Field of the Invention

The present invention relates to a food product and process. In particular, the invention relates to a method for producing a meat alternative product by using a high moisture extrusion process, whilst maximising the marbling colouring effect in the meat alternative product and maintaining vitamins and flavours in the extruded product. It is for example applicable to vegetarian or vegan analogues to meat or fish.

Background

Veganism and vegetarianism is an increasingly common lifestyle choice around the globe, and particularly in the UK and USA. Veganism is defined as not consuming dairy, meat, fish or egg products. This means that their diet must consist of plant based food products that maintain the highest sources of nutrients. Vegetarianism is defined as the practice of not eating meat or fish. As a result of this change in eating habits among the general population there is an increased demand for meat free protein products and meat alternatives.

Additionally, issues around health, sustainability, traceability and animal welfare are also increasingly important influences in consumer purchasing decisions. As a result, meat free protein products are no longer exclusively sold to the consumer group that identifies as vegetarian or vegan. A flexible diet is becoming increasingly popular and the appeal of plant based foods is broadening to include people who also incorporate meat and diary in their diets but also wish to seek meat alternatives sometimes.

One method used to generate meat alternative products is through high moisture extrusion. High moisture extrusion cooking of plant or vegetable proteins (e.g. soy) has recently started being used to produce meat analogues. High moisture extrusion cooking is a process that allows the formation of a strand or larger pieces from protein rich powders, slurries or small pieces such as plant proteins or meat and fish. Typically plant proteins are mixed with water in an extruder barrel and the combination of heating and subsequent cooling of the mixture facilitates the texturization and creation process to produce a layered or fibrous structure with a‘meat-like’ appearance. There are several variables in the process of high moisture extrusion that can affect the end product. Raw material characteristics from various sources (wheat, soya, pea, chickpea, faba bean, lupine or other grain legumes and oilseeds such as rapeseed, sunflower, linseed and others) and from various manufacturing, protein purification and drying procedures (flours, press cakes, protein extracts, concentrates or isolates; defatted and/or dried products as well as slurries). Further the extruder and process design dictate the formation of fibrous structures like that of meat. Additionally, system parameters such as throughput, pressure, water content and temperature profile must also be considered.

Whilst high moisture extrusion is an effective method for producing a layered or fibrous structure like meat or fish, the outcome product typically does not look like meat or fish. This can be off-putting for consumers who prefer the look of and are more comfortable with the overall appearance of meat and fish. Organic colouring ingredients used to create meat analogues, such as plant extracts from red beetroot, paprika, red radish or black carrot do not withstand the high temperatures and fade or turn to unwanted brownish or dark colours. Additionally, heat sensitive flavouring compounds and spices as well as other heat sensitive ingredients such as vitamins can often be destroyed, inactivated or denatured in the mixing process under high temperature or simply get lost in the vapour phase.

For example, owing to the unusually high water content in the processed mass and to the elevated temperature, the mass viscosity in the extruder is relatively low. Therefore, under typical processing conditions mixing the mass within the extruder barrel is very effective. Therefore, added colourants are within very short processing time almost equally distributed and demonstrating no clear marbling effect remains. A method of achieving marble colouring and/or effect and maintaining vitamins and flavourings is needed.

The present invention seeks to address these, and other, disadvantages encountered in the prior art by providing an improved method of moisture extrusion.

Summary and Figures

An invention is set out in the independent claims, and optional features are set out in the dependent claims. The present invention will now be described, by way of example only, with reference to the accompanying drawings.

Figure 1 shows a cross sectional view of a high moisture extrusion apparatus according to a first embodiment of the disclosure.

Figure 2 shows a cross sectional view of a high moisture extrusion apparatus according to a further embodiment of the disclosure.

Figure 3 shows a cross sectional view of a high moisture extrusion apparatus according to a further embodiment of the disclosure.

Figure 4 shows a flowchart of an exemplary production line for suitable for high moisture extrusion.

