GB2516103A

GB2516103A - Method of manufacturing a comestible product

Info

Publication number: GB2516103A
Application number: GB1312500.0A
Authority: GB
Inventors: Xin Gu; Lydia Campbell
Original assignee: Nandi Proteins Ltd
Current assignee: Nandi Proteins Ltd
Priority date: 2013-07-12
Filing date: 2013-07-12
Publication date: 2015-01-14
Also published as: GB201312500D0

Abstract

The invention provides a method of manufacturing a comestible product, comprising the steps of incubating a mixture of a milk product and rennet; adjusting the pH of the mixture to above pH 7.0; and heating the mixture to inactivate the rennet. The milk product preferably comprises milk and one or more ingredients selected from a colour, flavour and sweetener. The comestible product may be thickened milk, milkshake, milk gel or yogurt. The mixture of milk product and rennet may be incubated at a temperature of between 35ÂºC and 45ÂºC, for a time period of between 5 minutes and 45 minutes. The milk products do not require additional thickening or stabilising agents.

Description

Method of Manufacturing a Comestible Product

Technical field of the invention

This invention relates to methods of manufacturing comestible products, in particular methods of manufacturing thickened milk products. The invention ftirthcr provides comestible products per se.

Background to the invention

Thickened milk products are known, such as milkshakes and thickened milk drinks, which may be flavoured and coloured.

Known thickened milk products of this type generally include thickening agents and/or stabilising agents in order to maintain the physical structure and integrity of the thickened milk. Carragccnan and xanthan gum arc some of the most widely used thickening and stabilising agents in commercial thickened milk products.

However, recent studies have indicated that carrageenan introduces inflammation in human intestinal epithelial cells (Borthakur A. et a!., 2007) likewise, xanthan gum suffers from problems including reduction of efficacy over time and interaction with other components of thc milk product. Tt would therefore be advantageous to be able to manufacture thickened milk products without the use of any thickening or stabilising agent, especially carrageenan and xanthan gum.

Milk, which may be liquid milk or milk powder reconstituted with an aqueous medium, comprises a colloidal system which is usually stable under natural conditions. The two most influential factors in the stability of casein micelles in milk arc electrostatic and stcric interactions that exist in the external hairy layer of J-cascin.

It is possible to remove these factors using rennet, which causes coagulation of milk, in traditional processes such as cheese making, resulting in curdling of the milk and separation of curds and whey. Rennet coagulation involves an enzymatic hydrolysis and a physical aggregation in which coagulation alters casein micelles in the milk. In general processes including cheese-making, rennet addition to milk products causes coagulation. The activity of the rennet can be influenced by several factors including temperature, pH, rennet concentration and the composition of the milk itself, and any change in activity of the rennet will result in a change in aggregation.

It would be advantageous to be able to manufacture a thickened milk product or other comestible, in which the thickening action is not by addition of thickening or stabilising agents, but is effected by control of milk gel formation or aggregation, through addition of rennet.

It is therefore a aim of embodiments of the invention to provide a method of manufacturing a comestible product such as a thickened milk product, by application of rennet in mill product manufacture, through control of the enzymatic hydrolysis and aggregation of casein micelles and denaturation of whey proteins during the process, to provide a suitable comestible product without the need for thickening or stabilising agents and without causing full separation of milk into curds and whey.

Japanese patent JP-A-5959151 describes a thickened milk product comprising a milk gel formed by modifying milk with trangiutaminase., but no addition of rennet is added to the milk.

US5670192 describes the manufacture of a "not acidified" edible gel milk product by addition of both trangiutaiminase and rennet followed by heat treatments.

However, the process and conditions described for the milk products produced by the methods claimed in 1JS5670192 involve acidic or neutral processing conditions (pH 7.0 or 6.3), and the resultant products are highly thickened gel, mousse or the like products.

It is therefore an aim of embodiments of the invention to provide a method for manufacturing a thickened milk product, in which the process is simplified by the addition of minimal ingredients, and in which the process does not necessitate lowering thc pH of the process mixture.

It is also an aim of embodiments of the invention to provide a process which does not require the use of tranglutaminase in the preparation of a comestible thickened milk product.

