Single-Screw Extrusion of Defatted Soy Flour, Corn Starch and Raw Beef Blends

Effects of feed moisture, fat and corn starch levels and process temperature on physical properties of extrudates of defatted soy flour-amylose corn starch-raw beef blends were investigated using response surface methodology. Contour plots showed a convex curve of expansion ratio (ER) with moisture, concave curves of bulk density (BD) and shear-force (SF) with moisture, and concave cmves of SF with each of the four extrusion variables. Fat decreased ER and increased BD, whereas corn starch increased ER. Products with high ER and low BD and SF tended to have prominent air cells, continuous protein matrices, and smooth cell wall surfaces in scanning electron micrographs. The optimum extrusion conditions for minimal SF values, with 20% non-dehydrated beef muscle and varied amounts of defatted soy flour, were: 29.1% feed moisture; 2.96% feed fat; 22% feed corn starch; and 162°C process temperature.     

Selected properties of native or modified maize starch/soy protein mixtures extruded at varying screw speed

Mixtures of soy protein isolate and native or modified (crosslinked) maize starch were extruded in a twin‐screw extruder at screw speeds of 80, 120 and 160 rpm and a moisture content of 250 g kg^?1 (dry basis). Increasing screw speed did not affect the specific mechanical energy and water solubility and absorption indices but did affect the sectional expansion index and bulk density, as the flow rate of the feed was not held constant during extrusion. The sectional expansion indices of modified starch/soy protein mixtures were higher than those of native starch/soy protein mixtures, suggesting an effect of feed material in addition to phase transition on the expansion of extrudates containing soybean. Since the bulk densities of modified starch/soy protein mixtures were lower than those of native starch/soy protein mixtures, it appears that bulk densities of extrudates containing high percentages of soy protein can be reduced by the presence of crosslinked starch in the feed. Copyright © 2005 Society of Chemical Industry     

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.     

Extrudates of Starch-Xanthan Gum Mixtures as Affected by Chemical Agents and Irradiation

Mixtures of starch, xanthan gum and either polyvinyl alcohol, epichlorohydrin, valeric acid or adipoyl chloride were extruded. Properties of extrudates including apparent viscosity, water solubility, water absorption indices and exrudate expansion were measured for different proportions of xanthan gum, 70% amylose starch (with or without irradiation) and chemical agents. Extrusion with chemical agents and irradiation changed physical properties of both starch and xanthan gum. Expansions of extrudates were higher than that of starch. Viscosity of extrudates increased with xanthan gum concentration. The addition of 1% (w/w) polyvinyl alcohol had the greatest effect of the chemical agents. Irradiation increased the apparent viscosity of starchxanthan gum mixtures.     

Effect of Extrusion on Physicochemical Properties,Digestibility, and Phenolic Profiles of Grit Fractions Obtained from Dry Milling of Normal and Waxy Corn

Extrusion behavior of grits obtained from 3 successive reductions of dry milling of 2 normal corn types and 1 waxy corn was studied at different extrusion temperatures (ET). The grit from each reduction stage (RS) showed the presence of base‐hydrolyzed bound protocatechuic acid, p‐coumaric acid, sinapic acid, ferulic acid, and quercetin, and the concentrations of these decreased after acid hydrolysis and that of gallic acid increased. African tall grit from all RSs showed the highest average specific mechanical energy (SME) and torque, while waxy corn grit had the lowest. Corn extrudates showed an increase in water solubility index (WSI) and a decrease in water absorption index (WAI), as well as in expansion ratio (ER) with an increase in ET. Extrudates from each corn type showed an increase in rapidly digestible starch (RDS) and a decrease in slowly digestible starch (SDS) and resistant starch with an increase in ET. Most of the phenolics were present in bound form in extrudates, and quercetin, and catechin observed in grit were not present in extrudates. Frying of extrudates showed lower L^* and higher a^* and b^* when compared to color parameters of raw extrudates. Lower expansion of fried extrudates from waxy corn than those from other corn types may be related to its higher protein and fat contents and to lower amylose content.     

Mechanical and microstructural properties of soy protein – high amylose corn starch extrudates in relation to physiochemical changes of starch during extrusion

