of Mechanical Properties of Coextruded Dual-phase Products
Lalitha Samula, Hulya Dogan, Scott McGrane & Jozef L. Kokini
Center of Advanced Food Technology and Department of Food Science, Rutgers University, USA with Masterfoods, Leicestershire, UK
Food coextrusion has introduced a wide variety of dual-phase products in the snack food, breakfast cereal and pet food sector. Generally, such foods products are comprised of a crispy/crunchy exterior shell enclosing a soft viscous filler material of a different texture. Inherent differences in the physical states and compositions of the two phases offer interesting textural variation to the consumer. In the case of dual-phase pockets, the main focus of such an analysis is to differentiate between the textural properties of each phase. In order to monitor their textural quality, simple and rapid measurements are needed on the whole food. The texture literature so far has not provided techniques that are fundamentally based on such products.
This paper focuses on the characterisation of mechanical properties as a marker of texture in dual-phase products. The differences in the mechanical properties of the shell and filler were used to deconvolute the textural differences between these two phases.
A method was developed in this paper using a 2mm penetration probe attached to a TA.XT2i Texture Analyser to assess the quality of dual-texture extruded products positioned on a base plate with an aperture. The diagram shown depicts the working of the penetration probe and the corresponding force deformation curves for such products. The probe is effectively able to differentiate between the mechanical resistances offered by different phases. The force deformation curves show an increasing force which is proportional to the length of the probe penetrating the firm material. Then, a sudden drop is observed consistent with the resistance offered by the softer material. The increase in the force during the penetration of the softer material is much less pronounced, consistent with the properties of the soft material. The final part of the curve shows again a sudden increase in the force during deformation as expected from the firm material.
The parameters derived from the force deformation curve of a penetration test in commercial pockets are well annotated and explained in this paper.
The paper reviewed is summarised from Journal of Texture Studies 38 (2007). This paper is not the property of Stable Micro Systems so we cannot therefore supply copies due to copyright laws. If you have trouble finding them then please contact us (email@example.com) and we will do our best to put you in touch with the author.
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