WO2015142167A1

WO2015142167A1 - Method for preparing food products by means of co-extrusion

Info

Publication number: WO2015142167A1
Application number: PCT/NL2015/050157
Authority: WO
Inventors: Johannes Marinus Quirinus KOOLS; Geert Johannes LOK; Johannes Martinus Meulendijks
Original assignee: Marel Townsend Further Processing B.V.
Priority date: 2014-03-19
Filing date: 2015-03-12
Publication date: 2015-09-24
Also published as: NL2012471A; NL2012471B1

Abstract

The present invention relates to a method for preparing food products by means of co-extrusion, comprising the steps of providing a food dough, providing a viscous gelling agent, co-extruding a strand of food dough and an external layer of viscous gelling agent, wherein the viscous gelling agent at least partially encloses the strand of food dough, treating the exterior of the food strand with an aqueous salt solution, dividing the food strand into separated parts, and further heating the separated parts, wherein during heating the separated parts according to processing step f) the temperature of at least the outer surface of the separated parts does not exceed the shrinkage temperature (T_s) of the viscous gelling agent. The present invention further relates to a sausage produced by the process according to the present invention.

Description

METHOD FOR PREPARING FOOD PRODUCTS BY MEANS OF CO-EXTRUSION

The present invention relates to a method for manufacturing sausage products by means of co-extrusion, wherein the method comprises the following steps of: a) providing a food dough; b) providing a viscous paste; c) co-extruding a strand of food dough and an external layer of viscous gelling agent, wherein the viscous gelling agent at least partially encloses the strand of food dough; d) treating the exterior of the food strand with an aqueous salt solution; e) dividing the food strand into separated parts; and f) heating the separated parts.

Such a method is known from, among others, NL 2001619. In the known method the co-extruded sausage strand is very vulnerable shortly after co-extrusion, whereby it can easily deform permanently. Therefore, NL 2001619 provides a method wherein the firmness is imparted to the co-extruded sausage strand in more rapid manner. NL 2001619 discloses that a sufficient firmness can already be obtained by coagulating the periphery of the meat dough or the coagulation of (a part of) the casing to enable further processing, such as particularly the manipulation of the sausage, e.g. separation of the food strand into individual separated parts. NL 2001619 provides for this purpose two methods of the type stated in the preamble of claim 1, with which the desired result can be obtained, i.e. adding a structure improver to the viscous paste during the co-extrusion and/or heating the outer side of the sausage within 50 seconds following co-extrusion, i.e. step c) as identified above, with a liquid-containing medium to at least the initial temperature of the coagulation range of the paste or the food dough. After separation of the food strand into individual separated parts, the formed sausages are heated, i.e. step f) as identified above, in a moist environment in order to cook them to increase the product stability to allow the formed sausages to be vacuum-packed and pasteurized.

The above-described method has the drawback that the surface conditions of the sausages formed, e.g. surface smoothness, surface colouring, surface cooking characteristics, or the like, may be negatively influenced by the necessary heating step f). An object of the present invention is to provide an improved method for manufacturing sausage products, such as for instance, though not exclusively, "Bratwurst",

Weisswurst", Frankfurters, hot dogs and fresh sausage, of the type stated in the preamble of claim 1 with which, while retaining the advantages of the prior art, co- extruded sausages can be manufactured wherein the surface conditions of the co- extruded formed sausages, such as surface smoothness, surface colouring, surface cooking characteristics, or the like, can be controlled.

The present invention provides for this purpose a method of the type stated in the preamble of claim 1 with which the desired control of the surface conditions of the formed food product can be obtained. It was found that a stable co-extruded food product can be obtained and the surface conditions of the co-extruded food product can be controlled during heating of the separated parts according to processing step f) if the temperature of at least the outer surface of the separated parts does not exceed the shrinkage temperature (T_s) of the viscous gelling agent. By providing a method wherein the temperature of the outer surface of the separated parts does not exceed the shrinkage temperature of the viscous gelling agent, at least the outer surface of the product is stabilized. Even further, the surface conditions obtained of the produced sausage are controlled during heating the separated parts according to processing step f) of the present invention and maintained during any subsequent heating step. The present invention therefore provides a method wherein the separated food products are sufficiently stabilized for further processing of the food product, without reduction of surface conditions during the stabilizing step, i.e. processing step f) of the present invention, and wherein the surface conditions of the obtained food product are maintained during any further processing step of the food product, including any subsequent heating step.

