WO2006051278A1

WO2006051278A1 - Method of producing a food product

Info

Publication number: WO2006051278A1
Application number: PCT/GB2005/004296
Authority: WO
Inventors: Carla Ponsen; Arie Boelens; Nicholas Charles Avery
Original assignee: Loders Croklaan BV
Current assignee: Loders Croklaan BV
Priority date: 2004-11-09
Filing date: 2005-11-07
Publication date: 2006-05-18
Anticipated expiration: 2007-05-09
Also published as: WO2006051274A1

Abstract

A method of producing a food product having an outer casing and a filling, comprises co-extruding the filling together with a gel-forming mixture comprising collagen such that the mixture encases the filling, and bringing the extrudate into contact with an aqueous salt solution to form the food product. The mixture comprises tartaric acid. The food product thus formed has structural integrity without substantial drying or cross-linking.

Description

METHOD OF PRODUCING A FOOD PRODUCT

This invention relates to a method of producing a food product, to a process for preparing an edible product from the food product, and to the products thereby produced.

Food products having a filling and an outer casing, such as conventional sausages, can be produced by pre- forming a casing and subsequently adding the filler to the preformed casing. Alternatively, they can be produced by co-extrusion of the filling (such as uncooked sausage meat) together with a casing. In the co-extrusion method, a collagen-containing mixture that is capable of forming a gel is generally extruded around the filler and is subsequently caused to gel or otherwise become more firm, for example by immersion in an aqueous salt solution. The mechanism of gelling can involve dehydration of the gel in the relatively concentrated salt solution. The co-extruded mass, after gel formation, is formed into separate sausages, for example by crimping.

US 3,993,790 discloses the formation of a tubular food casing and is thus an example of a process in which a casing is pre-formed and subsequently filled. The casing is produced using a mixture containing collagen together with a strong acid and a weak acid. A process for producing casings is also disclosed in GB 1493795.

A process for producing fresh sausage by co-extrusion is described in WO 00/02463. The casing is treated with a flowable anti-dehydration agent before or after linking. A disadvantage with conventional co-extrusion processes, such as described above, is that they require air drying before the sausage attains structural integrity. It is not possible to handle or manipulate the sausage directly before air drying. Air drying is energy intensive and can cause problems such as heating, or even partial cooking, of the sausage meat or other filler.

EP-A-882403 seeks to solve the problem of air drying by avoiding heated aii- drying.

A further disadvantage associated with conventional processes is that the collagen must be cross-linked before the collagen casing attains structural integrity. The cross-linking is generally earned out using agents such as liquid smoke or aldehydes such as glutaraldehyde. Cross-linking is also sometimes termed "coagulation" in the art. However, cross-linking is a separate process from dehydration of the gel in the salt solution.

Although EP-A-0882403 avoids air drying, it employs liquid smoke as a cross-linking agent and the examples show that a process carried out in the absence of liquid smoke fails to give a useful product because the casing is too weak.

The present invention aims to alleviate the problems of using air drying and cross-linking agents in the co-extrusion of food products. Cross-linking agents can have an adverse effect on the colour and/or the taste of a food product. Also, the use of some cross-linking agents is subject to legal constraints. Surprisingly, it has been found that co-extrusion can be carried out effectively without the need for drying or cross-linking agents if tartaric acid is employed in the mixture that is used to form the casing.

Accordingly, the present invention provides a method of producing a food product having an outer casing and a filling, which comprises co-extruding the filling together with a gel-forniing mixture comprising collagen such that the mixture encases the filling, and bringing the extrudate into contact with an aqueous salt solution to form the food product, wherein the mixture comprises tartaric acid such that the food product thus formed has structural integrity without substantial drying or cross-linking.

The invention also provides a process for preparing an edible food product which comprises cooking (e.g., baking, grilling and/or frying) the food product obtained or obtainable by the method of the invention.

Further provided by the invention is a food product or edible product obtainable by the method or the process of the invention.

The food product of the invention is preferably a product of the "sausage" type. Sausages are typically formed by forming twists or links or other constrictions along a continuous length of filling and casing. The filling in the sausage can comprise meat, fish, vegetables, dairy products (such as cheese) or combinations thereof. The filling may optionally contain one or more conventional additives such as preservatives (eg, ascorbic acid or its salts), colouring agents and flavouring agents (eg, sodium chloride and pepper). More preferably, the food product is a sausage containing uncooked sausagemeat (eg, comprising a meat selected from pork, beef, lamb, chicken or turkey, most preferably pork, or mixtures thereof) ie, a fresh sausage. Other conventional additives, such as sugars (including sucrose and lactose), breadcrumbs and fat, can be included in the filling.

Although the invention may be described herein with reference to the term "sausage", it is to be understood that food products other than conventional sausage are encompassed by the invention.

