Effects of Extrusion Process Variables on Quality Properties of Wheat-Ginseng Extrudates

The present study investigated the effects of extrusion process variables (feed moisture, screw speed, and barrel temperature) on the physical [expansion ratio, water absorption index (WAI), and water solubility index (WSI)], pasting, and thermal properties of wheat-ginseng extrudates (WGE). A wheat flour-ginseng powder (GP) blend (10% GP, w/w) was extruded in a twin-screw extruder (L/D ratio of 25:1) with full factorial combinations of feed moisture (25, 30, and 35%), screw speed (200 and 300 rpm), and zone 5 barrel temperature (110, 120, 130, and 140°C). The expansion ratios of WGE were significantly increased with decreasing feed moisture, decreasing screw speed, and increasing barrel temperature. Increasing feed moisture significantly increased WAI values of WGE and significantly decreased WSI values of WGE. However, an increase in either screw speed or barrel temperature caused a significant decrease in WAI values of WGE and a significant increase in WSI values of WGE. Rapid visco analyzer peak viscosity values of WGE were significantly affected by changes in extrusion process variables studied, indicating that the degree of starch degradation and/or gelatinization in WGE is a very important factor associated with their peak viscosity. WAI values of WGE were positively correlated (r = 0.88, p ≤ 0.001) with peak viscosity values of WGE samples, whereas WSI values of WGE samples were negatively correlated (r = 0.82, p ≤ 0.001). Increasing feed moisture resulted in an increase in values of transition peak temperature (T_p) of WGE, whereas increasing screw speed and barrel temperature each led to a decrease in T_p values of WGE, determined by differential scanning calorimetry.     

Physicochemical Properties of Casein‐Starch Interaction Obtained by Extrusion Process

Extruded samples of starch‐casein blends were processed by using a single‐screw extruder. The independent variables in the process were temperature (126–194°C), moisture content (18–29%) and starch‐casein blend (5–95%). These independent variables affected significantly the physicochemical and textural properties of the biopolymers. The highest values for expansion (EXP) and water absorption index (WAI) were found when a higher starch proportion was present in the blends, at 126°C barrel temperature and moisture content higher than 25%. By increasing the barrel temperature, from 126°C to 194°C, the water solubility index (WSI) and color parameter were increased. Initial viscosity (IV) and viscosity at 90°C (V90) were mainly affected by the barrel temperature at 194°C. However, the viscosity at 50°C (V50) was affected neither by the different extrusion variables nor by the biopolymer proportion in the blends. Compression force (CF) was strongly dependent on moisture content and casein proportion in the blend. The higher CF values were found at starch concentrations around 50% and 25% moisture content, for higher or lower values than these the obtained extruded products were softer and consequently had lower CF values.     

Effect of processing conditions on some functional characteristics of extrusion‐cooked cassava starch/wheat gluten blends

Extrusion‐cooked blends of cassava starch (CS) and wheat gluten (WG) were studied. The data were analysed using response surface methodology. The results showed the formation of new structures characterised by lower radial expansion (RE) and specific volume (SV) when gluten was added to CS. WG content was the most important variable affecting RE, water absorption index (WAI), water solubility index (WSI), SV and difference in colour (ΔE) of the extruded products, but feed moisture content and barrel temperature also influenced RE. WAI was affected by a significant interaction between WG content and barrel temperature. The extruded products had lower WAI values and higher WSI values than WG‐free products. Heat, high shear rate and high pressure during extrusion cooking caused mechanical destruction or denaturation of the WG and gelatinisation and dextrinisation of the starch components. The extruded blends could have diverse applications. © 2002 Society of Chemical Industry     

Functional Properties of Extrudates from High Starch Fractions of Navy and Pinto Beans and Corn Meal Blended with Legume High Protein Fractions

High protein fractions (HPF) of navy and pinto beans were mixed with high starch fraction (HSF) or corn meal and extrusion-cooked. HSF of pintos blended with hull fractions was extruded at 132°C. Expansion index (EI), density, color, water absorption (WAI), water (WSI) and nitrogen solubility (NSI), oil absorption (OAC) and emulsification (OEC) were evaluated. Extruded blends had lower EI and OAC, higher protein density and OEC than extruded corn or HSF. WAI and WSI were variable. EI decreased with increased protein. Scanning electronic microscopy showed protein level had pronounced influence on microstructure, size of air cells and smoothness of cell walls. Hull fraction added to HSF, caused decreases in EI, WAI, WSI while NSI, OAC and OEC were unaffected.     

