GB2154121A

GB2154121A - Skimmed milk product

Info

Publication number: GB2154121A
Application number: GB08502427A
Authority: GB
Inventors: Richard Woodford Lawes; William Robert Lawes
Original assignee: Balfour Manufacturing Co Ltd
Current assignee: Balfour Manufacturing Co Ltd
Priority date: 1984-02-16
Filing date: 1985-01-31
Publication date: 1985-09-04
Also published as: GB8502427D0

Abstract

A mixture of skimmed milk and polyunsaturated oil are fed under inert gas to a steam heating device in which steam is injected into the mixture, the steam and vapours are removed from the mixture, and the mixture is packed in hermetically sealed containers. Apparatus for maturing the product is also disclosed.

Description

SPECIFICATION Improvements in or relating to milk products This invention reiates to a food product which is made by replacing the butterfat In milk with a polyunsaturated oil. It has heretofore been known to provide sealed packs of a food product consisting of skimmed milk mixed with fats or oils such as coconut or other oils, which are substantially saturated oils which have acceptable organaleptic characteristics.

However, it has not heretofore been considered possible to use polyunsaturated oils for this purpose i.e. oils containing at least 50 per cent by weight of polyunsaturated oils, such as sunflower oil, corn oil, safflower oil or soyabean oil because of the unacceptable flavour characteristics.

For health reasons, there are strong recommendations to avoid the use of saturated fats.

It has not been possible to repiace saturated fats with unsaturated fats in milk because the odours and flavour of materials high in polyunsaturated fatty acids gives objectionable taste to the milk, partly due to the tendency of these fatty acids to oxidise rapidly, producing objectionable flavours which are foreign to the flavour of liquid milk products.

According to the present invention we provide a hermetically sealed container containing skimmed milk mixed with three to four per cent of a polyunsaturated oil, having been deodorised by steam and the mixture and container being free from any oxygen or oxidised product.

The invention also comprises a method of preparing the packed mixture comprising; (i) Feeding the oil and skimmed milk both under inert gas to a steam heating device in which the steam is injected into the milk and oil, and heats, blends and deodorises the mixture; (ii) Separating the steam and odorous vapours from the mixture and cooling the mixture; and (iii) Packing the mixture in hermetically sealed containers.

Heretofore the deodorising vessel draws in air.

The polyunsaturated oil which is now inert gas blanketed and contains only negligible quantities of dissolved oxygen is then passed to a road tanker similarly filled with inert gas. Antioxidant, such as "TBHQ" or "BHA" may be added at this stage where permitted e.g. about 200 ppm of oil. "TBHQ" is tertiary-butylhydroquinone made by Eastman Kodak. "BHA" is butylated hydroxyanisole made by May & Baker Ltd.

The inert gas must be a non-oxidising gas such as nitrogen or argon.

In carrying the invention into practice we may proceed as follows:- The skim milk is deaerated by passing it through a vacuum vessel in which the milk may be retained for about ten seconds.

The oil is pumped at a controlled rate into the deaerated skim milk stream and passed to a tubular vessel into which steam is Injected. The oil and milk are instantly mixed by the turbulence created by the steam and simultaneously heated to 140/160or. The mixture is passed to a holding tube sufficiently long to hold the product at the previously mentioned temperature for 2--4 seconds e.g. 2.5 seconds thereby achieving sterilisation within the same process. The mixture leaves the tube through an orifice and ehters a vacuum chamber in a fine spray which enables the volatile products of oxidisation and other volatile obnoxious flavours to vaporise with the water vapour evaporated as a result of the reduction in pressure.At the same time the evaporation causes a desirable sudden drop in temperature reducing the time to a minimum at which the product is held at the elevated temperature. The vapours are drawn off by a vacuum pump and the liquid mixture is pumped from the base of the vessel through a homogenizer and cooler into a packing machine e.g. a "Tetra Pak" machine (made byTetra Pak Co. of Sweden).

Test samples of the product so prepared surprisingly remained bland to the taste for many months after manufacture and even more surprisingly improved in flavour after the first few months.

The invention also includes an apparatus for producing a mixture of skimmed milk and polyunsaturated oil in hermetically sealed containers comprising a steam heating device which injects steam into the mixture, an oil preheater, means for supplying the oil under inert gas to the preheater and thence to said steam heating device, a silo for deaerated milk, milk preheating means, pumping means between the silo and the milk preheating means, pumping means between the milk preheating means and the steam heating device, a mixture packing machine and vacuum treatment and cooling means and a pump between the steam heating means and the packing machine.

An apparatus for carrying out the invention is illustrated by way of example in the accompanying diagrammatic drawings wherein: Figure lisa flow diagram of the oil supply operation at the oil refinery, and Figure 2 is a flow diagram of the operation at the mixing and packing plant.

