FI57046B - FOERFARANDE FOER BEHANDLING AV MJOELK MED VAETEPEROXID - Google Patents

Description

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Sweden-Sweden (SE) 7310076-0 (71) Alfa-Laval Aktiebolag, Postfack, S-lV? 00 Tumba, Sweden-Sweden (SE) (72) Ernst Anders Carl-Gustaf Rosen, Huddinge, Karl Erik Lennart Björck,

The present invention relates to a process in which hydrogen peroxide is used to increase the preservation of milk. means.

Methods of treating milk with hydrogen peroxide to increase the preservation of milk have been proposed several times before, as far back as 1881. Of the chemical compounds that can be added to foods to prevent or eliminate the growth of microorganisms, hydrogen peroxide is the only one has accepted.

The exact nature of the antibacterial activity of hydrogen peroxide is unclear, but in recent years it has been observed (Oram. JD and Reiter B: The Inhibition of Streptococci by Lactoperoxidase, Thiocyanate and Hydrogen Peroxide. Biochem. J. 100 (1966) 373-381) that about 20 At concentrations above ppm (ppm), in addition to the direct toxic effect, hydrogen peroxide may also be involved in dilute concentrates at 2 57046 in the naturally occurring antibacterial system in milk and thus act indirectly.

However, the method of adding hydrogen peroxide never succeeded, mainly perhaps because the potency of the additive was so short-lived. After rapid decomposition in milk, the hydrogen peroxide compound drops below the bactericidal level. In the described cases where hydrogen peroxide has been used, it has therefore been necessary to use starting compounds which are so high that the compound has remained above the critical level for a sufficiently long period of time or to use a lower starting compound, the treatment being repeated every few hours.

However, neither approach is entirely appropriate, since in the former case - and to some extent also in the latter - the concentration of hydrogen peroxide is sometimes so high that certain substances, such as milk, sometimes experience a consequent reduction in nutritional value. A similar, too high detrimental effect of hydrogen peroxide concentration is likely to affect a few substances, e.g. milk, which naturally forms an antibacterial system. The latter approach, on the other hand, requires a balancing system which is difficult to implement in practice.

The above-mentioned disadvantages associated with these prior art in using hydrogen peroxide to increase the shelf life of milk have been eliminated in the application of the method of the present invention. Thus, experiments with milk have shown that By applying the method, conditions can be obtained in which the concentration of hydrogen peroxide after rising from zero is maintained at a substantially constant level, just above the lowest level necessary to inhibit bacterial growth, by the direct or indirect action of hydrogen peroxide. at the same time, the level is low enough to cause only the least possible chemical effect on the milk, which effect is likely to be negligible.

The invention therefore relates to a process for treating milk with hydrogen peroxide to such an extent that none of the milk components are damaged but is large enough to activate the naturally occurring antibacterial system of lactoperoxidase and thiocyanate in milk 57046, and the invention is characterized by hydrogen peroxide to a maximum concentration of 25 ppm in the liquid to be treated.

Such enzymatic development of hydrogen peroxide can be accomplished by any of a number of enzyme systems known as oxidoreductases according to the following principle:

Growth medium ->

The practical application of the procedure may be in accordance with the examples below. Reference is also made to the drawing, in which Figures 1 and 2 are curves showing the development of bacterial growth over several days with and without the addition of the enzyme system according to the invention. Figure 3 shows how, for example, the machinery should be designed to take advantage of the method according to the invention.

For example, it is possible to add one enzyme and one substance capable of releasing hydrogen peroxide under the action of the enzyme, the added amounts of enzyme and substance being capable of providing the required hydrogen peroxide concentration. A system such as that described may contain glucose and glucose oxidase, which under the action of glucose releases hydrogen peroxide.

- In Figure 1, the vertical axis represents the logarithmic values of the number of bacteria found in each milliliter of milk and the horizontal axis the time in days.

The curve shows the development of bacterial growth in milk cooled to 4 ° C and mixed with 0.5% glucose and 2 units of glucose oxidase per milliliter. For comparison, the curve also shows the development in milk chilled to 4 ° C but to which no enzymes had been added.

As can be seen from the curve, the bacterial count decreased by about 1/100 on the first day and remained at this level for the next 10 days in milk supplemented with the enzyme system, whereas the bacterial count of untreated milk remained unchanged during the first day and then showed a large increase each day.

57046

Figure 2 shows the development in two milk samples, which had also been kept at 4 ° C, but to which 1 unit of glucose oxidase and 0.1% glucose and 3% glucose, respectively, had been added.