Detailed Description

The present disclosure will now be described by way of example only. These are not the only ways that the disclosure may be put into practise.

In overview, colourants or other ingredients into the extruder barrel are used for various reasons. Typically, for injection, a low pressure zone within the extruder barrel is chosen or created to make the injection easier. Usually, the newly added material or liquids have a considerably lower dry matter content compared to the processed mass already in the barrel. Because of this, conventionally the amount of lower dry matter content added towards the end of barrel (an area of high pressure) must be limited as it causes unsteady, irregular process conditions due to the high pressure.

This disclosure is directed towards a high moisture extrusion apparatus and method for producing foodstuffs. Primarily the disclosure is directed towards the late injection of a colourant or flavouring to produce a marbling effect and to maintain vitamins and flavours in an extruded product. A second aspect of the disclosure is directed towards a high pressure pump used in the high moisture extrusion apparatus to allow the late insertion of colourants and flavourings. A high pressure pump can be used to allow for colourants or flavourings to be inserted at a later stage in the high moisture extrusion process where the pressure is very high, contrary to known approaches where the high pressure area is avoided for practical reasons. It is found that, as a result, improved marble colouring and/or effect and maintenance of vitamins and flavourings is achieved. By way of background, as is well known, extrusion is a continuous mixing, kneading, and shaping process used to produce a desired product. Food extrusion is not new to the food industry and has been utilized to produce many different types of food products for more than 60 years. Well known extrusion applications in the food industry include pasta, breakfast cereals, baby food, pet food, and other confectionery products. Almost all of these applications take place at low to intermediate level moisture contents (for a water weight of less than 40%).

High moisture extrusion is a relatively new type of extrusion. High moisture extrusion cooking describes a process that allows the formation of strands or larger pieces from protein rich powders, slurries or small pieces such as plant proteins, meat and fish. High-moisture extrusion cooking of plant proteins has recently gained increasing attention for producing meat alternatives. The combination of heating and subsequent cooling of the protein-water mixture facilitates the texturization of the product and produces a layered or fibrous structure with a‘meat like’ appearance. High moisture extrusion is characterised by processing materials with a high water content, compared to traditional extrusion methods. Typically, the materials used in high moisture extrusion have a water weight higher than 40% and often higher than 50%. Due to the unusual high water content in the processed materials and due to the elevated temperature needed to produce the desired effect, the viscosity of the material in the extruder is relatively low (i.e. a creamy, puree like texture). The viscosity and high temperature means that the under typical processing conditions mixing the materials within the extruder barrel is very effective. Counterintuitively this can adversely affect for example the appearance of conventionally marbled products. Often, high moisture extrusion is therefore combined with a twin screw extruder for making unconventional food products.

The high moisture extrusion process can be affected by several independent process variables such as raw material characteristics, the high moisture extrusion apparatus and process design on the formation of fibrous structures. Concurrently, the effects of dependent system parameters such as pressure, temperature, and changes at a molecular level with focus on protein-protein interactions have also significantly affect the extruded product. In particular, the process is sensitive to a combination of temperature profile in the extruder, the exposed temperature of the injected products, the selected place of injection, the screw profile of the extruder, quantity and composition of the injected liquid as well as frequency of the injection. These factors are all considered in this application.

The high moisture extrusion process described herein is also characterised by a high protein content. A combination of heating and subsequent cooling of foodstuffs in the extruder barrel facilitates texturization of the resultant foodstuff. In particular the heating and cooling of protein and water mixtures facilitates the texturization to produce a layered or fibrous structures with a ‘meatlike’ appearance. Independent process variables such as raw material characteristics as well as extruder and process design on the formation of fibrous structures all have an effect of the output foodstuff product. Concurrently, the effects of dependent system parameters such as pressure, temperature, and changes at a molecular level with focus on protein-protein interactions have also been taken into consideration. A large number of parameters directly influence the product's quality and must therefore be carefully adjusted to obtain products with fibrous meatlike properties.

