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.     

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.     

Effect of extrusion conditions on the physical properties of desi chickpea-barley extrudates and quality attributes of their resulting flours

In this study, response surface methodology (RSM) was used to evaluate the effect of extrusion conditions on physical properties of chickpea:barley extrudates (60:40), and the resulting protein quality of their flours. Barrel temperature (150–170°C) and moisture content (16–20%) were chosen as independent variables to generate a central composite design. Hardness, expansion index, bulk density, and protein quality were analyzed as responses parameters. Expansion was found to be higher at lower temperatures and higher moisture for the 60:40 chickpea:barley blend; bulk density became reduced with increased moisture; and hardness was found to increase at higher temperatures and lower moistures. The protein quality of their resulting flours was found to be greater at moisture contents higher than 16%. The composition, protein quality, and functional attributes were also examined for raw and precooked flours of chickpea, barley, and their blend at the center point of the RSM design (18% moisture, 160°C). Extrusion also leads to improved water hydration capacities and reduced viscosities for precooked individual and blended flours relative to the raw. Moreover, extrusion also led to improved protein quality in the chickpea and chickpea-barley blend, but not the individual barley flour.     

挤压参数对小麦淀粉挤出物截面膨化率的影响

以小麦淀粉为原料,以德国布拉本德DSE-25型双螺杆挤压实验室工作站为设备,采用方差分析、回归分析等方法,在研究机筒温度和物料含水率对挤压产品截面膨化率的影响规律的基础上,进一步明确机筒温度、物料含水率、单位机械能耗与膨化率之间的关系。结果显示,当机筒温度在160～210℃,物料含水率为17%时,小麦淀粉挤出物截面膨化率平均值为5.18,变幅为2.91～8.67,变异系数为39.38%。当物料含水率在15%～23%,机筒温度为210℃时,挤出物截面膨化率平均值为2.10,变幅为1.13～2.91,变异系数为36.67%。机筒温度与挤出物截面膨化率之间的关系符合一元一次方程,方程决定系数为0.909。物料含水率与挤出物截面膨化率之间符合一元二次方程,方程决定系数为0.682。研究认为,随着机筒温度和物料含水率升高,单位机械能耗和挤出物的截面膨化率均呈下降趋势。随着单位机械能耗的增加,挤出物的截面膨化率呈现增加趋势。     

Effects of tomato pulp addition on the extrudate quality parameters and effects of extrusion on the functional parameters of the extrudates

Effects of addition of tomato pulp on the quality parameters of the extrudates, and effects of extrusion on the functional properties of the extrudates were investigated. Bulk density, volume expansion index, longitudinal expansion index and porosity did not indicate a significant difference between the extrudates with or without tomato pulp. Sectional expansion index showed a slight increase with pulp addition. Textural analysis indicated that hardness and fracturability of the extrudates with or without pulp did not show a significant difference. DPPH (2, 2‐diphenyl‐1‐picrylhydrazyl) radical scavenging activity test indicated that antioxidant activity of tomato pulp added extrudates decreased from 16.71 ± 0.42 to 12.84 ± 0.36 μmol Trolox equivalent/g dry weight after extrusion. Total phenol content decreased from 15.37 ± 0.09 to 7.49 ± 0.11 mg gallic acid equivalent/g dry weight after extrusion process. The results suggest that tomato pulp can successfully be added as a functional ingredient to develop new functional extruded food products.     

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.     

Hull-less barley flour supplemented corn extrudates produced by conventional extrusion and CO2 injection process

The effects of feed moisture content (20, 25%), exit–die temperature (80, 130 °C), and extrusion-cooking method (with/without CO₂ injection) on β-glucan (BG) levels and physicochemical properties of hull-less barley flour (HBF) supplemented (15, 30, 45%) corn extrudates were investigated. The highest HBF supplementation level (45%) resulted in higher BG levels (2.87–3.28%) in all extrusion conditions. In general, increasing feed moisture content from 20 to 25% and exit–die temperature from 80 to 130 °C resulted in small increases in enzyme resistant starch type-3 (RS₃) levels. However, the investigated extrusion conditions did not form substantial amount of RS₃ and the highest RS₃ content was 540 mg/100 g. Lower feed moisture content and higher exit–die temperature resulted in higher water solubility (WS) and lower water-binding capacity (WBC) values. Cold-paste viscosity (CV) was observed in all extrudates. High WS and WBC values of extrudates and the existence of CV values in RVA curves indicated complete starch gelatinization.Industrial relevanceCO₂ injection has been proved as a reliable alternative method to the conventional extrusion process used in the breakfast cereals and snack food industry. The overall quality of the product processed by CO₂ injection was comparable to that of the current process. The extrudates produced by CO₂ injection method had more uniform expansion and smoother surface. CO₂ injection did not have a reducing effect on β-glucan levels; however, it is expected to result in a better retention of heat labile micronutrients and hence more healthy food products.     

