NL8300088A - Prepn. of sterilised evaporated milk - using flow sterilisation - Google Patents

Abstract

In prepn. of sterilised evaporated milk with 0-10% fat content, standardised milk is pasteurised, evaporated, homogenised, stabilised with salt, and subjected to flowing sterilisation/ thermalisation at 110-125 deg. C for 5-20 mins. The milk is pref. homogenised before sterilisation.

Description

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I. VO 4512

PROCESS FOR THE PREPARATION · VAM EVAPORATED MILK

The invention relates to a process for the preparation of evaporated milk and to the products thus obtained.

Milk for human consumption comes in various forms.

The most traditional form is raw milk, which has been extracted on the farm 5 and is therefore immediately available for consumption. Obviously, there was a time when milk was only available this way. The heating technique has made an important contribution to an improvement of the shelf life and thus of the possibility of distribution and marketability of the milk.

10 A product such as sterilized milk, with a shelf life of several weeks to months, even without refrigeration, provides industry with unprecedented new possibilities with regard to the commercialization and distribution of milk products. Initially, this sterilization process was only a process in which the pretreated milk was packaged and sterilized in the pack. Tin and glass in particular were and still are common packaging materials. The sterilization takes place in suitable equipment, whereby the milk reaches temperatures of, for example, 115-125 ° C and is kept at that temperature for several minutes in order to effect sufficient killing of microorganisms.

More recently, the method is in which the milk is sterilized in a flowing process and then aseptically filled, eg in cardboard packaging or in plastic bottles. This process takes place at temperatures ranging from, for example, 135-150 ° C; so much higher temperatures than with the "classic" sterilization in the packaging. One speaks therefore of UHT heating ("Ultra High" Temperature) or of HTST (High Temperature Short Time). In order to obtain a sufficient sterilization effect, hot holding times of only a few seconds are sufficient at these ultra-high temperatures. This UHT milk differs from the classic sterilized milk by a white-30 delicate color and a less pronounced cooking taste. These specific characteristics of HTST milk also depend on the exact implementation of the UHT process, whereby a distinction must be made in particular between t 8300088 f * v 2 between the system of direct resp. indirect heating. In the first case, the milk is brought into direct contact with * highly heated steam and is thus brought to a high temperature very quickly. In indirect heating, the milk is heated in, for example, a tube or plate apparatus, in which it does not come into direct but indirect contact with the heating medium. * The directly heated milk generally has a slightly less distinct cooking flavor than the indirectly heated milk.

10 Another option to extend the shelf life of milk is concentration or evaporation of the milk. The extraction of water from milk decreases the α-value of milk, which reduces the possibilities of micro-organisms to grow in that milk. An extreme form of an evaporated milk product is milk powder, with an alpha value of approx. 0.1 15 and partly because of this, a bacteriological shelf life of years, without cooling.

An interesting product, which combines both forms of preservation techniques, is evaporated milk, a product prepared by extracting water from milk to a water content of 76 to 67% and subsequent sterilization. This liquid milk product has a very long shelf life and is therefore also suitable as an export product. Sterilized evaporated milk is a product which has an important application in coffee (coffee milk), but it is also useful in soups, sauces and the like.

Heretofore, sterilized evaporated milk has been prepared by packaging evaporated milk in tin or glass and then sterilizing it in the package. However, this preparation process includes some process steps necessary to overcome certain defects of the final product, such as creaming, sifting and sedimentation. Because of the increased content of milk solids and the resulting increased acidity, the product is sensitive to sifting as a result of heating. For this reason, certain stabilizing salts, such as phosphates and citrates, are added to the evaporated milk prior to sterilization. In addition, intensive homogenization treatment is required to counter cream 8300088 3 during long-term storage at sometimes high temperatures. With this known process (see: OF Hunziker "Condensed milk and milk powder" / 7th ed., Illinois - 1949), a product is obtained with a number of characteristic properties, such as a long shelf life of -5 due to complete sterility, a light beige-brown color, a certain viscosity (eg 25-50 mPa.s), a completely smooth, homogeneous structure, a good color when mixing in coffee, a homogeneous structure when dissolving in coffee and a stable structure when stored at different temperatures.

10

There is an increasing need to market evaporated milk in single-use packaging, eg made from cardboard. However, it is not possible to sterilize the product contained in such a package. Therefore, an attempt was made to use the well known UHT process, which is now known in milk, for the preparation of sterilized, evaporated milk. Attempts in this direction were unsuccessful because a product sterilized in this way was found to have completely different, less good properties than the conventional evaporated milk (evap) sterilized in the package. In particular, it was found that the viscosity of UHT-evap was lower than that of the classic evap, partly due to the fact that with OHT-evap homogenization must take place after sterilization, because otherwise during the sterilization screening symptoms will occur (Zuivelzicht 74 (1982), 48). This homogenization destroys certain protein structures that are formed during sterilization. In addition, the low viscosity results in an increased creaming, which will lead to storage problems.

However, the main problem that arises when using the UHT-30 process to prepare sterilized evaporated milk is the high thickening (J. Dairy Res. 38_ (1971), 323; J. Dairy Sci 64, suppl. 1 (1981), 46), in which it is extremely difficult to counteract this thickening. Surprisingly, it has been found that sterilized, evaporated milk with a fat content of 0-10% can be prepared in which standardized milk is pasteurized, evaporated, homogenized, stabilized with salts and 8300088 ¢ 7¾. The milk is then subjected to a flowing sterilization / thermization at a temperature of 110-125 ° C for 5-20 minutes. In a sterilized, evaporated milk thus prepared, the important advantage is obtained that the sterilization process does not have to take place in the final packaging, while the product obtained does not differ from conventional in a number of characteristic aspects, such as color, viscosity, thickening and creaming. sterilized evaporated milk in the package.