When producing‘meatlike’ products the aim is to create an extruder environment where the extruded product is layered and fibrous with a strand-like texture, similar to that of ‘real’ meat. This is achieved by using high moisture content. Notably, this is distinctly different from the extrusion process used to create sugar based products. Sugar based products are typically made with a relatively lower moisture content to achieve an even and smooth texture and uniform sugar distribution, for example chewing gum. Conversely, the aim with‘meatlike’ products is to provide the more fibrous texture.

Referring to figures 1 to 3, a high moisture extrusion apparatus 100 is shown and is suitable for manufacturing foodstuffs. The high moisture extrusion apparatus 100 comprises an extruder barrel 102. The extruder barrel 102 may take various shapes, for example a cylindrical or cuboid shape. The extruder barrel 102 could be formed of metal, most common type of metal used are nitriding steels, powder metallurgy steels, or bi-metals which are composed by two separates parts: a support base material and an internal lining. The extruder barrel 102 may be a heated extruder barrel. A heated extruder barrel 102 is used to ensure the materials inside the extruder barrel 102 are at the ideal temperature needed to form protein strand structures suitable for consumption. The heated extruder barrel 102 could have a heated exterior dissipating heat into the interior of the extruder barrel 102. The extruder barrel 102 comprises an inlet port 108 and an outlet port 1 18. The extruder barrel 102 has an inlet end 104 at or near which the inlet port 108 is located and an outlet end 106 at or near which the outlet port 1 18 is located. The inlet port 108 and the outlet port 1 18 could be located at opposing ends of the extruder barrel 102 or respectively downstream and upstream thereof. The extruder barrel 102 further comprises an injection port 1 14.

The extruder barrel 102 may comprise more than one inlet port 108. For example, the inlet port 108 may comprise a first inlet port, a second inlet port and optionally a third inlet port. The first inlet port may be used to input a dry powder mix (e.g. soy), the second inlet port may be used to input water and the third inlet port may be used to input oils into the extruder barrel 102.

The inlet port 108 is for input of a first material 1 10. The injection port 1 14 is for input of a second material 1 16. The outlet port 1 18 is for output of a combination of the first material 1 10 and the second material 1 16 from the extruder barrel 102. The injection port 1 14 is located intermediate to the inlet port 108 and the outlet port 1 18. The injection port 1 14 may be located closer to the outlet port 1 18 than the inlet port 108. The injection port 1 14 could be located adjacent to the outlet port 1 18. The outlet port 1 18 and injection port 1 14 could both be located at the outlet end 106 of the barrel.

The injection port 1 14 may be located anywhere along the extruder barrel 102. Several possible locations for the injection port 1 14 are given below.

Firstly, the injection port 1 14 may be located after the inlet port 108 (i.e. after the feeding of the first material 1 10) and closer to the inlet port 108 than the outlet port 1 18. This has the advantage of being in a relatively low pressure zone to allow easy injection of the second material 1 16. However, the second material 1 16 will still have a long residence time in the extruder barrel 102, which has a high thermal impact on sensitive components and a high level of mixing which leads to equal distribution of the components within the mass and therefore a reduced marbling effect.

Secondly, the injection port 1 14 may be located closer to the outlet port 1 18 than the inlet port 108. In this case the injection port 1 14 is not located in the high pressure zone directly next to outlet port 1 18. As the injection port 1 14 approaches the outlet port 1 18 of the extruder barrel 102 the second material 1 16 has a shorter residence time, therefore there is smaller thermal impact, lower mixing efficiency (but sometimes still high enough to produce an equal distribution of the inserted second material 1 16. Pressure at the injection port 1 14 is in this area depending on the screw profile and can be either high or low. It is desirable to place the injection port 1 14 somewhere with the low pressure, this depends on the impeller or screw profile.

