Physical evaluation of a maize‐based extruded snack with curry powder

Response surface methodology was used to analyze the effect of screw speed (200–280 rpm), feed moisture (13.0–17.0%, wet basis), and curry powder (6.0–9.0%) on the bulk density, lateral expansion, and firmness of maize‐based extruded snack with curry powder. Regression equations describing the effect of each variable on the responses were obtained. Responses were most affected by changes in feed moisture followed by screw speed and curry powder (p < 0.05). Lateral expansion increased linearly as the amount of curry powder added was increased whereas a quadratic increase was obtained in lateral expansion with decreasing feed moisture. The firmness of samples was increased with an increase in feed moisture. The bulk density of samples was increased with increasing feed moisture and screw speeds. Radial expansion was found to be a better index to measure the physical properties of the extruded product indicated by a higher correlation coefficient.     

Physical evaluation of a maize-based extruded snack with curry powder

Response surface methodology was used to analyze the effect of screw speed (200-280 rpm), feed moisture (13.0-17.0%, wet basis), and curry powder (6.0-9.0%) on the bulk density, lateral expansion, and firmness of maize-based extruded snack with curry powder. Regression equations describing the effect of each variable on the responses were obtained. Responses were most affected by changes in feed moisture followed by screw speed and curry powder (p < 0.05). Lateral expansion increased linearly as the amount of curry powder added was increased whereas a quadratic increase was obtained in lateral expansion with decreasing feed moisture. The firmness of samples was increased with an increase in feed moisture. The bulk density of samples was increased with increasing feed moisture and screw speeds. Radial expansion was found to be a better index to measure the physical properties of the extruded product indicated by a higher correlation coefficient.     

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.     

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.     

The Effects of Extrusion Conditions on the Physical Properties of Wheat Flour Extrudates

The effects of extrusion conditions (feed moisture content and rate, process temperature, screw speed and geometry, and die diameter) on expansion ratio, bulk density, and breaking strength of wheat flour extrudates were investigated. Extrudate samples were prepared by using a Brabender single-screw extruder. Higher feed moisture content and process temperature were required for proper expansion. At 3.18mm die opening, the relationship between expansion and bulk density was positive. Feed rate was the most effective factor for increasing bulk density. Breaking strength was significantly decreased with increasing process temperature. Under extrusion conditions of 22% feed moisture, 110g/min feed rate, 160°C process temperature, and 130rpm screw speed with 5:1 CR, wheat flour was puffed with low bulk density and breaking strength.     

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.     

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     

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%.     

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.     

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.     

Structural Properties of Corn-Legume Based Extrudates as a Function of Processing Conditions and Raw Material Characteristics

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 (150–230°C) on structural properties of corn-legume based extrudates was studied. Four different types of legumes, chickpea, mexican bean, white bean, and lentil were used to form mixtures with corn flour in a ratio ranging from 10 to 90% (corn/legume). A simple power model was used to correlate porosity with extrusion conditions and material characteristics. The influence of feed rate in the extrudates porosity is incorporated into mean residence time. Porosity of extrudates was found to increase with temperature and residence time and to decrease with feed moisture content and corn to legume ratio. Screw speed did not affect extrudates properties. Expansion ratio showed a similar behavior with porosity. The addition of legumes (protein source) led to more dense products. Comparatively, the usage of white bean in mixtures for the production of snacks, led to a product with higher porosity than those with other legumes.     

Twin-screw Extrusion of Corn Flour and Soy Protein Isolate (SPI) Blends: A Response Surface Analysis

The effects of feed moisture, screw speed, and barrel temperature on physical properties of extruded corn flour and soy protein isolate (SPI) blends were investigated in a co-rotating twin-screw extruder using a response surface methodology. Corn flour and SPI were mixed with a ratio of 4:1. The screw speed was set at five levels between 60 and 140 rpm, barrel temperature between 140 °C and 180 °C, and feed moisture between 18% and 38%. All physical properties of the extruded material evaluated—included expansion ratio, bulk density, breaking strength, water solubility index, rehydration ratio, and color—were significantly (p < 0.05) affected by the three process variables. Feed moisture was the most significant variable with quadratic effects on most of the physical properties. Response surface regression models were established to correlate the physical properties of the extruded product to the process variables. Understanding the effect of these variables on the product physical properties was deemed useful for the development of protein-rich extruded products.     

