The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
C G Oates - One of the best experts on this subject based on the ideXlab platform.
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the effect of Amylose lipid complex formation on enzyme susceptibility of sago starch
Food Chemistry, 1999Co-Authors: C G OatesAbstract:Abstract Native sago starch was incubated at 60°C with lysophosphatidylcholine, monomyristin, monopalmitin, and monostearin. Differential scanning calorimetry peaks centred at 100–120°C indicated formation of Amylose–lipid complexes. Among the four lipids, lysophosphatidylcholine showed the highest complexing ability, while that of the monoglycerides decreased with the increasing chain length. Part of the Amylose leached during the incubation, and the amount of leached material decreased in the presence of lipids. Starch–lipid samples were subjected to enzyme hydrolysis by porcine pancreatic α -amylase. The bioavailability of native and freshly gelatinised sago starch was decreased in the presence of lipids, while retrograded starch–lipid samples showed higher digestibility than starch control. ©
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the effect of retrogradation on enzyme susceptibility of sago starch
Carbohydrate Polymers, 1997Co-Authors: C G OatesAbstract:Abstract Gelatinized sago starch was stored for different times and under different temperature conditions for the investigation of retrogradation. DSC was used to monitor the thermal properties of retrograded starch. Bioavailability of starch samples was determined by porcine pancreatic α-amylase at 37 °C. Amylose retrograded rapidly at 5 °C, whereas amylopectin recrystallization was enhanced by sequential storage at 5 °C followed by 30 °C. Increased extent of retrogradation (high melting enthalpy values and melting temperature) caused reduced enzyme susceptibility of sago starch and sago products at 37 °C.
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sago starch as a biomass source raw sago starch hydrolysis by commercial enzymes
Bioresource Technology, 1996Co-Authors: Wei Wang, A D Powell, C G OatesAbstract:Abstract Raw sago starch and sago starch pretreated by heating at 60°C for 2 hours in sodium acetate buffer (pH 3·5) were hydrolysed using commercial glucoamylase-AMG (EC 3·2·1·3), α-amylases-BAN, Fungamyl and Termamyl (EC 3·2·1·1), debranching amylase-Promozyme (EC 3·2·1·41), and their mixtures in sodium acetate buffer, pH 5·0 at 35°C. Raw sago starch was a poor substrate for enzyme action compared to corn and tapioca starches tested under the same conditions, although pretreating the starch increased the extent and rate of hydrolysis. A strong synergism between glucoamylase and α-amylase on the hydrolysis of both untreated and pretreated sago starch was observed. The hydrolysis products were characterized by high-performance size-exclusion chromatography (HPSEC). The total carbohydrate concentration of hydrolysed sago starch decreased but the Amylose and amylopectin ratios in the residues remained the same.
R. Hoover - One of the best experts on this subject based on the ideXlab platform.
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impact of annealing on the molecular structure and physicochemical properties of normal waxy and high Amylose bread wheat starches
Food Chemistry, 2008Co-Authors: H Lan, R. Hoover, L Jayakody, Qiang Liu, Elizabeth Donner, Monica Baga, Eric K Asare, Pierre Hucl, Ravindra N ChibbarAbstract:Abstract Starch from normal (CDC teal), high Amylose (line 11132) and waxy (99 WAX 27) bread wheat cultivars was isolated and its morphology, composition, structure and properties were studied before and after annealing. Granule diameters, total phosphorus, total Amylose, lipid complexed Amylose chains, crystallinity, gelatinization temperature range, gelatinization enthalpy, swelling factor (at 90 °C), and Amylose leaching (at 90 °C), in the above starches ranged from 2–38 μm, 0.007–0.058%, 26.9–32.3%, 13.4–18.7%, 28.6–42.8%, 12.7–14.3 °C, 11.3–13.3 J/g, 27.6–72.2 and 22.2–26.2%, respectively. Peak viscosity, thermal stability, set-back and susceptibility towards acid hydrolysis followed the order: 99WAX27 > CDC teal > 11132, 11132 > CDC teal > 99WAX27, CDC teal > 99 WAX 27 > 11132, and 99WAX27 > 11132 > CDC teal, respectively. Susceptibility towards α-amylase hydrolysis followed the order: 99 WAX 27 > 11132 > CDC teal ( CDC teal > 99WAX27 (>24 h). The extent of retrogradation measured by spectroscopy and differential scanning calorimetry followed the order: 11132 > CDC teal > 99WAX27 and 99WAX27 > CDC teal > 11132, respectively. In all starches, concentration of Amylose, lipid complexed Amylose chains, gelatinization temperature range, swelling factor, Amylose leaching, peak viscosity, final viscosity, set-back, light transmission, susceptibility towards α-amylase and acid hydrolysis and the proportion of small (2–8 μm) B-type granules decreased on annealing. Thermal stability and crystallinity increased on annealing. In all starches, gelatinization, enthalpy, retrogradation rate and amylopectin chain length distribution remained unchanged on annealing. Pores and indentations were formed on the granule surfaces of CDC teal and 99WAX27 starches on annealing.
