15 The effect of structure on water diffusion in dough and pasta like products.

Anne-Marie Hermansson and Maud Langton. SIK, the Swedish Institute for Food and Biotechnology, P.O. Box 5401, SE 40229 Gothenburg, Sweden.

Pasta can be regarded as a multiphase system, where the distribution of water has a strong effect on the texture of the final product. A number of aspects where the structure determines the water diffusion and thereby the texture of the product will be covered in this paper. Gradients in the swelling of starch granules determine diffusion of water into the centre of the pasta and have therefore a bearing on the ‘al dente’ quality. Crack propagation and interfacial spaces between the gluten and the starch phase are important routes for water diffusion. The paper will also focus on the effect of processing on the water diffusion and the structure of pasta like products. Comparisons will be made between products where the same energy input has been achieved by conventional heating and microwave treatment, comparisons will also be made with high-pressure treatment. The results show that the different processes affected both the starch and the protein phase differently. Variations in the water content during heating had a large effect on the swelling of starch and the texture. The microstructure in this work has been characterised by light microscopy, confocal scanning laser microscopy and transmission electron microscopy and structure parameters quantified by image analysis. The texture has been characterised by large and small deformation tests.