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.     

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.     

Response surface analysis and extrusion process optimisation of maize–mungbean‐based instant weaning food

This study was conducted to produce high‐quality weaning food from easily available and low‐cost raw materials by extrusion technology. Weaning mix was developed using extrudates of maize (Zea mays) and mungbean (Vigna radiata) flour with a twin‐screw extruder. Experiments were designed using three independent variables [feed moisture (12.6 – 19.4%), screw speed (349 – 601 rpm) and barrel temperature (108 – 192 °C)] and five dependent variables (specific mechanical energy, bulk density, water absorption index, water solubility index and degree of gelatinisation) at five levels of central composite rotatable design (CCRD). Optimisation results indicated that feed moisture of 14.33%, screw speed of 524 rpm and barrel temperature of 174 °C would produce maize–mungbean extrudates of preferable functional properties. The optimised weaning mix contained maize–mungbean extrudates 40%, skim milk powder 35% and sugar 25% (w/w). The nutrient content of the weaning mix was in accordance with the standards specified by PFA, (2004) with high protein and starch digestibility.     

Effect of extrusion variables on antioxidant activity,total phenolic content and dietary fibre content of gluten‐free extrudate from germinated Chenopodium (Chenopodium album) flour

A Box‐Behnken design was used to study the effects of feed moisture content (18–20%), barrel temperature (115–135 °C) and screw speed (225–275 rpm) on the responses; antioxidant activity, total phenolics, dietary fibre, colour (L‐value), hardness, expansion ratio, water absorption index and overall acceptability for development of gluten‐free extrudate based on germinated Chenopodium album flour. Second‐order polynomial fitted model showed that temperature most significantly (P ≤ 0.05) affected the antioxidant activity (AoxA), total phenolics (TPC), expansion ratio, hardness and overall acceptability (OA). Antioxidant activity, total phenolic content and dietary fibre of extrudate varied from 11.56 to 15.93%, 56.77 to 81.28 mg/100 g and 18.65 to 22.06 g/100 g, whereas the lightness and hardness of extrudates ranged from 64.02 to 68.35 and 12.26 to 19.49 N, respectively. The results of this study validate the production of functional and acceptable snack product made from C.  album flour by extrusion cooking.     

Effects of selected process parameters in extrusion of yam flour (Dioscorea rotundata) on physicochemical properties of the extrudates

Raw yam (Dioscorea rotundata) flour was cooked and extruded in a Brabender single-screw laboratory scale extruder. Response surface methodology using an incomplete factorial design was applied with various combinations of barrel temperature [100, 125, 150 degrees C], feed moisture content [18, 22, 26%] and screw speed [100, 150, 200 rpm]. Initial viscosity at 30 degrees C, water solubility index, expansion and hardness were determined. The highest values of initial viscosity were at the highest barrel temperatures and the highest moisture contents. At high feed moisture content and high barrel temperatures the yam extrudate flour showed the greatest values of water solubility index. The physical properties of the extruded product showed that at high temperature the lower the moisture content the greater the expansion index. Hardness was influenced directly by moisture content and inversely by extrusion temperature. The extrusion of yam flour led to the production of snacks and pre-gelatinized flours of diverse properties. Also extruded yam flour can be successfully used in the preparation of 'futu' (pre-cooked compact dough), a yam-based food, popular in Western Africa.     

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.     

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.     

Effects of moisture,temperature and level of pea grits on extrusion behaviour and product characteristics of rice

A study was conducted to investigate the effect of feed moisture (18–24%), extrusion temperature (130–170 °C) and level of pea grits (0–30%) on the extrusion behaviour and extrudate properties of rice grits. The extruder die pressure, specific energy consumption, expansion ratio, density, water absorption index, and water solubility index were studied. Second-order polynomials were compared for extruder parameters and product characteristics as a function of feed moisture, extrusion temperature and pea grit level.     

Extrusion behaviour of different soya isolates and the effect of particle size

Eleven different commerically produced soya isolates, and one defatted soya flour, were extruded at temperatures of 120 and 180 °C at a moisture content of 35% on a dry solids basis (dsb), using a Brabender laboratory extruder. The pressure, torque and flow rate during extrusion, and product expansion and texture of the final extrudate following rehydration varied considerably between different soya isolate preparations. Analysis by multiple regression yielded about twenty significant (P < 0.05) correlations between the three extrusion variables (pressure, torque and flow rate), the four feed variables (bulk density, solubility in water, particle size distribution and angle of slope) and the three extrudate characteristics (resistance to shear, solubility in water and product diameter) measured. It was concluded that the best extrusion behaviour was obtained with feed containing insoluble but native protein. Fine powders containing insoluble protein were less prone to agglomeration, and, hence, were easier to feed than powders containing high levels of soluble protein. In addition, higher shear force values after retorting were obtained with extruded products prepared from feed containing insoluble, but native protein. This was interpreted in terms of the formation during extrusion of covalent disulphide linkage between initially insoluble regions of protein. The wide variation in extrusion behaviour of chemically similar materials prepared in different ways suggests that extrusion studies on single materials should be interpreted with caution.     

