GB2052949A - A method of and installation for pasteurizing and packaging milk - Google Patents

Abstract

A method of and installation for pasteurizing and packaging milk comprises a heater 3, a connecting network of pipes, a storage tank 9 and a packaging machine 8. The heater and the network of pipes comprise reversing valves for the introduction of hot water and for the selective connection of the network of pipes to the storage tank 9 and the packaging machine 8. The installation is sterilized before use by subjecting the heater 3 and the network of the pipes to the sterilizing action of hot water at substantially ambient pressure and separately sterilizing the packaging machine 8 by superheated steam and, during use, supplying pasteurized milk from the heater 3 directly to the packaging machine 8 and packaging it thus bypassing the unsterilized storage tank 9. <IMAGE>

Description

SPECIFICATION A method of and installation for pasteurizing and packaging milk The invention relates to a method for producing and bottling pasteurized milk in containers on an installation, which comprises a heater with adjoining network of pipes, a storage tank for pasteurized milk and a bottling machine, in which before producing and bottling milk, the network of pipes after the heater and the bottling machine are sterilized. Furthermore, the invention relates to an installation for carrying out the method.

It is known that the keeping quality of pasteurized milk is substantially impaired by reinfection of the pasteurized milk in parts of the bottling installation following the heater.

In order to prevent reinfection of this type and thus to considerably extend the time for which pasteurized milk can be kept, it has already been proposed in the prior art to operate under predominantly aseptic conditions at the time of bottling. For this purpose, the network of pipes after the heater including the storage tank and as far as the bottling machine should be pre-sterilized with hot water at a temperature of 120-1 30 C before the bottling operation. Also, intermediate storage of the milk should be carried out in an aseptic storage tank with an excess pressure of sterile air (c.f.

"Die Molkerei-Zeitung Welt der Milch"), (the dairy newspaper World of Milk), 32nd year of publication 1978/48, page 1542/43).

These proposed measures for increasing the time for which pasteurized milk can be kept are expensive and uneconomical. Above all, in the case of plants which have already been installed, they require considerable conversion work or even cannot be carried out. Thus, storage tanks for pasteurized milk which are to be kept sterile, which tanks precede the bottle machine, are decidedly expensive to create and maintain, since the valves necessary for this must likewise be kept sterile and a special plant must be provided for producing the sterile air supplied at excess pressure.

Furthermore, pre-sterilization of the network of pipes after the heater with hot water at a temperature of 1 20 to 1 30 C requires such a high hot water pressure that the pressurisation limit of the network of pipes of existing installations and above all also of the heater is reached if not exceeded.

Based on the afore-described prior art, it is therefore the object of the invention to propose a method and bottling installation intended therefor, which make it possible with considerably simpler means, to prevent reinfection of pasteurized milk at the time of bottling and thus to extend the time for which pasteurized milk can be kept.

This object is achieved according to the invention by the fact that the heater including the subsequent network of pipes are sterilized with hot water at substantially ambient pressure and separate from the heater and network of pipes, the bottling machine is sterilized with superheated steam and that at the time of bottling, the milk pasteurized in the heater is supplied directly to the bottling machine and bottled whilst bypassing the nonsterilized storage tank.

Thus, within the framework of the method according to the invention, separate circuits and sterilization means are used for the presterilization of the heater and of the adjoining network of pipes on the one hand and bottling machine on the other hand. The heater and network of pipes are sterilized with hot water which according to the respective ambient pressure has a temperature of between 95"C and a maximum 11 5 C. With this method of operation, there is virtually no compressive load, so that even the heater itself can be sterilized.

Most bottling machines are designed so that they allow sterilization with superheated steam at a temperature of 1 30 to 1 45"C for example. Consequently, within the scope of the method according to the invention, the bottling machine is sterilized separate from the heater part and subsequent piping. Due to sterilization by steam, the bottling machine can be sterilized so that in practice it is completely germ-free and this is achieved with short sterilization times. A further advantage of separate sterilization of the bottling machine consists in that sterilization can be undertaken during periods when the bottling machine is not required, because the heater is operating on other parts of the installation.

Finally it is of considerable significance that the actual bottling of the pasteurized milk takes place whilst bypassing the unsterilized storage tank. The pasteurized milk thus passes from the heater, in which any germs which exist are killed, directly to the pre-sterilized bottling machine and therefore comes into contact neither with the latter nor with the ambient air which is not germ-free and is contained therein. Reinfection is therefore precluded.

The method according to the invention can be carried out on existing installations without appreciable changes. In addition to the heater, the subsequent network of pipes, the storage tank and the bottling machine, an installation for carrying out the method according to the invention contains only reversing valves before the heater and at the end of the adjoining network of pipes for introducing hot water and at the end of the network of pipes for the selective connection of the heater to the storage tank and bottling machine. However, reconstruction or even an exchange is unnecessary at any of the essential components of the installation.

Since as a rule the capacity of the heater exceeds the capacity of the bottling machine, in the known method for bottling pasteurized milk, the entire quantity of milk coming from the heater is stored in the storage tank, which acts as a buffer. However, as aforementioned, when carrying out the method according to the invention, the storage tank is bypassed at least by the quanity of milk which is bottled in the container by the bottling machine as pasteurized milk. The surplus of pasteurized milk exceeding the capacity of the bottling machine, which milk comes from the heater, can either be supplied to the storage tank or directly to other processing devices, which are not so critical as regards reinfection.

The invention will be described in detail hereafter with reference to the accompanying drawings. In the drawings: Figure 1 is a block circuit diagram of the installation used for carrying out the method according to the invention, in the stage of presterilization and Figure 2 is a similar block circuit diagram of the installation in the stage of producing and bottling pasteurized milk.

