WO2002069725A1

WO2002069725A1 - A method of producing sweetened condensed milk

Info

Publication number: WO2002069725A1
Application number: PCT/SE2002/000304
Authority: WO
Inventors: Cecilia Svensson; Tien Yeow Kong; Lim Juay Ho; Kong Weng Hong; Sigit Trisnanto; Sharon Kong
Original assignee: Tetra Laval Holdings & Finance Sa
Priority date: 2001-02-23
Filing date: 2002-02-21
Publication date: 2002-09-12
Also published as: SE0100628D0; SE0100628L; SE521844C2

Abstract

The invention relates to a method of producing sweetened condensed milk. A milk mixture at the desired total solids content is produced by recombination or alternatively by evaporation. A stabiliser is added to this milk mixture, the stabiliser consisting of two part components. The first part component consists of a plant gum and is included in the mixture at a proportion of 0-1%. The second part component consists of a second plant gum and is included in the mixture at a proportion of 0-1%. However, the sum total of the first and the second part component quantities should amount to at least 0,01% of the mixture. The milk mixture is heat treated and homogenised, whereafter it is cooled and packed.

Description

A METHOD OF PRODUCING SWEETENED CONDENSED MILK

TECHNICAL FIELD

The present invention relates to a method of producing sweetened condensed milk comprising the method step of producing a milk mixture with the desired total solids content, the milk mixture having undergone heat treatment and possibly homogenisation, and also that the milk mixture is cooled after production and is packed.

BACKGROUND ART

Sweetened condensed milk is a major product, above all in the developing countries. Initially, sweetened condensed milk was a product which, with good shelf life, constituted an access to milk in countries where there is a shortage of dairy produce or countries that lack a tradition in this context. Despite the fact that sterile milk, so-called UHT milk, has been introduced on the market, sweetened condensed milk maintains its position as an important product.

Sweetened condensed milk is highly viscous and, in terms of appearance, is reminiscent of mayonnaise. It is employed as an additive in coffee or tea, as a spread or as an ingredient in beverages or in cooking. Sweetened condensed milk also constitutes a raw material in the manufacture of ice cream and confectionery.

Despite not being a sterile product, sweetened condensed milk has long shelf life because of its high sugar content. It is packed in a multiplicity of different ways depending upon the user it is intended for. This means that sweetened condensed milk is sold in everything from large drums to consumer packages or cartons of single-use disposable type.

A large proportion of sweetened condensed milk is produced by recombination, above all in countries which do not have access to fresh milk to any major extent. Recombined sweetened condensed milk implies that the raw materials, milk powder, water, fat and sugar are mixed and treated in order to produce the desired product. Sweetened condensed milk can also be produced direct from raw milk which is evaporated or vaporised in order to remove a fraction of the aqueous content of the milk. Evaporated condensed milk is above all produced in developing countries with ready access to raw milk and where there is a large market for this type of product. Regardless of the production method employed, the milk mixture is heat treated. During the subsequent cooling, the most critical phase of the -p oduction occurs. Since sweetened condensed milk is saturated with lactose, this forms crystals on cooling. If crystallisation is not controlled, these crystals become too large and the condensed milk gives a grainy sensation in the mouth on consumption. In order to prevent the lactose from crystallising uninhibitedly, use is made of so-called particle forming crystallisation, i.e. a mixture of finely ground lactose crystals and water is added. The method requires powerful agitation of the product for roughly an hour.

OBJECTS OF THE INVENTION

One object of the present invention is to realise a method for producing sweetened condensed milk where there will be obtained a controlled crystallisation without the need to add slurried, ground lactose crystals.

A further object of the present invention is to render the production of sweetened condensed milk more economical in that crystallisation tanks with agitators are no longer necessary. This assists in cutting both investment costs and running costs.