Mechanical and microstructural properties of expanded extrudates prepared from blends of high amylose corn (Zeamays L. ssp. Mays) starch (HACS) and soy protein concentrate (SPC) were studied in relation to the physicochemical changes in starch. Effects of screw speed (230 and 330 rpm) and SPC level (10%, 20%, 30% and 50%) on expansion and mechanical properties were determined. Compared with 230 rpm, screw speed at 330 rpm resulted in increased specific mechanical energy, expansion ratio, water absorption and water solubility indices and decreased bulk density and piece density. Varying screw speeds did not significantly affect the mechanical strength of extrudates or starch molecular weight distribution. Bulk and piece densities, and water absorption index (WAI) only slightly increased or exhibited no significant trends as SPC level increased to 20%. A substantial increase in bulk and piece densities and decrease in expansion ratio and WAI were observed as SPC level increased from 20% to 30%. The trends were either reversed or moderated as SPC increased to 50%. These results in combination with average crushing force and water solubility index data provided a significant insight into the interactions between HACS and SPC during extrusion processing. As compared to an earlier baseline study by our research group on normal corn starch – SPC extrudates, results from the current study indicated that the expansion of extrudate containing HACS alone was lower than that of extrudates containing normal corn starch. However, expansion of the HACS–SPC blends was not significantly impacted at 10–20% SPC levels, whereas the expansion of normal corn starch was significantly reduced.     

EFFECTS OF EXTRUSION CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF A MUTANT RICE CULTIVAR,GOAMI2 – HIGH IN NONDIGESTIBLE CARBOHYDRATES

ABSTRACT

A mutant rice Goami2, a cultivar high in nondigestible carbohydrates (NDCs), was extrusion‐cooked at feed moisture (20, 25%), screw speed (200, 300 rpm) and barrel temperature (110, 120 and 130C). Effects of extrusion conditions on the physical and functional properties were investigated. NDCs were determined by total dietary fiber (TDF) and resistant starch (RS) contents. Increasing moisture resulted in an increment of density, water absorption index (WAI) and hardness, and a decrement in expansion and water solubility index (WSI). A higher barrel temperature decreased the hardness and increased the WSI probably due to a higher proportion of gelatinized starch. Extrusion caused a reduction in TDF in the extrudates, as well as a significant decrease in RS contents. However, extrudates processed at moisture (%), screw speed (rpm) and barrel temperature (C) combinations of 25/200/110 and 25/200/120 showed no significant difference in TDF contents compared with its raw rice. Multiple regression models showed that feed moisture had the most pronounced effect on extrudate qualities, followed by barrel temperature and screw speed.

PRACTICAL APPLICATIONS

Rice, being one of the primary dietary sources of carbohydrates worldwide, is the major energy and nutritional sources. In recent years, demands have been increasing for rice with a wide range of value‐added properties, such as enhanced nutrient, aroma, color and rice kernel shape, including functional properties. Goami2 is a mutant rice of Ilpumbyeo, a high japonica rice cultivar, and has been revealed to have higher nondigestible fractions. However, Goami2 rice has unsuitable properties for traditional cooking because of the difficulty of gelatinization, which might result in a hard texture of cooked rice compared with that of ordinary rice. On the basis of its nutritional and functional benefits, exploiting the possible utilization of Goami2 for processed food products would increase the potential consumption of Goami2 for various food products.     

Effect of Mesona Blumes gum on physicochemical and sensory characteristics of rice extrudates

The aim of this study was to evaluate effects of Mesona Blumes gum (MBG) on some physical, chemical, sensory and antioxidant properties of rice extrudates. MBG was added to rice flour at 0%, 5%, 10%, 15% and 20% (w/w). The water solubility index (WSI) increased from 4.19% to 15.32% with MBG addition. Both water absorption index (WAI) and moisture retention (MR) reached maximum at 15% MBG. Bulk density (BD) was the highest at 5% (131.22 g cm^?3) and the lowest at 15% MBG (121.44 g cm^?3). Hardness was maximal at 5% (8.44 N mm^?2) and minimal at 15% MBG (5.98 N mm^?2). Expansion ratio (ER) and lightness (L*) decreased for all extruded products with MBG. MBG at 5% or 10% level could improve sensory characteristics of final products. The extract of extrudates at 15% MBG had the highest antioxidation ability among those extrudates. Thus, it was possible to produce a new palatable rice extrudate with MBG.     

Composition,Rheological and Extrusion Behaviour of Fractions Produced by Three Successive Reduction Dry Milling of Corn

The composition, rheological and extrusion behaviour of three fractions, i.e. coarse (>500 μm), medium-coarse (300–500 μm) and fine (<300 μm), obtained from three successive reduction dry milling of corn was studied. Fractions from different reduction stages vary in composition, pasting and structural characteristics. All the fractions from third reduction stage had higher protein, lipid, ash and b* value while with lower crystallinity and L* value. These fractions also showed higher pasting temperature and lower breakdown viscosity than the fractions from first and second reduction stages. The characteristics of extrudates varied with the composition as well as particle size of the fractions. The fractions with higher lipid and protein content resulted into extrudates with lower water solubility index (WSI) and expansion; however, fine fractions resulted into extrudates with higher WSI and expansion.     

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.     