Functional properties of corn and corn–lentil extrudates

Functional properties of corn and corn–lentil extrudates were investigated as a result of extrusion conditions, including feed rate (2.5–6.8 kg/h), feed moisture (13–19% wet basis) and extrusion temperature (170–230 °C). Lentil was used in mixtures with corn flour at a ratio of 10–50% (legume/corn). The water absorption index of extrudates increased with extrusion temperature and feed moisture content and decreased with feed rate and lentil/corn ratio. The water solubility index of extrudates increased with temperature, but decreased with feed moisture content and feed rate. The oil absorption index of extrudates increased with extrusion temperature and decreased with feed rate, feed moisture content and lentil/corn ratio. Generally, the use of lentil flour led to products with lower values for functional properties. Principal component analysis of functional properties discriminated samples with appropriate functionality based on industrial use.     

Effect of extrusion conditions on the physicochemical properties of a snack made from purple rice (Hom Nil) and soybean flour blend

Soy flour was added at levels of 5%, 10%, and 15% of Hom Nil rice flour for extrusion at 190 °C barrel temperature and 350 rpm screw speed. The extruded snack qualities decreased inversely with soy flour. However, product qualities were considered to be optimised when soy flour at 5% was added. The effect of feed moisture content (15, 17, 19 g (100 g)^?1 wb), barrel temperature (150, 170, 190 °C) and screw speed (350, 400, 450 rpm) on physicochemical properties of the snack were then investigated. The physicochemical properties of the product including expansion ratio, density, water absorption index (WAI), water solubility index (WSI) and hardness were evaluated. All properties were related, as linear equations, in terms of feed moisture content, barrel temperature, screw speed with relative correlation (R²) at 0.83–0.94. The snack properties along with consumer acceptance were all highest when the extruded condition were 15 g (100 g)^?1 wb feed moisture content, 170 °C of barrel temperature and 450 rpm of screw speed.     

Physico‐chemical and antioxidant properties of extrudates developed from honey and barley

Barley flour and honey, being concentrated source of nutrients, were used to develop extruded product using twin‐screw extruder. Response surface methodology was applied to study the effects of honey (5–25%), moisture content (17–21%) temperature (120–160 °C) and screw speed (180–220 rpm) on product responses. The variation in moisture content and die temperature affected the physicochemical properties of extrudate but screw speed had significant effect only on hardness. It was established that with increase in honey levels from 5% to 20%, there was increase in antioxidant activity (up to 106.9%), total phenolic content (up to 90.2%) and total flavonoid content (up to 89.2%) in interaction with other extrusion cooking variables. The optimal condition corresponds to honey content of 18.86%, feed moisture of 18%, die temperature of 148.62 °C and screw speed of 209.99 rpm. The results suggest that honey can be extruded with barley flour into a healthful snack food.     

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.     

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.     

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.     

Cassava Starch or Amylose Effects on Characteristics of Cassava (Manihot esculenta Crantz) Extrudate

Blends of cassava flour with cassava starch or amylose were processed on a Wenger X-5 laboratory extruder. Cassava starch added to cassava flour increased total carbohydrate in feed, reducing yellow color, water absorption and extrudate bulk density but increased expansion, product moisture, water solubility and total reducing sugars. Amylose addition increased extrudate surface regularity with reduced water solubility, total reducing sugars, and bulk density. Expansion was highest in mixtures containing 60% amylose. Textural properties of extrudate increased on addition of amylose or cassava starch. Differences in microstructures existed between cassava flour and cassava starch extrudate.     

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 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.     

Determination of formulation and processing factors affecting slowly digestible starch,protein digestibility and antioxidant capacity of extruded sorghum–maize composite flour

High‐temperature high‐pressure extrusion of sorghum–maize composite flour, of potential for healthy food manufacture, was investigated by factorial experimental design to determine the effect of level of sorghum in dry mix (15–60%); final barrel zone temperature (120–150 °C); total moisture in barrel (21.4–25.8%); total input rate (2.3–6.8 kg h^?1); and screw speed (250–450 rpm) on extrudate slowly digestible starch (SDS), phenolic content, antioxidant capacity, protein digestibility, density and expansion ratio. Extrudate SDS increased with increasing sorghum level and decreased as the barrel temperature increased. Total phenolic content and antioxidant capacity were positively associated with sorghum level. Protein digestibility was associated negatively with sorghum level and positively with barrel temperature. Extrudate density was associated positively with total moisture and negatively with barrel temperature and input rate. Sorghum in dry mix, final barrel zone temperature and total moisture in barrel were the three most significant independent variables influencing extrudate dependant variables.     

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℃。