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.     

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.     

Degradation of aflatoxins by extrusion cooking: Effects on nutritional quality of extrudates

Extrusion of artificially contaminated food is reported to degrade aflatoxins to varying degrees depending on the extrusion conditions. This work sought to determine the (1) efficacy of extrusion cooking in destroying naturally contaminated peanuts and (2) nutritional quality of decontaminated peanut meal. Naturally contaminated peanut meal was extruded by varying the moisture (20, 28, 35 g/100 g), pH (7.5, 9.5) and extruder die diameter (2.5, 3, 3.5, 4.0 mm). Aflatoxins levels in the extrudates were determined using HPLC procedures, and the nutritional quality was assessed using in-vitro methods. The highest aflatoxin reduction in naturally contaminated peanut meal was 59% at feed moisture content of 35 g/100 g. Higher (91%) reduction was achieved in the artificially contaminated peanut meal at moisture of 20 g/100 g. In-vitro protein digestibility and Fluorodinitrobenzene (FDNB)-available lysine of the extrudates were not significantly different from non-extruded peanut meal. Extrusion conditions for aflatoxin reduction did not adversely affect protein nutritional quality.     

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.     

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.     

Effect of Starch Sources on Properties of Extrudates Containing DDGS

Various levels of DDGS (20, 40, and 60% wb) were blended with starch sources (cassava, corn, and potato), and other ingredients to produce an iso-nitrogenous feed (28% protein) at varied moisture contents (15, 20, and 25% wb). The feed blends were extruded in a single-screw extruder at a preset screw speed of 130 rpm (13.6 rad/s) with three temperatures profiles 90–100–100°C, 90–120–120°C, and 90–140–140°C. The effect of these variables on processing conditions (extruder torque and die pressure) and other extrudate properties (expansion ratio (ER), unit density (UD), color (L*, a*, and b*), sinking velocity (SV), water absorption, water solubility, and pellet durability indices (PDI)) were analyzed. For all the three starch extrudates, changing the levels of DDGS, feed moisture content, and extruder barrel temperature had a significant effect on SV, PDI, a*, and b* values at α = 0.05.     

Effects of Processing Conditions on Single Screw Extrusion of Feed Ingredients Containing DDGS

Distillers dried grains with solubles (DDGS), a feed coproduct from the fuel ethanol industry, has been shown to be a viable potential alternative protein source for aquaculture feeds. To investigate this, three isocaloric (3.5kcal/g) ingredient blends containing 20, 30, and 40% DDGS, with a net protein adjusted to 28% (wet basis, wb), were prepared for use as Nile tilapia feed. Extrusion processing was then conducted using three DDGS contents (20, 30, and 40%, wb), three moisture contents (15, 20, and 25%, wb), three barrel temperature gradients (90–100–100°C, 90–130–130°C, and 90–160–160°C), and five screw speeds (80, 100, 120, 140, and 160rpm) using a single screw laboratory extruder. Several processing parameters, including mass flow rate, net torque required, specific mechanical energy consumption, apparent viscosity, and temperature and pressure of the dough inside the barrel and die, were measured to quantify the extrusion behavior of the DDGS-based blends. For all blends, as the temperature profile increased, mass flow rate exhibited a slight decrease, die pressure decreased, and apparent viscosity exhibited a slight decrease as well. Likewise, the net torque requirement, specific mechanical energy consumption, and apparent viscosity decreased as screw speed increased, but mass flow rate increased. Additionally, as moisture content increased, die pressure decreased. At higher temperatures in the barrel and die, the viscosity of the dough was lower, leading to lower torque and specific mechanical energy requirements. Increasing the DDGS content, on the other hand, resulted in a higher mass flow rate and decreased pressure inside the die. As demonstrated in this study, the selection of suitable temperature and moisture content levels are critical for processing DDGS-based ingredient blends.     

Effect of cooking and sterilisation on the composition of amino acids in immature seeds of flageolet bean (Phaseolus vulgaris L.) cultivars

The aim of the work was to evaluate the amino acid content and protein quality in products of immature bean seeds with a dry matter content of 40%. The investigation included raw seeds, fresh seeds after cooking to consumption consistency and seeds after canning. Raw seeds of the cultivar Alamo contained more amino acids in 100 g fresh matter than the seeds of the cultivars Flaforte and Mona. Cooking and sterilisation brought about decreases in the content of all the amino acids in the investigated cultivars; 1–50% and 9–60% respectively. Higher losses being noted in sterilised seeds. If the results were expressed in 16 g N, the differences in amino acid content were much smaller. The amino acid content of Mona was lower than that of the remaining cultivars. The cooking of seeds did not bring about changes in relation to the raw material (except tyrosine which showed a decrease 35–45%); however, sterilisation affected the content of most amino acids (from −45 to +17%). Compared with the standard (FAO/WHO/UNU, 2007), the limiting amino acid was cystine with methionine (amino acid score 70–83). Of the seeds prepared for consumption, sterilised bean seeds had a higher EAA index value, while of the cultivars, the seeds of Alamo had the highest value (147–162).     

