WO1996024261A1

WO1996024261A1 - Food product and method of manufacture

Info

Publication number: WO1996024261A1
Application number: PCT/EP1996/000489
Authority: WO
Inventors: Malcolm John Mcbride; Serge Alfred Symien; Peter Walker; Alan Wooten; James Thomas Mullin
Original assignee: Unilever Plc; Unilever N.V.
Priority date: 1995-02-09
Filing date: 1996-02-06
Publication date: 1996-08-15
Also published as: AU4788096A

Abstract

A three-dimensional product and a process for the manufacture thereof is disclosed. The process comprises the steps of: (a) forming a primary shape from a food dough; (b) transferring the primary shape into a split mould; (c) applying pressure to the mould such that the primary shape is deformed into the shape of the mould; and (d) removing the shaped product from the mould; wherein during moulding the primary shape has an outer layer having a temperature of no higher than -3 °C, and a core having a temperature in the range of from -3 °C to 80 °C.

Description

Food Product and Method of Manuf c ure

Technical Field of the Invention

The invention relates to three-dimensional shaped food products, especially three-dimensional shaped, filled food products and particularly three-dimensional shaped poultry products, and a method of manufacture.

Background of the Invention

It is desirable to be able to manufacture true three- dimensional shaped food products.

Conventional three-dimensional shaping has been conducted on frozen food products (typically at -20°C) because it was taught that the frozen condition was required to retain the shape imparted to the food during the shaping step.

EP-A-0153024 discloses a method for forming a non- cylindrical coextrudate having a meat body and a fat coating, wherein the coextrudate is superficially frozen in a tunnel freezer prior to being moulded, thereby hardening at least the surface of the product to make it dimensionally stable.

However, for food products which require pasteurisation or sterilisation prior to storage, for example poultry products, it is desirable to limit the proportion of ice in the product during shaping and to concentrate the ice in the outer layer of the product during shaping, such that the thermal energy required for pasteurisation or sterilisation is as low as possible.

Superficially freezing a meat body in a tunnel freezer does not minimise the proportion of ice in the product, since a relatively deep frozen outer layer is formed. This is because freezing using a tunnel freezer is relatively slow.

There is a clear requirement for a highly flexible and low energy shaping process which can be used to manufacture true three-dimensional food products, which may contain a filling if desired, and which may be of any complex geometrical shape.

Disclosure of the Invention

Accordingly, the invention provides a process for the manufacture of a three-dimensional food product comprising the steps of;

(a) forming a primary shape from a food dough;

(b) transferring the primary shape into a split mould;

(c) applying pressure to the mould such that the primary shape is deformed into the shape of the mould;

(d) removing the shaped product from the mould;

wherein during moulding the primary shape has an outer layer having a temperature of no higher than -3°C, and a core having a temperature in the range of from -3°C to 80°C.

The primary shape therefore consists of a core enclosed by an outer layer. The core and the outer layer may be of the same material . The core optionally comprises a filling (ie. of a different material) .

Providing a primary shape with such a temperature profile during moulding minimises the thermal energy required to achieve pasteurisation or sterilisation thereof, whilst giving the primary shape sufficient rigidity to extract the final shaped product from the mould and to prevent loss of the shape during subsequent handling of the product. It is important that the thickness of the frozen outer layer is as small as possible, so that a minimal amount of energy is required to heat the frozen outer layer through its latent heat zone when the shaped product is subsequently heated during pasteurisation or sterilisation and the frozen outer layer consequently defrosts.

Keeping the core at a temperature of at least -3°C avoids the core going through a latent heat zone when the shaped product undergoes subsequent pasteurisation or sterilisation.

In a preferred process the primary shape is submerged in a cryogenic liquid, for example liquid nitrogen, for a time sufficient to freeze only the outer layer of the primary shape to a temperature of no higher than -3°C, the core of the product being at a temperature of from -3°C to 80°C. In this process the outer layer of the primary shape will, at least initially, be at a very low temperature. The product is subsequently transferred to a split mould, as soon as possible, preferably within 30 seconds, more preferably within 10 seconds.