According to the block circuit diagram of Fig. 1, the instllation for producing and bottling pasteurized milk comprises a storage tank 1 for the raw milk, which is connected by a pipe 2 to a two-stage heater 3. A cooling arrangement 6 adjoins the heater 3, to which a centrifuge 4 located between the two stages of the heater and a homogenization machine 5 are connected. Connected to the pipe 7 following the cooler 6 are a bottling machine 8, a storage tank 9 for pasteurized milk and further processing devices 10, 11. The components of the installation 8 to 11 branch off respectively from the pipe 7.

The block circuit diagram according to Fig.

1 shows the condition of pre-sterilization of the essential components of the installation.

As aforementioned, the existing network of pipes in the heater 3 leading to the bottling machine 8 and in the bottling machine 8 itself is utilised for pre-sterilization. The heater 3 and adjoining part of the pipe 7 leading to the bottling machine 8 is sterilized with hot water at substantially atmospheric pressure. Accordingly, the hot water has a temperature within the limits of 95 to 11 5at maximum.In order to limit the circuit, in which the hot water moves through the heater, a reversing valve 1 2 is incorporated in the pipe 2, which valve opens the hot water circuit to a connection 1 3. Likewise, a reversing valve 14 is located in the pipe 7 upstream of the bottling machine 8, by which valve 14 the hot water is returned to a hot water outlet 1 5. An open circuit is thus formed, which facilitates simple preheating of the hot water to the desired temperature. The hot water circuit is shown in bold line in Fig. 1.

The bottling machine 8 is sterilized by superheated steam at a temperature of 1 30 to 145"C, which is indicated by connections 1 6,1 7 for the supply and discharge of steam.

It will be understood that the connections 1 6,1 7 are located at corresponding reversing valves, which facilitate a steam circuit in the bottling machine 8 separate from the pipe 7.

As can be seen from the illustration of Fig.

1, the centrifuge 4 and homogenization machine 5 are not included in the hot water circuit through the heater 3.

Fig. 2 shows the condition of the installation, in which pasteurized milk is produced and bottled in containers by the bottling machine 8. The flow path of the milk is drawn in thick line in the block circuit diagram. The latter shows that the raw milk passes from the storage tank 1 through the pipe 2 and the appropriately controlled reversing valve 1 2 to the heater 3 and is preheated firstly to 55"C in both stages of the latter, is centrifuged and homogenized and then pasteurized at a temperature of 74"C. The milk is cooled to a temperature of approximately 4"C. in the cooling arrangement 6.The reversing valve 14 upstream of the bottling machine 8 is now controlled so that the quantity of pasteurized milk, which is supplied by the heater 3 and corresponds to the capacity of the bottling machine 8, passes directly to the bottling machine 8 and is bottled in containers at this point. Only the surplus of pasteurized milk, which possibly exceeds the capacity of the bottling machine 8, is sent to the storage tank 9 and if necessary to further devices 10,11.

Since the area of the installation between the reversing valve 1 2 and the bottling machine 8 is completely sterile, there is no reinfection of the pasteurized milk, such as is inevitable for example in the storage tank 9 owing to the contact of the pasteurized milk with nonsterile ambient air and the valves provided in the latter. Nevertheless, it is possible to operate with subtantially the same installation as was installed hitherto.

The sterilization times for hot water sterilization of the heater 3 are of the order of 30 minutes and of the order of 1 5 minutes for the bottling machine.

The effectiveness of the method according to the invention can be demonstrated in the following example: at a storage temperature of 10 to 12"C, pasteurized milk produced and bottled according to the method of the invention contained less than 50 X 103 germs/ml after four days. Only after seven days does the number of germs exceed 100 X 103/ml.

Even after seven days, the taste and appearance of the milk were not altered. Accordingly, with a pasteurized milk which had been produced on the same installation in the previous manner, this was found to have a germ content of more than 500 X 103/ml after three days and as regards taste there was an appreciable drop in quality.

Claims (8)

1. A method of pasteurizing and packaging milk by means of an installation including a heater connected to a network of pipes, a storage tank for pasteurized milk and a packaging machine, said method comprising sterilizing the installation before use by subjecting the heater and the network of pipes to the sterilizing action of hot water at substantially ambient pressure and separately sterilizing the packaging machine by superheated steam and, during use, supplying pasteurized milk from the heater directly to the packaging machine and packaging it thus bypassing the unsterilized storage tank.

2. A method as claimed in claim 1, wherein a surplus quantity of pasteurized milk produced by the heater and exceeding the requirements of the packaging machine is supplied to the storage tank or to other processing devices.

3. A method as claimed in claim 1 or 2, wherein the installation includes a centrifuge and a homogenization machine connected to the heater but not sterilized therewith.

4. A method as claimed in any one of claims 1 to 3, wherein the superheated steam is at a temperature of 135-145 C.

5. Installation for pasteurizing and packaging milk, comprising a heater, a connecting nework of pipes, a storage tank and a packaging machine, wherein the heater and the network of pipes comprise reversing valves for the introduction of hot water and for the selective connection of the network of pipes to the storage tank and the packaging machine.

6. Installation as claimed in claim 5, wherein further reversing valves are provided in the network of pipes for connecting the heater to other processing devices for pasteurized milk.

7. A method of pasteurizing and packaging milk substantially as herein described with reference to the accompanying drawings.

8. An installation for pasteurizing and packaging milk, substantially as herein described with reference to and as iliustrated in the accompanying drawings.