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starch from hull less barley v in vitro susceptibility of waxy normal and high Amylose starches towards hydrolysis by alpha amylases and amyloglucosidase
Food Chemistry, 2004Co-Authors: Thava Vasanthan, R. Hoover, B G RossnagelAbstract:Abstract Waxy (CDC Alamo), normal (CDC Dawn), and high-Amylose (SB 94893) hull-less barley (HB) starches were isolated and their susceptibilities to porcine pancreatic α-amylase (PPA), Bacillus species α-amylase (BAA), and Aspergillus niger amyloglucosidase (AAG) were determined. Scanning and transmission electron micrographs showed that the patterns of enzyme hydrolysis (surface erosion, endoerosion, and the erosion at the equatorial groove plane) were dependent on the enzyme source and starch types. The outer layers of normal and high-Amylose HB starch granules were more resistant to enzyme hydrolysis. The hydrolysis rate of waxy HB starch by the three amylases at 37 °C was significantly higher than those of normal and high-Amylose HB starches. The degree of hydrolysis by PPA, after 72 h, reached 91–97% in all three starches. However, BAA and AAG showed significantly lower degrees of hydrolysis in normal ( 67%). Glucose, maltose, and maltotriose contents of the hydrolysates, collected at different time intervals, were determined by HPLC. The concentration and composition of soluble sugars in hydrolysates varied with enzyme source, starch types, and condition of hydrolysis. The study suggested that both morphological and ultrastructural features influence in-vitro hydrolysis and the ultrastructure of waxy HB starch may be more open than those of normal and high-Amylose HB starches.
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composition molecular structure and physicochemical properties of starches from four field pea pisum sativum l cultivars
Food Chemistry, 2001Co-Authors: Wajira S Ratnayake, R. Hoover, Fereidoon Shahidi, C Perera, J JaneAbstract:Abstract Starch from four cultivars (Carneval, Carrera, Grande and Keoma) of field pea ( Pisum sativum L.) was isolated and its physicochemical properties were compared with those of other legume starches. The yield of starch was in the range 32.7–33.5% on a whole seed basis. The starch granules were round to elliptical with smooth surfaces. The free lipid was 0.05% in all starches. However, bound and total lipids ranged from 0.24 to 0.29% and from 0.28 to 0.34%, respectively. The total Amylose content ranged from 48.8–49.6%, of which 10.9–12.3% was complexed by native lipid. The degree of polymerization (DP) of Amyloses ranged from 1300 to 1350. The chain length distributions of debranched amylopectins of the starches were analyzed using high performance anion-exchange chromatography equipped with a post-column amyloglucosidase reactor and a pulsed amperometric detector. The proportion of short branch chains, of chain length DP 6-12, ranged from 16.2 to 18.6%. Keoma displayed a larger portion (19.4%) of long branch chains (DP>37) than the other three starches (16.2–16.9%). The average amylopectin branch chain length ranged from 22.9 to 24.2. The maximum detectable DP was higher in Keoma (71) than in the other three starches (64–65). The X-ray pattern was of the ‘C’ type. The relative crystallinity was in the range 20.8–25.1%. The proportion of ‘B’ polymorphic form was higher in Keoma (25.6%) than in the other three starches (22.1–24.1%). There were no significant differences in swelling factor. The extent of Amylose leaching at 95°C ranged from 25.20 to 26.85. All four starches exhibited nearly identical gelatinization transition temperatures and enthalpies. However, the gelatinization temperature range ( T c – T o ) followed the order: Grande∼Keoma>Carneval∼Carrera. The four starches showed identical pasting temperatures and exhibited only marginal differences with respect to 95°C viscosity and to the increase in consistency during the holding period at 95°C. However, the set-back viscosity for Carneval was lower than that of the other starches. There were no significant differences in the extent of acid hydrolysis. However, susceptibility towards hydrolysis by α-amylase followed the order: Carneval∼Carrera∼Grande>Keoma. The extent of retrogradation (monitored by changes in enthalpy) during storage at 40°C/24 h followed the order: Carneval>Carrera>Grande>Keoma. However, differences in the extent of retrogradation among starches were not discernable by freeze-thaw stability measurements.