Influence of sunflower flour on the extrusion behaviour of soya grits and the functional properties of the extrudates (Short communication)

Texturizing is the key to produce meat-like products from vegetable proteins; by application of texturized protein products it is possible to increase the substitution rate of meat in meat products, because such products have their own structure, and their addition will not cause such a structure loss as it is connected with addition of proteins as a powder. Thermoplastic extrusion is a relatively simple procedure to process flours to structurates [1, 2]. Our aim was to study the extrusion of mixtures of soybean and sunflower flours, because the amino acid compositions of the two proteins supplement each other.     

Relative effect of particle size on the physical properties of corn meal extrudates: Effect of particle size on the extrusion of corn meal

Corn meal of various particle sizes ranging from 180 to 710 μm were processed in a twin-screw extruder to produce directly expanded extrudates. The extrusion process effects on the specific mechanical energy (SME), expansion indexes (radial, longitudinal and volumetric), pasting viscosity, water absorption index (WAI) texture properties, and microstructure were determined. Increasing the particle size decreased the SME input. Extrudates produced with corn meal of higher particle sizes expanded more than extrudates produced with smaller particle sizes. For all treatments there was no peak viscosity at 95 °C. But expanded corn meal extrudate from the 180 μm fraction showed a discontinuous gel matrix phase. Increasing corn meal particle size decreased WAI values. The mechanical resistance of the extrudates from the smallest particle size was significantly higher (p < 0.05) than that of the largest particle size. The microstructure of raw corn meal revealed large fractured particles with small rounded particles adhering to the surface.     

Influence of some husbandry practices on the physical properties of spring barley grain

Specific weight, 1000 grain weight, and percentages of grain held by a 2.5 mm sieve and passing through a 2.2 mm sieve were measured in husbandry trials carried out on spring barley at Craibstone, Aberdeen, from 1975 to 1979. Sowing date had the greatest influence on these properties, apparently due more to poor crop development than to increased foliar disease following late sowing. Fungicide treatment, particularly a spray application of tridemorph, resulted in an improvement, but growth regulators, especially when applied late or at high rates, had the reverse effect and both chemicals affected specific weight less than other parameters. The mean specific weight, 1000 grain weight and grain size of a number of varieties declined at nitrogen application rates above 50 kg ha^?1, but there were significant differences between varieties, with short-strawed, small-grained varieties such as Midas and Maris Mink being most affected. Different levels and application methods of phosphatic fertiliser had little effect on the parameters measured.     

Supercritical fluid extrusion: Die design and physicochemical properties of milk protein extrudates

Extrusion processing has been used to modify the functional properties of proteins. The protein-protein interactions, surface hydrophobicity, and rheological properties of milk protein concentrate extruded using dies of different geometries (circular, annular and slit) were quantified. With the same extrusion treatment history prior to the die, extrudates generated using dies with higher wall shear (slit 1.4 × 10⁴ s⁻¹ > annular 1.1 × 10⁴ s⁻¹ > circular 2.9 × 10³ s⁻¹) showed greater protein extractability, higher index of surface hydrophobicity, and enhanced water solubility index indicating significant breakdown of protein aggregates. Higher viscoelastic moduli (G' and G") and apparent viscosity were observed for slit die extrudate dispersions. However, low flow behavior indices (0.04–0.23(−)) and a high viscous activation energy (43 kJ/mol) of slit die extrudate dispersions implied their shear and temperature sensitivity, respectively. Thus, extrudate functionality can be optimized by selection of the appropriate die design.     

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 process variables and addition of polydextrose and whey protein isolate on the properties of barley extrudates

Extrusion cooking is commonly used in the production of snacks. In the present study, extrudates were prepared using barley flour alone and with the addition of either polydextrose (PD) or whey protein isolate (WPI) and both PD and WPI. Independent process variables were water content of the mass (17%, 20% and 23%), screw speed (200, 350 and 500 rpm) and temperature of section 6 and die (110, 130 and 150 °C). Expansion, hardness, water content, porosity and chemical composition of the extrudates were analysed. Highly porous and expanded snack products with high dietary fibre and protein contents were obtained from barley flour and WPI when water content of mass was 17%, screw speed 500 rpm and temperature of section 6 and die 130 °C. Barley flour alone or with PD resulted in hard and non‐expanded extrudates. Expansion of extrudates was statistically significantly increased with decreasing water content of the mass and increasing screw speed in all trials.