Screw Configuration Effects on Macroscopic Characteristics of Extradates Produced by Twin-screw Extrusion of Rice Flour

The effects of 29 screw configurations on rice flour extrudates were investigated. The moisture content, screw speed and feed flow rate during all extrusion experiments were 15%, 400 rpm, and 12kg/h, respectively. Temperature profile in the 8 barrel sections from feed to die end were set at 0, 30, 30, 30, 70, 100, 150, and 150°C. Incorporation of kneading block (KB) and reverse screw element (RSE) in screw profiles significantly influenced apparent density, product expansion (radial, axial and overall), and breaking strength. Apparent density and overall expansion were functions of die temperature. KB was the best element for maximizing radial expansion. Product hardness (breaking strength) decreased with increasing radial expansion.     

Effects of extrusion conditions on secondary extrusion variables and physical properties of fish, rice-based snacks

A formulation containing rice flour, fish powder, menhaden oil and vitamin E was extruded at a feed rate of 10 kg/h using a co-rotating twin-screw extruder. Primary extrusion (independent) variables were temperature (125-145 °C), screw speed (150-300 rpm) and feed moisture (19-23 g/100 g db). Response surface methodology (RSM) was used to study the effects of extrusion conditions on secondary extrusion variables (product temperature, pressure at the die, motor torque, specific mechanical energy input and mean residence time) and physical properties of the extrudates. Second-order polynomial models were computed and used to generate contour plots. Increasing feed moisture and screw speed decreased pressure at the die. Increased screw speed increased product temperature at the die but increased feed moisture lowered it. Increased barrel temperature, feed moisture and screw speed decreased motor torque. Increased screw speed increased specific mechanical energy, while increased feed moisture reduced it. Longer mean residence times were observed at lower screw speeds. Product density increased as feed moisture increased, but decreased with screw speed. Increased feed moisture decreased radial expansion.     

Effects of extrusion variables on the properties of waxy hulless barley extrudates

The objective of this research was to investigate the extrudability of waxy hulless barley flour under various extrusion conditions. Waxy hulless barley flour was processed in a laboratory-scale corotating twin-screw extruder with different levels of feed moisture content (22.3, 26.8, and 30.7%) and die temperature (130, 150, and 170 degrees C) to develop a snack food with high beta-glucan content. The effects of extrusion condition variables (screw configuration, moisture, and temperature) on the system variables (pressure and specific mechanical energy), the extrudate physical properties (sectional expansion index, bulk density), starch gelatinization, pasting properties (cold peak viscosity, trough viscosity, and final viscosity), and beta-glucan contents were determined. Results were evaluated by using response surface methodology. Increased extrusion temperature and feed moisture content resulted in decreases in exit die pressure and specific mechanical energy values. For extrudates extruded under low shear screw configuration (LS), increased barrel temperature decreased sectional expansion index (SEI) values at both low and high moisture contents. The feed moisture seems to have an inverse relationship with SEI over the range studied. Bulk density was higher at higher moisture contents, for both low and high barrel temperatures, for samples extruded under high shear screw configuration (HS) and LS. Cold peak viscosities (CV) were observed in all samples. The CV increased with the increase in extrusion temperature and feed moisture content. Although beta-glucan contents of the LS extrudates were comparable to that of barley flour sample, HS samples had generally lower beta-glucan contents. The extrusion cooking technique seems to be promising for the production of snack foods with high beta-glucan content, especially using LS conditions.     

