Method for producing structured, fermented milk products having a fat content of 1 to 40% by weight, packed in containers

Abstract: Structured, fermented milk products having a fat content which varies from 1% by weight to at least 4% by weight, contain an added percentage of fat free dry milk solids which decreases linearly from 3 to 0% by weight as the fat content of the products increases from 1 to 4% by weight and furthermore are free from other added binders and also from binders formed by slime-forming lactic acid bacteria, and a method for structuring of fermented milk products, wherein a starting milk having a fat content of at least 1 to 40% by weight, after standardization of the fat and dry solids content is pasteurized and homogenized and non-slime-forming lactic acid bacteria mix cultures or slime-forming lactic acid bacteria in liquid, frozen or deep-frozen form in the customary percentages are added and incubated for a predetermined period in a temperature range which is suitable for aroma development and wherein the slime formation is minimal and the coagulum of the fermented and not yet cooled product, which depending on the fat content may or may not contain added fat free dry milk solids, is subjected to a controllable shearing force or energy dissipation, as a result of which slightly viscous characteristics result which, after a period of standing, change to highly viscous characteristics, then cooling to at most 10°C and subsequently filling in containers.

Description: The present invention relates to a method for structuring fermented milk products, having a fat content of from 1 to 10 % by weight. In US-A- 2,832,687 a method for the preparation of cultured cream, having a fat content of from about 16 to about 20 % by weight and being free of added non-dairy type thickening agents and skimmed milk powder as well is disclosed. The steps of ripening said cream are: mixing the starting cream having a temperature of 70°F with a mesophilic starter containing S.lactis as acid forming bacteria and undefined other flavor producing bacteria, in a vat, ripening at same temperature, stirring the resulting cultured cream and subjecting the cultured cream before cooling to a passage through a restriction at 103 to 209 kPa (15 to 30 lbs/square inch), subsequently the cultured cream is chilled, whereby a heavy-bodied, smooth and shiny cultured cream is produced. The publication by Steenbergen in NIZO-Mededeling (NIZO information sheet) no. 7, 34-43 (1973) teaches that yoghurt consists of a network of protein chains and slime which has grown in and through one another in the fluid. As long as these chains are still entangled in one another, the fluid exhibits viscous flow and the viscosity is high. However, when the connection is broken the viscosity falls. This occurs when layers of yoghurt shift along one another. It is pointed out that at a certain flow rate the viscosity of yoghurt no longer falls after some time. It appears that certain structures are strong enough to withstand the shear forces that arise. Steenbergen concludes that it is obvious that an attempt will be made to prepare yoghurt very carefully, so that a high initial viscosity and also a high resistance to damage are obtained. The author of this article emphasizes that the damage to the structure of yoghurt already starts when stirring in the culture tank to obtain a smooth texture. Therefore, this can best be carried out with the aid of a stirrer with large stirrer blades rotating at low speed. The stirring time may not be longer than is strictly necessary. According to Steenbergen transitions in the diameter of the transport lines must be avoided. The shape of the construction is not very important, but the degree of construction is decisive. It is therefore also important to ensure that shut-off valves are not in half-opened position. Drawbacks of the known products are that they have to contain added binders foreign to milk, binders formed by slime-forming lactic acid bacteria and/or a considerable amount of added fat-free dry milk solids if they are to have a desired viscosity and firmness. As already stated, the addition of binders foreign to milk is not permitted in all countries, the polysaccharides formed by slime-forming lactic acid bacteria mask the taste and the addition of fat-free dry milk solids make the product expensive. Surprisingly it was found that fermented milk products, being free of added non-dairy type thickening agents, and of slime substances masking the original taste and aroma, and having a fat content of from 1 to 10 % by