Browsing by Author "Salman, H"

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    Form and functionality of starch.
    (Elsevier, 2008-08) Copeland, L; Blazek, J; Salman, H; Tang, MCM
    Starch is a macro-constituent of many foods and its properties and interactions with other constituents, particularly water and lipids, are of interest to the food industry and for human nutrition. Starch varies greatly in form and functionality between and within botanical species, which provides starches of diverse properties but can also cause problems in processing due to inconsistency of raw materials. Being able to predict functionality from knowledge of the structure, and explain how starch interacts with other major food constituents remain significant challenges in food science, nutrition, and for the starch industry generally. This paper describes our current understanding of starch structure that is relevant to its functionality in foods and nutrition. Amylose influences the packing of amylopectin into crystallites and the organization of the crystalline lamellae within granules, which is important for properties related to water uptake. Thermal properties and gel formation appear to be influenced by both amylose content and amylopectin architecture. While amylose content is likely to have an important bearing on the functional properties of starch, subtle structural variations in the molecular architecture of amylopectin introduces uncertainty into the prediction of functional properties from amylose content alone. Our ability to relate starch granule structure to suitability for a particular food manufacturing process or its nutritional qualities depends not only on knowledge of the genetic and environmental factors that control starch biosynthesis, and in turn granule morphology, but also on how the material is processed. © 2008, Elsevier Ltd.
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    Structural characterization of wheat starch granules differing in amylose content and functional characteristics
    (Elsevier, 2009-02-24) Blazek, J; Salman, H; Rubio, AL; Gilbert, EP; Hanley, TL; Copeland, L
    Small-angle X-ray scattering (SAXS) together with several complementary techniques such as differential scanning calorimetry and X-ray diffraction, have been employed to investigate the structural features that give diverse functional properties to wheat starches (Triticum aestivum L.) within a narrow range of enriched amylose content (36-43%). For these starches, which come from a heterogeneous genetic background. SAXS analysis of duplicate samples enabled structural information to be obtained about their lamellar architecture where differences in lamellar spacing among samples were only several tenths of nanometer. The SAXS analysis of these wheat starches with increased amylose content has shown that amylose accumulates in both crystalline and amorphous parts of the lamella. Using waxy starch as a distinctive comparison with the other samples confirmed a general trend of increasing amylose content being linked with the accumulation of defects within crystalline lamellae. We conclude that amylose content directly influences the architecture of semi-crystalline lamellae, whereas thermodynamic and functional properties are brought about by the interplay of amylose content and amylopectin architecture. © 2008, Elsevier Ltd.
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    Structure-function relationships in A and B granules from wheat starches of similar amylose content
    (Elsevier, 2009-02-11) Salman, H; Blazek, J; Lopez-Rubio, A; Gilbert, EP; Hanley, TL; Copeland, L
    Five wheat (Triticum aestivum L.) starches, from the varieties Sunco, Sunsoft, SM1118. and SM1028, with similar amylose content, and a waxy wheat were separated into large (A) and small (B) granules. The unfractionated starches, and isolated A and B granules, were characterized structurally and evaluated for their functional properties. The amylopectin chain length distribution revealed that A granules had a lower proportion of short chains with degree of polymerization (DP) 6-12 and a higher proportion of chains with DP 25-36 than B granules. X-ray diffraction (XRD) patterns showed predominantly A-type crystallinity for all of the starches. No differences in the crystallinity were found between unfractionated, A and B granules. Small-angle X-ray scattering (SAXS) patterns of the starches at 55% hydration showed that the lamellar repeat distance in A granules was larger than that of B granules for all the starches examined. However, the lamellar distances of both A and B granules from the waxy wheat were smaller than those of Sunco, Sunsoft, SM1118 and SM1028 starches. The swelling power of the B granules was greater than that of A granules from all five starches. The kinetics of digestion of A and B granules with α-amylase in vitro were complex, with B granules initially digested to a greater extent than A granules. After 4 h of incubation, A granules showed greater digestibility than B granules, except in the case of waxy starch where unfractionated and fractionated granules had similar in vitro digestibility. Correlations between structural and functional parameters were more significant for the isolated A and B granules than for the unfractionated starches. This study demonstrates that A and B granules differ in structure and functionality, and that some correlations between these properties could be masked in unfractionated starches with bimodal granule size distribution. © 2008, Elsevier Ltd.