In an alternative preferred embodiment, the desired temperature profile of the primary shape during moulding is achieved by contacting the primary shape with a cryogenically-cooled mould (eg. a mould cooled using liquid nitrogen) . This eliminates any heat transfer between the freezing and moulding steps.

The actual temperature of the primary shape will generally be selected according to the subsequent processing steps.

In accordance with this invention, the temperature of the primary shape during moulding increases from its outer surface to its core. Preferably, the average temperature increase (or thermal gradient) over a distance of 1mm from the external surface of the outer layer to a distance of 3mm from the external surface of the outer layer (measured towards the core) is at least 0.5°C per mm, preferably at least 1.0°C per mm, more preferably at least l.5°C per mm. In a preferred embodiment (see examples 1 and 2) it is 2°C per mm.

The primary shape may conveniently be formed by any suitable means, for example, plate moulding or extrusion of the food dough.

The primary shape will have the same volume as the final three-dimensional shape to be formed.

It is preferred that the primary shape is formed by extrusion because this permits greater flexibility, for example, the food dough may be co-extruded with a suitable filling such that a filled three-dimensional shape can be formed.

When the dough is co-extruded with a filling, the primary shape thus formed is such that the filling is completely encased by the food dough.

The filling material may be any edible foodstuff and includes for example cheese, mashed potato, vegetable pieces, fish, meat, herbs, sauce and mixtures thereof.

The dough and filling may be coextruded at different temperatures . To minimise thermal processing during subsequent pasteurisation or sterilisation, the filling may have a temperature during moulding of from 0°C to 80°C.

An example of a suitable filling is as follows: % by weight Full fat milk powder 5

Modified starch 3.2

Cheese 23.8 Salt 0.4

Herbs & spices 3

Water 49.6

Food pieces 15

The food pieces may, for example, be diced mushrooms, vegetable pieces, ham, fish and mixtures thereof.

The mould is provided in two halves, and may provide an infinite number of complex shapes. Examples of moulds used are shown in Figures 1 to 4.

The pressure to be applied to the mould need only be sufficient to deform the primary shape into the required three-dimensional shape. The pressure may be applied by any suitable means. Typically a pressure of from 30 to 150 psi will be required to deform a primary shape having an outer surface temperature of approximately -6°C and a core temperature of 20°C.

The food dough may be of any composition and may comprise finely comminuted food pieces or much larger food pieces mixed with salts and extenders to form a matrix, the composition of which is obvious to those skilled in the art.

The food dough may comprise vegetable, meat or a mixture thereof. The meat may be selected from fish, poultry, beef, lamb, pork, veal, ham and mixtures thereof. Preferably the meat is poultry.

After moulding, the product is normally pasteurised at 75°C for 8 seconds or at 72°C for 2 minutes, before being deep frozen for storage.

Description of Figures 1 to 4

Figures 1 to 4 show examples of a suitable mould.

Figure 1 Shows a split mould in the closed position where

1 and 2 represent the two halves of the mould Figure 2 Shows a cross section along the line A-A in figure 1. 3 is the true 3D-shaped cavity formed by the mould Figure 3 Shows a cross section along the line B-B in figure 1 Figure 4 Shows an open mould wherein the cavity defines a complex 3D chick shape

Examples

Example 1 3-D shaping of a poultry meat produce from a shell frozen primary shape

The following ingredients were mixed together on a twin intermesh paddle mixer to form a dough.

Finely comminuted poultry meat at -1°C 84%

(prepared on Comitrol mill fitted with 360 head)

Flavouring + rusk + salt 5%

Vegetable pieces 5%

Water 6%

The dough was transferred to an extrusion device where it was shaped into a continuous rope of approximately 34mm diameter. The rope was subsequently sectioned into lOOg portions.