weight, can be structured by: (1) pasteurizing and homogenizing a starting milk, after standardization of the fat and dry solids contents, wherein, depending on the fat content of the starting milk up to 3% by weight of fat-free dry milk solids are added; (2) adding mixed cultures of non-slime forming lactic acid bacteria alternatively slime-forming lactic acid bacteria in liquid, frozen or deepfrozen form in the customary percentages; (3) incubating for a pre-determined period within a temperature range at which said slime formation is minimal and which is suitable for the aroma development and the coagulum formation, by the particular micro-organisms, (4) before cooling the coagulum formed according to item (3) is subjected to a controllable shearing force or energy dissipation, creating a pressure of at least 25 kPa, selected from passing through a reducing valve, feeding the product through at least one sieve or feeding the product through a pipeline wherein a rotating stirrer is located, (5) cooling to a temperature of 25°C at a maximum and (6) filling it into containers and leaving it standing for a period, wherein highly viscous characteristics are developed. In this context fat-free dry milk solids are understood to mean not only the totally fat-free dry milk solids, but also caseinates and whey protein preparations. If caseinates and whey protein preparations are used, the percentages indicated must, of course, be adjusted. The method according to the invention can be carried out either continuously or batchwise. Similar products to those prepared according to the invention are available commercially but, as already mentioned, these differ from the products in question in that they contain other added binders, polysaccharides formed by slime-forming lactic acid bacteria and/or a quantity of added fatfree dry milk solids which does not decrease linearly from 3 to 0 % by weight as the fat content increases from 1 to 4 % by weight. Examples of such commercially available products are given in Table A. Milk contains on average 3.36 % by weight and skimmed milk powder 36 % by weight protein. By addition of skimmed milk powder (fat-free dry solids: ffds) the protein content of the products is increased. This can be seen in the composition given for a number of products which are relevant within the scope of the present patent application and which were obtained by purchasing from the market. The percentage added ffds was determined by calculation. These data are given in Table A. Product Manufacturer + sell-by date Indicated % by weight fat Indicated % by weight protein Calculated % by weight extra ffds (invention) Biogarde Almhof/CEMA 19.06.87 3.5 4.8 4.0 (0.5) Biogarde MONA 28.06.87 1.5 4.4 2.9 (2.5) Biogarde Danone 27.06.87 1.5 4.55 3.3 (2.5) Biogarde Menken 17.06.87 1.5 4.5 3.2 (2.5) Yoghurt Stassano 16.09.87 3.0 4.0 1.8 (1.0) code c: ffds From the compisition of the products shown in Table A it can clearly be seen that the percentages of fatfree dry milk solids have been increased by the addition of fatfree dry milk solids. EXAMPLES Example IA, 1B, 1C Preparation of Yoghurt 45 grammes skimmed milk powder per portion were added to three 4.5 litre portions of milk with a fat content of 3.05 % by weight. The mixtures were warmed to 65°C, with stirring, homogenized under a pressure of 20 MPa and then further heated to 90°C and kept at this temperature for 10 minutes. The portions of milk were then cooled to 32°C, 37°C and 43°C respectively. 225, 112 and 112 grammes respectively of fresh, non-slime-producing yoghurt culture consisting of L.delbrueckii subsp. bulgaricus and S.thermophilus were added per portion of milk and the mixture stirred for 10 minutes. The portions of milk were incubated at the said temperatures for 7, 4.5 and 3 hours respectively until a pH of 4.4 was reached. The coagulums formed were then subsequently stirred loose with the aid of a propeller stirrer for 2 minutes at a speed of 250 revolutions per minute. With the aid of a lifting pump (type Waukesha, 3D0, delivery 30 litres per hour), the coagulums were pumped through two sieves. The first sieve consists of a perforated plate with a diameter of 25 mm provided with 42 circular perforations per cm² with a diameter of 0.55 mm. The second sieve consisted of metal gauze with a diameter of 25 mm, with a mesh width of 0,4 mm and a wire thickness of 0.2 mm. The preparation conditions are given in the appendid Table B. The sieved yoghurts were collected in 500 ml plastic beakers, closed off with an aluminium capsule and then cooled to 7°C in a forced stream of air at 