2 ENZYMATIC STABILITY OF STARCHES

摘要

1 INTRODUCTION Starch is probably the most important energy reserve in higher plants. It is synthesised in different organelles for 'transitory' as well as the more obvious longer term energy depot roles in seeds, grains, piths, tubers and roots. Depending on which organelle type the starch is synthesised within, it has a characteristic form with different functionality. In chloroplasts the transitory starch (in the form of granules) is synthesised during the day and degraded at night, supporting the growth of the plants or providing energy whenever it is needed. In contrast, the storage/reserve (depot) starch is produced in the amyloplasts of storage tissues (again as granules) during the development of the plants. It is hydrolysed (ultimately to glucose) and utilised as a carbon source during sprouting, germination or ripening of the crop (usually translocated as sucrose). The storage starch can thus be found widely in plant tissues that require a significant energy sink. This type of starch is not only vital for the survival for higher plants survival but also for humans as a food supply. The storage starch (native or modified) has been widely used in the food industry as a texture modifier, stabiliser and thickener and in non-food industries for abrasion resistance improvement in textile manufacturing, for strength and printability enhancement during paper production and as excipient forms in pharmaceutical products. In addition, with a nutritional focus, the hydrolysis resistance of starch to intestinal enzymes has been optimised to provide enhanced nutritional benefits of foodstuffs.