Effects of extrusion with CO<Subscript>2</Subscript> injection on physical and antioxidant properties of cornmeal-based extrudates with carrot powder

Carrot powder and cornmeal were extruded at ratios of 0:100, 10:90, and 20:80 with and without CO₂ injection at die temperatures of 80, 100, and 120 °C. The effects of the composition of the extrudate, die temperature, and CO₂ injection on physicochemical and antioxidant properties of extruded products were studied. The results showed that die temperature had a significant effect on expansion ratio (ER), specific length, piece density, color, water absorption index (WAI), and water solubility index (WSI) (p < 0.05). The injection of CO₂ significantly affected the ER, WAI, WSI, lightness, redness, microstructure, total phenolic content, and the 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity of extrudates (p < 0.05). Increasing the proportion of carrot powder in extrudates resulted in better antioxidant properties and higher levels of crude ash, crude fat, crude protein, and redness; however, it resulted in lower WAI, lightness, and yellowness (p < 0.05). The study demonstrated that extrusion with CO₂ injection and addition of carrot powder may improve the nutritional quality and structure-forming ability of extrudates.     

Evolution of functional,thermal and pasting properties of sprouted whole durum wheat flour with sprouting time

This research investigated the evolution of functional, pasting and thermal properties of durum wheat (Triticum durum) with sprouting time. Particle size, flour and flour gel hydration properties (Water Holding Capacity (WHC), Swelling Volume (SV), Water Absorption Index (WAI), Water Solubility Index (WSI), Swelling Power (SP)), Oil Absorption Capacity (OAC), Pasting and thermal properties were evaluated on different sprouting time: 12, 24, 36, 48 and 72 h. Results showed that more than 12 h decreased significantly particle size, WHC(−14.8%), SV (−19%), SP (−14%) and WAI (−36.5%) while WSI (+383%) and OAC (+7.3%) increased. Pasting properties drastically decreased with sprouting time. DSC results showed a significant increase in onset temperature (T₀) (from 55.2 to 58.2 °C), peak temperature (T_p) (from 62.4 to 63.8 °C) while conclusion temperature T_c decreased (from 76 to 72.6 °C). Despite these changes, sprouted whole wheat flour could be suggested as an improver of some cereal products’ functionality.     

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.     

Development of a Protein-rich Composite Sorghum-Cowpea Instant Porridge by Extrusion Cooking Process

To develop an instant high protein porridge, various ratios of sorghum and cowpeas were extruded at 130 and 165 °C and a water content of 200 g/kg using a twin-screw extruder. An increased proportion of cowpeas resulted in an increase in protein content, nitrogen solubility index (NSI), yellow colour, water absorption (WAI) and solubility (WSI) indexes and in a decrease in total starch (TS), enzyme-susceptible starch (ESS), expansion ratio (ER), and porridge firmness. The higher extrusion temperature gave lower NSI, TS and WAI. ESS, ER and WSI increased with severity of heat treatment. The composite of 50% sorghum and 50% cowpeas extruded at 130 °C was the most similar to a commercial instant maize-soya composite porridge in terms of composition and functional properties. A serving of 100 g would contribute 28% of the recommended dietary allowance (RDA) for protein. This represents a 110% increase in the protein RDA compared to sorghum only.     

Development of extruded snacks using taro (Colocasia esculenta) and nixtamalized maize (Zea mays) flour blends

Extruded snacks were prepared from flour blends made with taro and nixtamalized (TF-NMF) or non-nixtamalized maize (TF-MF) using a single-screw extruder. A central composite design was used to investigate the effects of taro flour proportion in formulations (0-100 g/100 g) and extrusion temperatures (140-180 °C) on the following indices: expansion (EI), water solubility (WSI), water absorption (WAI) and fat absorption (FAI). Moreover, selected TF-NMF and TF-MF extruded products were partially characterized through proximate chemical analysis, resistant starch, color, pH, water activity, apparent density, hardness, and sensory analysis. Results indicated that EI and WSI of both TF-MF and TF-NMF extrudates were significantly increased by the use of higher proportions of taro flour, while the opposite behavior was observed for the FAI (p < 0.05). Taro flour at higher proportions in both extrudates did not produce a significant change of WAI, while the use of higher extrusion temperatures only caused a significant increase of FAI in TF-MF extrudates (p < 0.05). This study showed that flour mixtures made from taro and nixtamalized maize flour produced puffed extruded snacks with good consumer acceptance.     

