Effects of Extrusion Temperature and Plasticizers on the Physical and Functional Properties of Starch Films

Cornstarch, at 20% moisture content (dry basis, d.b.), was mixed with glycerol at 3:1 ratio to form the base material for extruded starch films. Stearic acid, sucrose and urea, at varying concentrations, were tested as secondary plasticizers for the starch‐glycerol mixture. The ingredients were extruded at 110 and 120°C barrel temperatures to determine the effects of extrusion temperature, plasticizer type and their concentrations on the film‐forming characteristics of starch, as well as their effects on selected physical and functional properties of the films. The physical and mechanical properties of the films were studied by scanning electron microscopy (SEM) and tensile testing, while the glass transition and gelatinization properties were analyzed using differential scanning calorimetry (DSC). The interactions between the functional groups of starch and plasticizers were investigated using Fourier‐transform infrared (FTIR) spectroscopy. The water vapor permeability (WVP) properties of starch films were determined using ASTM standard E96‐95. Scanning electron micrographs exhibited the presence of native and partially melted starch granules in the extruded films. The tensile stress, strain at break and Young's modulus of starch films ranged from 0.9 to 3.2 MPa, 26.9 to 56.2% and 4.5 to 67.7 MPa, respectively. DSC scans displayed two glass transitions in the temperature ranges of 0.1 to 1°C and 9.6 to 12°C. Multiple melting endotherms, including that of amylose‐lipid complexes, were observed in the thermoplastic extrudates. The gelatinization enthalpies of the starch in the extruded films varied from 0 to 1.7 J/g, and were dependent largely on the extrusion temperature and plasticizer content. The shift in the FTIR spectral bands, as well as the appearance of double‐peaks, suggested strong hydrogen bonding interactions between the starch and plasticizers. The WVP of starch films ranged from 10.9 to 15.7 g mm h^‐1 m^‐2 kPa^‐1, depending on the extrusion temperature and the type of plasticizer used.     

Physicochemical Properties of Pin Oak (Quercus palustris Muenchh.) Acorn Starch

Physicochemical properties of acorn (Quercus palustris) starch were studied. Acorn starch granules were spherical or ovoid, with diameters ranging from 3–17 μm. Acorn starch exhibited A‐type X‐ray diffraction pattern, an apparent amylose content of 43.4% and absolute amylose content of 31.4%. Relative to other A‐type starches, acorn amylopectin had a comparable weight‐average molar mass (3.9×10⁸ g/mol), gyration radius (288 nm) and density (16.3 g mol⁻¹nm⁻³). Average amylopectin branch chain‐length corresponded to DP 25.5. Onset gelatinization temperature was 65.0°C and peak gelatinization temperature was considerably higher (73.7°C). The enthalpy change of gelatinization was very high compared to non‐mutant starches (20.8 J/g). An amylose‐lipid thermal transition was not observed. Starch retrograded for 7 d at 4°C had very high peak melting temperature (54.2°C) relative to other A‐type starches. Final (260 RVU) and setback (138 RVU) viscosity of an 8% acorn starch paste was high relative to other starches and pasting temperature was 71.5°C.     

Gamma-Irradiation Affects Some Physical Properties of Dry Bean (Phaseolus vulgaris) Starch

Gamma-irradiated great northern (GN) bean starch (2.5–20 kGy) showed apparent increased susceptibility to central fissures. Bean damage during scanning electron microscopy was observed using ≥400OX magnification on GN bean starch samples. Approximate molecular weights estimated by gel filtration chromatography Sepharose Cl-2B of control GN bean starch were: amylopectin >2×10⁶ and amylose 2×10⁵. Amylose-like fraction of irradiated bean starch (20 kGy) revealed two peaks ～6.9×10⁴ and 1.5×10⁵ daltons. Differential scanning calorimetry showed an increase in gelatinization enthalpy and a small increase in gelatinization peak temperature at 20 kGy suggesting a reorganization of the crystalline and amorphous phases of the starch granule.     

Extrusion of Rice,Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin

The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V^® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V^® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion.     

