CS235070B2 - Method of hydrogen peroxide removal from sterilized milk - Google Patents

Abstract

Liquid food products, particularly milk, are sterilised by a cold treatment in which oxygenated water is the sterilising agent, which is then removed completely by passing a stream of the products through a mass of fibres in which the enzyme catalase is incorporated. The process can also be carried out by bringing the fibres into contact with the products treated with oxygenated water and removing the fibres by filtration when the reaction is completed. In both cases the organoleptic properties of the food products, particularly of milk, remain unchanged.

Description

The invention relates to a process for removing hydrogen peroxide from sterilized milk by the action of catalase, firmly occluded in cellulose triacetate fibers and having an activity of 625,000 IU / ml.

The invention relates to a method of sterilization. milk and liquid foods or foods in the form of an aqueous suspension.

Preservation of milk intended for direct consumption or for the manufacture of products such as cheese, yogurt and the like creates. in practice, considerable problems. Due to its chemical composition, milk forms an excellent culture medium for bacteria, making sterilization difficult.

Milk is a high-value food for humans, but is perishable due to its characteristics. Therefore, many methods of industrial milk preservation, such as sterilization and pasteurization, have been tested which allow it to be preserved without substantial modification of the nutritional value.

All known methods are based on the heat treatment of milk and require expensive devices that are predominantly centralized and often remote from the production centers.

However, the problem of milk retention is in any case determined by the time interval between milking and heat treatment, i.e. during transport and storage prior to such processing. Milk cooling only partially solves this problem since it is not always applicable, notwithstanding the fact that cooling only slows the growth of bacteria. It is understandable that the time interval between milking and heat treatment of milk must be as short as possible.

On the other hand, there is a sterilization procedure that is extremely simple and inexpensive and does not require any special equipment and can be performed immediately after milking. According to this procedure, hydrogen peroxide at a concentration of 500 to 2000 ppm (parts per million) is added to the freshly milked milk to give an absolutely sterile product that requires no further processing. The presence of hydrogen peroxide preserves the sterility of the product during transport and storage, eliminating the need for cooling.

However, this efficient and simple procedure has not been used so far because of the toxicity of hydrogen peroxide, which had to be removed from the milk with chemicals that adversely affect the chemical and organoleptic properties of the milk.

It has now been found that it is possible in a simple manner to remove hydrogen peroxide without affecting the chemical composition of the milk by utilizing a catalase enzyme encapsulated in fibers of a polymeric material by the process described in Italian Patent No. 836,426.

The catalase enzyme, which catalyzes the conversion of hydrogen peroxide to water and oxygen, can be easily removed by simply separating the enzyme-encapsulating fibers from the milk upon completion of the reaction.

SUMMARY OF THE INVENTION The present invention provides a method for removing hydrogen peroxide from sterilized milk by the action of carrier-bound catalase comprising the use of a firmly occluded catalase. in cellulose triacetate fibers having an activity of 625,000 IU / ml.

Obviously, the whole process of sterilization and subsequent separation of hydrogen peroxide does not affect the composition of the milk in addition to the slightly increased water content.

This sterilization process can be applied to any food in solution or suspension.

The invention will now be illustrated by way of examples.

Example 1 g of triacetate cellulose was dissolved in one liter of methylene chloride at room temperature. To the polymer solution cooled to 1 ° C was added 150 g of a 12.5 mg proteinase / ml catalase solution, equivalent to 625,000 International Units / ml in 0.01% potassium phosphate. N in the form of a buffer (pH 7.0) containing 30% by weight glycerol. An emulsion consisting of a finely dispersed enzyme solution in the polymer solution was formed by mixing.

Subsequently, the emulsion was passed through a powder immersed in a toluene coagulation bath. The formed fiber was wound on a supply drum and air dried to remove the solvent.

To one liter of milk in which it was determined by the APHA standard (“Standard Dairy Product Testing Procedures”, 13th edition, American Public-Health Association, Inc., New York, 1972), 120. . 10 ³ bacteria in 1-ml, 1000 -ppm hydrogen peroxide was added.

The milk was kept in a sealed container for 1 hour at -35 ° C. Subsequently, 1 g of catalase encapsulating fibers were added to the milk and left for 1 hour at 25 ° C with gentle stirring. After separation of the fibers, no bacteria were found. »

The determination of hydrogen peroxide was carried out on the AMEL Mod polarograph. 463 with a mercury drop electrode, mix 10 ml of milk with an equal volume of 0.05 M phosphate buffer, pH 7.0 in the form of an auxiliary electrolyte, and reduce the oxygen level by bubbling nitrogen for 5 minutes.

The hydrogen peroxide concentration in milk, determined by comparison with the calibration curve of milk samples with known H2O2 content, was zero.

Example 2 g of the fibers described in Example 1 were placed in a cylindrical reaction vessel (diameter 12 mm, height 1000 mm), thermostated at 25 ° C. The fibers were arranged in such a way that their longitudinal axes were parallel to the reactor axis. The reactor was continuously fed with 10 L of milk per hour, after standing in a closed vessel for 12 hours at 35 ° C containing 800 ppm hydrogen peroxide.

Prior to the addition of hydrogen peroxide, the content of 1150 * ¹⁰ bacteria per ml of milk was determined as described in Example 1.

After passing the milk through the column, zero hydrogen peroxide and 7 bacteria per ml of sample were found.

Example 3

Whey, obtained in the manufacture of cheese, which had a pH of 6.8 and a content of ¹⁰ 8 10 ³ bacte per milliliter, was added 500 ppm hydrogen peroxide. After standing for 12 hours at 35 ° C in a closed vessel, the solution was allowed to flow through the reactor described in Example 2 at a rate of 10 liters per hour. No hydrogen peroxide was detected in the elution solution. The number of bacteria per milliliter was 6.

Example 4

Hydrogen peroxide at a concentration of 4500 ppm was added to one liter of milk. 250 mg catalase-encapsulating fibers prepared according to Example 1 were added to the milk thermostated at 25 ° C. After 60 minutes the fibers were separated and the milk content was determined to contain 2000 ppm hydrogen peroxide. After a further two hours, during which the milk was again kept thermostatically at 25 ° C in the absence of fibers, the hydrogen peroxide content was still 2000 ppm. Subsequently, the fibers were again added to the milk mass and after 1 hour of reaction the hydrogen peroxide content was reduced to 950 ppm. The fibers were removed again and the hydrogen peroxide content was still 950 ppm after another two hours under the same reaction conditions.

This experiment demonstrates that separation of fibers from milk ensures complete removal of the catalase enzyme.

Claims (1)

OBJECT OF THE INVENTION A process for removing hydrogen peroxide from sterilized milk by the action of carrier-bound catalase, characterized in that a catalase tightly occluded in cellulose triacetate fibers having an activity of 625,000 IU / ml is used.