4°C. After storing for 1 day and for 2 weeks at 7°C, the pH and the flow-through time of the 3 portions of yoghurt were measured at 7°C, the flow-through time being measured with the aid of a Posthumus funnel with an outlet orifice with a diameter of 8 mm. The portions of yoghurt were also assessed organoleptically at these times. The yoghurt which was cultured at 32°C has a flow-through time of 50 seconds after storing for 1 day and 54 seconds after storing for 2 weeks. The pH at said times was 4.14 and 3.91 respectively. After storing for 1 day the product had a good yoghurt consistency and taste. After storing for 2 weeks the product had hardly changed and retained its smooth, thick consistency and clean yoghurt taste. The yoghurt which was cultured at 37°C had a flow-through time of 60 seconds after storing for 1 day and 67 seconds after storing for 2 weeks. The pH at said times was 4.12 and 3.91 respectively. After storing for 1 day, the product had a good yoghurt consistency and taste. After storing for 2 weeks, the product had hardly changed and retained its smooth, thick consistency and clean yoghurt taste. The yoghurt which was cultured at 43°C had a flow-through time of 156 seconds after storing for 1 day and of 166 seconds after storing for 2 weeks. The pH at said times was 4.07 and 3.88 respectively. After storing for 1 day, the product had a good yoghurt consistency and taste. After storing for 2 weeks the product had hardly changed and retained its smooth, very thick consistency. Despite this very thick consistency the product retained a clean yoghurt taste. Example II As Example I, except that the quantity of starting milk, the fat content and fatfree dry solids content of the starting milk, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the quantity of microbiological culture added, the stirring time and the incubation time are as indicated in the appended Table B. The coagulum was stirred loose with the aid of a spiral stirrer for 2 min. at 60 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 180 litres per hour), the product was pumped through a rectangular channel made of stainless steel, the dimensions of which are given in Table B. This applies also for the pressure drop and the temperature to which the product is cooled. The pressure drop over the plate condenser was 150 kPa. The yoghurt, flowing with the aid of a lifting pump (type Waukesha, 3D0, delivery 30 litres per hour), was then cooled to 10°C with the aid of a tube condenser and ice water at 2°C. The tube condenser consisted of two tubes, each with a length of 2 m and a diameter of 25 mm. The cooled yoghurt was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. The penetration depth determined with the penetrometer of this product was 5.8 and 4.9 mm after storing at 7°C for 1 day and 2 weeks respectively. The measurement results with the texture analyzer were 139 and 153 grammes respectively after the said storage times. The pH fell from 4.15 after 1 day to 3.98 after 2 weeks. After 1 day the product had a smooth appearance and a very thick consistency. The product had a creamy, typical yoghurt taste. Both taste and consitency were maintained during the storage period. No separation of whey found. Example III Preparation of yoghurt As Example I except that the quantity of starting milk, the fat content and the fatfree dry solids content of the starting milk, the quantity of added skimmed milk powder, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the amount of added microbiological culture, the stirring time and the incubation time are as indicated in the appended Table B. The coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 60 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a lifting pump (type Waukesha 10D0, delivery 90 litres per hour), the product was pumped through a rectangular channel made of stainless steel. The dimensions of the flow-through orifice of the rectangular channel, the pressure drop over the said channel and the temperature to which the product was cooled are given in Table B. The pressure drop over the plate condenser was 50 kPa. The yoghurt, flowing with the aid of a lifting pump (type Waukesha 3D0, delivery 30 litres per hour), was then cooled to 10°C with the aid of a tube condenser and ice water at 2°C. The tube condenser consisted of two concentric tubes, each with a length of 2 m and the inner tube with a diameter of 25 mm. The cooled yoghurt was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. The penetration depth determined with the penetrometer of this product was 18.3 and 13.7 mm after