Effects of molecular characteristics of on konjac glucomannan glass transitions of potato amylose, amylopection and their mixtures

BACKGROUND: The purpose of this study was to explore further the functions of konjac glucomannan (KGM) in starch‐based foods. Experiments were carried out using the mixed amylose/amylopectin/KGM system as a model. High‐speed differential scanning calorimetry (hyper‐DSC) with the support of high‐performance size exclusion chromatography (HPSEC) equipped with multi‐angle laser light scattering (MALLS) and differential refractive index (RI), X‐ray diffractometry (XRD) and viscosimetry was used to investigate the effects of KGM on glass transition temperatures (T_gs) of mixtures with different amylose/amylopectin ratios. RESULTS: Hyper‐DSC results showed that the T_gs of amylose, amylopection and their mixtures decreased with increasing concentration of KGM. Based on the molecular characteristics of KGM, HPSEC‐MALLS‐RI, viscosimetry and XRD results showed that the molar masses of KGM ranged from 1.023 × 10⁶ to 1.329 × 10⁶ g mol^?1; the root mean square (RMS) radii were distributed from 110.5 to 129.6 nm, and M_w/M_n was 1.017. KGM was a linear molecule with random‐coil conformation in solution and the crystallinity was 0.00%. CONCLUSION: It is suggested that the addition of KGM has plasticizing effects on the structures of amylose and amylopectin, which can increase free volume and molecular movement of amylose and amylopectin chains, resulting in a decrease in their T_gs. Copyright © 2010 Society of Chemical Industry     

Twin-screw extrusion cooking of starches: Flow behaviour of starch pastes,expansion and mechanical properties of extrudates

Several starches, corn and durum wheat semolina, and wheat flour were extruded with a twin-screw, pilot-scale machine (Creusot-Loire BC 45). After grinding, pastes of the extruded samples were made and flow curves were obtained at 60°C with a coaxial-cylinder viscometer: a power law can be used to describe them from about 20 to 2600 s^?1. Apparent Young's moduli and rupture strengths of extrudates were evaluated with an Instron, and their diametral and longitudinal expansion measured. The following variables were studied: corn semolina water content, barrel temperature and the corn starch amylose/amylopectin ratio. When water content and barrel temperature vary within certain limits, the values of the constants in the power law equation describe a characteristic line which depends on the amylose and lipid contents of the starch. The formation of an amylose-lipid complex during extrusion is suggested as a key factor in the flow properties of pastes and probably also in the rupture strength of extrudates. There is generally a negative correlation between longitudinal and diametral expansion. It is considered that volume expansion phenomena are mainly dependent on viscous and elastic properties of melted starch.     

Characterization of Physical Properties of Flour and Starch Obtained from Gamma‐Irradiated White Rice

Physical and structural characteristics of rice flour and starch obtained from gamma‐irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A‐type X‐ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight‐average molecular weight (M_w) and gyration radius (R_z) of amylopectin analyzed by using HPSEC‐MALLS‐RI (high‐performance size‐exclusion chromatography equipped with multiangle laser‐light scattering and refractive index detector) decreased gradually from 1.48×10⁹ (M_w) and 384.1 nm (R_z) of native rice starch to 2.36×10⁸ (M_w) and 236.8 nm of 9 kGy‐irradiated starch. The branch chain‐length distribution of amylopectins determined by HPAEC‐ENZ‐PAD (high‐performance anion‐exchange chromatography with amyloglucosidase post‐column on‐line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13≤DP≤24 and 37≤DP, but produced more branch chains with 6≤DP≤12 when the irradiation dosage was less than 9 kGy. It might be deduced that gamma irradiation caused the breakage of the amylopectin chains at the amorphous regions, but had little effects on the crystalline regions of starch granules, especially at low dosage irradiation.     

Chemical and Physical Properties of Kiwifruit (Actinidia deliciosa) Starch

Chemical and physical properties of kiwifruit (Actinidia deliciosa var. ‘Hayward’) starch were studied. Kiwifruit starch granules were compound, irregular or dome‐shaped with diameters predominantly 4–5 µm or 7–9 µm. Kiwifruit starch exhibited B‐type X‐ray diffraction pattern, an apparent amylose content of 43.1% and absolute amylose content of 18.8%. Kiwifruit amylopectins, relative to other starches, had low weight‐average molecular weight (7.4×10⁷), and gyration radius (200 nm). Average amylopectin branch chain‐length was long (DP 28.6). Onset and peak gelatinization temperatures were 68.9°C and 73.0°C, respectively, and gelatinization enthalpy was high (18.5 J/g). Amylose‐lipid thermal transition was observed. Starch retrograded for 7 d at 4°C had a very high peak melting temperature (60.7°C). Peak (250 RVU), final (238 RVU) and setback (94 RVU) viscosity of 8% kiwifruit starch paste was high relative to other starches and pasting temperature (69.7°C) was marginally higher than onset gelatinization temperature. High paste viscosities and low pasting temperature could give kiwifruit starch some advantages over many cereal starches.     