Physico-chemical,structural and sensory quality of corn-based flax-snack

The effect of incorporating increasing percentage of flaxseed flour on the chemical, physical, microstructure and sensory quality of corn-based snack were studied. A Brabender laboratory single screw extruder was used to prepare the extrudates under fixed extrusion conditions. Feed moisture content was 18%, barrel temperature before the die was 200°C, and screw speed was 200 rpm. Proximate composition, expansion ratio, bulk density, breaking strength, colour, water absorption and soluble indices were examined. Experimental work showed significant difference due to the increased proportion of flaxseed flour. Fiber, fat and protein content were altered in extrudates by the addition of flax. Expansion ratio decreased, bulk density and breaking strength increased almost recilinearly and resulted in a more dense snack. Higher degree of lightness ‘L’ values were obtained in blend containing a lower percentage of flaxseed. Water absorption decreased as the percent of flaxseed increased. Water solubility index showed similar trend. Sensory evaluation by 15 members sensory panel showed that within the observed concentration ranges, total score gradually decreased by increasing proportion of added flaxseed but still acceptable for the panellists. Microscopic examination revealed that increasing the percentage of flaxseed resulted in a denser product, while a lower percent gave a more hollow snack. Consequently, there is a parallelism between the flaxseed percent and the microstructure of the extrudates.     

Effect of extrusion conditions on resistant starch formation from pastry wheat flour

Pastry wheat flour was extruded under various conditions of feed moisture (20%, 40%, and 60%) and screw speed (150, 200, and 250 rpm), at constant barrel temperature profile (40, 60, 80, 100, and 120 °C, feed port to exit die). The extruded samples were stored at 4 °C for 0, 7, or 14 days, at which times resistant starch (RS) formation was analyzed. Thermal and pasting properties of extruded samples stored for 14 days were analyzed using a differential scanning calorimeter and rapid visco analyzer (RVA), respectively. The RS content increased after extrusion compared to non-extruded pastry wheat flour. High significant positive correlations of feed moisture (P < 0.01) and storage period (P < 0.05) with RS formation were observed. The RS derived from extrusion and storage showed higher thermal stability with decreasing feed moisture and screw speed. Statistically significant differences in pasting properties were observed with feed moisture or screw speed. In particular, the setback value from RVA of the sample was significantly increased with increasing feed moisture. These results indicate that feed moisture and storage time were both important factors for the formation of RS from pastry wheat flour during extrusion.     

挤压膨化对紫糯全麦粉理化性质及抗氧化活性的影响

通过改变挤压膨化的工艺条件,分析了不同膨化条件下紫糯全麦粉的主要理化指标变化情况。结果表明:随着膨化温度、螺杆转速的升高,紫糯全麦粉的膨化度、水溶性指数、总膳食纤维、可溶性膳食纤维以及总酚含量均有所升高,而吸水性指数则有所下降。挤压膨化可使紫糯全麦粉的可溶性膳食纤维含量增加约6%~26%,总酚含量在膨化温度160℃、物料含水量13%时,达到最高1.03mg/g。膨化紫麦粉的WSI和WAI分别比原料提高70%和37%;物料含水量的增加则使水溶性指数和总酚含量下降,吸水性指数及其他指标均有所升高;膨化产品的总抗氧化能力随着膨化温度、物料含水量以及螺杆转速的增加均有所降低。      

EFFECT of EXTRUSION VARIABLES ON EXTRUDATE CHARACTERISTICS of FISH MUSCLE-RICE FLOUR BLEND IN A SINGLE-SCREW EXTRUDER

Effects of extrusion variables on extrudate characteristics of fish muscle-rice flour blend containing intermediate moisture (30–50%) were studied in an indigenously developed single screw cooking extruder. Data analysis of the statistically designed response surface experiments showed that expansion ratio and bulk density of extrudates were most influenced by the barrel temperature followed by fish content of the feed. In contrast fish and moisture contents of the feed significantly influenced hardness. A set of optimum process conditions was arrived at 160C barrel temperature, 12% fish content and 27% moisture content. Under these conditions experimental expansion ratio and bulk density matched well with the values predicted from the response model, but hardness deviated significantly. Experimental properties of the extrudates were not, however, affected by the fish variety.     

Extrusion Cooking Process for Amaranth (Amaranthus caudatus L.)