storing at 7°C for 1 day and for 2 weeks respectively. The measurement results with the texture analyzer were 59 and 62 grammes respectively after the said storage times. The flow-through times were 34 and 45 seconds respectively. The pH fell from 4.04 after 1 day to 3.89 after 2 weeks. After 1 day the product had a smooth appearance and a good yoghurt consistency. The product had a creamy, typical yoghurt taste. Both taste and consistency were retained during the storage period. No separation of whey was found. Example IV Preparation of yoghurt As Example I except that the quantity of starting milk, the fat content and the fat-free dry solids contents of the starting milk, the quantity of added skimmed milk powder, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the quantity of added microbiological culture, the stirring time, the incubation time and the pH after incubation are indicated in the appended Table B. The coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 60 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through two sieves. The first sieve consisted of a perforated plate with a diameter of 25 mX^T provided with 42 circular perforations per cm³ with a diameter of 0.5 mm. The second sieve consisted of metal gauze with a diameter of 25 mm, with a mesh width of 0.4 mm and a wire thickness of 0.2 mm. The yoghurt, flowing with the aid of a lifting pump (type Waukesha 3D0, delivery 60 litres per hour), was then cooled to 18°C with the aid of a plate condenser with ice water at 2°C. The product was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. The product had a flow-through time of 24 seconds after 1 day and a flow-through time of 23 seconds after 2 weeks. The pH fell from 4.05 after 1 day to 3.91 after 2 weeks. After 1 day the product had a smooth appearance and a good yoghurt consistency. The product had a good yoghurt taste and the typical yoghurt aroma. Both taste and consistency were retained during the storage period. No separation of whey was found. Example V Preparation of yoghurt As Example 1 except that the quantity of starting milk, the fat content and fat-free dry solids content of the starting milk, the quantity of added skimmed milk powder, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the quantity of added microbiological culture, the stirring time, the incubation time and the pH after incubation are indicated in the appended Table B. The coagulum was stirred loose with a spiral stirrer for 2 minutes at 60 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type 22R5, delivery 90 litres per hour), the product was pumped through a reducing valve. The pressure drop over the reducing valve is shown in Table B. Using a lifting pump (type Waukesha 3D0, delivery 90 litres per hour), the yoghurt was then cooled to 10°C via a plate condenser with ice water at 2°C. The cooled yoghurt was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. The flow-through times were 35 and 50 seconds respectively. The pH fell from 4.07 after 1 day to 3.93 after 2 weeks. After 1 day the product had a smooth appearance and a good yoghurt consistency. The product had a good yoghurt taste and the typical yohurt aroma. Both taste and consistency were retained during the storage period. No separation of whey was found. Example VI Preparation of yoghurt As Example I except that the quantity of starting milk, the fat content of the starting milk, the quantity of added skimmed milk powder, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the quantity of added microbiological culture, the stirring time, the incubation time and the pH after incubation are as indicated in the appended Table B. The coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 50 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through a reducing valve. The pressure drop over the reducing valve is shown in Table B, 50 litres of yoghurt were then cooled to 15°C, while flowing with the aid of a plate condenser with the ice water at 2°C. The other 50 litres of yoghurt were cooled in the same way, but to 25°C. The pressure drop over the plate condenser was 74 kPa and 65 kPa respectively. The two portions of yoghurt were then collected in plastic beakers, closed off with an aluminium capsule and cooled to 7°C in a forced stream of air at 2°C. The flow-through times of the portion of yoghurt pre-cooled to 15°C while flowing were 40 and 41 seconds after 1 day and 2 weeks respectively. The pH of this portion of yoghurt fell from 4.08 after 1 day to 3.99 after 2 weeks. The flow-through times of the portion of yoghurt precooled to 25°C while flowing