Enzymes and Their Action on Starch

Robyt, John F.

doi:10.1016/b978-0-12-746275-2.00007-0

Cited by 39 publications

(37 citation statements)

References 236 publications

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“…Moreover, the subsites possess variable affinities: the affinity of the first subsite is very low, whereas subsite 2 has the highest affinity and the affinity of the individual sites decreases from subsite 3 to 7 (Hiromi, Nitta, Numata, & Ono, 1973). Amyloglucosidase has a multichain hydrolysis mechanism, i.e., after the glycosidic bond is cleaved by amyloglucosidase, the remaining starch chain must dissociate and leave the active sites before glucose can leave (Robyt, 2009). The active sites of the amyloglucosidase are 'pocket like', which ensure that only a single, b-conformational glucose can be produced.…”

Section: Starch Digestion In Vitro: Enzyme Interactionmentioning

confidence: 98%

Densely packed matrices as rate determining features in starch hydrolysis

Zhang

Dhital

Gidley

2015

Trends in Food Science & Technology

141

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To aid in the design of starch-containing foods with slow and/ or incomplete digestion in the upper gastrointestinal tract, the starch structural factors which control the rate of action of alpha-amylase are reviewed. It is concluded that local starch molecular density has the major influence on amylase digestion kinetics, and that density sufficient to either limit enzyme binding and/or slow down catalysis can be achieved by either crystallization or dense amorphous packing. IntroductionStarch, a major digestible carbohydrate in human diets, is synthesized in a condensed semi-crystalline granular form by the ordered packing of two hydrophilic glucose polymers (amylose and amylopectin) during photosynthesis. It has a complex hierarchical structure, which can be described by at least four levels of organization (i.e., molecular, lamellae, growth ring, and granular levels), ranging in length scale from nanometer to micrometer. Several detailed comprehensive reviews (

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Section: Starch Digestion In Vitro: Enzyme Interactionmentioning

confidence: 98%

Densely packed matrices as rate determining features in starch hydrolysis

Zhang

Dhital

Gidley

2015

Trends in Food Science & Technology

141

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“…The linear amylose has very low water solubility (61 mg/ mL) and precipitated from solution by forming double helices (retrogradation). 5,6 The retrograded amylose was removed by centrifugation, and the supernatant was found to give a blue color with KI 3 solution. This supernatant solution was concentrated 10-fold and allowed to stand at 4°C.…”

Section: Introductionmentioning

confidence: 99%

Isolation, structure, and characterization of the putative soluble amyloses from potato, wheat, and rice starches

Mukerjea

Robyt

2010

Carbohydrate Research

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“…The carboxylate group abstracts a proton from water, making the water more nucleophilic for its attack on the p-linked acetal ester. The anomeric carbon atom of the resultingglucopyranosyl unit that is released from the enzyme complex thushastheaconfiguration, giving retention of the configuration of the product at itsreducingend (Robyt, 2009). …”

Section: Double Displacement Mechanismmentioning

confidence: 99%

The impact of heat-moisture treatment on the molecular structure and physicochemical properties of normal and waxy potato starches

Varatharajan

Hoover

Liu

et al. 2010

Carbohydrate Polymers

148

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Heat-moisture treatment (HMT) is a physical modification technique that modifies starch structure and properties without destroying its granular structure. HMT has been shown to cause starch chain interactions and crystallite disruption/reorientation within the amorphous and crystalline domains. However, the part played by amylose (AM) during HMT of starches is not properly understood. Furthermore, a systematic study has not been carried out to examine how variations in HMT temperatures influence molecular structure, physicochemical properties and digestibility of normal potato (NP) and waxy potato (WP) starches. Thus, the objective of this study was to determine changes to molecular structure, physicochemical properties and digestibility ofNP and WP starches on HMT at different temperatures (80,100,120 and l30°C) for 16 h at 27% moisture. Structural changes on HMT were monitored by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), polarized light microscopy (pLM), wide angle X-ray scattering (WAXS), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, fluorophore assisted capillary electrophoresis (FACE) and KlS spectra. Changes to physicochemical properties on HMT were determined by granular swelling, amylose leaching, gelatinization parameters and pasting properties. Digestibility of normal and waxy potato starches before and after HMT by porcine pancreatic a-amylase (PPA) was monitored by measuring initial velocity and by exarninationofthe granular structure at different stages of hydrolysis by SEM, CLSM and PLM. The results showed that structural changes on HMT were influenced by differences in starch chain mobility at different temperatures of HMT. Starch chain mobility, in turn, was influenced by the interplay between the extent to which B-type crystallites were transformed into A+B-type crystallites, kinetic energy imparted to starch chains and amylose content. The main type of structural changes influencing physicochemical properties at different temperatures of HMT were starch chain interactions (at 80 and IOO°C), disruption of hydrogen bonds between amylose-amylopectin and amylopectin-amylopectin (at 120 and l30°C), disorganization of amylopectin chains near the vicinity of the hilum (at 100, 120 and l30°C)andformationofinterruptedhelices(atl30°C).The susceptibility ofNP and WP starches towards a-amylase decreased at 80°C, but increased in the range 100 to l30°C. NPand WPstarches exhibited heterogeneity in degradation (NP>WP) Most studies have been on the impact ofHMT on the thermal properties, crystallinity and pasting propertiesofnorrnalstarches. Some researchers (Hoover and Manuel, 1996; Kweon el al., 2000;Zavareze et al., 2010) have attempted to explain the impact of HMT on the structure and physicochemical properties of starches varying in amylose content. However, the part played by amylose during HMT of starches is still not properly understood. Unlike in cereal starches, amylose has been shown to be co-crystallized with amylopectin...

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Enzymes and Their Action on Starch

Cited by 39 publications

References 236 publications

Densely packed matrices as rate determining features in starch hydrolysis

Densely packed matrices as rate determining features in starch hydrolysis

Isolation, structure, and characterization of the putative soluble amyloses from potato, wheat, and rice starches

The impact of heat-moisture treatment on the molecular structure and physicochemical properties of normal and waxy potato starches

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