In Figure 1, an oil deodorizing unit 10 is fed with oil at 9 and supplied with nitrogen from a cylinder 11 of nitrogen. Steam is injected at 12 and vacuum is applied at 13. The treated oil is supplied by pump 16 to a tanker 17 which is maintained under nitrogen from a cylinder 18.

The tanker 17 is transferred to the mixing and packing station shown in Figure 2. At this station there is a silo 20 containing deaerated skimmed milk. In accordance with the present invention the oil is treated separately by applying nitrogen to the tanker 17 from a nitrogen cylinder 21 and is pumped by pump 22 to a preheater 23 where it is heated to about 80"C. The milk from the silo 20 is pumped by pump 26, vacuum chamber 20A which deaerates the milk and thence to a balance tank 27 which is under nitrogen from a cylinder 27A of nitrogen. From tank 27 the milk is pumped by pump 28 to a preheater 30 where it reaches a temperature of about 800C (approximately the same as the oil) and from there by pump 31 through a flow control valve 29.

The oil from 23 and the milk from 29 are both fed to a sterilising device such as a "Uperiser" made by APV Co. Ltd., Crawley, which consists of a tubular vessel 33 into which the oil and milk are passed and into which also the steam is injected through valve 34 which is connected to temperature control device 35. The turbulance created by the steam blends the oil and milk and at the same time deodorises the mixture and raises the temperature of the mixture to 140--160"C.

The sterilised mixture is fed through a tube 38 long enough to hold the mixture at that temperature for 2-4 seconds. The mixture is then fed to a flash cooling device 39 which is maintained under vacuum. The mixture leaves the cooling device 39 at about 80"C and is fed through a pump 40 to a homogenizing constant speed pump 41 to a cooler 42 where the mixture is cooled to 20"C. The mixture from the cooler is fed to a packing machine 43.

Overspill mixture is fed via valve 45 and cooler 46 back to the balance tank 27 which may also be maintained under inert gas from a cylinder 27A. All pipelines and vessels are cleaned and sterilised by an in-place system before commencement of process.

The cooling device 39 has a "Foxboro" level control 50 connected to a level controller 51. The valve 29 and pump 22 are controlled by Thyristor motor speed control 52, signal converter 53, signal converter 54 to maintain a required output of mixture and a required ratio beween the supply of oil and milk.

Claims

1. A hermetically sealed container containing skimmed milk mixed with three to four per cent of a polyunsaturated oil, the mixture having been deodorised by steam and the mixture and container being free from any oxygen or oxidised product.

2. A container as claimed in claim 1 wherein the oil is selected from sunflower oil, corn oil, safflower oil and soya bean oil.

3. A container as claimed in claim 1 or 2 containing an antioxidant.

4. A method of preparing a skimmed milk product comprising; (i) Feeding polyunsaturated oil and skimmed milk both under inert gas to a steam heating device in which the steam is injected into the milk and oil, and heats, blends and deodorises the mixture; (ii) Separating the steam and odorous vapours from the mixture and cooling the mixture; and (iii) Packing the mixture in hermetically sealed containers.

5. A method as claimed in claim 4 wherein the polyunsaturated oil for use in the mixture is treated under vacuum and an inert gas to deodorise it and the oil is fed to a tanker which also is supplied with inert gas, the tanker is also supplied with inert gas and conveyed to a milk mixing and packing station.

6. A method as claimed in claim 4 or 5 wherein the skimmed milk is deaerated by vacuum treatment and fed via a balance tank (27), preheater (30) and flow control valve (29) to the steam heating device (33), and the oil fed at a controlled rate via a preheater (23) to the steam heating device, the mixture from the steam heating device being subsequently fed to a flash cooler (39) which removes the steam and inert gas and thence to a packing machine (43).

7. An apparatus for producing a mixture of skimmed milk and polyunsaturated oil in hermetically sealed containers comprising a steam heating device (33) which injects steam into the mixture, an oil preheater (23), means for supplying the oil under inert gas to the preheater (23) and thence to said steam heating device (33), a silo (20) for deaerated milk, milk preheating means (30), pumping means (28), between the silo (20) and the milk preheating means (30), pumping means (31) between the milk preheating means and the steam heating device (33), a mixture packing machine (43), and vacuum treatment and cooling means (39) and a pump (40) between the steam heating means (33) and the packing machine (43).

8. Apparatus as claimed in claim 7 including means for subjecting the milk to vacuum treatment prior to reaching the steam heating device (33), means for holding the mixture leaving the steam heating device (33) at the steam heated temperature for 2-4 seconds before it enters the vacuum treatment means (39) and a homogenizing means (41) between the vacuum treatment and cooling means (39) and the packing machine (43).

9. A hermetically sealed container as claimed in Claim 1 and substantially as herein described.

10. A method of preparing a skimmed milk product as claimed in Claim 4 and substantially as herein disclosed.

11. An apparatus for producing a mixture of skimmed milk and polyunsaturated oil in hermetically sealed containers as claimed in Claim 7 and substantially as herein described with reference to the accompanying drawings.