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.     

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.     

Residence Time Distribution (RTD) in a Single Screw Extrusion of African Breadfruit Mixtures

Mixtures of African breadfruit (Treculia africana Decne), corn, and defatted soybean were extruded in a single-screw Brabender laboratory extruder at process variables derived from a second-order central composite design. The variables consisted of feed composition (0–100% breadfruit, 0–55% soybean, and 0 or 5% corn); fed moisture (15–27%), and screw speed (100–180 rpm). Effects of these variables on residence time distribution were investigated using Congo red as tracer. The extrudate spent longer time in the extruder as feed moisture or screw speed was decreased from 27% to 15% or 180 to 100 rpm, respectively, thereby increasing the residence time distribution characteristics. At 70% feed composition and screw speed of 140 rpm, mean residence time ([`(t)]\overline t ) increased from 40 to 50 s, whereas extrudate total collection time (t <sub>c</sub>) increased from 65 to 70 s. At screw speed of 100–180 rpm, mean residence time ([`(t)]\overline t ) decreased from 55 to 35 s, whereas extrudate total collection time (t _c) decreased from 75 to 65 s. At 100% African breadfruit composition, these time values decreased to 35 and 70 s, respectively, at the same screw speed, indicating the significant influence of feed composition and soybean addition to the mixture on residence time distribution. Residence time distribution curves indicated an early breakthrough time of 20 s at maximum screw speed (180 rpm), minimum tail of 65 s, and a plug flow pattern of the extrudates.     

Evaluating Energy Consumption and Efficiency of a Twin-Screw Extruder

ABSTRACT: Using the results from twin-screw extrusion of corn meal, both energy consumption and extruder efficiency were found to be significantly correlated with screw speed and specific feeding load (SFL). An increase in the SFL decreased the total specific mechanical energy, but increased the extruder efficiency. SFL influenced the extruder efficiency more than the screw speed. Increasing the screw speed from 300 to 450 rpm at a constant SFL level increased the extruder efficiency by 6 to 11%, whereas an increase of SFL from 0.0026 to 0.0038 kg rev ¹ raised the extruder efficiency by 30%. Of the mechanical energy consumed per unit mass of extrudate, over 98% were used for shearing or viscous dissipation and less than 1.5% were for pumping during twin-screw extrusion of corn meal.     

Extrusion of Maize–Cowpea Blends in a Modified Oil Expeller

A laboratory oil expeller was modified by using a press cylinder without openings for expelling the oil. Central composite rotatable design for k=3 was used to study the effects of process variables, cowpea level (0–25%), feed moisture (10–25%) and barrel temperature (130–200°C) on product indices (moisture, expansion index, bulk density, water absorption, extractable solids, swell volume and the degree of gelatinisation of flour from the extrudate). Regression models developed to predict product indices were significant and showed no significant lack of fit. The model for moisture content of the extrudate had an R² of 0·98. Product moisture was influenced by the amount of cowpea in the feed, the temperature of extrusion and feed moisture. Furthermore, the product moisture measured at each cowpea level was dependent on the temperature of extrusion. The model for product expansion index showed that this index decreased with feed moisture and the cowpea level. Regression models for bulk density, water absorption, extractable solids and the maximum swell volume of flour from the extrudate were influenced by the process variables. The degree of gelatinisation decreased with cowpea level and increased with extrusion temperature. © 1997 SCI.     

挤压参数对酿造酱油原料糊化度的影响

利用挤压技术对酿造酱油的芝麻粕和面粉等原料进行预处理,可以起到淀粉糊化的作用。在单因素试验的基础上,以挤出物 糊化度为考察指标,以挤压温度、螺杆转速、面粉含量、含水量为挤压参数,运用Box-Behnken试验设计对挤压芝麻粕酿造酱油中挤压 参数进行优化。 结果表明,最佳挤压参数为挤压温度90 ℃,螺杆转速200 r/min,面粉含量26%,含水量21%。 在此最优条件下,挤出物 的糊化度为91.23%。     

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.     

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 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.     

Reduction of Cyanogenic Compounds in Flaxseed (Linum usitatissimum L.) Meal Using Thermal Treatment

Flaxseed (Linum usitatissimum L.) provides multiple nutritional benefits, including high quality protein, dietary fiber, and is the most abundant source of α-linolenic acid (C_18:3). However, the presence of anti-nutritional factors, such as cyanogenic compounds, restricts flaxseed's consumption as a food or feed. This study investigated the reduction of cyanogenic compounds, measured as hydrocyanic acid (HCN), in full-fat flaxseed using extrusion processing without a die by following the response surface methodology. The ranges of processing variables selected were: barrel exit temperature of 76.3–143.6°C; screw speed of 59.6–160.5 rpm; and feed rate of 26.4–93.6 kg/h. The experimental values of HCN reduction obtained were from 60.8 to 86.6%. Optimum extrusion conditions of barrel exit temperature, screw speed, and feed rate were found to be 143.6°C, 133.5 rpm, and 57.8 kg/h for maximum (89.1%) reduction of HCN. This effect was mainly dependent on barrel exit temperature, whereas screw speed and feed rate had no or minimal effect. The mutual interaction effect of barrel exit temperature and screw speed was found to be significant (p ≤ 0.01). The degree of correlation (R²) for HCN reduction was 97.2%, which showed the validity of applied second-order response model. The results of this study demonstrated that significant reduction of HCN in flaxseed can be achieved commercially using an extruder without a die.     