The effect of starch gelatinization and solute concentrations on T g′ of starch model system

The effect of starch gelatinization on glass transitions in a starch/water model system and how the concentrations of added solutes (sucrose and sodium chloride) affect the glass transition temperatures of the gelatinized starch solution was investigated. The starch suspension samples were heat treated in a Differential Scanning Calorimeter (DSC) under different time and temperature regimes to achieve different degrees of gelatinization. The gelatinization characteristics (onset, peak and end temperatures and enthalpy) and the glass transition values of a potato starch were determined using the DSC. The results showed that the starch concentrations had no effect on gelatinization characteristics and the T_g′ of the gelatinized potato starch but had clearly increased their ΔC_p in the T_g′ region. Annealing at a temperature slightly below the T_g′ of −5 °C, led to maximal freeze‐concentration in the total/partial gelatinized starch and a higher T_g′ value at about −3 °C was obtained. The T_g′ values of the totally gelatinized starch samples were slightly lower than those of partially gelatinized samples. The T_g′ of the gelatinized starch decreased with increasing concentrations of sucrose or sodium chloride. Sodium chloride had a stronger depressing effect on T_g′ than sucrose. © 2000 Society of Chemical Industry     

Resistant starch production from mango starch using a single‐screw extruder

Resistant starches were prepared from mango starch by extrusion. An experimental design with independent variables temperature, screw speed and moisture content produced 20 samples that were studied to determine the effect of these variables on resistant starch (RS) content, water absorption index (WAI) and water solubility index (WSI). RS content was affected by moisture content and temperature. Screw speed and temperature also influenced RS content, the highest level (97 g kg⁻¹) being obtained at low screw speed and high temperature, this pattern can be associated with a longer residence time, which gives rise to more opportunity for amylose chain association. The regression model fitted to the RS experimental results showed a good correlation coefficient (0.80). When moisture content and temperature decreased, WAI increased (105–142 g kg⁻¹), but low WAI values (70–77 g kg⁻¹) were obtained at moisture contents between 200 and 300 g kg⁻¹ and high temperatures (140–150 °C). When moisture content and temperature increased, WSI increased (222–332 g kg⁻¹), but at high temperature value (120 °C) assayed and the lowest moisture content (150 g kg⁻¹), WSI also increased. In the range of moisture contents tested and at low temperatures, only partial gelatinisation occurred and low solubility was obtained. Copyright © 2005 Society of Chemical Industry     

Combinatorial effects of mechanical activation and chemical stimulation on the microwave assisted acetylation of corn (Zea mays) starch

The changes in the physical characteristics of ball milled corn starch (BMS) after chemical modification were investigated. The SEM and XRD analysis of BMS granules showed a fragmented aspect with a total loss of their initial crystallinity and an increase of their potential hydroxyl substitution sites. This morphology facilitated the access of the esterifying solvents into the starch molecule as corroborated by the spectacular increase of the water solubility index (WSI) and water absorption index (WAI). Following the acetylation, the degree of substitution (DS) increased up to 2.83 with the augmentation of the iodine catalyst content (p = 0.011). However, under the same condition of esterification, the DS of the BMS was slightly lower in comparison to the control, due to an increase in the number of free hydroxyl groups. Consequently to the modification, a reduction in the T_g, strong hydrophobicity and important exo‐corrosion affecting the granules were noticed.     