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studies on isolation and characterization of starch from oat avena nuda grains
Carbohydrate Polymers, 1992Co-Authors: R. Hoover, Thava VasanthanAbstract:Starch from AC Hill oat grains (Avena nuda) was isolated and some of the characteristics determined. The yield of starch was 23·4% on a whole grain basis. The shape of the granule was polyhedral to irregular, with granules 6–10 μm in diameter. Lipids were extracted by acid hydrolysis and by selective solvent extraction with chloroform-methanol 2:1 v/v (CM) at ambient temperature, followed by n-propanol-water 3:1 v/v (PW) at 90–100°C. The acid hydrolyzed extracts which represented the total starch lipids (TSL) was 1·13%. The free lipids in the CM extract (1% TSL) was 6·2%, whereas the free and bound lipids in the PW extracts was 93.0%. Neutral lipids formed the major lipid class in the CM and PW extracts. The monoacyl lipid content in both CM and PW extracts was 61·0%. The total Amylose content was 19·4%, of which 13·9% was complexed by native lipids. X-ray diffraction was of the ‘A’ type. Oat starch differed from wheat starch in showing a higher swelling factor, decreased Amylose leaching, coleaching of a branched starch component and Amylose during the pasting process, higher peak viscosity and set-back, low gel rigidity, greater susceptibility towards acid hydrolysis, greater resistance to α-amylase action and a higher freeze-thaw stability. Furthermore, in comparison to wheat starch, the Amylose chains of oat starch appear to be more loosely arranged in the amorphous regions, whereas in crystalline regions, oat starch chains are more compactly packed. Lipid removal from oat and wheat starches decreased their swelling factor, peak viscosity, set-back, gelatinization temperatures, freeze-thaw stability and paste clarity (at pH > 4·0), and increased their thermal stability, Amylose leaching, enthalpy of gelatinization, susceptibility towards α-amylase and paste clarity (at pH < 4·0). The results also showed that the properties of AC Hill oat starch is not representative of oat starch in general.
B Svihus - One of the best experts on this subject based on the ideXlab platform.
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starch structure and degree of starch hydrolysis of small and large starch granules from barley varieties with varying Amylose content
Animal Feed Science and Technology, 2006Co-Authors: A Stevnebo, S Sahlstrom, B SvihusAbstract:Starch structure is considered to have an impact on the rate of starch digestion in cereals, and is therefore an important factor in regard to optimise the starch quality in animal feed. The purpose of the study reported was to investigate the impact of Amylose level and starch particle size on starch degradation in vitro. A two-step in vitro method was conducted to degrade starch enzymatically. The method consisted of a pre-incubation in HCl and pepsin, and thereafter an incubation with buffers, porcine pancreatic α-amylase and amyloglucosidase. Degree of starch hydrolysis was calculated based on free glucose content. Milled grains, isolated starch and A and B granules from barley cultivars with various level of Amylose were hydrolysed. Particle size, thermal characteristics and chemical components were determined to characterise the material. Cultivars with low level of Amylose had a higher degree of starch hydrolysis than cultivars with normal and high Amylose content for all time intervals (P<0.05). This was observed both for incubated flour and purified starch. A higher degree of starch hydrolysis was found for normal Amylose cultivars compared to high Amylose cultivars when incubating flour (P<0.05). This difference was not significant for the purified starch fraction. Due to a higher surface area and lower crystallinity, small starch granules were degraded at a higher level than large granules (P<0.05), despite a slightly higher Amylose content. The range in starch hydrolysis between Amylose groups within granule size was similar to the results from incubations with total starch fractions. Low Amylose cultivars contained, however, less small granules by volume than the two other Amylose groups (P<0.05). This indicates that the Amylose level and the Amylose lipid complex are the limiting factors regarding starch degradation for these barley cultivars.