SOLUTION These and other objects have been attained according to the present invention in that the method of the type described by way of introduction has been given the characterising feature of adding, to the milk mixture, a stabiliser which consists of a first part component constituted by a plant gum and which is included in the mixture at a proportion of 0-1%, and also a second part component which consists of a second plant gum and which is included in the mixture at a proportion of 0-1%, and that the sum total of the first and second part components constitutes at least 0.01% of the mixture.

Preferred embodiments of the present invention have further been given the characterising features as set forth in the appended subclaims.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

One preferred embodiment of the present invention will now be described in greater detail hereinbelow, with particular reference to the accompanying Drawings, in which: Fig. 1 shows a block diagram relating to a prior art method where the milk mixture is recombined;

Fig. 2 shows a block diagram relating to a prior art method where the milk mixture is evaporated; Fig. 3 shows a block diagram relating to a method, according to the present invention, where the milk mixture is recombined; and

Fig. 4 shows a block diagram relating to a method, according to the present invention, where the milk mixture is evaporated.

Sweetened condensed milk is defined as a product with a total solids of 74.5% according to European standard, or 73.4% according to US standard. Sweetened condensed milk is not a sterile product, but because of the high content of sugar it has a long shelf life on storage without refrigeration. In that the sugar content is at least 62.5%, there will be obtained such a high osmotic pressure that the growth of bacteria is prevented. However, the sugar content must not exceed 64.5% so as not to cause problems on the crystallisation of lactose.

Fig. 1 illustrates one of the prior art methods for producing sweetened condensed milk. The block diagram shows the different stages for producing recombined sweetened condensed milk (RSCM, Recombined Sweetened Condensed Milk). This method takes as its point of departure milk powder which is mixed together with water, fat and sugar. The mixture is moist generally given lower total solids than that which is required in the end product. The milk mixture, which is produced at a temperature of approx. 50°C, thereafter undergoes the following method steps.

Preheating to a temperature of approx. 60°C which is followed by homogenisation and pasteurisation at 80-90°C for 30-120 seconds. The milk mixture is thereafter cooled stepwise, normally also using so-called flash-cooling where any possible surplus water departs from the mixture.

The cooling is most critical phase in the production of sweetened condensed milk. Since the mixture is saturated with lactose, there is a risk that the lactose crystallises into large crystals which feel like grain on consumption of the sweetened condensed milk. In order to avoid such crystallisation, it must be controlled, which normally takes place using so-called particle formation crystallisation. This implies that, when the milk mixture is at approx. 30°C, a mixture of ground lactose crystals and water is added. The lactose crystals are ground to a size of less than 10 im and are slurried in water in order to facilitate the admixture. The ground lactose crystals may also be added as a powder. As a result of this method, the lactose ih the milk mixture is caused to crystallise into crystals that are not larger than 10 im. Such small crystals cannot be sensed on consumption. The crystallisation takes place in special crystallisation tanks and under powerful agitation. The agitation may continue for a period of time of up to one hour and naturally requires both major investments in equipment and high running costs.

During the crystallisation, the mixture is cooled to the desired temperature and thereafter the finished product is ready to be packed in suitable containers. The block diagram in Fig. 2 shows the different steps for producing sweetened condensed milk, SCM (Sweetened Condensed Milk), where the starting material is fresh raw milk. The milk is heat treated normally at a temperature of 82°C for 10 minutes if a product with relatively high viscosity is desired. If a low viscosity product is desired, heat treatment is most generally undertaken at 116°C for a period of time of 30 seconds. Thereafter, the milk is evaporated or vaporised until the desired total solids is obtained.

The sugar can be added to the milk either before the heat treatment and it is then most generally added as a dry product. Alternatively, the sugar can be added during the evaporation, and in such instance is added as a syrup. Thereafter, the milk mixture is normally homogenised and subsequently cooled. During the cooling, the lactose crystallisation takes place in the same manner as was described above for the recombined sweetened condensed milk. Finally, the finished product is packed.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figs. 3 and 4 are block diagrams illustrating the production of RSCM and SCM, respectively, according to the present invention, and these methods will be described in greater detail.