The shrinkage temperature (T_s), also referred to as shrink temperature, shrinking temperature or crimp temperature, is dependent on the type and quality of the viscous gelling agent used. For example, the shrinkage temperature of collagen is, depending on the quality and type of collagen used, about 60-70°C, whereas the shrinkage temperature of myofibrillar proteins lies in the temperature range of 30-50°C. The shrinkage temperature of the viscous gelling agent can be determined by methods known in the art. For example, the shrinkage temperature of the viscous gelling agent may be determined by a calorimeter measurement carried out by a differential scanning calorimeter (DSC). The onset of the endothermic transition may be taken to be the shrinkage temperature of the samples (see for example: Calderon et al.; European Cells and Materials; Type II Collagen-Hyaluronan Hydrogel - A Step Towards a Scaffold for Intervertebral Disc Tissue Engineering; 2010, vol. 20, p. 134-148; Chang et al.;

DSC Analysis of Heat-induced Changes in Thermal Characteristics of Connective Tissue Collagen from Beef Semitendinosus Muscle; 2011, vol. 32(13), p. 49- 53; and Fernandez-Martin et al.; Journal of Food Science; Protein Denaturation and Structural Damage During High-Pressure-Shift Freezing of Porcine and Bovine Muscle; 2000, vol. 65(6), p. 1002-1008). Other measurement techniques, such as dynamic mechanical thermal analysis (DMTA) or thermo mechanical analysis (TMA) may be used as well to determine the shrinkage temperature of the viscous gelling agent (see for example: Jeyapaline, et al.; Journal of the Society of Leather Technologists and Chemists; Dynamic Mechanical Thermal Analysis (DMTA) of Leather; 2007, vol. 91, p. 236).

The viscous gelling agent may be any edible gelling agent suitable for providing an external layer of viscous gelling agent, e.g. casing material, at least partially enclosing a strand of food dough. Preferably the viscous gelling agent is selected from collagen, alginate, cellulose and/or combinations thereof. In an embodiment of the present invention, the viscous gelling agent is selected from an alginate or an alginate comprising viscous gelling agent. The alginate comprising viscous gelling agent may further comprise proteins, such as collagen, dairy protein (e.g. casein), whey protein, meat protein (e.g. myofibrillar protein), egg albumen protein, blood plasma, soy protein, or the like.

For co-extrusion of a strand of food dough and an external layer of viscous gelling agent, a rotating nozzle, such as a spinning nozzle, may be used. The aqueous salt solution of processing step d), also called 'brining' step, may be applied onto the exterior of the extruded food strand using different techniques. In an embodiment of the present invention the aqueous salt solution is sprayed onto the food product and/or the food strand is guided through a bath comprising the aqueous salt solution. Optionally, the aqueous salt solution may further comprise an acid buffer solution, e.g. a citric acid buffer solution, to increase the casing stability.

Different techniques may be applied for heating the separated parts during processing step f) of the present invention. For example, the separated parts may be heated by using conduction, e.g. via heated air using an oven, radiation, e.g. a microwave, or the like. Particularly good results are obtained when the separated parts are heated with an aqueous medium. Preferably the aqueous medium is water. The separated parts may be heated during processing step f) of the present invention by bringing them in an aqueous medium bath and/or by bringing them in a flow of aqueous medium, e.g. steam. It is noted that during processing step f) of the present invention the temperature of the aqueous medium is chosen such that at least the outer surface of the separated parts does not exceed the shrinkage temperature (T_s) of the viscous gelling agent. Consequently, the temperature of the aqueous medium during processing step f) of the present invention may be higher than the shrinkage temperature (T_s), as long as the temperature of the outer surface of the separated parts does not exceed the shrinkage temperature (T_s). The chosen temperature of the aqueous medium depends on the time the separated parts are in contact with the aqueous medium and the starting temperature, e.g. surface or core temperature, of the separated parts themselves.