The casing for the food product of the invention comprises collagen and tartaric acid. Although the collagen can be from any suitable source, it is preferably obtained from animal sources, such as bovine hide. The casing typically constitutes from 1- 10% by weight of the food product and preferably has a thickness of from 0.1 mm to 0.5 mm, more preferably about 0.2 mm.

The casing is formed from a gel-forming mixture which is co-extruded with the filling. The term "gel" is not necessarily used in its strict technical meaning and covers any structural change in the mixture that increases its strength. The mixture preferably has a pH of less than 4, more preferably less than 3. The protein (eg, collagen) content of the mixture is preferably 2 to 10% by weight, more preferably 3.5 to 5% by weight, such as 4.0 to 4.5% by weight. The amount of tartaric acid in the mixture is preferably from 0.1 to 5% by weight, more preferably 0.2 to 4% by weight, such as 0.5 to 2% by weight. The water content of the gel-forming mixture is typically 90 to 95% by weight. Other components, such as colouring agents, can be included in the gel-forming mixture, typically in an amount of less then 1% by weight. Vegetable oil can optionally be included in the mixture. Cellulose fibre, preferably in an amount of up to 2% by weight of the mixture, is a further optional component. The tartaric acid is preferably the sole acid in the mixture ie, the mixture preferably does not contain any other added inorgam^'c or organic acid ( apart from any residual acids derived from the extraction of the collagen). However, the mixture may comprise other orgam^'c and/or inorgam^'c acids such as hydrochloric acid, sulphuric acid, phosphoric acid, lactic acid, acetic acid and citric acid. If the mixture contains other organic and/or inorganic acids, these are preferably present in an amount of less than 50 % by weight, more preferably less than 30 % by weight, most preferably less than 10 % by weight, based on total acids in the mixture.

Without wishing to be bound by theory, it is believed that the ability of tartaric acid to form a mixed dibasic salt with relatively large amounts of water of crystallisation may contribute to its effectiveness. As tartaric acid is capable of forming a mixed salt with sodium and potassium (Rochelle or Seignette salt) having four molecules of water of crystallisation, it may thus act to remove surrounding water from the casing during crystal formation. The tartaric salts may also form a bridge between the filling (which ma}' comprise sodium ions) and the casing (which may comprise potassium ions).

The gel -forming mixture is caused to form the casing in the process of the invention by contact with an aqueous salt solution. The mixture may be cooled to below 20⁰C (eg, from 5 to 15⁰C) before extrusion. The mixture and the solution may be brought into contact by immersion of the extradate (ie, the mixture and the filling after co-extrusion) into the solution (eg, in a bath), by spraying the solution onto the extradate, or in other ways.

The salt solution is preferably a solution of a neutral or alkaline salt (more preferably a food grade salt), such as sodium carbonate or sodium chloride, sodium hydroxide, sodium bicarbonate, ammonium sulphate, ammonium hydroxide or dipotassium hydrogen phosphate, with the latter being particularly preferred. Potassium salts are generally preferred. The concentration of salt in the solution is typically from 5% to 70% w/v, more preferably 40% to 60% w/v, such as 45% to 55% w/v. The pH of the salt bath is preferably 8 to 12 more preferably 9 to 10. The temperature of the salt bath is preferably 5 to 40 ⁰C.

The contact time between the salt solution and the mixture is preferably 10 seconds to 5 minutes such as 10 seconds to 2 minutes, more preferably 20 seconds to 1 minute.

The method of the invention can be carried out using conventional apparatus for co-extrusion of sausages, such as that sold by Townsend Protecon. The method can be operated as a batchwise or continuous process, preferably as a continuous process.

Surprisingly, food products produced according to the invention retain structural integrity without needing to be air dried or cross-linked. The term "structural integrity", as used herein, means a structure that is self- supporting at 7 ⁰C (eg, the casing does not split or burst) when placed on a flat surface and that can be subsequently handled without the casing splitting or bursting. Structural integrity can be alternatively or additionally defined in terms of the tensile strength of the food product. Preferably, the tensile strength is at least 3 N, more preferably 3 to 15 N₅ even more preferably 5 to 10 N. Tensile strengths are measured in the extrusion direction and can be determined using methods that are well-known in the art, preferably using an Instron model 6022 Materials Testing Machine. Tensile strength expressed in the units N represent the maximum weight that an individual sausage can support without fracture. The food product of the invention preferably has a peelable skin after storage for 7 days (eg, at less than 10⁰C, such as 1 °C to 10⁰C, for example 7°C) and more preferably retains a peelable skin after storage under the same conditions for 14 days. The feature that the casing is peelable means that the casing can be removed manually from the filling in pieces or strips.