Thermally Stimulated Luminescence in Powdered Soy Proteins

Heating powder isolated soy proteins (ISPs) in a N₂ environment produced thermally stimulated luminescence (TSL), in 2 major temperature regions, 50 to 250°C (region R1) and 250 to 350°C (region R2). In soy protein 7S fraction, strong TSL was detected in both regions with glow peak maximum (T_m) at 150 ± 15°C and at 300 ± 10°C. Two additional satellite or shoulder peaks were detected from the ISP and 7S protein fraction within region R1 at T_m = 90°C and T_m = 210°C. The soy protein 11S fraction produced a broad, poorly defined TSL peak in the low‐temperature region. Electron paramagnetic resonance spectroscopy data from the control ISP sample, deuterium sulfide‐treated ISP, ISP stored in either N₂ or O₂, and defatted soy flour, indicated that the trapped radicals present in ISP is associated with the production of the primary TSL peak at 150 ± 15°C. Activation energies required to release the trapped charges (for luminescence to occur) are approximately 0.70, 0.78, 1.50, and 1.8 eV for TSL at T_m = 100, 150, 200, and 300°C, respectively. The reaction mechanism that leads to the release of the trapped charges for TSL to occur followed a mixed order kinetic, between 1.5 and 1.8. The frequency factor varied between 10⁷/s and 10¹⁷/s.     

Physicochemical, mechanical and thermal properties of brown rice grain with various moisture contents

The effects of moisture content on the mechanical and thermal properties of either a short‐grain variety (Akitakomachi) or two long‐grain varieties (Delta and L201) of brown rice were studied. Total starch contents of the three varieties were comparable, but the amylose content of L201 was significantly higher than that of the other two varieties. The maximum compressive strength of brown rice grain was much higher than the maximum tensile strength. L201 showed the highest maximum compressive and tensile strengths. The phase transition temperatures (glass transition temperature T_g and melting temperature T_m) were examined by differential scanning calorimetry. The T_g and T_m for L201 were higher than those for Delta and Akitakomachi. The maximum compressive strength, maximum tensile strength, T_g and T_m for the three varieties of brown rice grains decreased with increasing moisture content. The T_g of individual brown rice kernels decreased from 53 to 22 °C as moisture content increased from 12 to 25% wet basis. A statistical model was calculated by using linear regression to describe the change in T_g in terms of moisture content.     

Effects of partial substitution of potato flour on cooking characteristics,texture properties and in vitro starch digestibility of fresh extruded rice-shaped kernels

Effects of partial substitution of potato flour (0%, 10%, 20%, 30% and 40%) for rice flour on cooking characteristics, textural properties and in vitro starch digestibility of fresh extruded rice-shaped kernels (FER). With the increase in potato flour content, the water absorption index (WAI) increased gradually, the water solubility index (WSI) decreases gradually. Hardness, elasticity, adhesion and chewiness first increased and then decreased. When the potato flour content was 30%, the peak viscosity, trough viscosity, breakdown viscosity, final viscosity and setback viscosity of the pasting test were 325, 168, 157, 312 and 144 cp, respectively. The WAI of the cooking test was 7.50 g g⁻¹, and the WSI was 4.71%. The texture test had a hardness of 1211.82 g, flexibility of 0.85 mm, cohesiveness of 0.73 gs, adhesion of 715.38 g and chewiness of 519.28 g. The highest overall acceptability score was 4.51 in sensory evaluation. Finally, the predicted glycaemic index indicated that potato flour is a suitable raw material for low GI products.     

Effect of extrusion cooking on structure and functional properties of pea and kidney bean proteins

Pea (Pisum sativum L cv Ballet) and kidney bean (Phaseolus vulgaris L cv Pinto) seeds were extruded at 148 and 156 °C respectively. Protein solubility at various pH values and in various solvents was determined and analysis of protein fractions was carried out by SDS‐PAGE. Also, sulphhydryl and disulphide groups, water‐holding capacity (WHC), water solubility index (WSI) and oil absorption capacity (OAC) were determined. No changes in total nitrogen content of pea and kidney bean seeds occurred as a result of thermal treatment. Protein solubility from raw and extruded legumes was significantly higher in saline solutions than in water in the pH range 2–10. The solubility of proteins from extruded pea and kidney bean flours was greatly decreased with respect to native flours when extraction was in buffer (pH 7.0) alone. Extraction with buffer containing 2‐mercaptoethanol (2‐ME) or sodium dodecyl sulphate (SDS), alone or in combination, greatly increased protein extractability. As a result, the relative solubility was nearly 100% in buffer with SDS and 2‐ME for both raw and extruded samples. Total and free sulphhydryl group and disulphide contents decreased significantly (P < 0.05) after extrusion cooking. Moreover, extrusion treatment caused major changes in the band patterns of the albumin and globulin fractions obtained by SDS‐PAGE. WHC and WSI of extrudates increased significantly in both peas and kidney beans. A significant reduction in OAC was observed in extruded kidney bean flour. © 2000 Society of Chemical Industry     

