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C G Oates – One of the best experts on this subject based on the ideXlab platform.

  • the effect of Amylose lipid complex formation on enzyme susceptibility of sago starch
    Food Chemistry, 1999
    Co-Authors: C G Oates


    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. ©

  • the effect of retrogradation on enzyme susceptibility of sago starch
    Carbohydrate Polymers, 1997
    Co-Authors: C G Oates


    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.

  • sago starch as a biomass source raw sago starch hydrolysis by commercial enzymes
    Bioresource Technology, 1996
    Co-Authors: Wei Wang, A D Powell, C G Oates


    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.

  • impact of annealing on the molecular structure and physicochemical properties of normal waxy and high Amylose bread wheat starches
    Food Chemistry, 2008
    Co-Authors: H Lan, R. Hoover, L Jayakody, Qiang Liu, Elizabeth Donner, Monica Baga, Eric K Asare, Pierre Hucl, Ravindra N Chibbar


    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.

  • 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, 2004
    Co-Authors: Thava Vasanthan, R. Hoover, B G Rossnagel


    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.

  • composition molecular structure and physicochemical properties of starches from four field pea pisum sativum l cultivars
    Food Chemistry, 2001
    Co-Authors: Wajira S Ratnayake, R. Hoover, Fereidoon Shahidi, C Perera, J Jane


    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.

B Svihus – One of the best experts on this subject based on the ideXlab platform.

  • 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, 2006
    Co-Authors: A Stevnebo, S Sahlstrom, B Svihus


    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.