GB1582113A

GB1582113A - Apparatus for making yogurt

Info

Publication number: GB1582113A
Application number: GB12288/78A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-04-18
Filing date: 1978-03-29
Publication date: 1980-12-31
Also published as: BE865753A; CA1072897A; DE2814563A1; FR2387603A1; IT7822352A0; FR2387603B3; IT1094392B

Description

(54) APPARATUS FOR MAKING YOGURT (71) We, ROLAND ST-PIERRE, JEAN CLAUDE FORTIN and JACQUES Roy, all citizens of Canada, residing at 281 Mortagne Boulevard, Boucherville, 48 Dauphin Street, Vimont, Laval and 3362 Jean Cabot Street, Ste-Foy, all of the Province of Quebec, Canada respectively, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for making yogurt for domestic use. Electrical heating devices are available specifically designed for home preparation of yogurt which employ conventional thermostatic controls. However, we have found that there are certain disadvantages associated with these conventional devices which are directly reflected in the relatively long incubation period (about 8 hours) and consequently in the quality of the yogurt so obtained.

An object of the present invention is to provide apparatus for making yogurt whereby a maximum quantity of living bacterial culture is obtained within a minimum of time. It is known that if the incubation period is shorter, the resulting yogurt is sweeter and the number of living bacteria is greater. It is also known that if the incubation period is longer the yogurt has a sharp sour taste and its lactic acid content is greater. It is generally true that if the time of incubation exceeds about 4 hours or so, the first generation of bacteria so produced will have aged and died.

Another object of the disclosed apparatus of this invention consists of conducting the incubation under optimum temperature con ditions by carefully controlling the tempera ture fluctuations.

It is known that as the temperature of milk is lowered below the optimum incuba tion temperature, the more the bacterial growth is retarded, while on the other hand a temperature only slightly higher than the optimum incubation temperature kills the bacteria.

These objects, as well as others, are obtained in accordance with the apparatus which provides an optimum incubation temperature of the inoculated milk and culture mixture of 112"F. and by controlling the fluctuations that temperature within a relatively narrow range of +0.5 F.

According to the present invention there is provided apparatus for culturing and growing yogurt from milk using a lactic bacteria culture including a main body having an outside shell open at one end and an internal body positioned within and fastened to the main body and leaving a space therebetween, electrical heating means attached to said internal body and positioned in said space between said outside shell and said internal body, said heating means including a metallic, heat-absorbing foil secured to the outer lower surface of said internal body, and electric heating elements attached to said foil and uniformly spaced apart from each other by separators, a temperature regulator for protecting the heating elements from overheat- ing, and an outer heat-reflecting metal foil covering said heating elements and said temperature regulator and serving to concentrate heat on said heat absorbing foil, control means connected to said heating means for controlling the temperature within said internal body including a current source, a control circuit connected to said source and having a relatively short response time and providing in operation, control of the fluctuations of temperature within said internal body to within +0.5 F., said temperature control means maintaining a predetermined yogurt incubation temperature, a container for the lactic acid yogurt mak inP culture dispersed in milk, said container being received within said internal body and a removable lid enclosing the open end of said shell.

In an embodiment of the invention, the apparatus constructed for optimum incubation includes a main container into which is placed an internal body serving as a receptacle for a container which holds the milk/ yogurt. A fluid, such as water, is introduced between the internal body and the milk/ yogurt container. A heating unit, which provides the heat source, is located around the outside of the internal body and includes a metallic foil on the outer surface of the internal body. On the foil is placed electrical heating means and a temperature regulator for limiting the temperature to prevent against overheating, both of which are covered by another metallic foil which reflects heat inwardly. The heating unit is electrically connected to the electronic regulating means to ensure an optimum incubation temperature for the milk within preset limits. The temperature control unit includes a temperature detector and a control element which has a relatively short response time assuring a very precise control of the temperature within a range of +0.5"F.

The main body which forms an assembly with the internal body is closed with a lid composed of outer and inner parts which are fastened together.

The invention will now be described by way of example only with particular reference to the accompanying drawings wherein: FIGURE 1 is a vertical section across the assembly main body, inner body and lid; FIGURE 2 is a perspective view of the internal body with the outer body removed; FIGURE 3 is an exterior p]an view of the bottom of the internal body; and FIGURE 4 is an enlarged sectional view of the inner and outer circular rims of the two piece lid and an enlarged sectional view of the heating unit of the internal body of FIGURE 1.