Response surface methodology in the control of thermoplastic extrusion of starch

Effect of extrusion temperature, screw speed and moisture content on the gelatinisation properties of extruded corn starch using a single-screw extruder were studied using response surface methodology. The degree of gelatinisation can be effectively controlled by controlling the moisture content of the raw material and the extrusion temperature; control by manipulation of screw speed is also possible when the raw material has a high moisture content. The extrudate produced from starch with a low moisture content exhibited a very low retrogradation capacity, which was independent of the screw speed. It was evident that variation of operating conditions permits the production of an extrudate with various technological characteristics to meet varying food and industrial applications, and the use of response surface analysis seems to be an effective means of studying and optimising these conditions for extrusion technology.     

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.     

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.     

挤压蒸煮对豆粕体外消化率的影响

以脱脂豆粕为原料,采用双螺杆挤压技术,研究了喂料速度、物料含水量、螺杆转速、挤压温度对蛋白质消化率的影响,在单因素试验的基础上,通过正交试验确定出了豆粕最佳的挤压工艺条件。结果表明:影响消化率的主要因素是挤压温度和物料含水量,而喂料速度与螺杆转速影响较小。豆粕挤压蒸煮的最佳工艺条件是:喂料速度0.35 kg/min、物料含水量33%、螺杆转速130 r/min、挤压温度150℃,在该工艺条件下,消化率达到95.7%,比原始豆粕消化率提高12.1%。     

Extrusion Studies of Aquaculture Feed using Distillers Dried Grains with Solubles and Whey

Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% distiller-dried grains with solubles (DDGS) along with 5% whey were prepared with a net protein content adjusted to 28% (wet basis [wb]). Other ingredients in the blends included soy flour, corn flour, fish meal, vitamin, and mineral mix. These blends were extruded in a single-screw extruder at 15, 20, and 25% (wb) moisture content and at 130 and 160 rpm screw speeds. Compared to previous research, the durability and unit density of the extrudates in this study were found to increase substantially by the addition of whey to the blends. Increasing the DDGS content from 20 to 40% resulted in a 5.8 and 16.8% increase in extrudate moisture content and redness, respectively, but produced a decrease of 11.2% in brightness and 3.6% in yellowness of the extrudates. Increasing the moisture content of the ingredient blends from 15 to 25% resulted in an increase of 16.1, 8.7, and 9.3% in moisture content, durability, and redness, respectively, but a decrease of 9.8 and 5.6%, respectively, in brightness and yellowness of the extrudates. Neither DDGS level nor screw speed significantly affected extrudate durability or unit density. In fact, changing the screw speed had no significant effect on many of the properties of the extrudates studied, except for moisture content, redness, and yellowness. As demonstrated in this study, ingredient moisture content and screw speed are critical considerations when producing extrudates with feed blends containing DDGS; further work is needed to optimize processing conditions and to produce floating feeds.     

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。      

Effects of Salt, Sugar and Screw Speed on Processing and Product Variables of Corn Meal Extruded with a Twin-Screw Extruder

The effects of screw speed and additives (sugar and salt) on processing and product variables of corn meal extruded with a twin-screw extruder were studied. Higher salt (0–3%) and sugar concentrations (0–4%) in the feed decreased the die pressure, % torque and specific energy. But at 6 and 8%, sugar increased the three processing parameters. Higher screw speed (250 vs 200 rpm) decreased die pressure and % torque, but increased specific energy. The addition of salt and sugar enhanced extrudate radial and axial expansions, but reduced product bulk density and breaking strength. An increase in screw speed decreased radial expansion and bulk density, but increased axial expansion and breaking strength.     

双螺杆挤压机工艺参数对组织蛋白的影响

本文采用新型双螺杆食品挤压机,进行了挤压加工大豆组织蛋白和工程内制品的试验研究,获得了螺杆转速,含水量和温度对挤压过程和产品组织化质量的影响规律,研究表明,螺杆转速在80r/min,100r/min之间,含水量在38％－44％之间,大豆组织蛋白的挤压组织化质量良好,螺杆转速在60r/min,80r/min这间,含水量在60％－65％之间,工程内制品的挤压组织化质量良好,优化的机筒温度和机头温度分布为：30℃－45℃－80℃100℃－130℃－150℃－100℃。     

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.