Robin Manelius - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Ca2+-Ions on the α-Amylolysis of Granular Starches from Oats and Waxy-Maize
Journal of Cereal Science, 1996Co-Authors: Robin Manelius, Eric BertoftAbstract:Abstract Granular oat starch was subjected to hydrolysis withBacillus subtilis alpha-amylase in either calcium acetate or sodium acetate buffer and compared with the hydrolysis of waxy-maize starch granules. The enzyme was pumped through a thin layer of starch packed into a special column and further into an ion-exchanger that retained the enzyme but not the dextrins solubilised from the granules. Both the Amylose and the amylopectin components of oat starch granules were attacked by the enzyme. Calcium ions increased the rate of solubilisation of the oat starch granules but not of the waxy-maize starch granules. However, the composition of the solubilised dextrins was clearly affected with both types of granules so that the molecular weight distribution of the products shifted to smaller sizes in the presence of calcium. Other salts that were tested with the oat starch granules did not affect the solubilisation rate. Scanning electron micrographs showed that the attack pattern ofalpha-amylase on oat starch is different from the attack on waxy-maize granules.
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Studies on the Structure of Pea Starches Part 4: Intermediate Material of Wrinkled Pea Starch
Starch-starke, 1993Co-Authors: Eric Bertoft, Robin ManeliusAbstract:β-Limit dextrins were isolated from wrinkled pea starch, fractionated into different sizes, and their molecular weight distribution analysed by gel chromatography. A minor part of the dextrins had high molecular weight and long chains typical for Amylose. The major part of the dextrins had low molecular weight and possessed unit chains of the same types as was found in the amylopectin of smooth pea starch. However, the proportion of long chains was significantly higher. The hydrolysis of wrinkled pea starch with α-amylase was fast and reflected the large content of Amylose, whereas the hydrolysis of the β-limit dextrin was slow. The intermediate dextrin products obtained from the latter had similar molecular weights as those produced from other amylopectins, which indicated that it was build up of clusters of branchings. Structure models that show the mode of interconnection of the clusters in the intermediate material are suggested. Untersuchungen uber die Struktur von Erbsenstarken. Teil 4: Zwischenproduktmaterial von Runzelerbsenstarke. Aus Runzelerbsenstarke wurden β-Grenzdextrine isoliert und mittels Gelchromatographie nach ihrer Grosenverteilung und ihrem Molekularverteilungsgewicht fraktioniert. Ein kleiner Anteil der Dextrine hatte ein hohes Molekulargewicht und fur Amylose typische lange Ketten. Der Hauptteil der Dextrine hatte ein niedriges Molekulargewicht und besas einheitliche Ketten vom gleichen Typ wie sie im Amylopektin von Palerbsenstarke gefunden wurden. Der Anteil an langen Ketten war jedoch deutlich hoher. Die Hydrolyse der Runzelerbsenstarke mittels α-Amylase gelang rasch und spiegelte den hohen Anteil an Amylose wider, wogegen die Hydrolyse des β-Grenzdextrins langsam verlief. Die aus dem letzteren erhaltenen mittleren Dextrinprodukte hatten ahnliche Molekulargewichte wie die aus anderen Amylopektinen gewonnenen, was darauf hinweist, das sie aus Clustern von Verzweigungen aufgebaut waren. Strukturmodelle, Modelle, welche die Art der Verschrankung der Cluster im mittelgrosen Material aufzeigen, werden vorgeschlagen.