were 48 and 48 seconds after 1 day and 2 weeks respectively. The pH of this portion of yoghurt fell from 4.11 after 1 day to 3.99 after 2 weeks. After 1 day both portions of yoghurt had a smooth appearance and a good yoghurt consistency. The product had a good yoghurt taste and the typical yoghurt aroma. Both taste and consistency were retained during the storage period. No separation of whey was found. Example VII Preparation of yoghurt As Example I except that the quantity of starting milk, the fat content of the starting milk, the quantity of added skimmed milk powder, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the quantity of added microbiological culture, the stirring time, the incubation time and the pH after incubation are as indicated in the appended Table B. The coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 50 revolutions per minute. During further processing, the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through a reducing valve. The pressure drop over the reducing valve is shown in Table B. The yoghurt was then cooled to 25°C, while flowing with the aid of a plate condenser with ice water at 2°C. The pressure drop over the plate condenser was 65 kPa. One portion of yoghurt was then collected in plastic beakers, closed off with an aluminium capsule and cooled to 7°C in a forced stream of air at 2°C. A second portion of yoghurt was cooled to 10°C, while flowing with the aid of a lifting pump (type Waukesha 3D0, delivery 30 litres per hour), via a tube condenser. This tube condenser consisted of two tubes, each with a length of 2 m and the inner tube with a diameter of 25 mm. This deep-cooled yoghurt was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. The flow-through time of the first portion of yoghurt which was deep-cooled to 7°C in a forced stream of air in the packaging, was 48 seconds after 1 day and 48 seconds after 2 weeks. The pH of this portion of yoghurt fell from 4.11 after 1 day to 3.99 after 2 weeks. The flow-through times of the second portion of yoghurt which was deep-cooled to 10°C while flowing, were 37 and 36 seconds after 1 day and after 2 weeks respectively. The pH of this portion of yoghurt fell from 4.13 after 1 day to 4.04 after 2 weeks. After 1 day both portions of yoghurt had a smooth appearance and a good yoghurt consistency. The product had a good yoghurt taste and the typical yoghurt aroma. Both taste and consistency were retained during the storage period. Some separation of whey was detected only in the case of the yoghurt deep-cooled while flowing. Example VIII Preparation of yoghurt As Example I except that the quantity of starting milk, the fat content of the starting milk, the quantity of added skimmed milk powder, the temperature in the second heating step, the duration of the second heating step, the temperature to which the product is cooled, the quantity of added microbiological culture, the stirring time, the incubation time and the pH after incubation are as indicated in the appended Table B. The coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 50 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through a reducing valve. The pressure drop over the reducing valve is shown in Table B. The yoghurt was then cooled to 25°C, while flowing, with the aid of a plate condenser with ice water at 2°C. The pressure drop over the plate condenser was 62 kPa. The yoghurt was then divided into two portions. The first portion of yoghurt was collected in plastic beakers, closed off with an aluminium capsule and cooled to 7°C in a forced stream of air at 2°C. The second portion of yoghurt was stored for five hours at 25°C. During this storage period the pH fell 0.1 pH unit. This portion of yoghurt was then collected in plastic beakers and closed off with an aluminium capsule and cooled to 7°C in a forced stream of air at 2°C. The flow-through times of the first portion of yoghurt, which after precooling to 25°C was deep-cooled directly to 7°C, were 48 seconds after 1 day and 48 seconds after 2 weeks. The pH of this portion of yoghurt fell from 4.11 after 1 day to 3.99 after 2 weeks. The flow-through times of the second portion of yoghurt, which after precooling to 25°C while flowing was stored for 5 hours at 25°C, were 60 seconds after 1 day and 76 seconds after 2 weeks. The pH of this portion of yoghurt falls from 4.11 after 1 day to 3.99 after 2 weeks. After 1 day both portions of yoghurt had a smooth appearance and a good yoghurt consistency. The product had a good yoghurt taste and the typical yoghurt aroma. Both taste and consistency were retained during