Effect of the extrusion process on allergen reduction and the texture change of soybean protein isolate-corn and soybean flour-corn mixtures

Soy protein and corn meal are widely used as main ingredients in the cereal and snack industries. We studied the effect of extrusion processing on the immunoreactivity of proteins in soy protein isolate-corn meal (SPI-corn) blends and soy flour-corn meal (SF-corn) blends using a full-factorial design with two levels of temperature, moisture, and screw speed (SS). The changes in protein solubility, protein secondary structure and physical properties, such as the expansion ratio, specific volume, water hydration capacity (WHC), texture, and color, were also studied. The western blotting results illustrated that extrusion processing decreased the immunoreactivity of proteins in SPI-corn and SF-corn blends and eliminated certain allergenic proteins in SF-corn extrudates. The enzyme-linked immunosorbent assay (ELISA) results indicated that different extrusion conditions decreased the immunoreactivities of SPI-corn and SF-corn blends in the ranges of 53%–68% and 80%–86%, respectively, compared with the raw material. The protein solubility decreased after extrusion by >58.7% for SPI-corn extrudates and by 66.3% for SF-corn extrudates compared with the initial materials and decreased significantly for both SPI-corn and SF-corn extrudates with the increase in extrusion temperature (P < 0.05). The α-helix structure decreased and β-strand structure increased after extrusion for both SPI-corn and SF-corn blends. Higher moisture significantly decreased the expansion ratio, specific volume and WHC of SPI-corn and SF-corn extrudates, as well as increased the energy required to cut the samples. Thus, the effect of extrusion on allergenic proteins using the human plasma of subjects allergic to soybean and corn showed that moisture had a clear effect on their reduction. Product treated with low moisture (20%), regardless of the starting material used, was the most effective based on the reduction of allergenic proteins.     

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 extrusion cooking using different water feed rates on the quality of ready-to-eat snacks made from food by-products

The effect of different levels of feed moisture (12–17%) during extrusion cooking, using a co-rotating twin-screw extruder on selected nutritional and physical properties of extruded products was investigated. Four different formulations were used based on wheat flour and corn starch with the addition of 10% brewer’s spent grain (BSG) and red cabbage (RC) trimming reducing the flour and starch. The samples were: wheat flour + BSG (WBSG), corn starch + BSG (CBSG), wheat flour + red cabbage (WRC) and corn starch + red cabbage (CRC). Process conditions utilised were: constant feed rate of 25 kg/h, screw speed 200 rpm and barrel temperature of 80 and 120 °C. The results indicated that increasing the water feed to 15% increased the level of total dietary fibre (TDF) in all the extrudates while extrusion processing increased the level of TDF in WBSG, CBSG and CRC but decreased in WRC products. Extrusion cooking increased the level of total antioxidant capacity (TAC) and total phenolic compounds (TPC) in WRC and CRC. In addition to water feed level affecting the TDF of the extrudates, also affected were the expansion ratio, bulk density, hardness, WSI, SME and colour. The protein level of the products and hardness of extrudates were related to the different formulations.     

Extrusion behaviour of grits from flint and sweet corn

Studies were conducted to investigate the effect of feed moisture, extrusion temperature and screw speed on the extrusion behaviour and product characteristics of flint and sweet corn grits. The extruder die pressure and extrudate properties, such as expansion and water solubility index (WSI), were analyzed. Second order polynomials were computed to describe the extruder response and product properties of grits from both corn types as a function of feed moisture, extrusion temperature and screw speed. Among feed moisture, extrusion temperature and screw speed, feed moisture showed the most pronounced effect on die pressure, expansion and WSI. Die pressure of the extruder was significantly greater for sweet corn than flint corn grits. The grits from both the corn types differ significantly with respect to extrusion behaviour and product characteristics under similar extrusion conditions. The particle size distribution revealed that flint corn grits had more fine and opaque particles and resulted in extrudates with lower WSI and expansion than those from sweet corn grits which had fewer fine particles.     

Physical and Functional Properties of Arrowroot Starch Extrudates

ABSTRACT:  Arrowroot starch, a commercially underexploited tuber starch but having potential digestive and medicinal properties, has been subjected to extrusion cooking using a single screw food extruder. Different levels of feed moisture (12%, 14%, and 16%) and extrusion temperatures (140, 150, 160, 170, 180, and 190 °C) were used for extrusion. The physical properties—bulk density, true density, porosity, and expansion ratio; functional properties such as water absorption index, water solubility index, oil absorption index, pasting, rheological, and textural properties; and in vitro enzyme digestibility of the extrudates were determined. The expansion ratio of the extrudates ranged from 3.22 to 6.09. The water absorption index (6.52 to 8.85 g gel/g dry sample), water solubility index (15.92% to 41.31%), and oil absorption index (0.50 to 1.70 g/g) were higher for the extrudates in comparison to native starch (1.81 g gel/g dry sample, 1.16% and 0.60 g/g, respectively). The rheological properties, storage modulus, and loss modulus of the gelatinized powdered extrudates were significantly lower ( P < 0.05) and these behaved like solutions rather than a paste or a gel. Hardness and toughness were more for the samples extruded at higher feed moisture and lower extrusion temperature, whereas snap force and energy were higher at lower feed moisture and temperature. There was a significant decrease in the percentage digestibility of arrowroot starch (30.07% after 30 min of incubation with the enzyme) after extrusion (25.27% to 30.56%). Extrusion cooking of arrowroot starch resulted in products with very good expansion, color, and lower digestibility, which can be exploited for its potential use as a snack food.     