The device as shown in Figures 1 and 2 includes a main body 1, having a lower section 2 with a cylindrical shape narrowing slightly towards the bottom, where it is closed. The upper section 3 is a continuation of the lower part and resembles the shape of a frustrum cone. In the lower section 2, an opening 4 is provided for the entry of a source of electrical current. The upper part 3 of the main body 1 is provided with an inner circular rim 5. On this circular rim 5, a correspondingly shaped outer circular rim 6, which is part of the internal body 7, is provided the two rims 5 and 6 cooperating, as shown in more detail in Figure 4, and fastened together to support the internal body 7. The internal body 7 is in the shape of a cylinder narrowing towards the base.

A heating unit 8 is provided around the circumference of the lower section of the internal body 7. The heating unit 8 includes a metallic foil 9 having heat-absorbing properties which foil is placed on the outer surface 10 of the bottom portion of the internal body 7. Several electrical type heating means or elements 11 are attached to metallic foil 9 and uniformly distributed by non-conducting separators 12. The heating means 8 also contains in its electrical circuit a temperature regulator 13 which protects the apparatus from overheating. The heating means 8 and the temperature regulator 13 are covered by a metallic foil 14 having heat-reflecting properties, thus permitting a concentration of heat on the metallic foil 9.

As shown in more detail in Figure 3, the heating unit 8 is connected to electronic control means 15, which provides an optimum incubation temperature for the milk, which in the present invention is 112 F. +0.5 F.

The electronic control means 15 includes conventional temperature detector 16 which is conveniently placed in one of the cavities 17, provided on the bottom 18 which are on the outside of the internal body 7. This temperature detector 16 is covered by a heatinsulating element 19 and thus separated from the base portion of the main body.

Using this arrangement, the temperature detector 16 responds only to the heat fluctuations of the internal body 7.

The electronic control means 15 also includes a conventional control element 20 with a relatively short response time which provides control of the temperature fluctuations sensed by the temperature detector to within +0.5 F. The control element 20 is, in turn, electrically connected to the source of current by wires 22, which enter into the interior of the main body 1 by an apparatus 4. Current is supplied to the heating unit 8 by the electronic control means 15 in accordance with the temperature fluctuations sensed by the temperature detector 16.

The cavities 17, when viewed from the interior bottom 18 of the internal body 7, form knobs or platforms which serve to elevate a milk-yogurt container 23. The container 23 is removable from the device for convenient filling, storage of the produced yogurt and washing.

Between the internal body 7 and the container 23 a fluid is used, for example water, by which the heat is uniformly distributed from the interior body to the milk yogurt container positioned therein. As shown in Figure 4, the main body 1, which when properly positioned, forms a unit with the internal body 7, is closed by a lid 24 having an outer part 25 and an inner part 26. The outer part 25 is of a generally cylindrical shape closed on one side by an outer cover 27 provided with a circular groove 28, which serves to retain the lid 24 in position. The outer part 25 and the inner part 26 are provided with inner circular rims 29 and 30 which engage each other to allow a tight fit when fastening; see also Figure 4.

The main body 1, internal body 7, milk/ yogurt container and associated lid 24 may be formed from a heat-resistant plastics type material, glass or the like. Preferably the attached portions of the apparatus are made of a synthetic resin or plastics material and the removable milk/yogurt container 23 is of a heat resistant glass.

Using the apparatus for making yogurt as described above, milk is sterilized by heating then cooled to a temperature suitable for maintaining a live culture of yogurt growing lactic bacteria. A culture of the lactic bacteria is dispersed into the cooled milk which mixture is placed into the milk/yogurt container 23 which is then positioned within the internal body 7. The lid 24 is attached. The apparatus may be preheated to the preset temperature or heated after the milk/culture mixture is introduced. Warm water is supplied to the internal body 7 which surrounds the container 23 and provides for uniform transfer of heat between the heating unit 8 and the container 23. The temperature within the container 23 is maintained at 112 F+ 0.5"F. by the electronic control means 15 and associated electrical heating units.

There are several sources of milk that may be used to advantage in making yogurt.

These include pasturized milk; powdered milk, which is sometimes identified as spraydried nonfat dry milk solids; fresh farm milk; and sterilized or long-preserving milk.

Pasturized milk is typically available as whole, half-skim, skim or homogenized milk, depending upon the butter fat content and its manner of distribution through the milk.

Pasturization does not necessarily mean that the milk is sterilized for purposes of making yogurt, and in order to properly use this milk it must be sterilized, such as by heating it to 82"C. (180"F.) or up to the boiling point, and maintaining it at this temperature for about one or two minutes. This preliminary heating will serve to destroy any bacteria that may be present and also any enzymes that may be present in the milk which act as an inhibitor of the yogurt culture.