the storage period. No separation of whey was found. Example IX Preparation of yoghurt Fresh milk having a fat content of 2.95 % by weight, to which 1.0 % by weight skimmed milk powder had been added, was warmed to 65°C, while flowing, homogenized under a pressure of 20 MPa, then pasteurized at 76°C, while flowing, with a residence time of 20 seconds, and cooled to 6°C while flowing. The following day 50 litres of said milk were warmed to 90°C in a double-walled tank, with stirring, kept at this temperature for 10 minutes and then cooled to 44°C. 1.35 litres fresh, non-slime-producing yoghurt culture consisting of L.delbrueckii subsp. bulgaricus and S. thermophilus were added to this milk and the mixture was stirred for 1 minute to obtain a homogeneous distribution of the bacteria. The mixture was incubated at 43°C. After 2.8 hours a pH of 4.46 was achieved, after which the coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 75 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through two sieves. The first sieve consisted of a perforated plate with a diameter of 25 mm, provided with 42 circular perforations per cm², with a diameter of 0.55 mm. The second sieve consisted of metal gauze with a diameter of 25 mm with a mesh width of 0.4 mm and a wire thickness of 0.2 mm. With the aid of a lifting pump (type Waukesha 3D0, delivery 90 litres per hour), the yoghurt was then cooled to 18°C, while flowing, with the aid of a plate condenser with ice water at 2°C. The product was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. Further cooling to 7°C took place in a forced stream of air at 2°C. After storing at 7°C for 1 day and for 2 weeks, the flow-through time of the yoghurt was measured at the storage temperature with the aid of a Posthumus funnel with an outlet orifice with a diameter of 8 mm. The pH was also measured and the product was assessed organoleptically at these times. The product had a flow-through time of 46 seconds after 1 day and a flow-through time of 66 seconds after 2 weeks. The pH fell from 4.12 after 1 day to 3.99 after 2 weeks. After 1 day the product had a smooth appearance and a good yoghurt consistency. The product had a good yoghurt taste and the typical yoghurt aroma. Both taste and consistency were retained during the storage period. No separation of whey was found. Example X Consumer test with low fat yoghurt and full fat yoghurt . The acceptance of low fat yoghurt, such as described in Example IV, and full fat yoghurt, such as described in Example IX, by the Dutch consumer was investigated. The investigation was carried out by means of 300 individual, structured interviews. Half of those tested were given low fat yoghurt and the other half of those tested were given full fat yoghurt. A summary of the consumer tests is given below. Paragraph 1. SUMMARY 1.1 On the basis of the draft description a positive reaction is obtained; a thick, oldfashioned and tasty yoghurt is expected. In particular the concept of "thick" is frequently mentioned. 1.2 On the basis of this draft description it is expected that this new yoghurt is considerably thicker than the existing yoghurts and will have a somewhat milder (also less sour) taste. 1.3 The interest on the basis of the appearance of the yoghurt and the draft description is great. Interest is shown by 84% for the full fat yoghurt and even by 90% for the low fat yoghurt. 1.4 Both the whole yoghurt and the low fat yoghurt look attractive. 74% think that the whole yoghurt looks (very) attractive; the corresponding figure for the low fat yoghurt is 80%. 1.5 Both products were found to taste good. No fewer than some 87% think the yoghurt tastes good. The only adverse comment is that both products are somewhat too sour. 1.6 About 2 in every 5 participants take "ordinary yoghurt" as the reference point. The other participants also compare the new yoghurt with, for example, cottage cheese, Bulgarian yoghurt and Biogarde. Example XI Preparation of fruit yoghurt . Fresh milk having a fat content of 3.06 % by weight, to which 1% by weight of skimmed milk powder had been added, was warmed to 65°C, while flowing, homogenized under a pressure of 20 MPa, then pasteurized at 76°C, while flowing, with a residence time of 20 seconds and cooled to 6°C while flowing. The following day 90 litres of this milk were warmed to 90°C in a double-walled tank with stirring, then kept hot at this temperature for 10 minutes and cooled to 44°C. 2.25 litres fresh, non-slime-producing yoghurt culture, consisting of L.delbrueckii subsp. bulgaricus and S.thermophilus were added to this milk and