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Case study II (Protein extrusion: Meat and cheese analogues)

7 important questions on Case study II (Protein extrusion: Meat and cheese analogues)

'use of extruders for the production of protein fibers and for the production of cheese analogues through a emulsification-gelation process. For both processes, a twin screw extruder connected with a slit die was used.' What is the reason for cooling both products?

Cooling is meant to increase the viscosity, with the aim to entrap/fixate the newly formed structure.

'use of extruders for the production of protein fibers and for the production of cheese analogues through a emulsification-gelation process. For both processes, a twin screw extruder connected with a slit die was used.' What could be reasons that soy protein isolate is more difficult to texturize than soy concentrate (p. 242)?

Soy protein isolate can be considered as a one phase system. One phase systems cannot be structured. The presence of carbohydrates makes the materials a two-phase systems, which can form structures upon deformation. The fact that the cellulose is an anisotropic fibre, probably helps making the final structure fibrous.

'use of extruders for the production of protein fibers and for the production of cheese analogues through a emulsification-gelation process. For both processes, a twin screw extruder connected with a slit die was used.' What could be reasons that a protein-fat mixtures form an emulsion instead of fibers? Assume that the formation of a fibrous structure occurs mainly in protein- polysaccharide mixtures.

Due to the high interfacial tension of oil, it tends to form droplets instead of elongated structures. Besides, oil might act as lubricant reducing the forces onto the materials, preventing the formation of an anisotropic structure as well.

'use of extruders for the production of protein fibers and for the production of cheese analogues through a emulsification-gelation process. For both processes, a twin screw extruder connected with a slit die was used.' What will be the flow pattern inside the slit die? Will the flow profile change upon cooling? Try to draw the flow profile at various positions in the die.

Here, the final answer is not known. In case the material behaves like a liquid, the parabolic flow pattern will be formed. In case of a solid material, a flat flow pattern will arise. However, it is not clear whether a transition from liquid to solid is possible and how the transition should look like. A possible reasoning is that the material behaves solid like through the complete die. In that situation though, it is not clear how the die can contribute to the formation of a structure.

Cheftel describes two processes to make cheese based products. One process uses a short cooling die using sodium polyphosphate. Another process uses a long slit die. What is the effect of sodium polyphosphate on the chemical and physical properties of casein?

Casein can form micelles, which are stabilized by calcium. Sodium polyphosphate forms soluble complexes with calcium, disrupting them from the micellar network. As a result, smaller micelles with less interaction will be formed. Besides, the proteins are less well bound in the micelles, making them more mobile and for example better available for oil-water interface stabilisation.

Cheftel describes two processes to make cheese based products. One process uses a short cooling die using sodium polyphosphate. Another process uses a long slit die. Why is a long die necessary in case sodium polyphosphate is not added?

In case no STP is added, stabilization of the structure should occur through an increase in viscosity. This requires cooling in the die. The product should be cooled below the melting temperature of fat to prevent fat coalescence or leakage.

Cheftel describes two processes to make cheese based products. One process uses a short cooling die using sodium polyphosphate. Another process uses a long slit die. How will the droplet formation change if the temperature increases of the material in the die (figure 15)? Consider also the effect the ‘reassociation of casein’, as described by the authors.

An increase in temperature will have an influence on many aspects. Probably, the main effect is that the viscosity of the continuous phase will decrease. Then the viscosity ratio will increase, meaning that smaller droplets can be formed (The critical We-number decreases as can be seen in the answer to question c). An additional effect of the temperature will be that the casein, which are mostly bound will dissolve more as free protein molecules, leading to faster stabilization of the small oil droplets.

The question on the page originate from the summary of the following study material:

FPE 30306 | 9990002019708 | Wageningen University

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Case study II (Protein extrusion: Meat and cheese analogues)

7 important questions on Case study II (Protein extrusion: Meat and cheese analogues)

'use of extruders for the production of protein fibers and for the production of cheese analogues through a emulsification-gelation process. For both processes, a twin screw extruder connected with a slit die was used.' What is the reason for cooling both products?

Cheftel describes two processes to make cheese based products. One process uses a short cooling die using sodium polyphosphate. Another process uses a long slit die. What is the effect of sodium polyphosphate on the chemical and physical properties of casein?

Cheftel describes two processes to make cheese based products. One process uses a short cooling die using sodium polyphosphate. Another process uses a long slit die. Why is a long die necessary in case sodium polyphosphate is not added?

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