Therefore, in another embodiment, the invention provides a method of producing a food product having an outer casing and a filling, which comprises co-extruding the filling together with a gel-forming mixture comprising collagen such that the mixture encases the filling, and bringing the extrudate into contact with an aqueous salt solution to form the food product, wherein the mixture comprises tartaric acid such that the food product thus formed has a tensile strength of at least 3 N, more preferably 3 to 15 N, even more preferably 5 to IO N.

A further embodiment of the invention is a method of producing a food product having an outer casing and a filling, which comprises co-extruding the filling together with a gel-forming mixture comprising collagen such that the mixture encases the filling, and bringing the extrudate into contact with an aqueous salt solution to form the food product, wherein the mixture comprises tartaric acid such that the food product thus formed has a peelable skin after storage for 7 days. More preferably, the product retains a peelable skin after storage under the same conditions for 14 days.

The method of the invention is preferably carried out in the substantial absence of drying of the food product ie, without a specific step of drying the food product (e.g., in air). More preferably, the method of the invention is carried out in the substantial absence of forced air drying of the food product i.e., in the absence of drying the food product in a moving stream of ail", In less preferred embodiments, some forced air drying may take place. More preferably, the process is carried out in the complete absence of drying the product after it exits the salt solution, other than allowing the excess salt solution to be removed from the surface (eg, by allowing it to drip off or by wiping). Conventional drying steps, such as forced air drying (ie, in a generated moving stream of air) at room temperature (20⁰C) or elevated temperature (>20°C) are preferably not involved in the method, but can be involved in the method of the invention.

The method of the invention is preferably carried out in the absence of a cross-linking agent. Cross-linking agents may be used, but this is less preferred. Cross-linking agents include liquid smoke (as defined in EP-A- 0822403), aldehydes such as glutaraldehyde and glyoxal, and mineral tanning agents. Cross-Unking agents are also termed "coagulation agents" in the art and are used to strengthen the casing, for example by reaction with the collagen. Preferably, the method of the invention involves the use of less than 1% of a cross-linking agent, more preferably less than 0.5% even more preferably less than 0.1% based on the weight of the gel-forming mixture that comprises collagen. In another preferred embodiment, the method is carried out in the substantial absence, or complete absence, of a cross-linking agent.

The collagen casing in the food product of the invention is preferably not cross-linked by cross-linking agents and is more preferably not cross-linked ^' after the casing is formed.

The collagen casing is preferably not chemically modified (eg, by cross- linking agents) during the process. Therefore, in another aspect, the invention provides a method of producing a food product having an outer casing and a filling, which comprises co- extruding the filling together with a gel-forming mixture comprising collagen such that the mixture encases the filling, and bringing the extrudate into contact with an aqueous salt solution to foπn the food product, wherein the mixture comprises tartaric acid and the collagen is not chemically modified during the process.

In a preferred embodiment of the invention, the food product is packaged after it is foπned (ie, after it exits the salt solution) without

forced air drying and/or chemical treatment (eg, by treatment with cross- linking agents). The food product is optionally washed (eg, with dilute salt solution or water), and any wash liquor removed, before packaging.

In another preferred embodiment, the invention provides a method which consists essentially of the following steps:

(i) providing a gel-forming mixture comprising collagen and tartaric acid;

(ii) providing a filling;

(iii) co-extruding the mixture and the filling such that the mixture encases the filling;

(iv) bringing the extrudate into contact with an aqueous salt solution to form the food product;

(v) removing the food product from the aqueous salt solution;

(vi) optionally, washing the food product; and removing excess wash liquor; and

(vii) packaging the food product. The food product is preferably formed into sausage links by twisi-linking, crimping or other mechanical separation before packing. A plasticiser, such as polyhydric alcohol containing 2 to 10 carbon atoms (eg, glycerol) can be 5 applied to the casing.

The food product can be packaged in conventional ways. For example, the food product can be wrapped in a layer of plastics material or coated paper.

] o The food product of the invention typically requires cooking before it can be eaten. Cooking can be effected by, for example, frying or heating in an oven.

All publications, patents and patent applications are incorporated herein by

15 reference. While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein may be varied 0 considerably without departing from the basic principles of the invention.

The following non-limiting examples illustrate the invention and do not limit its scope in any way. In the examples and throughout this specification, all percentages, parts and ratios are by weight unless indicated 5 otherwise. Examples

1. Collagen for fresh sausages

1.1 Hide treatment

Examples of two types of hide treatment are given below. However, for the purpose of this invention, the hide treatment is not critical and suitable treatments will be evident to those skilled in the art depending on the type of raw materials (hides) used.

All collagens are made from trimmed limed bovine splits. 3000 kg of hide- split collagen were introduced in a rotating drum processor (Dosemat®). After washing, de-liming (with acetic acid, pH 4.8) and washing again, the product was obtained.