the mixture was stirred for 5 minutes to achieve a homogeneous distribution of the bacteria. The mixture was incubated at 43°C. After 3.25 hours a pH of 4.24 was obtained, after which the coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 60 revolutions per minute. During further processing the product was stirred slowly to achieve a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through two sieves. The first sieve consisted of a perforated plate with a diameter of 25 mm provided with 42 circular perforations per cm² with a diameter of 0.55 mm. The second sieve consisted of metal gauze with a diameter of 25 mm, with a mesh width of 0.4 mm and a wire thickness of 0.2 mm. With the aid of a lifting pump (type Waukesha 3D0, delivery 90 litres per hour), the yoghurt was then cooled to 20°C while flowing, with the aid of a plate condenser with ice water at 2°C. Subsequently the yoghurt was cooled to 12°C while flowing, with the aid of a tube condenser and ice water at 2°C. The tube condenser consisted of a tube with a length of 3 m and a diameter of 25 mm. The cooled yoghurt was mixed with a strawberry fruit preparation (mixing ratio 78:22), collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. The pH fell from 4.1 to 4.0 as a result of the addition of the strawberry fruit preparation. After storing at 7°C for 2 days and for 2 weeks, the fruit yoghurt was measured after sieving out the fruit parts, at the storage temperature with the aid of a height-adjusted Posthumus funnel with an outlet orifice with a diameter of 8 mm. The pH was also measured and the product was assessed organoleptically at these times. The flow-through times through the Posthumus funnel were 30 and 55 seconds respectively after sotring at 7°C for 2 days and for 2 weeks. The pH fell from 4.0 after 2 days to 3.9 after 2 weeks. After 2 days the product had a smooth appearance and a good consistency for fruit yoghurt. In addition to a good yoghurt taste and the typical yoghurt aroma, the product had an excellent strawberry taste. Both taste and consistency were retained during the storage period. No separation of whey was found. Example XII Preparation of yoghurt . Fresh milk having a fat content of 2.96 % by weight, to which 1% by weight of skimmed milk powder had been added, was warmed to 65°C while flowing, homogenized under a pressure of 20 MPa, then pasteurized at 92°C while flowing, with a residence time of 6 minutes and cooled to 6°C, while flowing. The following day 65 litres of this milk were warmed to 44°C in a double-walled tank with stirring. 1.625 litres of fresh non-slime-producing yoghurt culture, consisting of L.delbrueckii subsp. bulgaricus and S.thermophilus were added to this milk and the mixture was stirred for 5 minutes to obtain a homogeneous distribution of the bacteria. The mixture was incubated at 43°C. After 4 hours a pH of 4.30 was obtained, after which the coagulum was stirred loose with the aid of a wicket stirrer for 2 minutes at 60 revolutions per minute. During further processing the product was stirred slowly in order to maintain a homogeneous distribution. With the aid of a monopump (type SH 22R5, delivery 90 litres per hour), the product was pumped through a reducing valve, with which the pressure drop over the reducing valve was set to various values (see Table C). The yoghurt was then cooled to 20°C, while flowing, with the aid of a plate condenser with ice water at about 2°C. The cooled yoghurt was collected in plastic beakers, closed off with an aluminium capsule, cooled in a forced stream of cold air and stored at 7°C. After storing at 7°C for 1 day and for 2 weeks, the firmness of the yoghurt at the storage temperature was measured with the aid of a penetrometer and the flowthrough time was measured with the aid of a Posthumus funnel with an outlet orifice with a diameter of 8 mm. The pH was also measured and the product was assessed organoleptically for appearance, serum separation and viscosity at these times. Using the penetrometer, manufacturer Sommer and Runge, the penetration depth of a plastic measuring body (diameter 38 mm, height 20 mm, mass 27 grammes) over 10 seconds was determined. The result of the measurement and organoleptic assessment are summarized in Table C. It can be seen from these results that it was possible to change the viscosity and smoothness of the product by choosing a different pressure drop over the reducing valve. All products had a good yoghurt taste and the typical yoghurt aroma. Both taste and consistency were retained during the storage period. No separation of whey was found. Example XIII Preparation of Biogarde . Fresh milk having a fat content of 2.90 % by weight, to which 1 % by weight skimmed milk powder had been added, was warmed to 65°C, while flowing, homogenized under a pressure of 20 MPa, then pasteurized at 92°C, while flowing, with a residence time of 6 minutes and cooled to 6°C, while flowing. 