ABSTRACT: Amaranth ( Amaranthus caudatus L.) extrusion was optimized by response surface methodology (RSM). Response (dependent) variables were: expansion ratio, shearing strength, and sensory texture acceptability. Independent variables were processing temperature and feed moisture. All other process variables (screw speed, screw compression ratio, feed speed, and die diameter) were kept constant (200 rpm, 70 g.min⁻¹, and 3 mm, respectively). The most expanded products also had the best texture and were obtained at 150 °C and 15% moisture. These conditions resulted in greater expansion, greater shearing force of extrudates, greater extrudate surface area per unit weight, and reduced shearing stress at maximum shearing force. This study showed that under conditions that induced the maximum expansion ratio, extrusion produced a highly acceptable snack product based on amaranth flour.     

Development of a bulgur‐like product using extrusion cooking

In this study we (1) developed a new bulgur‐like foodstuff using a durum wheat cultivar and an extrusion technique, (2) investigated the physicochemical properties of the extrudates produced and (3) sensorially evaluated the end‐product after cooking. Durum wheat was processed in a laboratory‐scale co‐rotating twin‐screw extruder with different levels of moisture content of the feed (367, 417 and 455 g kg^?1), screw speed (150 and 200 rpm) and feed rate (2.4 and 2.9 kg h^?1) to develop the bulgur‐like product. The effects of extrusion conditions on system variables (die pressure and specific mechanical energy (SME)), physical properties (die swell and bulk density), pasting properties (peak, trough and final viscosities) and cooking and sensory properties of the bulgur‐like products were determined. The results indicated that increased feed moisture content resulted in significant decreases in the die pressure and SME values of the extruded durum wheat products. As the moisture content and screw speed increased, the changes in die swell values were not significant. The lowest die swell and highest bulk density values were obtained at the highest feed moisture content. The extrusion variables also affected the pasting properties of the extrudates. Significant increases in each of the pasting properties occurred when the moisture content of the feed was increased. Some of the sensory properties (bulkiness, firmness, stickiness and taste–aroma) improved significantly as the feed moisture content increased, indicating better quality. Increased feed moisture content significantly improved cooking quality as determined by a decrease in colorimetric test results. Extrusion seems to be promising for the production of dry, relatively inexpensive bulgur‐like products with acceptable sensory properties. © 2003 Society of Chemical Industry     

Effect of Extrusion Variables on Cassava Extrudates

Cassava flour was extruded by varying parameters of feed moisture; temperature; screw speed and feed rate. We investigated significance of each variable and interactions between variables on each extrudate characteristic. Optimum expansion (2.82) was at 11% feed moisture 120–125 °C; screw speed, 520rpm; feed rate, 250g/min. Effect of feed moisture was most significant on expansion, bulk density and extrudate moisture. Increasing temperature, increased expansion and water solubility, but decreased bulk density, extrudate moisture and water absorption. Screw speed most influenced water absorption and solubility. Extrudate moisture correlated negatively (P<0.01) with extrudate expansion. Water solubility index of extrudate negatively correlated (P<0.05) with extrudate moisture and water absorption index but correlated positively (p<0.05) with expansion.     

Mechanical Properties of Corn-Legume Based Extrudates

The effect of extrusion conditions, including feed rate (2.52–6.84 kg/h), feed moisture content (13–19% wet basis), screw speed (150–250 rpm), and extrusion temperature (150–260°C) on the mechanical properties of corn/legume-based extrudates was studied. White bean and lentil were used in mixtures with corn flour at a ratio of 10:90 up to 90:10 (corn:legume). Simple power models were used to correlate breaking stress and corresponding strain with extrusion conditions and material characteristics. The influence of feed rate on the extrudates mechanical properties was incorporated in the mean residence time. The breaking stress of extrudates decreased with temperature, residence time, and corn to legume ratio, and it increased with feed moisture content. The corresponding strain showed an opposite trend. Screw speed did not affect the extrudate properties. The use of lentil flour led to a product with higher breaking stress. Furthermore, in a previous work, the porosity of these products was modeled and, now, it was found that breaking stress and porosity of the extrudates could be correlated by an exponential relationship.     

