Chain-extended starch is prepd. in that starch is polymd. in an aq. soln. at pH 6.0-8.3 by means of glucosyl fluoride in the presence of inorg. phosphate, sucrose phosphorylase, and potato phosphorylase. [on SciFinder(R)]
Amylomaltases or D-enzyme (4-α-glucanotransferases; E.C. 2.4.1.25) are carbohydrate-active enzymes that catalyze the transfer of glucan units from one α-glucan to another in a disproportionation reaction. These enzymes are involved in starch metabolism in plants or maltose/glycogen metabolism in many microorganisms. The amylomaltase of the hyperthermophilic bacterium Thermus thermophilus HB8 was overproduced in Escherichia coli, partially purified and used to modify potato starch. The action of amylomaltase caused the disappearance of amylose and the broadening of the side-chain length distribution in amylopectin, which resulted in a product with both shorter and longer side chains than in the parent starch. Amylomaltase-treated potato starch showed thermoreversible gelation at concentrations of 3% (w/v) or more, thus making it comparable to gelatin. Because of its animal origin, gelatin is not accepted by several consumer groups. Therefore, the amylomaltase-treated potato starch might be a good plant-derived substitute for gelatin. ? 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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This study provides insights into novel combinations of hydrothermal modifications and mineral enrichment by demonstrating the versatility of this environmentally more benign approach compared to other common chemical starch modifications like crosslinking. Heat-moisture treatment (HMT) (15 % moisture, 100 °C) of native potato starch (NPS) affords granular products that gelatinise at lower temperatures, hold more water as gel, and are more susceptible to enzymatic digestion. Prior mineral enrichment of NPS with sodium, potassium, magnesium and calcium ions yielded significant changes in pasting curves, with monovalent cations increasing peak viscosity, while divalent cations decrease peak viscosity through ionic crosslinking of phosphate groups, allowing further fine tuning of swelling behaviour. Both short and long HMT (4 h and 16 h) triggered partial disruption of crystallinity and an increase in particle size without visible surface damage as evidenced by X-ray diffraction, laser diffraction and scanning electron microscopy. These novel products may find applications where a thickening agent is needed, and high levels of target minerals are desirable like sport nutrition. The viscosity behaviour, available energy and essential minerals may be beneficial to the formulation and nutritional value of energy gels, while adhering to clean-label requirements of today`s food industry.
