool them evenly such that certain regions of the foodstuff are not heated more than other regions.
Suitable mass heating methods such as pressure controlled ohmic heating and microwave heating, which permit even heating throughout the foodstuff are described in WO 94/08475. A method of processing a solid foodstuff using a mass heating method is described, according to which, during at least part of the heating step, the environmental pressure of the foodstuff being heated is so controlled in relation to the saturated vapour pressure of the foodstuff as to achieve a substantially uniform temperature throughout the solid foodstuff at the maximum target temperature to be attained. Furthermore WO 94/08475 suggests that after heating a preferred method of cooling is by evaporation, achieved by applying a partial vacuum to the foodstuff.
However, such methods, although providing an even heating and cooling regime, do not necessarily provide foodstuffs which have a high product quality. By high product quality is meant products which are of comparable quality to frozen foodstuffs, but are ambient stable.
We have determined that in order to achieve plant material, eg. vegetables and fruit, having a high quality it is necessary to restrict certain conditions during heating.
SUMMARY OF THE INVENTION
Accordingly the invention provides a method of processing a solid plant foodstuff comprising which, during at least part of the heating step, the environmental pressure of the foodstuff being heated is so controlled in relation to the saturated vapour pressure of the foodstuff as to achieve a substantially uniform temperature throughout the solid foodstuff at the maximum target temperature to be attained; and environmental pressure of the foodstuff lower than the saturated vapour pressure of the foodstuff; above 118.degree. C. is less than 29 seconds, and the time for which the plant foodstuff is above 70.degree. C. is less than approximately 100 seconds.
In this specification and the appended claims the term "solid foodstuffs" is used to define foods containing water which does not have a flow capability, but whilst having a shape-defining structure contain, or through a cooking process develop, pathways enabling the passage of a fluid from one part of the structure to another. Examples are vegetables such as peas and broccoli and fruits such as strawberries.
Additionally, the class of heating/cooling methods with which the invention is concerned is referred to in the specification and the claims as a mass heating or cooling method, being a method in which the entire mass of the solid foodstuff (as hereinbefore defined) is subject to the effect of applied heat or to the cooling effect respectively, as distinct from a method in which heat or the cooling effect applied to the exterior is transmitted by conduction to the interior.
Furthermore, by plant foodstuff is meant a food product deriving from any part of a plant, ie root, stem, leafage, flower, fruit, vegetable or seed.
Examples of mass heating methods are ohmic heating and microwave heating; retort heating is not an example of such a mass heating method. Vacuum or reduced pressure evaporative cooling is an example of a mass cooling method.
Preferably the time the plant foods
REFERENCES:
patent: 4560567 (1985-12-01), Rausing
patent: 4739140 (1988-04-01), Reznik
Jones Robert David
Stephenson Peter Richard
Wilding Peter
Unilever Patent Holdings B.V.
Yeung George
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