Food or edible material: processes – compositions – and products – Direct application of electrical or wave energy to food... – Heating by electromagnetic wave
Patent
1998-02-23
1999-11-02
Lacey, David
Food or edible material: processes, compositions, and products
Direct application of electrical or wave energy to food...
Heating by electromagnetic wave
426522, 99451, 99452, 99467, 422 21, A23C 307, A01J 1100
Patent
active
059765925
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for sterilizing biological liquids, for alimentary, sanitary, and cosmetic use, in particular milk and its by-products.
Various methods for preserving and sterilizing milk are known. It is known that the main components of this food product are constituted by water, sugars, mineral salts, fats, vitamins, biochemical compounds, such as enzymes, antibodies, and hormones, together with biological components of microbial and viral origin. Namely, milk is an emulsified solution of lactose, casein, fats, and some mineral salts in a water content of more than 85%. The pathogenic microorganisms that are present in this food product constitute the so-called bacterial flora, which includes, among others, Mycrobacterium tuberculosis, a wide range of viruses, including the poliomyelitis virus, as well as thermoresistant, thermophilic, psycrophilic and anaerobic germs.
The problem that must be solved by the sterilization of these products essentially consists in the total destruction of the bacterial flora without affecting the active principles that determine the original organoleptic, chemical and physical properties of the products allowing a shelf life comprised between 4 and 9 months depending on the national legislation.
Conventional preservation methods used on an industrial scale are of the physical, chemical-physical, chemical, and biological types. In particular, physical methods use refrigeration, heat transmission, or desiccation.
Among these methods, processes based on the application of heat are by far the most effective and most widespread in solving the above mentioned problems. The heat application conditions depend not only on the nature of the product to be treated but also on the type of microorganisms contained in it and finally on the simultaneous use or not of other preservation processes. The degree of heat resistance of the microorganisms has to be linked to external and environmental factors, such as the initial microbial concentration of the medium, the characteristics of the medium itself, and the time and temperature parameters, as well as to intrinsic factors such as the heat resistance of germs and spores.
In the conventional sterilization method, the product is superheating to temperatures of over 140.degree. C. for a time between 5 and 12 minutes.
The temperature and duration of the thermal treatment depend on the heat application method and on the type of product. Furthermore, at the end of the treatment the product must be subjected to cooling down to temperatures of less than 35.degree. C. before introducing it in sterilized containers (glass bottles or Tetra-pak.RTM. containers).
Heat can be applied by indirect exchange, in which the product and the heating medium are separated by the wall of an exchanger, or by direct exchange, in which the product and the heating medium are in direct contact.
Current thermal preservation methods are the most important ones from the industrial point of view, but have some drawbacks.
In fact, in order to increase the sterilization effectiveness, it is necessary to increase the maximum temperature of the process, with the consequence of damaging the product from the organoleptic, physical and chemical point of view, destroying proteins and essential enzymes and giving it a cooked or burnt taste or reducing its natural taste and aroma.
Furthermore, in indirect-transmission systems the heat is transmitted from the outside inward, so that it is necessary to increase the temperature of the exchange surface in order to destroy the microorganisms even in the innermost regions. This can cause a partial non-uniformity and ineffectiveness of the process.
In direct-exchange systems, the heating medium is generally constituted by steam, which has the inconvenience of condensing inside the product itself, thereby reducing the concentration of the active principles; the steam must be eliminated before the condensation (degassing).
Electronic preservation devices without an exchange surface have recently been devised which
REFERENCES:
patent: 5403564 (1995-04-01), Katschnig et al.
patent: 5697291 (1997-12-01), Burgener et al.
"Deposit Formation in UHT Plants. I. Effect of Forewarming in Indirectly Heated Plants," Milchwissenschaft, by G.R. Patil et al., vol. 41 (6), 1986, pp. 337-339.
Becker Drew
Coleman Henry D.
Lacey David
Officine di Cartigliano S.p.A.
Sudol R. Neil
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