Summary of the invention

According to a first aspect of the invention there is provided a method of manufacturing a comestible product, comprising the steps of: a) incubating a mixture of a milk product and rennet b) adjusting the pH of the mixture to above pH 7.0; and c) heating the mixture to inactivate the rennet.

By "milk" we mean whole milk (full fat milk), semi-skimmed milk, skimmed milk, sweetened condensed milk, evaporated milk or milk powder that has been reconstituted in an aqueous medium. The milk product can include the milk of any

suitable animal.

The milk product used in the invention, may comprise in addition to milk, as defined above, further suitable ingredients including colours, flavours, sweeteners, cocoa products (such as cocoa powder), fats, proteins, plant extracts and materials (such as fruit pieces), or any combination thereof; for example.

Suitable sweeteners include bulk sweeteners and high-intensity sweeteners.

Suitablc bulk sweeteners include saccharidcs such as sucrosc, glucosc, fructose, lactose, maltose, high fructose corn syrup, high glucose corn syrup, or any combination thereof; sugar alcohols (polyhydric alcohols) such as mannitol, maltitol, isomalt, sorbitol, xylitol, erythritol, or any combination of the aforesaid saccharides and sugar alcohols.

Suitable high intensity sweeteners include, aspartame, acesuifame-K, cyciamates, saccharin, sucralose, neohesperidin, dihydrochalcone, alitame, neotarne.

Lo F-ian (Juo. stevia. mona.tin, givcyrrillzm. or any combination thereof The milk product may comprise both a bulk sweetener and a high intensity sweetcncr.

The steps of incubating mill product and rennet, adjustment of pH to alkaline and controlled inactivation of the rennet results in no distinct separation of curds and whey in the milk, whilst the milk becomes thickened, with a good mouth-feel and texture. The method of the first aspect of the invention does not require any thickening agents such as carrageenan or xanthan gum to be added to the milk product to thicken it, and removes the need to add further viscosity or structural stabilisers.

Furthermore the rennet concentration can be relatively dilute compared to prior art methods of rennet-based thickening of milk products.

In some embodiments the mcthod does not includc addition of any carrageenan or xanthan gum, and in other embodiments does not include addition of any thickening agents, during any step of the methods.

Step a) may comprise incubating the mixture of milk product and rennet at a tempcrature of between 1°C and 50°C, for a time period of between 10 minutes and 72 hours.

In some embodiments step a) may comprise incubating the mixture of milk product and rennet at a temperature of at Icast 35°C, 36°C, 37°C, 38°C, 39°C or 40°C and no more than 50°C, 45°C or 42°C, which may be in the range 37°C-42°C or 38°C-40°C in some preferred embodiments, for an incubation time period of at least minutes, 12 minutes, 15 minutes or 20 minutes and no more than 45 minutes, 40 minutes, 35 minutes or 30 minutes. In some preferred embodiments the incubation time period may be between 25-35 minutes, or 20-30 minutes.

In other embodiments step a) may comprise incubating the mixture of milk product and rennet at a temperature of at least 1°C, 2°C, 3°C, 4°C, 5°C or 10°C and no more than 25°C, for a time period of at least 6 hours, 12 hours, 18 hours, 24 hours, 36 hours or 48 hours. In some embodiments the mixture is incubated at between 2°C and 5°C for a time period of between 24 hours and 72 hours, such as between 36 hours and 48 hours.

In some preferred embodiments of the invention the incubation of the mixture of milk product and rennet may comprise incubating at a temperature of between 35% -45% for a time period of between 15 minutes and 40 minutes, or at a temperature of 38 -40 for between 20 and 30 minutes.

The amount of rennet used in step a) may be at least 0.001%, 0.0015%, 0.0020% or 0.0025% w/w, or no more than 0.05%, 0.02%, or 0.01% w/w, relative to the concentration of milk protein in the mixture. This concentration of rennet results in a thickened comestible product with good organoleptic, mouth-feed and textural characteristiCs.

Step b) may comprise adjusting the pH to above 7.0 by addition of an alkali to the mixture. In some embodiments the pH is adjusted to above 7.1, 7.2 or 7.3, and in some preferred embodiments, the pH may be adjusted to between 7.3 -7.7, or 7.4 -7.5.