Thirdly, the injection port 1 14 may be located close to the outlet port 1 18. The injection port 1 14 may be located within a region of 10% of the outlet port 1 18 compared to the entire length of the extruder barrel 102. In this extrusion process the material is forced through a die section at the outlet port 1 18 in order to form the material into a strand or particular shape. This is aided by the cooled slit channel. As a consequence of forcing the material into a smaller region, the pressure rises in the area behind the outlet port 1 18, the pressure is highest where the cross sectional area of the die section is at its minimum. When the injection port 1 14 is located close to the outlet port 1 18 there is a short residence time in the extruder barrel 102, therefore there is a moderate thermal impact on sensitive components and moderate mixing in the extruder barrel 102. This leads to an unequal distribution of the second material 1 16 within the final extruded product and greater marbling effect. However, as the second material 1 16 is inserted into a high pressure zone a sophisticated injection system must be used. Further, the addition of a relatively lower viscosity second material 1 16 to the first material 1 10 may lead to an unsteady slow and unstable processing conditions.

The first material 1 10 could comprise a protein rich powders, slurries or small pieces such as plant protein or meat and fish. The first material 1 10 will also comprises a high level of water. The first material 1 10 has a first weight and typically more than 40% of the total first weight will be water. The water content is needed to ensure the high moisture extrusion process can occur effectively in the extruder barrel 102.

The second material 1 16 could comprise a colourant or flavouring or other nutrients (eg vitamins) or combination of both a colourant, flavouring or nutrient. For example, the second material could comprise organic colouring ingredients, such as plant extracts from red beetroot, saffron, paprika, red radish and/or black carrot. In conventional arrangements, these ingredients do not withstand the high temperatures present in the extruder barrel 102 and fade or turn to unwanted brownish or dark colours. Additionally, the second material 1 16 may also comprise heat sensitive flavouring compounds, spices and/or vitamins. These compounds are prone to denaturing under high temperatures.

However, the present disclosure is directed towards solving these problems and ensuring that colourants and flavourings are effective in the extruded product (i.e. a combination of the first material 1 10 and second material 1 16).

As shown in figure 1 , the high moisture extrusion apparatus may further comprise an impeller 1 12. The impeller may be a screw or other type of mechanical device rotatable inside the extruder barrel 102. The impeller 1 12 is located inside the extruder barrel 102. The impeller 1 12 is configured to move the first material 1 10 and second material 1 16 from the inlet end 104 to the outlet end 106 of the extruder barrel 102. The impeller 1 12 could be located at the inlet end 104 of the extruder barrel 102. The impeller 1 12 could extend the entire length of the extruder barrel 102. As shown in figure 2, the impeller could comprise a twin screw extruder system 120. A twin screw extruder system 120 consists eg of two intermeshing, co-rotating screws. The twin screw extruder system 120 could be mounted on inlet end 104 inside the extruder barrel 102. There are a wide range of twin screw designs, various screw profiles and process functions that may be used depending on the requirements of the extruded product. While co-rotating, intermeshing screws are widely used for low to high viscous materials other types of screw designs such as counter rotating screws or multi-screws (more than two screws) are knows as well.

A twin screw extruder system 120 ensuring effective transporting, compressing, mixing, cooking, shearing, heating, cooling, pumping, shaping, etc. with high level of flexibility. The major advantage of intermeshing co-rotating twin screw extruders is their remarkable mixing capability which ensure characteristics to extruded products and adds significant value to processing units, for example when compared to a single screw impeller 1 12.

As shown in figure 3, the high moisture extrusion apparatus may also include a slit channel 120. The slit channel is typically attached to the outlet port 1 18, however, it can also be situated further downstream from the outlet port. The slit channel 120 can be used in the high moisture extrusion apparatus used to regulate the temperature and shape of the extruded product. The slit channel 120 stabilises the flow coming out of the extruder barrel and can also be formed to shape the combined first material and second material into a desirable product. Therefore, the slit channel 120 may be formed into various shapes and have various lengths depending on the desired product. The high moisture levels in the high moisture extrusion apparatus 100 combined with elevated temperatures in the extruder barrel 102 may produce a material that is very soft and not self-supporting. However, in one embodiment the extruder may have a cooled slit channel 122 specially designed which provides cooling at this section will increase the viscosity of the hot extrudate before exiting, contributing to the correct elasticity and fluidity required for texturization. The cooled slit channel 122 may be a long die section.