Effect of Thermo-extrusion Process Parameters on Selected Quality Attributes of Meat Analogue from Mucuna Bean Seed Flour

Flour from mucuna beans (Mucuna pruriens) were used in producing texturized meat analogue using a single screw extruder with the intention to monitor modifications on some functional properties of the extrudate. Response surface methodology based on Box Behnken design at three levels of barrel temperature (110, 120, 130°C), screw speed (100, 120, 140 rpm) and feed moisture content (44, 47, 50%) were used in 17 runs. Regression models describing the effect of process variables on the product quality attributes were obtained. Result obtained showed that the moisture contents of the meat analogue samples decreased from 13.23 to 6.53%. Increasing feed moisture content resulted in extruded meat analogue with a higher density (0.988), water absorption index (WAI) (2.30), oil absorption index (OAI) (2.350), swelling power (3.47) and lower lateral expansion (0.84). Lateral expansion, OAI and swelling power increased as barrel temperature increased with peak values of 1.39, 2.39 and 3.47 respectively, while bulk density and WAI decreased. The product functional responses with coefficients of determination (R²) ranging between 0.658 and 0.894 were most affected by changes in barrel temperature and feed moisture and to lesser extent by screw speed. Optimization results based on desirability concept indicated that a barrel temperature of 120.15°C, feed moisture of 47% and screw speed of 119.19 rpm would produce meat analogue of preferable functional properties.     

Functional and Nutritional Properties of Extruded Whole Pinto Bean Meal (Phaseolus Vulgaris L.)

Pinto bean meals with 18, 20, and 22% moisture were extruded at 140,160 and 180°C, using screw speeds of 150,200 and 250 rpm in a single-screw laboratory extruded. Expansion index, bulk density, water absorption and solubility indices, in vitro protein digestibility, and trypsin inhibitor activity in extrudate were measured. Temperature and feed moisture influenced (p<0.05) expansion index, bulk density, water absorption index and in vitro protein digestibility. Water solubility index was affected by temperature only. Trypsin inhibitors were inactivated completely for all conditions. Screw speed had no effect on any dependent variable. Best product was produced with 22% feed moisture at 160°C.     

Effect of extrusion process on the antioxidant activity and total phenolics in a nutritious snack food

The effect of screw speed (220–340 rpm), moisture content of the feed (11.0–15.0%, wet base) and feed rate (22.0–26.0 kg h^?1, wet base) on the total antioxidant capacity (TAA) and concentration of total phenolics (TP) in a nutritionally balanced extruded snack were investigated. Regression equations describing the effect of each variable on the responses were obtained. Results indicated that screw speed, moisture content of the feed and feed rate had an effect on the TAA values of the samples at 95% confidence interval (CI). The interaction between the three factors was also found to be significant at 95% CI for TAA values. Extrusion conditions applied in this study did not change the TP values in the samples. The TAA value of samples decreased with an increase in screw speed and decrease in moisture content.     

System Parameters and Product Properties Responses During Extrusion of Fura from Millet-Soybean Mixtures

A three-factor, three-level central composite rotatable composite design (CCRD) was adopted to study the effect of feed composition (X₁), feed moisture content (X₂) and screw speed (X₃) on the system parameters (torque, pressure, and specific mechanical energy) and fura extrudate properties (expansion ratio and bulk density) from blends of pearl millet and soybean flour mixtures. The torque was influenced negatively but significantly (p < 0.05) by linear effects of feed composition and screw speed. The die pressure was also influenced negatively by the linear effects of the screw speed significantly (p < 0.05). The response surface plot showed that the specific mechanical energy SME was decreasing as screw speed increased while SME marginally decreased as feed moisture increased. The linear effects of the independent variables significantly (p < 0.05) affected the expansion ratio. The linear and quadratic effects of the independent variables significantly (p < 0.05) affected the bulk density. The CCRD was effective in explaining the effect of the process conditions on fura as influenced by feed composition, feed moisture and screw speed. The importance of process variables on system parameters and physical properties could be ranked in the following order: Feed Composition (X₁) > Feed Moisture (X₂) > Screw Speed (X₃). Response variables predicted with model equations under optimum conditions were in general agreement with experimental data. The data obtained from the study could be used for control of product characteristics and possible projection for the commercial production of fura.     