The invention will be further elucidated by means of the following examples.

Comparative example I 15

Sterilized evaporated milk with a fat content of 4% and a water content of 76% was prepared using a UHT sterilization on the one hand and the method of the invention on the other.

The results are grouped in the following table.

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Sterilization

Temperature Time Mode pH _Features_ ___seconds___shifting thickening 25 142 4 flowing 6.35 + yes 125 300 flowing 6.25 - no '120 480 flowing 6.21 - no 116 840 flowing 6.19 - no 120 480 classic 6.20 - no 30

The data shows that flowing sterilized evap differs greatly from the classic evap. However, when sterilizing using the method of the invention, the evap obtains the properties characteristic of the classically sterilized evap. The flowing heating is more intensive than is necessary for bacteriological killing, which is why this is also referred to as thermization.

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Example II

Whole milk with a fat content of 3.9% and skimmed milk are mixed in such a way that a milk with a fat content of 1.83% and a water content of 89.0% is produced. 1000 l of this milk is pasteurized for 5 3 minutes at a temperature of 118 ° C. The milk is then evaporated in a 3-stage vacuum evaporator to a fat content of 4.5% and a water content of 73.0%. This evaporated milk is homogenized at a temperature of 50 ° C at a pressure of 20 MPa. Water is then added to this product with an amount of disodium salt of phosphoric acid dissolved therein, such that the water content of the evaporated milk is increased to 76%, the fat content falls to 4% and the product contains 0.05% of that salt .

The product thus standardized is flow sterilized in a laboratory pasteurizer, provided with tubes with an internal diameter of 2 resp. 10 mm. The evaporated milk is heated in 3 sections to 125 ° C and kept at that temperature for 5 minutes. The product is then flow-cooled to 30 ° C and aseptically filled into pre-sterilized glass bottles. The products were stored at 20 and 30 ° C. Various analyzes have been carried out, with the same product as reference, but filled in a can and sterilized in the packaging at 121.1 ° C for 7.5 minutes.

Analysis results

Storage time Sterilization Viscosity Color White power Separation 25 - —----- "- fresh flowing 30 86.5 40 no in cans 35 84.5 41 no 3 months flowing 25 83.5 39 no 20 ° C in cans 35 82 40 no 3 months flowing 30 81 37.5 no 30 30 ° C in a can 30 79.5 38 no

This shows that the flowing sterilized and homogenized product has similar properties compared to the corresponding canned product sterilized. Viscosity, color and whitening power are very similar; there is no question of sifting, nor of thickening when stored at different temperatures.

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Example III

2000 1 milk with a fat content of 3.6% and a water content of 88% is pasteurized for 3 minutes at 118 ° C. The milk is then evaporated in a 3-stage vacuum evaporator to a fat content of 8.0% and a water content of 74.4%. The evaporated milk is homogenized at a temperature of 55 ° C at a pressure of 25 MPa. Water is then added to this product with an amount of sodium citrate dissolved therein such that the water content of the evaporated milk is increased to 75%, the fat content falls to 7.5% and the product contains 0.06% of that salt .

The product thus standardized is flow sterilized in a tube pasteurizer, with tubes with an internal diameter of 10 resp.

26 mm. The evaporated milk is heated in 4 sections to a temperature of 122 ° C and kept at that temperature for 7 minutes. The product is then flow-cooled to 25 ° C and aseptically filled in one-off carton packaging. The products were stored at 20 and 30 ° C. Various analyzes were carried out, with the same product as reference, but filled in a can and sterilized in the packaging at 121.1 ° C for 7.5 minutes.

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Analysis results

Storage time Sterilization Viscosity Color White power Separation fresh - flowing 30 91.0 47.5 no 25 canned 35 90.5 49.0 no 3 months flowing 30 88.5 45.0 no 20 ° C canned 30 87.5 46, 0 no 3 months flowing 35 86.0 43.5 no 30 ° C in a can 40 86.0 45.0 no 30 These figures also show that the sterilized product flowing in this way has well comparable properties compared to the corresponding canned product.

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Example IV

This example is entirely similar to Example III except that milk evaporated at 120 ° C for 4 minutes is made with evaporated milk containing 9% fat, 69% water and 0.08% of the di-5 sodium salt of phosphoric acid, homogenized in 2 steps at pressures of 20 and 5 MPa, respectively, sterilized in a plate pasteurizer at 116 ° C for 14 minutes.

Analysis results 10 Storage time Sterilization Viscosity Color White power Separation fresh flowing 55 87.0 49.5 no in tin 90 87.0 49.0 no 3 months in flowing 50 84.0 45.0 no 20 ° C in tin 80 83.5 45, 0 no 3 months flowing 50 82.5 43.5 no 1.5 30 ° C in a can 85 83.0 44.0 no

And here too the conclusions are in accordance with the preceding examples. In this case, the viscosity of flowing sterilized evap is lower than the canned sterilized evap, but it nevertheless falls well within the set standards.

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Claims (2)

1. A process for the preparation of sterilized, evaporated milk I with a fat content of 0-10%, whereby standardized milk is pasteurized, evaporated, homogenized, sterilized with salts and sterilized with the characteristic that the milk is flowing sterilization / thermization is subjected to a temperature of 110-125 ° C for 5-20 minutes. Method according to claim 1, characterized in that homogenization is carried out prior to sterilization. 8300088