Food or edible material: processes – compositions – and products – Processes – Heating above ambient temperature
Patent
1984-07-13
1987-08-25
Yeung, George
Food or edible material: processes, compositions, and products
Processes
Heating above ambient temperature
99453, 99483, 261 76, 426474, 426522, A23L 316, A23C 302
Patent
active
046892370
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a field of technology of processes and devices for thermal treatment of a fluid by vapor injection into this fluid.
There is a large number of vapor injection devices which are known and employed particularly for the sterilization of liquid foodstuffs. These devices generally consist of a chamber (for mixing a product with vapor, inside which chamber a part of the vapor condenses, extended by a holding section, inside which condensation is completed, resulting in a rise in temperature. The product is then cooled in a vacuum evaporation chamber in which the condensed vapor is evaporated. Maintenance of the required temperature is usually provided by regulation of the pressure of the injected vapor, controlled by a temperature measurement in the holding section.
There may be mentioned by way of example the injector described in the document FR-A-1,114,013 which permits this type of treatment and which consists of a section of straight tubing which is surrounded by a vapor jacket; this vapor enters the stream of the product to be treated, through orifices in the wall of the tubing, in the region of maximum flow velocity, the orifices for introducing vapor being inclined in the direction of the flow.
Using this treatment, in the case of foodstuffs, bacteria which are detrimental to their long preservation are destroyed without, however, changing their nutritional value or their physico-chemical characteristics. In the case of milk, for example, the heat treatment which is referred to as U.H.T. sterilization consists, after preheating, of an abrupt increase in the temperature up to 150.degree. and of this temperature being held for several seconds. The characteristics of the heat treatment are generally prescribed by regulations for each type of product, depending on its destination. The international standards which define the treatments of pasteurization, sterilization and "U.H.T" treatment are well known to the experts.
The known systems have the following disadvantages:
1. Stability of the sterilization temperature is very difficult to produce and, in practice, considerable fluctuations around the set point are observed as soon as a flow parameter or an environmental parameter is slightly changed. The reason for this will be given later. A known remedy, described in the document FR-A-2,441,344, for reducing these considerable fluctuations in temperature consists in getting rid of the oscillations of the vapor injection by the expedient of a critical flow of this same vapor, upstream of the mixing chamber, in the entry nozzle of the injector; this arrangement provides a constant flow of vapor into the mixing chamber which, combined with a constant flow of the product to be treated, should provide good stability of the treatment.
2. Completion of the condensation in the holding section is reflected in an unevenness of the heat treatments owing to the absence of temperature uniformity within the product. Moreover, the fact that the volume occupied by the fluid is unknown makes it difficult to evaluate the residence time at high temperature.
These two disadvantages make it necessary for the sterilization conditions to be exaggerated, at the cost of the physico-chemical and organoleptic properties of the product to be treated.
In addition, the presence of a holding section, which is essential for completion of the temperature rise and for establishing a certain uniformity of the heat treatment, does not make it possible to envisage a treatment the duration of which would be less than a second.
While the device of the document FR-A-2,441,344 permits good temperature stability, it does not, however, provide satisfactory efficiency in respect of the control of the time of contact between product and vapor, and this scatter of contact times can give rise to noticeable changes in the treated product.
One of the objectives of the present invention is to ensure complete condensation of the vapor injected inside the injector.
Another objective is to provide a thermal treatment which is s
REFERENCES:
patent: 2060557 (1936-11-01), Davis
patent: 2089132 (1937-08-01), Murray
patent: 2115470 (1938-04-01), Rogers
patent: 4161909 (1979-07-01), Wakeman
Institute National de la Recherche Agronomique
Yeung George
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