Portions were immersed in liquid Nitrogen. After 15 seconds, the portions were removed and temperatures were measured at 3 locations:

Approximately 1mm below the surface -8°C Approximately 3mm below the surface -4°C

At the centre of the product +2°C

Portions thus treated were located into the lower half cavity of a metal mould in the shape of a chicken breast. The upper half of the mould was applied to the lower half using a pneumatic press registering 75 psi on the dial .

On release of the pressure, the mould was separated and the product in the perfect shape of a chicken breast was extracted.

Example 2 : 3-D shaping of a filled poultry meat product from a shell frozen primary shape

Finely comminuted poultry meat at -1°C 84%

(prepared on Comitrol mill fitted with 360 head) Flavouring + rusk + salt 5%

Vegetable pieces 5%

Water 6%

A filling was prepared by mixing the following ingredients in a Hobart bowl mixer. The filling had a temperature of about 20°C.

Potato granules 28%

Water 70% Salt 2%

The dough and filling were transferred to a twin stream co- extrusion device where an outer annulus of meat dough was extruded around discrete slugs of filling of 17mm diameter and approximately 8.5cm length to form a continuous cylindrical rope of approximately 34mm diameter. This rope was subsequently sectioned into lOOg portions each containing a fully encased slug of filling.

Portions were immersed in liquid Nitrogen. After 15 seconds, the portions were removed and temperatures were measured at 4 locations:

Approximately 1mm below the surface -8°C

Approximately 3mm below the surface -4°C

At the interface between meat and filling +10°C At the centre of the product +20°C

Portions were located into the lower half cavity of a metal mould in the shape of a chicken breast. The upper half of the mould was applied to the lower half using a pneumatic press registering 30 psi on the dial.

On release of the pressure, the mould was separated and the product in the perfect shape of a chicken breast was extracted. On sectioning the product, it was found that the filling had remained as an undivided entity fully encased in a substantially regular outer layer of meat.

Example : 3-D shaping of filled poultry meat product from a shell frozen primary shape

The following ingredients were mixed together on a twin intermesh paddle mixer to form a dough. The resulting mixture had a temperature of -3°C.

Finely comminuted poultry meat 84%

(prepared on Comitrol mill fitted with 360 head) Flavouring + rusk + salt 5% Vegetable pieces 5%

Water 6%

A filling was prepared by mixing the following ingredients in a Hobart bowl mixer. The filling had a temperature of about 73°C during mixing.

Potato granules 28%

Water 70% Salt 2%

The dough and filling were transferred to a twin stream co- extrusion device where an outer annulus of meat dough was extruded around discrete slugs of filling of 17mm diameter and approximately 8.5cm length to form a continuous cylindrical rope of approximately 34mm diameter. The temperature of the filling was 56°C. This rope was subsequently sectioned into lOOg portions each containing a fully encased slug of filling.

Portions were immersed in liquid Nitrogen. After 10 seconds, the portions were removed and temperatures were measured at 3 locations:

Approximately 1mm below the surface -8°C

Approximately 3mm below the surface -3°C

At the centre of the product +55°C

On release of the pressure, the mould was separated and the product in the perfect shape of a chicken breast was extracted. On sectioning the product, it was found that the filling had remained as an undivided entity fully encased in a substantially regular outer layer of meat

Description of Figures 5 to 12

Figures 5 to 12 show the results of simulations of the shell freezing of poultry products. In each figure, predicted temperature profiles are shown, by plotting the distance from the centre of the product x (cm) against temperature y (°C) . Table I is a key to the lines plotting the temperature profiles for each figure.

Table I

0 seconds

1 second

2 seconds

o seconαs

10 seconds

30 second

The product investigated in these simulations was a cylindrical poultry product possessing a mash potato core; the diameter of the product was 3.4 cm, and the diameter of the potato core was 1.7 cm. The product was considered to be exposed to a very cold environment for a short time, and then withdrawn therefrom. The resulting thermal changes were considered to be confined to a thin shell at the exterior surface of the cylindrical product.

The scenarios that were simulated were (i) dipping in a liquid Nitrogen bath and (ii) contacting with a cylindrical cryogenic plate (or mould) .