As can be seen from the curve, the decrease in bacterial count appeared to be milder on the first day than in the example of Figure 1 and then remained constant at a somewhat higher level than in the previous example, but only for six days in the 0.1% glucose sample. A better result was obtained with 0.3% glucose.

The examples show that milk can be easily protected against bacterial growth for several days by applying the method according to the invention. This makes it possible, for example, to store milk on the farm for a considerable period of time, which reduces the number of transports to the dairy and the costs involved.

The following concentrations are recommended, depending on how long the chilled milk must be protected from bacterial growth: 0.1-2 units of glucose oxidase per milliliter of milk 0.1 to 0.5% by weight of glucose

In another example according to a detailed embodiment of the present invention, the the liquid is mixed with an enzyme system containing 20 units of L-amino acid oxidase per milliliter of milk 0,5% by weight of glycine

In the above application examples, the milk was cooled to 4 ° C. The method is, of course, more effective if the milk is kept cold. As the curves showed, even after ten days, the number of bacteria was about 100 times lower than in the original milk. However, the method can be applied to any temperature which is considered suitable for economic or other reasons 5 57046. In such cases, the appropriate composition of the enzyme system and the compound must be experimentally adjusted to the desired temperature. As an example, milk to which 2 units of glucose oxidase per milliliter and 0.5% glucose have been added can be stored for two days at 22 ° C without an increase in the number of bacteria.

In the above-mentioned examples of the application of the method according to the invention, an enzyme and a substance which releases hydrogen peroxide under the action of the enzyme were mixed into the milk. In the case of milk in particular, it is advisable instead to use an enzyme capable of releasing hydrogen peroxide by means of a substance present in the milk. The compound that meets this requirement is milk lactose, which releases hydrogen peroxide by galactose oxidase.

'The proposed concentrate is the following 0,1 to 2 units of galactose oxidase per ml of milk

Even better results are obtained by the addition of β-galactosidase and glucose oxidase, from which β-galactosidase causes the lactose to break down in the milk, releasing glucose, which is then oxidized by the added glucose oxidase and releasing hydrogen peroxide. The proposed concentrations are as follows: 1 to 10 units of 8-galactosidase per milliliter of milk 0.1 to 2 units of glucose oxidase per milliliter of milk

Such an embodiment of the invention apparently causes a partial consumption of lactose in the milk, but if the amount of lactose is as high as 5%, then only a small part of it decomposes during a couple of days of storage when, for example, galactose oxidase is added.

Another suitable method for applying the invention, especially in the treatment of milk to improve its shelf life, is to utilize an enzyme naturally present in milk to generate hydrogen peroxide. One such enzyme is xanthine oxidase, which together with hypoxanthine releases hydrogen peroxide. The appropriate addition for this purpose is as follows.

0.5% by weight of hypoxanthine 57046

According to one embodiment of the present invention, which is very useful in the treatment of milk and other liquid nutrients to improve their shelf life, those enzymes which are not naturally present in liquids may be associated with a solid carrier and the the liquid is made to flow past this solid support, for example by a circulating pump. With this method, a certain amount of enzyme, which is in principle nothing more than a kind of catalyst, can be used repeatedly, e.g. for additional amounts of milk. This, of course, results in a significant reduction in the cost of this treatment. The preparation of the described solid carriers to which the enzymes have been associated is described in the relevant scientific literature cf. e.g., Siiman, I.H. and E. Katchalski: Water-insoluble Derivatives of Enzymes, Antigenes, and Antibodies. Ann.

Rev. Biochem. _35 (1966) 873.

A common method of practicing the present invention is to mix the such large amounts of said reagents into the liquid that hydrogen peroxide is evolved in such a unit of time that it compensates for the dispersion in the milk and maintains the necessary but not excessive concentration for a predetermined period of time.

These amounts must be determined individually in each case and take into account factors such as thermal conditions, the quality and resistance of the bacterium present, the sensitivity and function of the various components of the liquid, etc. and, of course, the desired target. However, the amounts and other conditions mentioned in the examples are believed to be suitable for standard cases.

The present invention is also intended to be used to improve the retention of liquids which result from the dissolution or dispersion of solid or semi-solid mixtures or preparations, e.g. in water. In such cases, the enzymes and / or ingredients intended for the production of hydrogen peroxide are mixed. solid or semi-solid mixtures. Apparently they only start to react when said products, in which they have been mixed, have been added and dissolved or dispersed in e.g. water.

The drawing in Figure 3 shows an example of how the machinery for handling and storing milk should be arranged in agriculture