The extruder barrel 102 necessarily has a differential pressure along the extruder barrel 102 (see the length L denoted in figure 3), where the pressure is greater at the outlet port 1 18 than the input port 104. The pressure is typically maximum or at least relatively high at or close to the outlet port 1 18 of the extruder barrel 102. As a result in embodiments the injection port 1 14 includes a high pressure pump. As a late injection point of the second material is desired, this is preferably done within a high pressure zone within the extruder barrel 102 that demands a high pressure pump to overcome the high pressure within the extruder barrel 102. Therefore, a high pressure pump must be used to allow the second material 1 16 to be fed into the extruder barrel 102.

The high pressure pump could be piston pump or a diaphragm pump. The high pressure pump could be configured to exert a pressure greater than the pressure within the extruder barrel 102 at the outlet port 1 18. The high pressure pump could be located in a region where the pressure is greater than the midpoint of the differential pressure. The closer the injection port 1 14 is located to the outlet port 1 18 the less mixing that the second material 1 16 will experience, leading to more marbling. However, the higher the pressure at the outlet port 1 18 leads to a higher risk of unstable processing conditions.

A method of high moisture extrusion suitable for manufacturing foodstuffs is disclosed herein. The method of high moisture extrusion is suitable for manufacturing foodstuffs. The method is formed from several steps. Firstly, inputting a first material 1 10 into an extruder barrel 102 through an inlet port 108. Secondly, inputting a second material 1 16 into the extruder barrel through an injection port 1 14. Lastly, outputting a combination of the first and second material through an outlet port 1 18 of the extruder barrel 102. In the described method the second material is input adjacent to the outlet end. The first material 1 10 may be fed into the extruder barrel 102 close to the input end 104 of the extruder barrel and the second material 1 16 is fed into the extruder barrel 102 close to the output end 106 of the extruder barrel 102.

It is desirable to inject the second material 1 16 at a late stage in extrusion process with the extruder barrel 102. Injection takes place intermediate to the inlet port 108 and the outlet port 1 18. The injection could take place closer to the outlet port 1 18 than the inlet port 108. The injection of the second material 1 16 could take place adjacent to the outlet port 1 18. The injection could take place at the outlet end 106 of the barrel.

These ingredients are fed at the inlet ports of the extruder that are located close to one end of the extruder screws. Within the extruder barrel one or more impellers push the fed material forward to the other end of the extruder barrel. Thereby, the impeller 1 12 mixes the first material 1 10 and second material 1 16 and heats them by dissipating mechanical energy. At the outlet of the extruder barrel there could be a slit channel 122 attached to form the mass and to cool it down prior to the release to atmosphere. Additionally, the slit channel could be a cooled slit channel to reduce the temperature of the extruder product more quickly. Typically, the mass is heated during the transfer of the extruder barrel to a temperature of 100-150°C while pressures of up to around 50bars or more towards the screws end may be reached.

Figure 4 shows a how the high moisture extrusion apparatus 100 may fit into a wider production line for generating foodstuffs and more specifically for generating meat alternatives.

The invention thus provides advantages based on a combination of temperature profile in the extruder barrel and slit die, the exposed temperature to the mass, the selected place of injection, the screw profile of the extruder, quantity and composition of the injected liquid as well as frequency of the injection.