Effects of the Barley amo1 and wax Genes on Starch Structure and Physicochemical Properties

Starch structural mutants showing abnormal endosperm characteristics have been used for investigating the effects of the mutation on structure and physicochemical properties of starches. Inbred lines of barley cultivars ‘Shikoku Hadaka 97’ and ‘Glacier AC38’ were used to investigate the impact of amo1 and waxy genes on starch properties. The amo1 type starch had high apparent amylose content and low starch content. The amo1+waxy type starch contained very little amylose. The content of long chains of amylopectin as detected with high‐performance size‐exclusion chromatography (HPSEC) was decreased, and that of amylopectin chains with the degree of polymerization (DP) of 12‐36 was increased in amo1 and amo1+waxy type starches. The amo1 and amo1+waxy type starches exhibited high gelatinization temperatures and low gelatinization enthalpies.     

Rice Starch Molecular Size and its Relationship with Amylose Content

The composition and starch molecular structure of eight rice varieties were studied. Waxy and non‐waxy (long‐, medium‐, and short‐grain) rice varieties from California and Texas were used. The amylose contents were measured using the Concanavalin A method and were found to be related to the type of rice: waxy ≈ 1.0%, short and medium grain 8.7–15.4%, and long grain 17.1–19.9%. The weight‐average molar masses (M_w) of the starches varied from 0.52 to 1.96×10⁸ g/mol. As would be expected, a higher M_w of rice starch correlated to lower amylose content. The range of M_w of amylopectin was 0.82 to 2.50 ×10⁸ g/mol, and there was also a negative correlation of amylopectin M_w with amylose content. Amylose M_w ranged from 2.20 to 8.31×10⁵ g/mol. After debranching the amylopectin with isoamylase, the weight‐average degree of polymerization (DP_w) for the long‐chain fraction correlated positively with a higher amylose content. California and Texas varieties were significantly different in their amylose content, starch M_w (short‐ and medium‐grain only), and amylopectin M_w (p < 0.05).     

Solubility Behavior of Granular Corn Starches in Methyl Sulfoxide (DMSO) as Measured by High Performance Size Exclusion Chromatography

The extent of corn starch dispersibility and the relative molecular solubility of amylose and amylopectin in methyl sulfoxide (DMSO) were determined. Granular corn starches with <l, 25, 53, and 70% amylose were dispersed in 0–100% DMSO (in water) solutions at 30°C for 30 min. Maximum dispersibility for all starches (98%) was obtained when 90% DMSO/10% water was used; regular (normal) dent corn starch was equally dispersed in solutions with 88–94% DMSO. Molecular solubility, the presence of individual molecules of amylose and amylopectin, of starches was also measured (after centrifugation and filtration) by high performance size-exclusion chromatography (HPSEC). Starches were dispersed in 90% DMSO and heated for 10 min at temperatures of 35–120ºC. At low temperatures, high coefficients of variation resulted from additional DMSO solubilization after treatment. At 120ºC, 70% amylose starch was >90% solubilized, while waxy starch was only 47% solubilized. When starches were treated for 18–89 h in 90ºC DMSO, solubility stopped increasing after 67 h. High amylose starch (70%) was mostly solubilized, but 53% amylose, waxy and regular starches could only be fully solubilized after exposure to shear. Amylopectin molecules appeared more susceptible to shear induced depolymerization than amylose. The percent amylopectin in the high amylose starches reflected that as determined by iodine binding analysis and the manufacturer; while the percent amylopectin in regular starch was too low (manufacturers: 75%, HPSEC: 65%). Undispersed components were mostly amylopectin. Since amylose is fully solubilized, however, the HPSEC can be used to quickly determine percent amylose in starch.     

