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.     

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.     

Effect of formulation and processing parameters on acrylamide formation: A case study on extrusion of blends of potato flour and semolina

Acrylamide formation in extruded snacks prepared using blends of potato flour:semolina in ratios ranging from 30:70 to 70:30 showed maximum acrylamide formation in the 70:30 blend. The extrusion was carried out at a screw speed of 120 rpm, temperature of 170 °C and moisture content of 18%. Further, the influence of extrusion processing parameters on the acrylamide formation in extruded snacks prepared from a 70:30 blend of potato flour:semolina was investigated using response surface methodology (RSM). The feed moisture was varied from 12.6% to 19.4%, die temperature from 163 to 197 °C and screw speed from 106 to 173 rpm. The extrudates so obtained showed acrylamide content ranging from 704 to 1560 μg/kg. The effect of different additives such as citric acid, calcium salts, amino acids, vitamins and their combinations on the mitigation of acrylamide formation showed calcium chloride at 50 μmol/g flour blend to reduce acrylamide formation by 65% without altering the sensory properties of the extrudates.     

Structural and textural characterization of corn–lentil extruded snacks

Structural and textural properties of extruded corn and corn–lentil mixtures were investigated as a result of process conditions, including extrusion temperature (170–230 °C), feed rate (2.52–6.84 kg/h) and feed moisture content (13–19% wb). Lentil was used in mixtures with corn flour at a ratio of 10–50% (legume/corn). Apparent density increased with feed rate, moisture content and material ratio and decreased with temperature, while expansion ratio showed an opposite behavior. Modulus of elasticity increased with feed composition and decreased with extrusion conditions. Number of peaks during compression decreased with extrusion temperature and feed composition. Similar behavior was also found for sensory evaluated structural and textural characteristics. The examination of macrostructure confirmed the effects of extrusion conditions and feed composition on structural and textural properties. The properties correlation revealed critical relationships among instrumental and sensorial characteristics. Hence, simple power model equations were developed, which enable their prediction and consequently the design of extruded snacks with acceptable quality characteristics.     

The physico-chemical characteristics of extruded snacks enriched with tomato lycopene

Adding tomato derivatives to traditional starchy extruded snacks can improve their nutritional properties by adding lycopene and fibre; however the physico-chemical properties of these products must also be considered. Ingredients and extrusion parameters, including temperature, alter these properties, but their effect on lycopene content is not known. In this study, crisp low density extruded snacks were manufactured from corn, wheat and rice, with or without dried tomato skin or paste powder extruded at temperatures of 140, 160 or 180 °C. Lycopene content and the physico-chemical properties (expansion, density, hardness, colour parameters and percentage of moisture loss) of the extruded products were measured. Lycopene retention was higher in products containing tomato skin powder and significantly lower when wheat flour was used to make the snacks. Increases in the processing temperature improved the physico-chemical characteristics of the snacks but had no significant effect on lycopene retention (P > 0.05).     

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 conditions on physical and chemical properties of high protein glutinous rice-based snack

Two glutinous rice-based snack formulations were designed using a linear-programming model to minimize total cost to meet the FAO/WHO/UNU. (1985). Energy and protein requirements. Report of a joint FAO/WHO/UNU expert consultation. Technical report series 724. Geneva: WHO requirements for lysine and sulphur amino acids. Effects of protein concentration, feed moisture content and barrel temperature on the chemical and physical properties of the extruded product were investigated. Response surfaces for the parameters were generated using a second-degree polynomial. The high protein nutritious snack was obtained using glutinous rice flour, vital wheat gluten and toasted soy grits. A factorial design was employed to investigate the influence of feed protein content (20 and 30 g/100 g wb), feed moisture (20, 25, and 30 g/100 g wb) and barrel temperature (150 and 180 °C) on the physical and chemical properties of extrudates. Results showed that increasing feed moisture and reducing barrel temperature reduced non-protein nitrogen (NPN) and enhanced lysine retention. The protein and moisture content of raw material and barrel temperature had no significant influence on cysteine and methionine content. The conditions providing high expansion, low bulk density, and low shear strength of extruded snack were feed moisture of 20 g/100 g wb and 180 °C.     

Expansion mechanism of extruded foams supplemented with wheat bran

Addition of bran reduces the expansion of extruded starchy foams. This may be attributed to changes in parameters driving expansion. Wheat flour was supplemented with wheat bran to achieve two levels of fibers (12.6% and 22.4%) and extruded under different conditions of barrel temperature (120 or 180 °C), water content in the feed (18% or 22%) or screw speed (400 or 800 rpm). Increasing the bran concentration decreased sectional and volumetric expansions and increased longitudinal expansion. Finer cellular structures consisting of an increased number of small cells with more spherical shapes were generated. This may be linked to an increased nucleation at the die. The reduction in volumetric expansion was associated with an increase in shear viscosity only at the highest bran concentration. At same extrusion conditions the glass transition temperature of starch was reduced by down to 15 °C by supplementation with bran. This may induce a decrease in the viscosity of the starch phase and counteract the matrix viscosity increase linked to the properties of bran. A higher surface porosity was observed in the bran containing recipe due to earlier burst of the bubbles during growth.     