螺杆转速和原料含水率对糯米单螺杆挤出过程的影响

本文利用组合实验研究了糯米单螺杆挤出过程中操作参数(螺杆转速、原料含水率]对挤出设备和产品性能(生产率、功耗、度电产量、膨化指数、吸水指数、水溶性指数)的影响,建立了相互影响关系的回归方程,得出随螺杆转速的增加,生产率、功耗、水溶性指数增大,而度电产量、膨化指数、吸水指数开始上升,然后下降,存在极大值,综合各指标,该设备的最佳螺杆转速在240—260rpm;随原料含水率的增加,生产率、度电产量、吸水指数增加,而功耗、膨化指数、水溶指数减小,该设备挤出膨化糯米时的最佳原料含水率在18％～21％范围内。     

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.     

Impacts of the Particle Sizes and Levels of Inclusions of Cherry Pomace on the Physical and Structural Properties of Direct Expanded Corn Starch

An effort was made to understand the impacts of dried cherry pomace (by-product of cherry juice processing) inclusion into corn starch extrudates on their direct expansion characteristics. The effect of pomace particle sizes (whole unfractionated (<125 to >500 μm), <125, 125–250, 250–500, and >500 μm) and levels of pomace inclusion (0, 5. and 15% (w/w)) were specifically investigated. Feed moisture content of 15.5 ± 0.5% (w.b.) and the extruder barrel temperature of 140 °C were kept constant with varying extruder screw speed (150, 200, and 250 rpm). The radial expansion ratio (ER) increased with 5% pomace level of inclusion compared with control but decreased significantly (p < 0.05) at 15% inclusion. Particle sizes significantly affected ER (p < 0.05) with smaller particle sizes resulting in increased ER at all levels of pomace. Adding cherry pomace significantly decreased water absorption index (WAI) and water solubility index (WSI) with smaller particles leading to higher WSI. Extrusion process did not reduce the total phenolic content (gallic acid equivalents). Inclusion of the smallest particle size (<125 μm) cherry pomace at 5% level of inclusion yielded extrudates with the highest expansion ratio among all treatments, including the control. The scanning electron images suggested improvements in the extrudate surface and the internal cell structures. The results indicated the presence of active interactions between the cherry pomace and starch during the expansion process which is not present as an inert material.     

Properties of extruded whole grain cereals and pseudocereals flours

Common cereals such as wheat are widely used worldwide in extruded products. Nevertheless, other locally available grains would be beneficial for local consumers regarding taste preference, nutritional needs and sustainability. Locally available cereals, that is millet, teff, sorghum and pseudocereals, that is quinoa and amaranth flours were extruded at the same processing conditions, and the resulting properties were compared to those of extruded refined wheat flour. Amaranth flour contained the highest protein content (16%). Sorghum was the highest in calories because of its high lipid content (10%). The extrusion process greatly increased a water solubility index (WSI) of amaranth from 11% to 61%, while the WSI level of quinoa was almost not affected (WSI of 4%). The expansion properties varied differently among grain types. These grains had a sectional expansion index (SEI) ranging between 11 and 13, which could not achieve the performance of the refined wheat (SEI of 22). The lowest expansion was observed for amaranth flour which contained the lowest starch content. Sorghum extrudates, interestingly, provided comparable stress at rupture value to that of wheat. For the mechanical properties, none of these local grains could fully replace refined wheat at the employed extrusion conditions.     

Changes in the Starch Fraction During Extrusion-cooking of Corn

Whole ground corn was extruded at 23.7, 18.5, 15.4,13.9 and 7.6% moisture contents (EMC). Decreasing EMC resulted in increases in water solubility index (WSI), enzyme susceptibility (ES), degree of gelatinization and blue values, while water absorption index and water insoluble carbohydrates decreased. ES and WSI of several blends prepared by combining raw (R), gelatinized (G), and dextrinized (D) corn were compared to those of extruded products. Corn extrudates had properties similar to blends containing G and D corn only. The relative proportion of D corn increased from about 10 to 60%, as EMC decreased. “Dextrinization” appears to become the predominant mechanism of starch degradation during low-moisture, high-shear extrusion. Viscoamylographs, scanning electron and light photomicrographs support these findings.