Starch gelatinization using sodium silicate: FTIR,DSC, XRPD,and NMR studies

The chemical and physical modifications of native maize starch subjected to treatment with aqueous Na silicate have been investigated. The application of FTIR, DSC, XRPD, and NMR analysis is discussed herein with respect to the interaction of Na silicate with starch in relation to gelatinization. XRPD results indicate that Na silicate, in the ionized form, disrupts the molecular structure of starch in a manner similar to thermally induced starch gelatinization. In addition, Na silicate forms new CO–O–SiO₂Na moieties with the amylopectin starch component. This was ascertained by the detection of the in‐plane vibration of the –Si–O as a distinctive FTIR band at 580–600 cm⁻¹ and the appearance of a new carboxyl group (–COOH) NMR chemical shift at 168 ppm for the amylopectin/Na silicate system. DSC analysis showed two adjacent endothermic transitions at 192 and 198°C for starch/amylopectin treated with Na silicate whereas amylose treated with Na silicate did not show any new endothermic/or exothermic transitions.     

Fine Structure,Thermal and Viscoelastic Properties of Starches Separated from Indica Rice Cultivars

Starches were separated from indica rice cultivars (PR‐113, Basmati‐370, Basmati‐386, PR‐115, IR‐64, and PR‐103) and evaluated using gel permeation chromatography (GPC), X‐ray diffraction, differential scanning calorimetry (DSC) and dynamic viscoelasticity . Debranching of starch with isoamylase and subsequent fractionation by GPC revealed 9.7–28.3% apparent amylose content, 3.7–5.0% intermediate fraction (mixture of short amylose and long side‐chains of amylopectin), 20.6–26.6% long side‐chains of amylopectin and 45.8–59.4% short side‐chains of amylopectin). IR‐64 starch with the highest crystallinity had the highest gelatinization temperatures and enthalpy, T_o, T_p, T_c, and ΔH_gel being 71.8, 75.9, 82.4°C and 5.1 J/g, respectively, whereas PR‐113 starch with lower crystallinity showed the lowest gelatinization temperatures (T_o, T_p, T_c, of 60.8, 65.7 and 72.2°C, respectively). Basmati‐386 starch exhibited two endotherms during heating, the first and second endotherm being associated with the melting of crystallites and amylose‐lipid complexes, respectively. T_o, T_p, T_c and ΔH_gel of the second endotherm of Basmati‐386 starch were 99.0, 100.1, 101.1°C and 2.0 J/g, respectively. During cooling, Basmati‐386 also showed an exotherm at a peak temperature of 87°C. PR‐113 starch with the highest amylose content and the lowest content of short side‐chains of amylopectin had the highest peak storage modulus (G′= 1.6×10⁴ Pa). The granules of PR‐113 starch were the least disintegrated after heating. The effects of heating starch suspensions at different temperatures (92°C, 130°C and 170°C) on intrinsic viscosity [η], transmittance and viscoelasticity were also studied to evaluate the extent of breakdown of the molecular structure. The intrinsic viscosity of starch suspensions heated at 92, 130 and 170°C ranged between 103–114, 96–110 and 28–93 mL/g. Transmittance value of starches cooked at 92°C decreased with increase in storage duration. All starches except PR103, cooked at 130°C also showed decrease in transmittance during storage, however, at lower rate. PR103 starch heated at 130°C did not show any change in transmittance up to a storage time of 48 h. The changes in viscoelasticity of starch pastes cooked at different temperatures during cooling and reheating were also evaluated. G′ and G′′ increased with decrease in temperature during cooling cycle. Starches heated at 130°C with apparent amylose content ≤ 21.2% showed an improvement in G′ and G′′ in comparison to the corresponding starches heated at 92°C, this improvement was observed to be higher in starches with lower amylose content. All starches heated at 170°C had a higher proportion of breakdown in molecular structure as indicated by lower G′ and G′′ than the same starches heated at 130 and 92°C.     