Effect of the addition of whole‐grain wheat flour and of extrusion process parameters on dietary fibre content,starch transformation and mechanical properties of a ready‐to‐eat breakfast cereal

This study evaluates the effect of the incorporation of whole‐grain wheat flour (WGWF) and of extrusion process parameters on the nutritional and technological quality of breakfast cereals. The corn flour‐based breakfast cereals were elaborated in a twin‐screw extruder following a rotatable central composite design with varied WGWF (0–100%), feed moisture (14–24%) and zones 3 and 4 barrel temperature (76–143 °C). Dietary fibre and resistant starch were significantly increased with WGWF addition. Total and digestible starch showed a decrease when WGWF increased. The RVA parameters were significantly affected by all the extrusion conditions and WGWF content. The cell structure of the extrudates was dependent of WGWF and moisture.     

蛹虫草复合谷物杂粮膨化产品的工艺优化及糊化特性

目的：采用双螺杆挤压工艺制备蛹虫草复合谷物杂粮膨化产品,并研究蛹虫草对谷物杂粮膨化产品淀粉糊化特性的影响。方法：以大米粉、糯米粉、薏米粉、红豆粉、黄豆粉、蛹虫草粉为原料,按照一定比例混合制成蛹虫草复合谷物杂粮粉进行挤压膨化实验,并在单因素试验的基础上,选择物料水分含量、螺杆转速、进料速率、挤压温度为影响因素,产品径向膨化率、糊化度、水分含量、吸水性和水溶性指数为指标,设计正交试验,用极差分析法优化出蛹虫草复合谷物杂粮膨化产品的最佳工艺,并利用快速黏度仪测定谷物杂粮膨化产品和蛹虫草复合谷物杂粮膨化产品的淀粉糊化特性。结果：蛹虫草复合谷物杂粮膨化产品的最优工艺参数为物料水分含量16%、螺杆转速180 r/min、机筒的5 段挤压温度80-90-120-140-165 ℃、进料速率15 r/min,此时蛹虫草复合谷物杂粮膨化产品的径向膨化率、糊化度、水分含量、水溶性和吸水性指数分别为3.015、84.32%、6.11%、29.65%、416.39%;与谷物杂粮膨化产品相比,蛹虫草复合谷物杂粮膨化产品峰值黏度、保持黏度、最终黏度、回生值显著下降。结论：蛹虫草复合谷物杂粮膨化产品挤压工艺可行,添加蛹虫草能够显著降低谷物杂粮膨化产品的糊化特征值,并抑制其淀粉分子的回生或重排。     

挤压加工对苦荞粉理化性质的影响

为了阐明挤压加工技术对苦荞粉理化性质的影响,分别研究了不同挤压温度、物料水分和螺杆转速对挤压苦荞粉的吸水性指数、水溶性指数、膨胀势、糊化及凝胶特性的影响规律。结果表明:与未挤压苦荞粉相比,经挤压改性后的苦荞粉在30℃水浴时有更好的吸水性和水溶性;在100℃水浴时的水溶性增大,吸水性减小;膨胀势、糊化特征值及凝胶特征值均明显升高。随挤压温度升高,挤压苦荞粉的峰值粘度、衰减值增大,谷值粘度、回生值降低,制成的凝胶品质更好;随物料水分升高,吸水性指数、膨胀势、各糊化特征值显著增大,水溶性指数明显降低,低物料水分形成的凝胶品质较好;随螺杆转速升高,水溶性指数增大,吸水性指数和峰值粘度、谷值粘度、衰减值稍降低,膨胀势先增大后减小,转速越高的苦荞粉的凝胶品质越好。综合而言,物料水分变化对挤压苦荞粉的各理化性质影响最大。吸水性指数和水溶性指数与糊化特性、凝胶特性都有显著相关性(P0.05);膨胀势与糊化特性极显著正相关(P0.01),与凝胶特性没有显著相关性。     

Effects of processing conditions and the use of modified starch and monoglyceride on some properties of extruded rice vermicelli

Pasting profile and gel appearance of rice flour, rice flour mixed with the modified starch, MYK-500T and monoglyceride, Monomul 90-35P were examined. The optimum conditions for the extrusion of rice vermicelli obtained were: screw speed 30 rpm; feeder speed, 50 rpm; temperature of three zones, 90 °C:100 °C:100 °C. The rice noodle had white color, good retention of shape but stuck together after cooking. The use of modified starch, and monoglyceride could reduce the stickiness of the product. The noodle extruded from rice flour added with MYK-500T (4 g/100 g blend), and Monomul 90-35P (1 g/100 g blend) was firm and not sticky, showing cooking time at 2 min, cooking weight 315 g/100 g dry noodle, cooking loss 11.1 g/100 g dry noodle and degree of gelatinization 88.9%. The hardness of the product was 1230 g and tensile strength 9.5 g. Sensory evaluation showed that the acceptance of the extruded rice vermicelli was not significantly different from other 3 commercial products prepared by conventional method.     