Effect of extrusion variables on fermented maize-finger millet blend in the production of uji

The effects of screw speed, feed moisture, glucose, fructose, sucrose and maltose on extrusion of lactic fermented and dried maize-finger millet blend was investigated. Fermentation caused a reduction in sectional expansion index, flour bulk density and water absorption index (WAI) but increased specific volume, water solubility index and darkened the extrudates. Increase in feed moisture (13-25%) reduced sectional expansion index, specific volume and yellowness but increased extrudate moisture content, bulk density and darkness of the extrudates. Increasing screw speed (158-242 rpm) had a negative correlation only with specific volume and lightness (P<0.05). An increase in the content of any of the sugars reduced extrudate moisture content, sectional expansion index, WAI and specific volume but increased bulk density and water solubility index. Extrudates treated with monosaccharides were darker than extrudates treated with disaccharides.     

Tapioca-Fish and Tapioca-Peanut Snacks by Twin-Screw Extrusion and Deep-Fat Frying

Two half-products were prepared from tapioca starch/catfish fillet-belly flap mince (60:40) and tapioca starch/partially defatted peanut flour (PDPF) (60:40) by twin-screw extrusion. The process variables were temperature in the last two zones of the extruder (90,95,100°C) and screw speeds (100, 250, 400 rpm). Moisture content (40%, wet basis) and feed rate (27 g/min) were held constant. Simultaneously increasing temperature and screw speed resulted in increased expansion, and decreased bulk density and shear strength. Degree of starch gelatinization in half-products ranged from 87 to 95%. Optimum conditions predicted by response surface methodology were: for fish half-products 94–100°C and 220–400 rpm and for peanut half-products, 95–100°C and 230–400 rpm.     

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.     

An experimental study of twin-screw extrusion-cooking of maize grits

The use of a twin-screw extrusion-cooker to process maize grits is described. The expansion, bulk density, colour and aqueous dispersion rheology have been related to the extrusion cooking variables: screw speed, feed rate, moisture content and barrel zone temperature. A pseudo-viscosity quantity has been defined to describe the extrudate viscosity at the die which was also related to the extrusion-cooking variables. The pressure and temperature profiles in the extruder were recorded together with the mechanical and thermal energy consumption as a function of the extrusion-cooking variables. These experiments with a highly instrumented cooking-extruder indicate the condition of the material in the barrel prior to formation of the product.     

Influence of the extrusion parameters on the physical properties of chickpea and barley extrudates

In this research, the effects of extrusion processing [exit-die temperature (120–150°C), moisture content (20–24% wet basis), and screw speed (260–340 rpm)] on the specific mechanical energy and physical properties (expansion ratio, bulk density, and hardness) of desi chickpea and hullless barley extrudates were estimated using response surface methodology. Exit-die temperature and feed moisture content, as well as the interaction between them were the factors that affected the product responses the most. Significant correlation was found between the hardness and bulk density (positive), hardness and expansion ratio (negative), and bulk density and expansion ratio (negative) for both chickpea and barley extrudates. Desirable characteristics (high expansion, low bulk density, and hardness) for chickpea were obtained at high exit-die temperature, relatively high moisture, and high screw speed. As for the barley extrudates, high exit-die temperature, low moisture, and moderate to high screw speed were identified as optimal.     