Adjusting the pH in step b) may comprise adding and alkali selected from sodium hydroxide, potassium hydroxide calcium hydroxide, calcium carbonate, or mixtures thereof The alkali maybe added as on aqueous solution of the alkali, and in some embodiments an IM solution of alkali may be used.

Step c) may comprise heating the mixture to a temperature of at least 65 C, 67 C or 69 C, and no more than 77 C, 75 C or 73 C for a time period of at least 20 seconds, 30 seconds or 60 seconds, and no more than 15 minutes, 12 minutes or 10 minutes. In some embodiments heating is preferred at between 65 C and 73 C for between 1 and 10 minutes.

In other embodiments step c) may comprise heating the mixture to at least 78 C, 79 C or 80 C, and no more than 85 C, 83 C or 82 C, for a time period of at least 15 seconds, 20 seconds or 30 seconds and no more than 3 minutes, 2.5 minutes or 2 minutes. In some embodiments step c) comprises heating the mixture at between 79 C and 85 C for between 15 seconds and 3 minutes, or at a temperature between C and 82 C for a time period of between 30 seconds and 2 minutes. The mixture may also be heat treated by Ultra High Temperature (UHT treatments, for example between 1 second and 5 seconds at a temperature of between 110°C and 130°C.

The method may include a step d) of cooling the mixture to below ambient temperature after step c). The mixture may be cooled to a temperature of no more than C, 10 C or 5 C, as in some embodiments may be cooled to between 2 C and 5 C. One embodiment of the invention provides a method of manufacturing a comestible product comprising the steps of: a) incubating a mixture of milk product and rennet at a temperature of between C and 45 C for a time period of between 15 minutes and 40 minutes; b) adjusting the pH of the mixture to between 7.1 and 7.7; e) heating the mixture between 65 C and 73 C for a time period of between 30 seconds and 15 minutes, or at a temperature of between 78 C and 85 C for a time period of between 15 seconds and 5 minutes; and d) cooling the mixture.

According to the method of the invention the resultant comestible product comprises a thickened milk product having good organolcptic and textural properties that requires no stabilising or thickening agents.

According to a second aspect of the invention there is provided a comestible product manufactured by the method of the first aspect of the invention.

The comestible product may be a thickened milk product, and may for example be a thickened milk, milkshake, milk gel, or the like.

The invention will now be described with reference to the following non-

limiting Examples.

Examples

Example 1

A comestible milk drink was prepared by the method of the invention in the following manner: Strawberry flavour, colorant, 20 g sucrose and 480 ml of semi-skimmed milk were mixed well and the mixture was incubated in a water bath until the temperature of milk mixture reached 40°C. The protein content was 3.4% (w/w). 5 ml of 102 diluted rennet was added to the milk mixture, and subsequently the rennet-milk was incubated at 40°C for 30 minutes. The pH of the rennet-milk mixture was raised to 7.4-7.5 with I M sodium hydroxide. Afterwards the rennet-milk mixture was heated to 80°C-82°C for 0.5-2 minutes. After heat treatment, the rennet-milk was cooled to 4°C with ice-water.

Positive and negative controls were also used to determine the characteristics of the milk products prepared by the method of the invention compared to milk products not prepared by the method of the invention.

Positive control: Commercial strawberry flavoured milk drink from a supermarket in the UK, which contained semi-skimmed milk (94%), sugar, skimmed milk powder, concentrated strawberry juice, stabiliser (Carrageenan, Xanthan gum), flavouring and colours.

Negative control: 480 ml of semi-skimmed milk added with 20 g sucrose, strawberry flavour and colorant was heat-treated under the same conditions as the Example 1 product rennet-milk. The negative control did not include the addition of rennet. This was used as control in all tests of functionality.

Results I. Measurement of turbidity Turbidity of the Example 1 milk product and the negative control was calculated as follows: The turbidity meter used was a Ratio White Light Nephclometer (operable in ratio and non-ratio modes). This equipment uses a nephelometric detector at 90° to the incidcnt light as the primary detector, and includes other detectors to minimize interference.

(I) Turbidity buffer The buffer contained 10% sucrose, 0.1 M Na2PO3, pH 9.0.