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Studies on the Structure of Pea Starches. Part 2: α‐Amylolysis of Granular Wrinkled Pea Starch
Starch-starke, 1993Co-Authors: Eric Bertoft, Robin ManeliusAbstract:Wrinkled pea starch, separated into fractions containing intact granules and fragmented granules together with small intact granules, respectively, was hydrolysed by the α-amylase of Bacillus amyloliquefaciens in a column. The solubilisation rate was similar for both fractions and occurred in three stages: initially increasing, then slowly decreasing, and finally it was very slow. The mixtures of solubilised dextrins had DP (degree of polymerization) 2–100 and their compositions changed as the solubilisation proceeded through the different stages. The products were mostly linear and the composition of the granular residues indicated that Amylose preferentially solubilised. Scanning electron microscopy could hardly reveal the site of the attack even though 20% of the granules had been solubilised. It is suggested that the enzyme attacked Amylose chains in an amorphous state, whereas chain residues with DP 50–300 remained in the crystalline parts within the granules.
Thava Vasanthan - One of the best experts on this subject based on the ideXlab platform.
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starch from hull less barley v in vitro susceptibility of waxy normal and high Amylose starches towards hydrolysis by alpha amylases and amyloglucosidase
Food Chemistry, 2004Co-Authors: Thava Vasanthan, R. Hoover, B G RossnagelAbstract:Abstract Waxy (CDC Alamo), normal (CDC Dawn), and high-Amylose (SB 94893) hull-less barley (HB) starches were isolated and their susceptibilities to porcine pancreatic α-amylase (PPA), Bacillus species α-amylase (BAA), and Aspergillus niger amyloglucosidase (AAG) were determined. Scanning and transmission electron micrographs showed that the patterns of enzyme hydrolysis (surface erosion, endoerosion, and the erosion at the equatorial groove plane) were dependent on the enzyme source and starch types. The outer layers of normal and high-Amylose HB starch granules were more resistant to enzyme hydrolysis. The hydrolysis rate of waxy HB starch by the three amylases at 37 °C was significantly higher than those of normal and high-Amylose HB starches. The degree of hydrolysis by PPA, after 72 h, reached 91–97% in all three starches. However, BAA and AAG showed significantly lower degrees of hydrolysis in normal ( 67%). Glucose, maltose, and maltotriose contents of the hydrolysates, collected at different time intervals, were determined by HPLC. The concentration and composition of soluble sugars in hydrolysates varied with enzyme source, starch types, and condition of hydrolysis. The study suggested that both morphological and ultrastructural features influence in-vitro hydrolysis and the ultrastructure of waxy HB starch may be more open than those of normal and high-Amylose HB starches.
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studies on isolation and characterization of starch from oat avena nuda grains
Carbohydrate Polymers, 1992Co-Authors: R. Hoover, Thava VasanthanAbstract:Starch from AC Hill oat grains (Avena nuda) was isolated and some of the characteristics determined. The yield of starch was 23·4% on a whole grain basis. The shape of the granule was polyhedral to irregular, with granules 6–10 μm in diameter. Lipids were extracted by acid hydrolysis and by selective solvent extraction with chloroform-methanol 2:1 v/v (CM) at ambient temperature, followed by n-propanol-water 3:1 v/v (PW) at 90–100°C. The acid hydrolyzed extracts which represented the total starch lipids (TSL) was 1·13%. The free lipids in the CM extract (1% TSL) was 6·2%, whereas the free and bound lipids in the PW extracts was 93.0%. Neutral lipids formed the major lipid class in the CM and PW extracts. The monoacyl lipid content in both CM and PW extracts was 61·0%. The total Amylose content was 19·4%, of which 13·9% was complexed by native lipids. X-ray diffraction was of the ‘A’ type. Oat starch differed from wheat starch in showing a higher swelling factor, decreased Amylose leaching, coleaching of a branched starch component and Amylose during the pasting process, higher peak viscosity and set-back, low gel rigidity, greater susceptibility towards acid hydrolysis, greater resistance to α-amylase action and a higher freeze-thaw stability. Furthermore, in comparison to wheat starch, the Amylose chains of oat starch appear to be more loosely arranged in the amorphous regions, whereas in crystalline regions, oat starch chains are more compactly packed. Lipid removal from oat and wheat starches decreased their swelling factor, peak viscosity, set-back, gelatinization temperatures, freeze-thaw stability and paste clarity (at pH > 4·0), and increased their thermal stability, Amylose leaching, enthalpy of gelatinization, susceptibility towards α-amylase and paste clarity (at pH < 4·0). The results also showed that the properties of AC Hill oat starch is not representative of oat starch in general.
