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R. F. TESTER, School of Biological & Biomedical Sciences, Glascow Caledonian Univ., Food Research Labs., 70 Cowcaddens Rd., Glasgow, G4 0BA, United Kingdom The process of starch gelatinisation involves a complex series of molecular events which depend on the availability of water as granules are progressively heated. Initially, the water acts as a plasticiser for the glass transition of amorphous starch. Next, it facilitates the dissociation of amylopectin (and possibly amylose) double helices and loss of crystallinity. Concurrently the granules imbibe water and swell. As the temperature is increased, amylose-lipid complexes (if present) dissociate. Finally, if heating is continued and the starch system is dilute (<4% solids), the a-glucans will form solutions/colloidal dispersions. Above 4% solids, the starch gels - the structure and strength of which depend on the type of starch being processed. Whilst integral features of starch (a-glucan structure, composition and architecture) interact to control the process of gelatinisation, if water is limiting, molecular mobility and dissociation is restricted. Consequently, in foods made with low water contents, much of the starch is ungelatinised. A good example of this is shortbread biscuits. In terms of food components/ingredients that restrict water mobility into starch granules during processing, non-starch polysaccharides (NSP) can be very effective in this respect. This presentation concerns a review of the gelatinisation process and the role that NSPs play with respect to regulating the process.
Session 4, Impact of starch-hydrocolloid interactions in food systems
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