(2) Measurement 1 ml of rennet-incubated milk product (or negative control) was added to 30 ml of turbidity buffer. The diluted sample was introduced into a 30 ml glass euvette for analysis in the turbidity-meter. The glass cuvette was capped and inverted twice to mix the solution and the turbidity was measured after 30 seconds. The results are shown in Table I below: Table 1 Turbidity of the samples Sample Turbidity Example I Milk mixture before addition of rennet (pH 6.6) 1921 Example 1 Milk mixture incubated with rennet for 20 1978 minutes (pH 6.6) Example 1 Milk mixture incubated with rennet for 25 1977 minutes (pH 6.6) Example 1 Milk mixture incubated with rennet for 26 2023 minutes (pH 6.6) Example 1 Milk mixture incubated with rennet for 27 2057 minutes (pH 6.6) Example 1 Heat-treated rennet-milk mixture (pH 7.5) 1607 Example 1 Negative control after the same heat treatment 2011 2. Viscosity measurement: Viscosity of the Example 1 milk product and positive and negative controls was analysed as follows: Viscosity of the Example I milk product and the controls was measured at 4°C with a Brookfield DV-l+yiscometcr, and the results are shown in Table 2 below: Table 2 viscosity of the samples Sample Viscosity (cP) Example I Milk mixture before addition of rennet (p1-I 6.6) 1.2 Example I Heat-treated rennet-milk mixture (pH 7.5) 9 Negative control after the same heat treatment 1.4 Positive control -Commercial strawberry flavoured milk 8 from supermarket (containing Carrageenan and xanthan gum) 3. Average particle size measurement Average particle size of the Example 1 milk product and negative control was measured as follows: The average particle size (D 0,5) of each sample was measured by laser light diffraction using a Mastersizer 2000 (Malvem Instruments Ltd, Malvern, U.K.) at a refractive index (RI) of 1.470, and the laser obscuration was about 10%. The results are shown in Table 3 below: Table 3 Average particle size of the samples Sample D 0,5 (pm) Example 1 Milk mixture before addition of rennet (pH 6.6) 0.178 Example 1 Heat-treated rennet-milk mixture (pH 7.5) 11.648 Negative control after the same heat treatment 0.189 4. Stability The milk product of Example 1 was stable after 7 days; no difference in stability or colour was observed, over the 7 day storage period.

5. Sensory evaluation The milk product of Example 1 had a creamier mouth-feel than the negative control and a similar mouth-feel to the positive control.

Example 2

A second Example of a milk product manufactured by the method of the invention was prepared as follows: Vanilla flavour, colorant, 20 g sucrose, 10 g skimmed milk powder and 470 ml of semi-skimmed milk were mixed well and the mixture was incubated in a water bath until the temperature of milk mixture reached 40°C. Protein content was 3.9% (w 1w).

ml of 102 diluted rennet was added to above milk mixture, and subsequently the rennet-milk was incubated at 40°C for 25 minutes. The pH of the rennet-milk mixture was raised to 7.4-7.5 with I M sodium hydroxide. Afterwards the rennet-milk mixture was heated to 69°C-73°C for 1-10 minutes. After heat treatment, the rennet-milk mixture was cooled to 4°C with ice-water.

Positive control: Commercial vanilla flavoured milk from a supermarket, which contained semi-skimmed milk(94%), sugar, skimmed milk powder, stabiliser (Carrageenan, Xanthan gum), flavouring and colours Negative control: 470 ml of semi-skimmed milk added with 20 g sucrose, 10 g skimmed milk powder, vanilla flavour and colorant was heat-treated as the same conditions as the milk products of Example 2. The negative control did not include addition of rennet. This was used as control in all tests of functionality.