The method of the present invention may further comprise the step of g) heating the separated parts such that the temperature of at least a part of the separated parts exceed the shrinkage temperature (T_s) of the viscous gelling agent. By heating the separated parts at a temperature such that the temperature of at least a part of the separated parts exceed the shrinkage temperature (T_s) of the viscous gelling agent, the temperature of the core of the product is raised. Therefore, by providing subsequent to processing step f) of the present invention a further heating step g), the safety of the food product can be guaranteed. Furthermore, by providing a subsequent heating step according to processing step g) wherein the temperature of at least a part of the separated parts exceed the shrinkage temperature (T_s) of the viscous gelling agent the separated food products may be vacuum-packed without deformation of the food product. It was found that by providing a first heating step according to processing step f) of the present invention, i.e. a 'precooking' step, followed by a subsequent heating step according to processing step g), i.e. a 'cooking' step, the food product obtained, e.g. sausage, has improved surface properties compared to a food product directly heated at a temperature exceeding the shrinkage temperature (T_s) of the viscous gelling agent. Again, different techniques may be used to heat the separated parts during processing step g). Examples of heating techniques may include, but are not limited to, infrared radiation techniques, steam, heat transfer via convection and the like.

It is further noted that by providing a heating step according to processing step f) of the present invention, the exterior part of the separated product, i.e. the outer surface of the separated product, is sufficiently stabilized to allow further processing of the separated product in between heating step f) of the present invention and further heating step g). In other words, by providing a processing step f) of the present invention wherein the temperature of at least the outer surface of the separated part does not exceed the shrinkage temperature (T_s) of the viscous gelling agent, a food product at least partially enclosed by a crust-like material is formed. The formed crust-like material allows further processing of the separated food product, without running the risk of

deformation of the food product or to change the surface properties, e.g. surface smoothness, of the formed food product.

In an embodiment of the method of the present invention, the period of time heating the separated parts during processing step f) of the present invention is at least 10 seconds. It was found that a relatively short period is needed to sufficiently set the casing, i.e. at least the exterior part of the casing partially enclosing the food dough. Particularly good results regarding stability of the product and further processability are obtained when the period of heating the separated parts during processing step f) of the present invention is between 30 seconds and 3 minutes. It is noted that the period of heating the separated parts during processing step f) of the present invention may be more than 3 minutes, even more than 10 minutes or even more than 30 minutes. The longer the period of heating, the more stable the resulting product will be. However, due to economic reasons and process efficiency it may be advantageous to combine a relatively short period of heating the separated parts according to processing step f) of the present invention with a relatively longer period of subsequently heating the separated parts according to processing step g) of the present invention. In an embodiment of the method of the present invention, liquid smoke, acids, e.g. acetic acid, and/or calcium may be used during processing step f) of the present invention. In case the separated parts are heated with an aqueous medium, the liquid smoke, acids and/or calcium may be added to the aqueous medium used. It was found that the setting of the casing, i.e. the stability of the product, is increased even further in this manner. In case the viscous gelling agent is selected from alginate or alginate comprising viscous gelling agent, the use of liquid smoke, acids and/or calcium in the described manner is particularly preferred to provide a food product having increased surface characteristics, e.g. increased surface smoothness, compared to products directly heated for a period at a temperature exceeding the shrinkage temperature (T_s) of the alginate and/or alginate comprising viscous gelling agent.

The temperature of heating step f) of the present invention may be a constant temperature. Furthermore, in case a subsequent heating step g) is provided, the temperature in step g) may be changed to a different (in this case higher) constant temperature. In an embodiment of the method of the present invention, the temperature during processing step f) of the present invention and/or processing step g) may be adjusted gradually. In this embodiment the period of heating of the separated parts during processing step f) of the present invention may be determined by the gradual change of temperature in time, i.e. the time needed to reach the shrinkage temperature (T_s) of the viscous gelling agent used. The starting time of processing step g) may be determined by when the temperature of at least the outer surface of the separated parts exceed the shrinkage temperature (T_s) of the viscous gelling agent. It is further noted that the rate of change of temperature may be changed during the process as well.