Influence of Particle Size Reduction on Structural and Mechanical Properties of Extruded Rye Bran

Rye bran is a high-fibre ingredient also containing starch and protein. The aim of this work was to investigate the effects of extrusion processing and bran particle size on the structural and mechanical properties of extruded rye bran. Native rye bran particle size of 750–1,250 μm was milled to produce feed material with three different average particle sizes (coarse, 440 μm; medium, 143 μm; fine, 28 μm). A co-rotating twin screw extruder was used for extrusion with various processing parameters. Extrusion processing did not have a significant (P?<?0.05) effect on soluble dietary fibre (SDF) content but the amount of insoluble dietary fibre (IDF) increased by 7.1–9.5 % in medium- and 11.3–12.3 % in fine-particle-sized rye bran extrudates as compared to the raw material prior to extrusion. Decreasing the particle size of rye bran to 28 μm resulted in lower amounts of IDF and total dietary fibre, but a higher amount of SDF after extrusion compared to coarse-particle-sized rye bran. Decreasing the particle size of rye bran to 28 μm gave more expanded (179–223 %), less hard (145–336 N), more crispy (2.7–7.2?×?10^?4) and porous (79.2–83.9 %) extrudates compared to the coarse-particle-sized rye bran extrudates, which were less expanded (151–176 %), harder (210–433 N), less crispy (0.5–2.8?×?10^?4) and less porous (64.4–65.1 %). Reduction of the particle size of rye bran significantly (P?<?0.05) increased the crispiness compared to the extrudates made of coarse-particle-sized rye bran. The results demonstrated that the structural and mechanical properties of rye bran extrudates can be improved without starch addition by reducing the particle size of bran.     

Material Properties and Glass Transition Temperatures of Different Thermoplastic Starches After Extrusion Processing

Four different starch sources, namely waxy maize, wheat, potato and pea starch were extruded with the plasticizer glycerol, the latter in concentrations of 15, 20 and 25% (w/w). The glass transition temperatures of the resulting thermoplastic products were measured by Dynamic Mechanical Thermal Analysis (DMTA). Beside mechanical and structural properties also the transition temperatures of the materials were evaluated during tensile and impact tests. Above certain glycerol contents, dependent on the starch source, a lower glass transition temperature T_g resulted in decreased modulus and tensile strengths and increased elongations. Lowering the T_g at different glycerol contents did not influence the impact strength. When the amylose/amylopectin ratio increased a decrease in T_g was found. For pea, wheat, potato and waxy maize starch the T_g was 75 °C, 143 °C, 152 °C and 158 °C, respectively. Therefore products with higher percentages of amylose are more flexible. The shrinkage of the specimens made by injection molding was considerable compared to the specimens made by pressing.     

Selected functional properties of waxy corn and potato starches after illumination with linearly polarised visible light

Aqueous suspensions (30%) of waxy corn and potato starches were illuminated for 5–50 h with linearly polarised visible light (λ > 500 nm). Molecular weights (M?_w) and radii of gyration (R?_g) of the amylopectin and amylose fractions of illuminated waxy corn starch, and the amylopectin, intermediate, and amylose fractions of illuminated potato starch were measured by high‐performance size exclusion chromatography coupled with multiangle laser light scattering and refractive index detection. The weight‐average molecular weight (M?_w) and radius of gyration (R?_g) of the amylopectin fraction of native waxy corn starch were 14.45 × 10⁷ and 161.1 nm respectively. After 15 h of illumination a decrease in M?_w (5.80 × 10⁷) and R?_g (117.6 nm) was observed. Illumination for 25 h, led to an increase in M?_w (7.60 × 10⁷) and R?_g (134.0 nm). Further illumination, up to 50 h resulted in a slight decrease in M?_w (6.74 × 10⁷). The molecular weight and radius of gyration of the amylopectin fraction of native potato starch were 21.30 × 10⁷ and 207 nm respectively. Illumination for 15 h led to a decrease in M?_w (14.87 × 10⁷) and R?_g (141.5 nm), followed by an increase in both values after 25 h (18.97 × 10⁷, 146.6 nm) and 50 h (19.69 × 10⁷, 207.1 nm) of illumination. Illumination influenced the swelling power, solubility, susceptibility to α‐amylolysis and X‐ray diffractogram of the starches. A varying increase in the solubility passed through a minimum after 25 h of illumination. The X‐ray diffraction pattern and susceptibility to enzymatic hydrolysis of waxy corn starch did not change, but in potato starch a gradual, illumination time‐dependent increase in the amylolysis rate took place. This effect could result from the reduction in crystallinity of the starch as indicated by the X‐ray diffraction pattern. Copyright © 2003 Society of Chemical Industry     

The Influence of Acid Hydrolysis of Potato Starch on the Stress-Strain Propoerties of Thermoplastic Starch