Subzero Glass Transition of Waxy Maize Starch Studied by Differential Scanning Calorimetry

A mixture of waxy maize starch and water (1:2, w/w) was heated in a differential scanning calorimeter (DSC) pan to different temperatures to obtain different degrees of gelatinization. Each pan was then quenched to ‐30°C and rescanned, and the subzero glass transition temperature (T_g′) of the content was determined. A three‐phase model of a starch granule—a mobile amorphous phase, a rigid amorphous phase, and a crystalline phase—was used to interpret results and explain the glass transitions in starch. Waxy maize starch had an onset gelatinization temperature (T_o) of 61.5°C, peak temperature (T_p) of 70.3°C, and completion temperature (T_c) of 81.7°C. The T_g′ was clearly noted after the starch and water mixture was heated to T_p and T_c, but was small and barely observable when the mixture was heated up to T_o and immediately cooled to ‐30°C. When the starch and water mixture was heated to 55°C, which was 6°C below the T_o, and held for 2 h, a T_g′ was observed. Moreover, T_g′ began to appear and was observable if the starch and water mixture was heated to 10°C below gelatinization onset temperature (51°C) and annealed for 2 h without any gelatinization. Further holding at ‐7°C showed a clear subzero glass transition of annealed native starch granules.     

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.     

Determining the effects of annealing time on the glass transition temperature of Pueraria lobata (Willd.) Ohwi starch

To probe the effects of annealing time on the glass transition temperature (T_g) and digestibility of Pueraria lobata (Willd.) Ohwi starch, the starch crystal structure and moisture distribution through the components of P. lobata (Willd.) Ohwi starch were investigated. Annealing times of 0, 1, 3, 6, 12 and 24 h were employed to determine the effect of starch T_g using differential scanning calorimetry (DSC) with the support of ¹H low‐field NMR, polarised light microscopy and ¹³C CP/MAS NMR. The T_g values of the starch increased with longer annealing times. The ¹H low‐field NMR results showed that the T₂ relaxation time decreased and starch–water interactions increased as the annealing time increased. Compared with native starch, annealed starch had higher contents of slowly digested starch (SDS) and resistant starch (RS). The starch crystal structure was not destroyed after annealing, but the relative crystallinity percentage increased slightly.     

A comparison between the properties of seed,starch, flour and protein separated from chemically hardened and normal kidney beans

The physicochemical, functional and thermal properties of starch, flour and protein isolates obtained from chemically hardened kidney beans were evaluated. A rapid chemical hardening procedure (soaking in acetate buffer, pH = 4.0, 37 °C, 6 h) was used to produce hardened kidney beans. Chemical hardening altered physicochemical, cooking, hydrating and textural properties of beans to a significant level (P < 0.05). Soaked and cooked chemically hardened beans had a higher value for different textural parameters than their normal counterparts. Chemical hardening increased cooking time (from 49 to 123 min) of beans and decreased swelling power and solubility of starch. The turbidity value of gelatinized starch suspensions from chemically hardened beans was significantly lower than that from normal beans. Chemical hardening of beans caused significant increase in transition temperatures (T_o, T_p, T_c) and enthalpy of gelatinization (ΔH_gel) of both starch and flour. Chemically hardened bean starch showed significantly higher pasting temperature (94.9 °C) as compared to normal bean starch (83.2 °C). Flour and protein isolate from chemically hardened beans showed significantly lower water absorption, oil absorption, foaming capacity and gelling ability than those from normal beans. The onset temperature (T_m), peak denaturation temperature (T_d) and heat of transition or enthalpy (ΔH) of protein isolate from hardened and normal beans did not differ significantly. Copyright © 2007 Society of Chemical Industry