In a further embodiment of the method of the present invention, the method further comprises the step of h) drying the heated separated parts using convection, air drying and/or electromagnetic radiation. By providing a separated food product heated according to processing step f) of the present invention, the food product is stabilized such that drying of the heated food product by applying a force to the exterior of the obtained food product is made possible.

In another aspect, the present invention relates to a sausage produced by the method according to the present invention. It was found that the sausage produced by the method of the present invention has improved surface characteristics, e.g. surface smoothness, surface colouring, surface cooking characteristics, or the like.

Example

An alginate gel was made based on an alginate powder and water wherein the ratio alginate/water was 8 to 100. The gel was made using a vacuum bowl chopper. The prepared alginate gel was co-extruded together with an emulsified meat dough using a stuff er and pump.

The extruded strand of food dough enclosed by alginate gel was guided through a brining bath containing 100 L water and 12 kg calcium chloride. After separation of the strand of food dough into separated food parts, the individual food parts were guided through a water bath comprising liquid smoke (ratio liquid smoke/water of about 1: 10) for 60 seconds. The temperature of the water bath was kept at a constant temperature of about 80°C.

Subsequently the separated food parts were cooked using a linear oven at a temperature in the range of 115°C to 135°C for 8 minutes.

The resulting products have a smoother surface compared to preparation methods wherein the separated food parts were cooked at a temperature in the range of 115°C to 135°C directly after separation of the extruded strand of food dough into separated food parts.

Claims

1. Method for preparing food products by means of co-extrusion, comprising the steps of:

a) providing a food dough;

b) providing a viscous gelling agent;

c) co-extruding a strand of food dough and an external layer of viscous gelling agent, wherein the viscous gelling agent at least partially encloses the strand of food dough;

d) treating the exterior of the food strand with an aqueous salt solution;

e) dividing the food strand into separated parts; and

f) heating the separated parts,

wherein during heating the separated parts according to processing step f) the temperature of at least the outer surface of the separated parts does not exceed the shrinkage temperature (T_s) of the viscous gelling agent.

2. Method according to claim 1, characterized in that the viscous gelling agent is selected from an alginate or an alginate comprising viscous gelling agent.

3. Method according to claim 1 or 2, characterized in that for the co-extrusion of the strand of food dough and the viscous gelling agent a rotating nozzle is used.

4. Method according to any of the preceding claims, characterized in that the aqueous salt solution is sprayed onto the food product and/or the food strand is guided through a bath comprising the aqueous salt solution.

5. Method according to any of the preceding claims, characterized in that the separated parts are heated during processing step f) with an aqueous medium.

6. Method according to claim 5, characterized in that the aqueous medium is water.

7. Method according to claim 5 or 6, characterized in that the separated parts are heated during processing step f) by bringing them in an aqueous medium bath.

8. Method according to any of claims 5-7, characterized in that the separated parts are heated during processing step f) by bringing them in a flow of aqueous medium.

9. Method according to any of the preceding claims, characterized in that the method further comprises the step of:

g) heating the separated parts such that the temperature of at least a part of the separated parts exceed the shrinkage temperature (T_s) of the viscous gelling agent.

10. Method according to claim 9, characterized in that in between heating step f) and heating step g) the separated part is further processed.

11. Method according to any of the preceding claims, characterized in that the time period of heating the separated parts during processing step f) is at least 10 seconds, preferably between 30 seconds and 3 minutes.

12. Method according to any of the preceding claims, characterized in that the temperature during processing step f) and/or processing step g) is adjusted gradually.

13. Method according to any of the preceding claims, characterized in that the method further comprises the step of:

h) drying the heated separated parts using convection, air drying and/or electromagnetic radiation.

14. Sausage produced by the method according to any of the preceding claims.