The model that was developed for these simulations was an axisymmetric MARC (Trade Mark) model (from MARC Europe) of the radial heat transfer in the cylindrical product. The associated 2-D Finite Element mesh consisted of a rectangle in the z-r plane of dimensions 0.2 cm by 1.7 cm. The bottom edge was the axis of the cylindrical product, the two side edges were zero heat flux surfaces perpendicular to the axis, and the top edge was the outer surface of the cylinder. The cylinder was considered to be infinitely long, and it was considered that all heat transfer took place in the radial direction; since the product was nearly 9.0 cm long, this was a reasonable approximation to make considering the very short time scales investigated compared to the thermal time scale of the product. The lower 0.85 cm of the model mesh was considered occupied by mash potato material, and the upper 0.85 cm was considered occupied by chicken material . The thermophysical properties of the chicken material that were used were the measured properties of chickstick, and the thermophysical properties of mash potato were the COSTHERM (Trade Mark of MRI Bristol) predicted properties of mash potato.

In the simulations, the product was exposed to liquid Nitrogen for 10 seconds, and then exposed to still air conditions at 10°C for 30 seconds. (i) Shell freezing usinσ a liquid Ni roσen Bath

The model simulations considered the heat transfer in the cylindrical product exposed to a liquid Nitrogen bath for 10 seconds, followed by the heat transfer for up to 30 seconds after removal from the bath. The boundary conditions during immersion were set to:

surface heat transfer coefficient = 150 W/sq.m. -°C. ambient temperature = -196°C

and after immersion, were set to:

surface heat transfer coefficient = 10 W/sq.m. -°C. ambient temperature = 10°C.

Four simulations were performed, consisting of all combinations of the mash potato core at initial temperatures of 20°C and 70°C, and the chicken at -3°C and -6°C. The radial temperature profiles for the four cases at 0, 1, 2, 5, 10 and 30 seconds after removal from the liquid Nitrogen bath are shown in figures 5 to 8.

Figure 5: chicken shell temperature -3°C mash core temperature 20°C

Figure 6: chicken shell temperature -3°C mash core temperature 70°C

Figure 7: chicken shell temperature -6°C mash core temperature 20°C

Figure 8: chicken shell temperature -6°C mash core temperature 70°C

In all four cases, at the instance of removal from the bath, the initial step change in temperature between the mash core and chicken layer was eroded but not significantly (the central core temperature was unchanged) and the surface temperature was below -30°C for the higher initial chicken temperature (-3°C) and below -40°C for the lower initial chicken temperature (-6°C) . In all four cases, the surface temperature rose rapidly in the first 10 seconds after removal, and changed much more slowly after that . In the cases where the chicken layer temperature was -3°C, a 1.5mm thick frozen shell was formed whose temperature varied from -8.7°C at 10 seconds after removal to -6.3°C at 30 seconds after removal; the remainder of the chicken layer largely remained at -3°C throughout, although a 1mm layer at the mash interface had undergone thawing by 30 seconds after removal. In the cases where the chicken layer temperature was -6°C, a 3 mm thick frozen shell was formed whose temperature varied from -18.0°C at 10 seconds after removal to -12.6°C at 30 seconds after removal; the remainder of the chicken layer did not maintain its original temperature, but none of it melted, even up to 30 seconds after removal from the bath.

(ii) Shell freezing using cryogenic plate contact-

The cryogenic plate contact freezing scenario was simulated using a three-material model consisting of the 1.7 cm radius product in contact with a 1 cm thick cylindrical stainless steel plate. Perfect thermal contact was assumed between the plate and the outer chicken layer for the first 10 seconds in each simulation; the outer surface of the plate layer was fixed at -120°C. At this point the plate was "removed" from contact, and a convective heat transfer boundary condition was imposed on the outer chicken surface for a further 30 seconds with

heat transfer coefficient = 10 W/sq.m. -°C; ambient temperature = 10°C. Four simulations were performed, consisting of all combinations of the mash potato core at initial temperatures of 20°C and 70°C, and the outer chicken layer at -3°C and - 6°C . The radial temperature profiles for the four cases at 0, 1, 2, 5, 10 and 30 seconds after removal from contact with the cryogenic plate are shown in figures 9 to 12.