Optionally, an alkali treatment can be performed. An example of an alkali treatment is:

All collagens are made from trimmed limed bovine splits. 3000 kg of hide- split collagen was introduced into a rotating drum processor (Dosemat®). After washing, de-liming (with acetic acid, pH 4.8) and washing again the product was equilibrated with a saturated sodium sulphate solution. The product resulting was alkali-treated (IN NaOH) and neutralised (aq. acetic acid). The product was washed.

1.2 Preparation of a collagen dough The collagen was, after mixing with water, comminuted to a very fine suspension of collagen fibres. After deaeration and homogenisation, the pH was adjusted to pH < 3 by addition of different kind of acids. The collagen fibres swelled as a result of this pH adjustment.

1.3 Specification of the collagen

TJie protein content is between 4.0 and 4.4 ^0/ό The pH is between 2.7 and 3.3.

Collagens containing the following acids A to E were used:

A tartaric acid

B phosphoric acid and lactic acid

C citric acid and lactic acid

D lactic acid and acetic acid

E lactic acid

1.4 Topical formulation fresh sausage

Pork shoulder 16.20O g Pork jowl/Bellies 1.80O g Water 1.000 g

Salt 300 g phosphate 60 g

Black pepper 30 g

Ascorbate 20 g

Sugar 100 g

Lactose 200 g

19.71 O g

1.5 Preparation of fresh sausage meat dough

Grind the raw material at a 6 mm plate and mix with vacuum at the bowl chopper.

1.6 Coextiusion line

The sausages are produced on the Coextrusion line produced by Townsend Protecon. The sausages were produced with the following parameters.

Nozzle 17 mm

Restrictor 8 mm

Crimperbodies 15 Weight 25 - 30 grain

Collagen weight app. 4 to 7%

In line mix None

Drying None

Crosslinking None Brine bath extended for 40 seconds, 50% (w/v) K₂HPO₄ solution (10 kg in 10 litre ) ,

Fresh sausages were produced with an extended brine bath of minimum 40 seconds containing DPP as dehydration agent. The sausages were picked straight from the belt and judged fresh. The sausages were put on a plate, wrapped with a plastic bag; a low vacuum is applied to the bag before sealing. The sausages were stored cool at max. 7⁰C, and judged on appearance and frying properties after 7 and 14 days, The following methods were used for the evaluation:

• peeling the skin

• frying in sunflower oil, 10 minutes

• deep-fried, 2 minutes at 165 ⁰C

1.7 Results

Collagen A has fresh a strong skin. The skin is still peelable after 14 days and gives the best result for frying and deep frying.

The results aie also set out in the following table.

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Claims

1. A method of producing a food product having an outer casing and a filling, which comprises co-extruding the filling together with a gel-forming mixture comprising collagen such that the mixture encases the filling, and bringing the extrudate into contact with an aqueous salt solution to form the food product, wherein the mixture comprises tartaric acid such that the food product thus formed has structural integrity without substantial drying or cross-linking.

2. Method as claimed in Claim 1 wherein the food product is an uncooked sausage and the filling is uncooked sausage meat.

3. Method as claimed in Claim 1 or Claim 2 which is caπied out in the absence of air drying of the food product.

4. Method as claimed in Claim 1 or Claim 2 which is carried out in the absence of forced air drying of the food product.

5. Method as claimed in any one of Claims 1 to 4 which is carried out in the absence of a cross-Unking agent.

6. Method as claimed in any one of Claims 1 to 5 wherein the mixture comprises tartaric acid as the sole added acid.

7. Method as claimed in any one of Claims 1 to 6, wherein the tartaric acid is present in the mixture in an amount of from 0.5 to 2% by weight.

8. Method as claimed in any one of Claims 1 to 7, wherein the salt solution comprises dipotassium hydrogen phosphate.

9. Method as claimed in any one of Claims 1 to 8, wherein the mixture has a pH of less than 3.

10. Method as claimed in any one of Claims 1 to 9, wherein the food product is removed from the salt solution and packaged without drying or chemical treatment.

1 1. Method as claimed in any one of Claims 1 to 10, wherein the food product has structural integrity defined as a tensile strength of at least 3 N in the extrusion direction.

12. Method as claimed in any one of Claims 1 to 11 which consists essentially of the following steps:

(i) providing a gel-forming mixture comprising collagen and tartaric acid; (ii) providing a filling;

(iii) co-extruding the mixture and the filling such that the mixture encases the filling; (iv) bringing the extrudate into contact with an aqueous salt solution to form the food product; (v) removing the food product from the aqueous salt solution;

(vi) optionally, washing the food product; and removing excess wash liquor; and (vii) packaging the food product.

13. Process for preparing an edible food product which comprises cooking the food product of any one of Claims 1 to 12.

14. Food product or edible product obtainable by the method of any one of Claims 1 to 12 or the process of Claim 13.