Powdered milk is also a good source of milk and, in fact, commercial yogurt is usually made from this milk source or is added to whole milk. Making yogurt from powdered milk is substantially the same as with other milk sources, however, we prefer to reconstitute the powder 24 hours before using it.

The sale of pure milk, fresh farm or crude (unpasturized) milk is generally closely supervised under strictly sanitary inspection.

It is sterilized for use in the method of the present invention by heating to 82"C. (180"F.) or up to the boiling point for a period of 1 2 minutes.

Sterilized milk is generally available as whole, half skim or homogenized and is itself already sterilized at very hifil temperatures. In making yogurt at home this milk source is conveniently used as is without previous heating or boiling. It is preferred, however, that sterilized milk be brought up from its storage temperature, usually room temperature, to about 43 or 44"C. (109- 112 F.) before the yogurt culture is added.

It may be seeded with yogurt culture in a cold state (usually about 20--25"C.) but an additional time period of 40 minutes or so to allow for complete yogurt culture growth.

EXAMPLE In order to culture full-flavoured yogurt, two liters of milk from an appropriate milk source are placed in a container, preferably a double boiler or water-bath, and heated to 82"C. (180"F) up to the boiling point.

This temperature is maintained for 1 to 2 minutes or so and the milk is sterilized.

Next, the milk is cooled down to about 43--44"C. (109--112"F.). This cooling may be accelerated by immersing the container in cold water. The milk is stirred occasionally as it cools. A small amount of the now luke warm milk is mixed with the contents of one envelope of lypholized yogurt culture, available from commercial sources, in a heatproof container, such as Pyrex (Registered Trade Mark) glass. Into this milk/culture mixture the remaining amount of luke warm milk is added, stirring well so that the culture if fairly evenly distributed throughout the milk.

Luke warm water is added to the yogurt maker shown in Figure 1 and described above, the unit is plugged into a source of electric current, the heat-proof glass container is placed inside the yogurt maker and the cover is applied. The culture is incubated at the closely prescribed temperature of 112 F. +0.5 F., until a yogurt having the desired firmness is produced. The time required is generally about 42 hours, although shorter or longer times may be used depending upon personal preference.

The heat-proof glass container is placed in the refrigerator, usually for a period of about 8 hours or so, and the yogurt is ready to eat. Kept in the refrigerator the yogurt will stay fresh and tasty for 3 to 4 weeks.

A firmer yogurt may be obtained by adding powdered milk solids to the milk source, then processing as above. Gelatine may also be added to the cold milk to produce a firmer yogurt.