Figure 9 : chicken shell temperature -3° mash core temperature 2CfC

Figure 10: chicken shell temperature -3°C mash core temperature 70C

Figure 11: chicken shell temperature -£C mash core temperature 2ff€

Figure 12: chicken shell temperature -ffC mash core temperature 7CTC

As with the previous cases, the initial step temperature change between the mash core and the chicken layer underwent some erosion. The outer surface of the chicken layer was cooled to approximately -100°C at the end of concact, and rapidly increased in temperature in the first 10 seconds after removal from contact, and less rapidly thereafter. In all cases, a 3mm thick deep frozen shell was formed. In the cases where the chicken layer temperature was -3°C, the shell temperature varied from -34.5°C at 10 seconds after removal from contact to -19.0°C at 30 seconds after removal. In the cases where the chicken layer was -6°C, the shell temperature varied from -48.0°C at 10 seconds after removal to -31°C at 30 seconds after removal .

In conclusion, the use of a liquid Nitrogen bath or cryogenic plate contact should result in frozen outer shells which maintain their lowered temperatures very well for up to 30 seconds after removal.

Claims

1. A process for the manufacture of a three-dimensional food product comprising the steps of;

(a) forming a primary shape from a food dough;

(b) transferring the primary shape into a split mould;

(c) applying pressure to the mould such that the primary shape is deformed into the shape of the mould; and

(d) removing the shaped product from the mould;

2. A process according to claim 1, wherein the average thermal gradient of the primary shape during moulding, over a distance of 1 mm from the external surface of the outer layer to a distance of 3 mm from the external surface of the outer layer, is at least 0.5°C per mm.

3. A process according to claim 2, wherein the average thermal gradient of the primary shape during moulding, over a distance of 1 mm from the external surface of the outer layer to a distance of 3 mm from the external surface of the outer layer, is at least 1.0°C per mm.

4. A process according to claim 3 , wherein the average thermal gradient of the primary shape during moulding, over a distance of 1 mm from the external surface of the outer layer to a distance of 3 mm from the external surface of the outer layer, is at least 1.5°C per mm.

5. A process according to claim 4, wherein the average thermal gradient of the primary shape during moulding, over a distance of 1 mm from the external surface of the outer layer to a distance of 3 mm from the external surface of the outer layer, is at least 2°C per mm.

6. A process according to any preceding claim wherein the outer layer has a temperature of no higher than -6°C.

7. A process according to any preceding claim, wherein the primary shape is dipped into liquid nitrogen prior to being transferred into the split mould.

8. A process according to any one of claims 1 to 7, wherein the split mould is cryogenically-cooled.

9. A process according to any preceding claim wherein the food dough comprises meat, vegetable or mixtures thereof.

10. A process according to claim 9 wherein the meat is selected from fish, poultry, beef, lamb, pork, veal, ham and mixtures thereof.

11. A process according to any preceding claim wherein the primary shape is formed by co-extrusion of the food dough and a filling, such that in the primary shape the food dough encases the filling.

12. A process according to claim 11, wherein the filling has a temperature of from 0°C to 80°C during the moulding of the primary shape.

13. A process according to claim 11 or claim 12 wherein the filling may be any edible material and includes, for example, cheese, mashed potato, vegetable pieces, fish, meat, herbs, sauce and mixtures thereof.

14. A three-dimensional food product obtainable by; (a) forming a primary shape from a food dough;

(b) transferring the primary shape into a split mould;

(d) removing the shaped product from the mould;

15. A three-dimensional food product obtainable by;

(a) co-extruding a food dough and a filling to form a primary shape wherein the food dough encases the filling;

(b) transferring the primary shape into a split mould;

(d) removing the shaped, filled, product from the mould;