I. Measurement of turbidity Turbidity of the Example 2 milk product and the negative control was calculated as follows: The method and buffer for measuring turbidity were the same as Example 1, and the results were as shown in Table 4 below: Table 4 Turbidity of the samples Sample Turbidity Example 2 Millc mixture before addition of rennet (pH 6.6) 2213 Example 2Milk mixture incubated with rennet for 10 minutes 2265 (pH 6.6) Example 2 Milk mixture incubated with rennet for 20 2291 minutes (pH 6.6) Example 2 Milk mixture incubated with rennet for 22 2301 minutes (pH 6.6) Example 2 Heat-treated rennet-milk mixture (pH 7.5) 1816 Example 2 Negative control after the same heat treatment 2281 2. Viscosity measurement: Viscosity of the Example 2 milk product, positive control and negative control was determined as follows: Viscosity of vanilla flavoured milk product and the controls was measured at 4°C with a Brookfield DV-1+viscometer. The results are shown in Table 5 below: Table 5 viscosity of the samples Sample Viscosity (cP) Example 2 Millc mixture before addition of rennet (pH 6.6) 1.4 Example 2 Heat-treated rennet-milk mixture (pH 7.5) 13 Negative control after the same heat treatment 1.7 Positive control Commercial strawberty flavoured milk from 9 supermarket (containing Carrageenan and xanthan gum) 3. Average particle size measurement Average particle size of the Example 2 milk product and negative control was determined as follows: The average particle size (D 0,5)of the samples milk product was measured by laser light diffraction using a Mastersizer 2000 (Malvern Instruments Ltd, Malvern, U.K.) at a refractive index (RI) of 1.470, and the laser obscuration was about 10%.

The results are shown in Table 6 below: Tabic 6 Average particle size of the samples Sample D 0,5 (jim) Example 2 Milk mixture before addition of rennet (pH 6.6) 0.178 Example 2 Heat-treated rennet-milk mixture (pH 7.5) 12.865 Negative control after the same heat treatment 0.203 4. Stability The milk product of Example 2 was stable after 7 days; no difference in stability or colour was observed.

5. Sensory evaluation The milk product of Example 2 had a creamier mouth-feel than thc negative control and a similar mouth-feel to the commercial vanilla flavoured milk.

As can be seen from the above results that comestible products can be made by the method of the invention which are at least as satisfactory as similar commercialised products if not better, but without the need for thickening agcnts such as carrageenan or xanthan gum, which suffer from a number of disadvantages as discussed above.

The above embodiments arc described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

Claims I. A method of manufacturing a comestible product, comprising the steps of: a) incubating a mixture of a milk product and rennet; b) adjusting the pU of the mixture to above pH 7.0; and c) heating the mixture to inactivate the rennet.
2. A method as claimed in claim I wherein the milk product comprises milk and optionally one or more ingredients selected from a colour, flavour and sweetener.
3. A method as claimed in claim 2 comprising at least one sweetener independently selected from a saccharide, sugar alcohol or high intensity sweetener.
4. A method as claimed in any one of claims I to 3 in which no thickening agent or stabilising agent is added to the mixture.
5. A method as claimed in any proceeding claim wherein step a) comprises incubating the mixture of milk product and rennet at a temperature of between 35°C and 45°C, for a time period of between 5 minutes and 45 minutes.
6. A method as claimed in any preceding claim wherein the concentration of rennet added to the milk product in step a) is between 0.00 1% and 0.05% w/w relative to the concentration of milk protein in the mixture.
7. A method as claimed in any proceeding claim wherein step b) comprises adjusting the pH to between pH 7.1 and pH 7.9.
8. A method as claimed in any proceeding claim wherein step b) comprises adjusting the pH to above 7.0 by addition of an alkali.
9. A method as claimed in claim 8 wherein the alkali comprises at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium carbonate or a mixture thereof
10. A method as claimed in any proceeding claim wherein step c) comprises heating the mixture to a temperature of between 65°C and 75°C for a time period of between 20 seconds and 15 minutes.
11. A method as claimed in any one of claims 1 to 9 wherein step c) comprises heating the mixture to a temperature of between 78°C and 85°C for a time period of between 15 seconds and 3 minutes.
12. A method as claimed in any preceding claim further comprising a step d) of cooling the mixture to below ambient temperature after step c).
13. Amethodasclaimedinclaiml2whereinthemixtureiscooledtoa temperature of no more than 10°C.
14. A comestible product manufactured by the method of any one of claims I to 13.
15. A comestible product as claimed in claim 14 comprising a thickened milk product, milkshake, milk gel or yogurt.
16. A method or comestible product substantially as described herein.