Because injection takes place at a late stage of the extrusion process the remaining processing time until the entry into the cooling die is sufficiently short that the increase of temperature does not lead to a rapid degradation. Also the efficient cooling of the material once entered into the cooled slit channel helps to maintain heat sensitive components. On the other hand the amount of injected mass is relatively low not to provoke a sudden decrease in temperature in the mix of first material 1 10 and second material 1 16 and respectively a sudden strong increase in viscosity that may disturb the stability of the process. A minor decrease in temperature may be helpful to maintain heat sensitive components.

As discussed previously the viscosity of the first material 1 10 in the extruder barrel 102 is relatively low. In other words, under typical processing conditions mixing the mass within the extruder barrel is too effective. Therefore, when the second material 1 16 is added at a late stage in the process, there is a short processing time and the colourants and flavourings are not evenly mixed in the extruder barrel 102. This generates a marbling effect in the extruded product.

Typically, late injection must take place in a high pressure zone within the extruder barrel 102. When adding liquids with a considerable lower dry matter content compared to the processed mass is limited this also causes the extruder barrel to become unsteady and irregular process conditions are present. The high pressure pump must be sufficiently adequate to control the amount of injection accurately.

The extruder barrel 102 may be a heated extruder barrel. Ideally, the first material is provided with a temperature high enough such that the desired product can be formed, with strands and layered formation whilst also maintaining a low enough temperature such as not to denature colourants and flavourings added through the injection port 1 14. The extruder barrel 102 could be configured to provide the first material with a temperature below 150°C. The extruder barrel 102 could be configured to provide the first material with a temperature below 130°C. It is ideal to provide the first material with a temperature below 130°C to ensure that the colourants and flavouring do not become immediately denatured upon contact with the first material 1 10. The extruder barrel 102 could configured to provide the first material and the second material with a temperature below 130°C. This is particularly applicable at towards the outlet end 106 of the extruder barrel 102, where both a combination of the first material 1 10 and second material 1 16 is present. The extruder barrel 102 could be configured to provide the second material 1 16 with a temperature below 130°C. Again, this ensures that the colourants and flavourings are at the ideal temperature for high moisture extrusion whilst not becoming denatured. 1 1 . The high moisture extrusion apparatus could be configured such that the second material 1 16 is provided with a temperature lower than the temperature of the first material

1 10.

The high moisture extrusion apparatus 100 could be configured such that the injection port 1 14 is configured to input a second material in liquid or solid form. The high moisture extrusion apparatus 100 could be configured such that the injection port 1 14 is configured to input a second material 1 16 in liquid form, such that the mass of the second material is 0.1 -10% of the total combined mass of the first and second material. The high moisture extrusion apparatus 100 could be configured such that injection port is configured to input a second material 1 16 in solid form and the mass of the second material is 0.1 -50% of the total combined mass of the first and second material.

Residence time is the duration of time the second material spends in the extruder barrel 102 after injection takes place. It is preferable to have a residence time of below 2 minutes, and even better is the residence time is below 1 minute. The high moisture apparatus 1 10 could be configured such that the second material 1 16 resides in the extruder barrel 102 for less than 1 minute after insertion through the injection port 1 14. This ensure that the second material 1 16 does not spend too long mixing in the extruder barrel 102. Too long spent mixing the first material 1 10 and second material 1 16 together would mean that they become uniformly mixed. Instead less than 1 minute have been determined as an optimum time to ensure that a marbling effect of colorants can be seen in the extruded product.

The high pressure pump could be configured to inject the second material 1 16 into the extruder barrel 102 at a variable rate. The variable rate of injection is between 10 injections per minute and 250 injections per minute high pressure pump is configured to inject between 0.001 and 0.05 per cent of the total massflow 1 10+1 16 of second material (1 16) per injection. Variable injection also aids the marbling effect in the extruder product by ensuring an ununiform mixture of the second material 1 16. This high moisture extrusion method and apparatus can be used for making lots of general food products, for example this may pasta, breakfast cereals, baby food, pet food and other confectionery products. In particular, the method is particularly suitable for producing meat analogues.