Extrusion cooking of barley flour and process parameter optimization by using response surface methodology

BACKGROUND: The nutritional profile of barley places it in a prime position for development of a new extruded–expanded snack food with health benefits. It was therefore the aim to investigate the effect of extrusion processing variables on system parameters (specific mechanical energy, die pressure and die melt temperature) and physical properties (expansion, bulk density, texture and color) of barley flour extrudates and to optimize processing conditions for production of extruded snack food from barley flour by response surface methodology. RESULTS: Barley flour with 219.7 g kg^?1 moisture content was extruded at different die temperatures (140–160 °C) and screw speeds (150–200 rpm) through a co‐rotating twin‐screw extruder. The system parameters as well as product responses were mainly dependent on temperature, whereas the screw speed imparted a lesser effect. Extrudates produced under extrusion conditions of 160 °C, 150 and 200 rpm and at 164 °C and 150 rpm had higher preference levels of appearance, taste, texture and overall acceptability than that of other selected extrudates for sensory analysis. The optimal conditions for minimum bulk density and desired textural characteristics and color of extrudates correspond to a temperature of 156 °C and screw speed of 166 rpm. CONCLUSION: The results suggested that use of barley flour in extruded snack products offers a desirable variation in diet and can take advantage of the nutritional quality of barley. Copyright © 2008 Society of Chemical Industry     

Effect of Process Conditions on the Physical and Sensory Properties of Extruded Oat-Corn Puff

ABSTRACT: The effect of processing variables, including screw speed (200,300, and 400 rpm), moisture content (18, 19.5, and 21%), and four different percentages (55,70,85, and 100%) of oat flour, on the extrudate physical properties (expansion, bulk density, and texture profiles) and sensory properties were studied. Increasing the percentage of oat flour resulted in extrudates with a lower specific length, higher bulk density, lower lightness, higher redness, lower yellowness, higher hardness, and lower springiness, gumminess, and chewiness. Higher moisture content reduced expansion, except for the 100% oat flour puffs. Screw speed had no significant effect on the bulk density, specific length, and expansion ratio. Principal Component Analysis showed that decreasing moisture content and increasing screw speed resulted in increased product temperature, which was highly correlated with attributes of a more expanded product such as lightness, crispness, shininess, and an open cell structure. With a higher screw speed and a higher product temperature, corn-related flavors were more likely to develop. High correlations between physical and sensory properties were observed.     

Effects of extrusion conditions on system parameters and physical properties of a chickpea flour-based snack

Response surface methodology (RSM) was used to study the effects of feed moisture content (16–18%), screw speed (250–320 rpm), and barrel temperature (150–170 °C) on extruder system parameters (product temperature, die pressure, motor torque, specific mechanical energy, SME) and physical properties (expansion, bulk density, hardness) of a chickpea flour-based snack. Second-order polynomials were used to model the extruder responses and product properties as a function of process variables. Product temperature and die pressure were affected by all three process variables, while motor torque and SME were only influenced by screw speed and barrel temperature. All three variables affected product responses significantly. Desirable products, characterized by high expansion ratio and low bulk density and hardness, were obtained at low feed moisture, high screw speed and medium to high barrel temperature. It was demonstrated that chickpeas can be used to produce nutritious snacks with desirable expansion and texture properties.     

PROCESS VARIABLES DURING SINGLE-SCREW EXTRUSION OF FISH AND RICE-FLOUR BLENDS

Extrusion cooking of fish and rice‐flour blends in a single‐screw cooking extruder was studied under a wide range of variables of barrel temperature, screw speed, fish content and feed‐moisture content which ranged from 100 to 200C, 70–110 rev/min, 5–45% and 20–60%, respectively. Experiments based on rotatable design showed that the physical properties of expansion ratio, bulk density, hardness and water solubility index (WSI) were significantly affected by all the process variables except screw speed. Barrel temperatures greater than 180C and feed moistures less than 58% result in a steep increase in expansion ratio and a decrease in bulk density. At a fish content of 5% and feed‐moisture content of less than 52.5%, the hardness values decreased. When the WSI is at 40–42% of fish content and the feed‐moisture content is less than 55%, a steep increase was noticed, but a maximum WSI value of 11.5% was observed at a fish content of 41.37% and a feed‐moisture content of 35%.