Structural Properties of Corn-Based Extrudates Enriched with Plant Fibers

Structural properties, such as apparent density, true density, expansion ratio, and porosity, of extruded corn grits enriched with plant fibers were measured. The effect of extrusion conditions, including feed rate (0.7–1.9 g/s), feed moisture content (13–19% wet basis), and extrusion temperature (150–230°C) on structural properties of corn-based extrudates enriched with apple and oat fibers was studied. The ratio of the two fibers to corn flour was ranging from 10 to 30% (fiber/corn). A simple power model was used to correlate porosity with extrusion conditions and material characteristics. Porosity of extrudates was found to decrease with temperature, feed moisture content and fiber to corn ratio, and to increase with feed rate for both the examined fibers. Generally, the addition of fibers led to more dense products. Comparatively, the usage of apple fiber in mixtures for the production of snacks led to a product with higher porosity than those with oat fiber.     

ENERGY CONSUMPTION IN SINGLE-SCREW EXTRUSION PROCESSING OF FULL FAT AFRICAN BREADFRUIT (TRECULIA AFRICANA) BLENDS

Full fat African breadfruit, corn and defatted soy blends with moisture content range of 6.20–7.50% (wet basis) were extruded in a single‐screw Brabender laboratory extruder (DCE 330, Brabender Instruments Inc., South Hackensack, NJ) at varying independent process variables of feed composition (fc), feed moisture (fm) and screw speed. A central composite design was employed to study the effects of these variables and extrusion cooking on several quality characteristics of the center point blend, and energy input as torque and specific mechanical energy (SME). SME is relevant in that the more the energy applied, the greater the degradation of starch while torque is directly correlated with power usage. Extrusion cooking significantly (P ≤ 0.05) affected bulk density, water absorption, water solubility and nitrogen solubility indices. Torque and SME ranged from 4.00 to 8.50 N·m and 216 to 376 kJ/kg, respectively. Regression analysis of data generated of experimental data showed that fc had significant (P ≤ 0.05) quadratic effect on both energy measurements. Screw speed and fm showed significant (P ≤ 0.05) linear effects on SME while screw speed alone showed significant (P ≤ 0.05) linear effect on torque. At 160‐rpm screw speed and 85% fc, the torque value was maximum (8.50 N·m). Maximum SME value of 376.72 kJ/kg was obtained at 85% fc, 24% fm and 120‐rpm screw speed. Economically, therefore, extruded products made from blends of breadfruit, corn and soy flours will require lower extruder power usage given the fat and fm levels. Findings of this research might be useful to processors for better process control and optimal energy utilization when extruding these or related blends in a single‐screw extruder.     

EXTRUSION COOKING OF RICE: EFFECT OF AMYLOSE CONTENT AND BARREL TEMPERATURE ON PRODUCT PROFILE

The effect of amylose content (5.0–28.6%) of rice and barrel temperature (80–120C) on extrusion system parameters torque and net specific mechanical energy and extrudate characteristics extrudate bulk density (ED), water solubility index, expansion ratio (ER) and Warner–Bratzler shear stress were studied using a twin‐screw extruder. The feed rate (15 kgh^?1), moisture content (20.0% ± 0.2) of feed and the screw speed (400 rpm) were kept constant. ED and ER of the product suggested that a barrel temperature of 120C was desirable to generate an expanded extrudate rice product from low‐amylose rice cultivar. Experimental data on system parameters and extrudate characteristics fit to second‐degree polynomial regression equations (r ≥ 0.904, P ≤ 0.01) with the amylose content of rice and barrel temperature of the extruder.     

Enhancing an Extruded Puffed Snack by Optimising Die Head Temperature,Screw Speed and Apple Pomace Inclusion

Extrusion cooking is recognised as a smart technology for food processors. It requires low cost, high temperature, short-time process and few ingredients to create a puffed snack. The only drawback is that it contains multiple parameters that need to be rigorously trialled to develop an optimal process. This study investigated the effects of two extruding parameters (die head temperature and screw speed) and examined the addition of apple pomace into a corn flour-based extruded snack formulation. A response surface design was utilised. A D-optimal design was chosen, which generated 21 combinations; within these combinations, the control formulation existed. Extrudate characteristics, i.e. bulk density and porosity, textural properties, cooked starch properties and moisture, were analysed. Screw speed was found to have the greatest effect on extrudate quality, e.g. bulk density increased as the screw speed increased (p?<?0.001). Both apple pomace addition and screw speed impacted expansion ratio; as they increased, expansion decreased (p?<?0.0001). The optimised and validated formulation contained the following parameter levels: 7.7 % apple pomace, 150 °C die head temperature and a screw speed of 69 rpm. As apple pomace and corn flour are naturally gluten free, the extruded product would appeal to people who suffer from intolerances, allergies and coeliac disease.