Food or edible material: processes – compositions – and products – Processes – Packaging or treatment of packaged product
Patent
1999-06-15
2000-09-12
Bhat, Nina
Food or edible material: processes, compositions, and products
Processes
Packaging or treatment of packaged product
426491, 426522, A23L 300, B65B 5502
Patent
active
06117470&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of producing aseptic consumer milk with a certain fat content by microfiltration.
BACKGROUND ART
It is known from SE 451 791 to produce milk products with extended shelf life. According to this patent, the milk is divided into two fractions in a centrifugal separator. The skimmed milk fraction is led to a microfilter and divided into a permeate flow of low bacterial content and a concentrate flow which contains minute cream globules and bacteria. The concentrate flow is sterilized and remixed with the permeate flow in order to give a milk product with a predetermined fat content. In order to achieve the desired bacteria separation, microfilters of a pore size of 0.2-1.0 .mu.m are employed.
U.S. Pat. No. 5,256,437 describes a method of producing milk with a bacteria content which is lower than in the raw milk. According to this patent specification, the milk is homogenized and, within five minutes of this treatment, the milk undergoes a dynamic microfiltration process.
OUTLINE OF THE INVENTION
According to the present invention, a method of producing aseptic (sterile) consumer milk with improved flavour is now proposed. The method according to the present invention is substantially characterized in that a continuous flow of milk with a certain fat content is caused to pass through a microfilter with a membrane having a pore size of 0.05-0.2 .mu.m, in which the milk is divided into two part flows, in which the one part flow--the retentate flow--contains fat and the major fraction of the casein, while the other part flow--the permeate flow--contains the major fraction of the whey proteins, whereafter the retentate flow undergoes a high temperature treatment, whereafter the two part flows are mixed, the mixture is homogenized and the milk is packed aseptically.
In this treatment, the part flow--the permeate flow--which has passed through the membrane in the microfilter will be sterile, since neither spores nor bacteria can pass through the membrane.
The milk which is obtained according to the present invention is sterile and thus displays long shelf life, since no bacterial growth can take place. The thus obtained milk is moreover of the same composition as the milk supplied to the microfilter, since no fraction is separated off.
According to the present invention, aseptic milk will be obtained which has good flavour, since only that fraction which contains the casein has undergone a high temperature treatment (sterilization).
If it is deemed necessary, the permeate flow may undergo a pasteurization process prior to the remixing process. Such a measure may be motivated by the desire to render any possible virus harmless.
The present proposed invention may be applied in practice irrespective of whether the supplied milk consists of whole milk or standardized milk. Whole milk consists of untreated milk with -4 percent fat, i.e. the fat content which the milk has when delivered to the dairy. Through the standardization process, the fat content of the milk is reduced to a level desired from the consumer's point of view, for example 0.5, 1.5 or 3 percent fat. Preferred fat contents vary from country to country and standardization thus provides the possibility of satisfying different consumer preferences. In this context, skimmed milk which contains -0.05 percent fat, i.e. most of the fat globules in the milk have been separated off, is deemed to fall within the overall category of standardized milk.
It has previously not been considered possible without homogenization to cause whole milk or standardized milk with a high fat content to be treated in a microfilter with such a small pore size as 0.05-0.2 .mu.m without operational stoppage after a short while.
When high demands are placed on the flavour of the milk, the standardized milk may be produced by cold separation. Normally, standardization takes place once the milk has been heated to a temperature of 50-60.degree. C. In cold separation, the fat separation is somewhat less efficient.
When the milk
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Bhat Nina
Tetra Laval Holdings & Finance S.A
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