WHAT WE CLAIM IS:- 1. Apparatus for culturing and growing

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. outer part 25 and the inner part 26 are provided with inner circular rims 29 and 30 which engage each other to allow a tight fit when fastening; see also Figure 4. The main body 1, internal body 7, milk/ yogurt container and associated lid 24 may be formed from a heat-resistant plastics type material, glass or the like. Preferably the attached portions of the apparatus are made of a synthetic resin or plastics material and the removable milk/yogurt container 23 is of a heat resistant glass. Using the apparatus for making yogurt as described above, milk is sterilized by heating then cooled to a temperature suitable for maintaining a live culture of yogurt growing lactic bacteria. A culture of the lactic bacteria is dispersed into the cooled milk which mixture is placed into the milk/yogurt container 23 which is then positioned within the internal body 7. The lid 24 is attached. The apparatus may be preheated to the preset temperature or heated after the milk/culture mixture is introduced. Warm water is supplied to the internal body 7 which surrounds the container 23 and provides for uniform transfer of heat between the heating unit 8 and the container 23. The temperature within the container 23 is maintained at 112 F+ 0.5"F. by the electronic control means 15 and associated electrical heating units. There are several sources of milk that may be used to advantage in making yogurt. These include pasturized milk; powdered milk, which is sometimes identified as spraydried nonfat dry milk solids; fresh farm milk; and sterilized or long-preserving milk. Pasturized milk is typically available as whole, half-skim, skim or homogenized milk, depending upon the butter fat content and its manner of distribution through the milk. Pasturization does not necessarily mean that the milk is sterilized for purposes of making yogurt, and in order to properly use this milk it must be sterilized, such as by heating it to 82"C. (180"F.) or up to the boiling point, and maintaining it at this temperature for about one or two minutes. This preliminary heating will serve to destroy any bacteria that may be present and also any enzymes that may be present in the milk which act as an inhibitor of the yogurt culture. Powdered milk is also a good source of milk and, in fact, commercial yogurt is usually made from this milk source or is added to whole milk. Making yogurt from powdered milk is substantially the same as with other milk sources, however, we prefer to reconstitute the powder 24 hours before using it. The sale of pure milk, fresh farm or crude (unpasturized) milk is generally closely supervised under strictly sanitary inspection. It is sterilized for use in the method of the present invention by heating to 82"C. (180"F.) or up to the boiling point for a period of 1 2 minutes. Sterilized milk is generally available as whole, half skim or homogenized and is itself already sterilized at very hifil temperatures. In making yogurt at home this milk source is conveniently used as is without previous heating or boiling. It is preferred, however, that sterilized milk be brought up from its storage temperature, usually room temperature, to about 43 or 44"C. (109- 112 F.) before the yogurt culture is added. It may be seeded with yogurt culture in a cold state (usually about 20--25"C.) but an additional time period of 40 minutes or so to allow for complete yogurt culture growth. EXAMPLE In order to culture full-flavoured yogurt, two liters of milk from an appropriate milk source are placed in a container, preferably a double boiler or water-bath, and heated to 82"C. (180"F) up to the boiling point. This temperature is maintained for 1 to 2 minutes or so and the milk is sterilized. Next, the milk is cooled down to about 43--44"C. (109--112"F.). This cooling may be accelerated by immersing the container in cold water. The milk is stirred occasionally as it cools. A small amount of the now luke warm milk is mixed with the contents of one envelope of lypholized yogurt culture, available from commercial sources, in a heatproof container, such as Pyrex (Registered Trade Mark) glass. Into this milk/culture mixture the remaining amount of luke warm milk is added, stirring well so that the culture if fairly evenly distributed throughout the milk. Luke warm water is added to the yogurt maker shown in Figure 1 and described above, the unit is plugged into a source of electric current, the heat-proof glass container is placed inside the yogurt maker and the cover is applied. The culture is incubated at the closely prescribed temperature of 112 F. +0.5 F., until a yogurt having the desired firmness is produced. The time required is generally about 42 hours, although shorter or longer times may be used depending upon personal preference. The heat-proof glass container is placed in the refrigerator, usually for a period of about 8 hours or so, and the yogurt is ready to eat. Kept in the refrigerator the yogurt will stay fresh and tasty for 3 to 4 weeks. A firmer yogurt may be obtained by adding powdered milk solids to the milk source, then processing as above. Gelatine may also be added to the cold milk to produce a firmer yogurt. WHAT WE CLAIM IS:-

1. Apparatus for culturing and growing

yogurt from milk using a lactic bacteria culture including a main body having an outside shell open at one end and an internal body positioned within and fastened to the main body and leaving a space therebetween, electrical heating means attached to said internal body and positioned in said space between said outside shell and said internal body, said heating means including a metallic, heat-absorbing foil secured to the outer lower surface of said internal body, and electric heating elements attached to said foil and uniformly spaced apart from each other by separators, a temperature regulator for protecting the heating elements from overheat- ing, and an outer heat-reflecting metal foil covering said heating elements and said temperature regulator and serving to concentrate heat on said heat absorbing foil, control means connected to said heating means for controlling the temperature within said internal body including a current source, a control circuit connected to said source and having a relatively short response time and providing in operation, control of the fluctuations of temperature within said internal body to within +0.50F., said temperature control means maintaining a predetermined yogurt incubation temperature, a container for the lactic acid yogurt making culture dispersed in milk, said container being received within said internal body and a removable lid enclosing the open end of said shell.

2. Apparatus as claimed in Claim 1 wherein said outside shell has a closed bottom portion, a cylindrical lower section and a continuing upper section in the shape of a frustrum cone and an internal circular rim for supporting said internal body.

3. Apparatus as claimed in Claim 2 wherein said internal body has a base and is cylindrical in shape, being slightly tapered inwardly towards the base and is provided with a plurality of platforms along the base thereof.

4. Apparatus as claimed in Claim 1 wherein said control means provides regulating and maintenance of the optimum temperature in association with and electrical connection to said heating means, and comprises a temperature detector and a control element connected to both the temperature detector and the source of electric current.

5. Apparatus as claimed in Claim 1 wherein said lid comprises a cylindrically shaped outer part, and an inner part, a handling means thereon and the outer and inner parts being provided with respective inner circular rims which engage each other to allow a secure fit, when fastening.

6. Apparatus for culturing and growing yogurt from milk using a lactic bacteria culture and substantially as hereinbefore described and as shown in the accompanying drawings.

7. Apparatus for making yogurt and substantially as hereinbefore described and as shown in the accompanying drawings.