Extrusion of a hard-to-cook bean (Phaseolus vulgaris L.) and quality protein maize (Zea mays L.) flour blend

Heated extrusion was tested as an alternative process for incorporating “hard-to-cook” beans into food products. A 3² factorial design was used to evaluate extrusion conditions for a 40/60 (w/w) blend of “hard-to-cook” beans and quality protein maize. Tested extrusion variables were temperature (155, 170 and 185 °C) and moisture content (15.5, 17.5 and 19.5 g/100 g). Screw speed was fixed at 130 rpm. The extrudates obtained at 155 and 170 °C with 15.5% moisture had the best physical characteristics and were chosen for comparative analysis of nutritional changes between the unprocessed “hard-to-cook” bean/quality protein maize flour blend and the resulting extrudates. In vitro protein digestibility was higher in the extrudates (80%) than in the flour blend (76%). In vitro starch digestibility was higher at 155 °C (89%) and 170 °C (92%) than in the flour blend (12%). Processing conditions decreased dietary fibre content by 38% at 155 °C and 44% at 170 °C.     

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.     

紫糙米粉挤压工艺优化及其理化性质分析

以紫糙米粉为原料,通过响应面分析法优选紫糙米粉的挤压工艺,利用黏度测定仪（RVA）、X-射线衍射（XRD）、扫描电镜（SEM）表征挤压前后紫糙米粉的糊化特性、结晶特性及微观结构的变化。结果表明:挤压温度147 ℃,水分含量18%,螺杆转速27 Hz,进料速率18 Hz,测得样品的WSI为11.32%、糊化度为93.15%、花色苷含量为97.38 mg/100 g,综合评分为92.43。与原料粉相比,该条件下制备的挤压膨化紫糙米粉,峰值黏度、低谷黏度、衰减值、最终黏度、回生值均显著降低（P<0.05）。挤压膨化后紫糙米粉的淀粉晶体结构由A型转变为V型,结晶度下降;紫糙米粉表面变得光滑,呈现出较多的孔洞结构。表明挤压膨化技术能显著改善紫糙米粉的糊化性质与水化特性,为紫糙米即食代餐粉产品开发提供理论与技术参数依据。     

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.     

Use of low-temperature extrusion for reducing phytohemagglutinin activity (PHA) and oligosaccharides in beans (Phaseolus vulgaris L.) cv. Navy and Pinto

Bean (Phaseolus vulgaris L.) lectins and oligosaccharides are the anti-nutrients that limit dry bean consumption. The objective of this study was to study the effects of low temperature (85 °C) extrusion and steam-cooking (82 °C) on the fate of lectin, analysed as phytohemagglutinin activity (PHA), and the oligosaccharides, raffinose and stachyose. Both extrusion processing and steam-cooking significantly (p ? 0.05) reduced the lectin in bean flour by 85–95% over raw bean flours (control). The stachyose content in extruded navy bean flours was comparable to that in raw and steam-cooked flours while extruded pinto bean flour had significantly lower stachyose content than that found in raw and steam-cooked flour. The raffinose content of both navy and pinto extruded flours, though lower than raw bean flours, was significantly higher than that in steam-cooked flours. The results of this study demonstrated that extrusion processing at relatively lower temperature can be effective in eliminating lectins and reducing oligosaccharides.     

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.     

Functionality of fruit powders in extruded corn breakfast cereals

Consumer interest in naturally colored foods such as breakfast cereals is growing. Degermed white cornmeal, sucrose, citric acid and dehydrated fruit powder (blueberry, cranberry, Concord grape and raspberry) were mixed in 84.3%:14.3%:0.4%:1.0% proportions, then extruded in a laboratory-scale twin-screw extruder. Feed rate was 255 g/min; water was pumped at a rate of 12.5 g/min; screw speed was 175 rpm. Cooking temperature during extrusion was generally <130 °C. Samples were cut into small spheres and dried to 5% moisture. Cereals were stored at room temperature in opaque bags. The control samples were lighter and less red than the fruit cereals. Soluble phenolics and anthocyanins were higher in the fruit cereals. At three and six weeks of storage, fruit cereals had smaller levels of hexanal, as measured by gas chromatography of headspace of ground cereals. Although anthocyanins from fruit powders survive extrusion and retain some antioxidant activity, the levels used in this study may have been too low. Higher levels of fruit will increase production costs, but the expense may be offset by the more attractive and functional cereals that result.