The production of recombined sweetened condensed milk (RSCM) takes as its point of departure the raw materials water, milk powder, fat and sugar being mixed into a homogeneous milk mixture (Fig. 3). The water which is included must be pure and of good quality and should be softened if it has a high calcium content. The milk powder is normally skimmed milk powder and this should also be of high quality in order that the end product maintains the desired quality standard. The fat may consist of milk fat or of vegetable oils. Finally, the sugar must be refined sucrose of high quality. Whole milk powder can also be employed as raw material for the production of RSCM, in which event the proportion of fat is then reduced or alternatively dispensed with entirely. In this method according to the present invention, the raw materials are mixed at a desired, final total solids content, for which reason no water need be removed from the mixture in a later method step.

A stabiliser is also added to this milk mixture. The stabiliser consists of two part components. The first part component consists of a plant gum, for example guar gum, LBG (Locust Bean Gum), CMC (Carboxy Methyl Cellulose), karragenan, algenate or pectin. The first part component is added in a quantity of 0-1% of the finished mixture, preferably 0-0.3%. The second part component consists of a plant gum, for example guar gum, LBG (Locust Bean Gum), CMC (Carboxy Methyl Cellulose), karragenan, algenate or pectin. However, the second part component is not the same plant gum as the first part component. The second part component is added in a quantity of 0-1 % of the finished mixture, preferably 0-0.3%. However, the sum total of the first and second part component quantities should amount to at least 0.01% of the mixture.

The different components in the milk mixture, as well as the stabiliser, are mixed together in a so-called vacuum mixer. The vacuum mixer is of the type which, under vacuum and under rotation, repeatedly flings the mixture outwards, the mixture being caused to pass through a number of peripherally placed holes or slots. Such a vacuum mixture is, for example a Tetra Almix®. The milk mixture is circulated over the vacuum mixer until it is homogeneous. The mixture is then permitted to hydratise for 15-20 minutes in order that all powder be dissolved in the water. To achieve an optimum mixture, this takes place at a temperature of approx. 50°C.

The finished milk mixture is thereafter preheated normally to 60°C and homogenised in one or more steps. The homogenisation may possibly be dispensed, but in order to obtain the desired viscosity of the finished product, homogenisation may be employed.

The milk mixture is then pasteurised at approx. 80-90°C for a period of time of 30-120 seconds. The pasteurisation may take place in a conventional plate heat exchanger or alternatively in a tube heat exchanger or scrape heat exchanger. The selection of heat exchanger is conditioned by the viscosity of the product. After the heat treatment, the product is finally cooled to packing, temperature and is packed in the desired package. The package may be drums, cans^",¹ consumer packages of single-use disposable type, or other suitable package. The cooling normally takes place in the same pasteuriser as the heat treatment takes place in. Since the production method according to the present invention gives a controlled crystallisation of the lactose of the milk mixture without the addition of ground, slurried lactose crystals, no crystallisation step is required. Nor does the method require costly crystallisation tanks with agitators.

The two part components which constitute the stabiliser cooperate so that the first part component prevents an uninhibited lactose crystallisation in the milk mixture, while the second part component prevents interaction between the milk proteins in the milk mixture and the first part component. Such an interaction could otherwise result in the mixture's coagulation, or that the milk proteins clot together.

The production of sweetened condensed milk (SCM) is illustrated in Fig. 4. The raw material for producing SCM is raw milk of good quality. The raw milk must possibly be standardised in order for the finished product to have the correct fat content.

The milk is thereafter heat treated in order to neutralise and deactivate microorganisms and enzymes which might otherwise influence the quality of the finished product. The heat treatment takes place at 82-116°C for a period of time of 0.5-10 minutes.

The addition of sugar to the milk may either take place before the heat treatment step and, in such an event, the addition of sugar takes place in the form of a dry product. The sugar should be refined sucrose of high quality. Alternatively, the sugar may be added during the evaporation of the milk proper and the addition of sugar then takes place in the form of a syrup. The point in time for adding the sugar may influence the viscosity of the end product.