120 litres of this milk were warmed to 39°C in a double-walled tank, with stirring. 3.6 litres fresh biogarde culture, consisting of L.acidophilus , B.bifidum and S.thermophilus were added to this milk and the mixture stirred for 5 minutes to obtain a homogeneous distribution of the bacteria. The mixture was incubated at 38°C. After 13.25 hours a pH of 4.39 was obtained, after which the coagulum was stirred loose with the aid of a spiral stirrer for 2 minutes at 60 revolutions per minute. During further processing the product was stirred slowly to maintain a homogeneous distribution. With the aid of a lifting pump (type Waukesha 10D0, delivery 90 litres per hour), the product was pumped through various rectangular channels made of stainless steel or pumped through a reducing valve, the pressure drop over the reducing valve being set to 50 KPa. The dimenions of the flow-through orifice of the rectangular channels are given in Table C. The product was then cooled to about 20°C, while flowing, with the aid of a plate condenser with ice water at about 2°C. The product was collected in plastic beakers, closed off with an aluminium capsule and stored at 7°C. Further cooling to 7°C took place in a forced stream of air at 2°C. After storing at 7°C for 1 day and for 2 weeks, the firmness of the product at the storage temperature was measured with the aid of a penetrometer and the flow-through time was measured with the aid of a Posthumus funnel with an outlet orifice with a diameter of 8 mm. The pH was also measured and the product was assessed organoleptically for appearance, serum separation and viscosity at these times. Using the penetrometer, manufacturer Sommer and Runge, the penetration depth of a plastic measuring body (diameter 38 mm, height 20 mm, mass 27 grammes) over 10 seconds was determined. The results of the measurements and organoleptic assessment are likewise given in Table D. It can be seen from this table that it is possible to influence the appearance and the viscosity by varying the dimensions of the rectangular channel.

Claims: Method for structuring fermented milk products being free of added non-dairy type thickening agents and having a fat content of from 1 to 10 % by weight, by: (1) pasteurizing and homogenizing the starting milk, after standardization of the fat and dry solids content, wherein, depending on the fat content of the starting milk up to 3 % by weight of fat-free dry milk solids are added, (2) adding mixed cultures of non-slime forming lactic acid bacteria alternatively slime-forming lactic acid bacteria in liquid, frozen or deepfrozen form in the customary percentages, (3) incubating for a pre-determined period within a temperature range at which said slime formation is minimal and which is suitable for the aroma development and the coagulum formation, by the particular micro-organisms, (4) before cooling the coagulum formed according to item (3) is subjected to a controllable shearing force or energy dissipation, creating a pressure of at least 25 kPa, selected from passing through a reducing valve, feeding the product through at least one sieve or feeding the product through a pipeline wherein a rotating stirrer is located, (5) cooling to a temperature of 25°C at a maximum and (6) filling it in containers and leaving it standing for a period, wherein highly viscous characteristics are developed. Method according to claim 1, wherein the prepared packed product is cooled in a cooling tunnel. Method according to claim 1, wherein the product is cooled by using a tube condenser. Method according to Claim 1, wherein the prepared produkt is, if necessary, first cooled to 20°C using a heat exchanger and is then stored, after packing, in a cooling cell. Method according to claim 1, wherein the micro-organisms used are: L.acidophilus , B.bifidus and S.thermophilus . Method according to claim 1, wherein a fermented milk product having a fat content of 1 to 10 % by weight is prepared and fruit is added thereto.

Inventors: DRIESSEN FRANCISCUS MARIA, KLUTS PETRUS BARBARA GUILLAUME, KNIP JACOB, DRIESSEN, FRANCISCUS MARIA, KLUTS, PETRUS BARBARA GUILLAUME, KNIP, JACOB
Applicants: HOLLAND MELKUNIE, MELKUNIE HOLLAND B.V.
Application year: 1988
Main classification: A23C9
IPC codes: A23C13, A23C9