Potato starch has been hydrolysed lowering the molecular mass. The influence of starch molecules mass on the mechanical properties of thermoplastic starch has been investigated. Acid hydrolysis was performed with hydrochloric acid in various concentrations and time spans. Acid hydrolysis of the granular potato starch decreased both the molecular mass of amylose and amylopectin. The thermoplastic materials have been made by extrusion processing of the various starches with fixed amounts of water and glycerol. The stress-strain properties showed to be influenced by molecular mass. The materials were rubbery at 20°C and 60% relative humidity. Although the tensile stress did not change significantly, the elastic modulus increased with an decrease in molecular mass. This increase was explained by differences in starch structure and morphology. The higher of the low molecular mass materials could result in a more rapid starch structural ordering. The elongation and tearing energy increased with incrasing molecular mass. Theses effects were explained by the higher amylose chain length and amylopectin endgroups chain length resulting in a more entangled polymer matrix.     

Extrusion-Cooking of Sorghum Containing Different Amounts of Amylose

Three sorghums containing different amounts of amylose (12.2, 21.5, and 26.7%) were decorticated, ground and extruded at three extrusion moisture levels (17, 32, and 45%). Highly expanded and brittle sorghum extrudates with high degrees of starch cooking were produced at 17% extrusion moisture content. All sorghum extrudates exhibited a V-amylose x-ray diffraction pattern. Functional characteristics, such as expansion, enzyme-susceptible starch ratio, and water solubility, indicated that low amylose extrudates were more cooked than other varieties. Thin porridges prepared from extruded sorghums had an intermediate consistency, smooth texture, roasted flavor and white color. Thin porridges (atoles) from extrudates containing 21.5% amylose, were preferred by a sensory panel over those from extrudates containing 12.2 and 26.7% amylose.     

Physicochemical,thermal, and rheological properties of acid-hydrolyzed sago (Metroxylon sagu) starch

The effects of acid hydrolysis on physicochemical and rheological properties of sago starch were investigated. Sago starch was hydrolyzed in hydrochloric acid at 50 °C for 6, 12, 18, and 24 h. The molecular weight distribution, physicochemical, thermal, and rheological properties of acid-hydrolyzed sago starch (AHS) were determined. After 24 h of hydrolysis, molecular weight of amylopectin and amylose were decreased to 3.57 × 10⁵ and 6.5 × 10⁴ g/mol, respectively. Differential scanning calorimetry studies showed that the gelatinization temperature and enthalpy of AHS increased with increasing degree of hydrolysis. Hydrolyzed sago starch containing low molecular weight fractions exhibited cold water solubility up to 100%. Setting temperature of AHS decreased with increasing hydrolysis time but amylose content and gel strength increased in the first 12 h of acid hydrolysis but decreased with extended hydrolysis time. Hydrolyzed sago starch in concentrations lower than 8 g starch per 100 g water was cold water soluble and could be used to modify properties of starch for specific applications such as yogurt and concentrated milk processing.     

Extrusion of Hulled Barley Affecting β-Glucan and Properties of Extrudates

Grits from eight different hulled barley cultivars were subjected to extrusion cooking on a twin screw extruder, and the effect of extrusion variables (temperature and moisture) on β-glucan and physicochemical properties was evaluated. The highest bulk density was observed for extrudates extruded at 150 °C and 20% moisture (low temperature high moisture, LTHM) while the highest expansion was observed for the extrudates extruded at 150 °C and 15% moisture (low temperature low moisture). Extrusion reduced the lightness (L*) of the extrudates and the highest decrease observed for LTHM extrudates. Increasing the feed moisture decreased water solubility index (WSI) significantly while increasing the extrusion temperature significantly increased WSI. The high temperature high moisture (HTHM) extrudates exhibited the highest water absorption capacity. The total β-glucan content was not affected by extrusion cooking, but a significant increase in soluble β-glucan was observed with the highest in high temperature low moisture extrudates. The ratio of soluble to insoluble β-glucan varied from 0.7 to 1.5 in the control barley, but after extrusion cooking, the ratio was changed from 1.2 to 3.1. The β-glucan extractability increased by up to 8% after extrusion with extrudates from HTHM showing the highest extractability. The extent of starch gelatinization varied from 80% to 100% upon extrusion, and the highest was observed in HTHM extrudates. A significant decrease in the peak and final viscosity of the extrudates at all the extrusion conditions was observed.