Evaporation or vaporisation normally takes place in conventional multi-step evaporators of the fall film type. The milk passes through steam-heated pipes under vacuum and then boils at a temperature of 65-70°C so that water is constantly boiling off from the milk. The evaporation process continues until the correct total solids content has been achieved. The evaporated milk mixture may thereafter be homogenised in one or more steps. Alternatively, the homogenisation may be dispensed with. The homogenisation also influences the viscosity of the end product.

The addition of a stabiliser to the milk mixture may take place during different phases in the above-described method. However, the addition of stabiliser must take place before the milk mixture is cooled. The stabiliser consists of two part components. The first part component consists of a plant gum, for example guar gum, LBG (Locust Bean Gum), CMC (Carboxy Methyl Cellulose), karragenan, algenate or pectin. The first part component is added in a quantity of 0-1% of the finished mixture, preferably 0-0.3%. The second part component consists of a plant gum, for example guar gum, LBG (Locust Bean Gum), CMC (Carboxy Methyl Cellulose), karragenan, algenate or pectin. However, the second part component is not the same plant gum as the first part component. The second part component is added in a quantity of 0-1 % of the finished mixture, preferably 0-0.3%. However, the sum total of the first and second part component quantities should amount to at least 0.01% of the mixture.

The finished milk mixture is finally cooled to the desired packing temperature and is packed in suitable packages. The package may be drums, cans, consumer packages of single-use disposable type, or other suitable package. Since the production method according to the present invention gives a controlled crystallisation of the lactose of the milk mixture without the addition of ground, slurried lactose crystals, no crystallisation step is required. Nor does the method require costly crystallisation tanks with agitators.

As will have been apparent from the foregoing description, the present invention realises a method of producing sweetened condensed milk (SCM or RSCM) which is considerably simplified and is more economical than conventional methods. Through the method according to the present invention, the lactose crystallisation is controlled by means of a stabiliser and a method will thereby be realised which gives both lower investment costs for necessary equipment and lower running costs for producing the product.

Claims

WHAT IS CLAIMED IS:

1. A method of producing sweetened condensed milk comprising the method step of producing a milk mixture with the desired total solids content, the milk mixture having undergone heat treatment and possibly homogenisation, and that the milk mixture is cooled after production and is packed, characterised in that to the milk mixture, is added a stabiliser which consists of a first part component constituted by a plant gum and which is included in the mixture at a proportion of 0- 1%, and also a second part component which consists of a second plant gum and which is included in the mixture at a proportion of 0-1%, and that the sum total of the first and second part components constitutes at least 0.01 % of the mixture.

2. The method as claimed in Claim 1, characterised in that the milk mixture is produced by recombination.

3. The method as claimed in Claim 1, characterised in that the milk mixture is produced by evaporation.

4. The method as claimed in any of the preceding Claims, characterised in that the first part component is included in the mixture at a proportion of 0-0.3%; and that the second part component is included in the mixture at a proportion of 0.03%.

5. The method as claimed in any of the preceding Claims, characterised in that the first part component may consist of guar gum, LBG (Locust Bean Gum),

CMC (Carboxy Methyl Cellulose), karragenan, algenate or pectin.

6. The method as claimed in any of Claims 1 to 4, characterised in that the second part component may consist of guar gum, LBG (Locust Bean Gum), CMC (Carboxy Methyl Cellulose), karragenan, algenate or pectin.

7. The method as claimed in any of Claims 5 or 6, characterised in that the first part component does not consist of the same plant gum as the second part component.

8. The method as claimed in any of the preceding Claims, characterised in that the first part component of the stabiliser controls the lactose crystallisation which takes place in the milk mixture when this is cooled, and that the second part component of the stabiliser prevents interaction between the proteins of the mixture and the first part component.