The effect of rice bran on physicochemical,textural and glycaemic properties of ready-to-eat extruded corn snacks

In this work, corn extruded snack products were enriched with rice bran (RB) at 10% and 15%. A co-rotating twin-screw extruder was used with a feed moisture content of 16 g 100 g⁻¹, a screw speed of 240 r.p.m. and four heating sections of the barrel (100, 140, 150 and 150 °C). The impact of RB inclusion on nutritional profile, starch digestion, physicochemical and textural properties of snack products was evaluated. RB-enriched extrudates showed a lower specific volume and hardness and higher crispness than control. RB at 15% gave a water-holding capacity lower than control. Rheology of extrudate dispersions indicated an increase in elastic interactions and solid-like behaviour with RB supplementation. Differences in rheological properties resulted in attenuation of predictive glycaemic response for RB-enriched snacks.     

Proximate composition and digestibility of fermented and extruded uji from maize-finger millet blend

The proximate composition, amino acid profile and in vitro starch and protein digestibilities of raw; fermented; fermented and cooked; unfermented and extruded; and fermented and extruded maize-finger millet blend was studied. Aspartic acid, glycine, cystine, methionine, tyrosine and lysine increased after fermentation, while contents of all other amino acids showed no significant changes. Greater losses of amino acids occurred when the fermented blend was extruded than when cooked. Fermentation improved protein and starch digestibilities, whereas cooking or extruding the fermented blend reduced the digestibilities. Extruding the unfermented blend increased protein and starch digestibilities and reduced nitrogen solubility index by 50%. Raw flour had 0.41 g/100 g water-soluble starch which declined to 0.05 g/100 g on fermentation but increased to 20-34 g/100 g after extrusion.     

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.     

Decrease of available lysine in thermally treated gelatin followed by LC–UV: Influence on molar mass and ability to helixes’ formation

Available lysine (AL) content, weight-average molar mass (M_w) and kinetic of α helixes’ formation have been determined in thermally treated gelatin (75 °C) during 2, 6 and 8 days. Quantification of available lysine in gelatin sample by LC–UV has been developed. Thermal treatment during 8 days led to a decrease of AL content from 3.1 g/100 g of gelatin to 2.3 g/100 g of gelatin. In the same time, M_w increased from 6.7 × 10⁵ g mol⁻¹ to more than 2.0 × 10⁶ g mol⁻¹ and α helixes’ formation ability was strongly affected. Thermal treatment led to the reaction of available lysine group with other functions present in its environment. Intermolecular cross-links led to a high molar mass compounds’ formation and limited protein chain unfolding which is an essential step for helixes’ formation.     

Effect on protein digestibility of different processing conditions in the production of fish meal and fish feed

The effect of processing conditions on protein digestibility and fluorodinitrobenzene (FDNB)‐reactive (available) lysine in the production of fish meal and extruded fish feed has been studied under pilot and commercial conditions using mink as model animals. Fish meal produced under pilot‐plant conditions at processing temperatures below 70–80 °C (FM1) had protein digestibility of 929 (grams of protein digested per 1000 g protein consumed) compared with 905 when processed at temperatures above 100 °C (FM2). A low‐temperature‐processed commercial fish meal (CFM1) had protein digestibility of 940 compared with 888 for a standard commercial fish meal (CFM2). Pilot‐produced extruded fish feed had protein digestibility of 913 when based on FM1 as the main protein source (95% of total protein) compared with 892 when based on FM2. Commercial extruded fish feed had protein digestibility of 912 when based on CFM1 compared with 871 when based on CFM2. Varying extrusion conditions at the pilot scale, ie temperatures from 100 to 126 °C and moisture contents from 21 to 12%, did not affect protein digestibility. Similarly, under commercial conditions, variation in temperature from 89 to 110 °C and moisture from 24.5 to 19.5% did not affect FDNB‐reactive lysine and protein digestibility. The FDNB‐reactive lysine content and protein digestibility of the extruded feed were less than the values calculated from the ingredient mixture before extrusion. Thus, despite different extrusion conditions not giving different FDNB‐reactive lysine and protein digestibility, the total process, ie extrusion, drying and oil coating, caused a reduction. Copyright © 2003 Society of Chemical Industry     

Comparative studies on the characterization and antioxidant properties of biodegradable alginate films containing ginseng extract

The physical and antioxidant properties of alginate biodegradable film incorporating white, red and extruded white ginseng extracts were investigated. No differences in moisture contents of all alginate film samples were noticeable (p > 0.05) except those film samples incorporated without ginseng extract, which had the highest moisture content. The addition of ginseng extract to alginate film decreased tensile strength and elastic modulus (p < 0.05) but increased the percent elongation at break. The presence of extracts did not significantly affect the water vapor permeability of the film samples. Alginate film containing extruded white ginseng extract at a barrel temperature of 130 °C presented the highest (61.12%) free-radical scavenging activity against the 2,2-diphenyl-1-picryhydrazyl radical (DPPH) in methanol, followed by film containing white ginseng extruded at a barrel temperature of 115 °C. Following these samples in terms of free-radical scavenging activity were film samples containing red and white ginseng extracts, respectively. These results revealed that extruded white ginseng extract has good potential to be incorporated into alginate to make antioxidant biodegradable film or coating for various food applications.     

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.     

新型鲜湿方便米粉二级挤压工艺的研究

研究新型鲜湿方便米粉二级挤压工艺,考察生产过程中挤压关键参数(进料水分、喂料速度、一级机筒温度、二级机筒温度、模板孔径)对米粉品质的影响。实验以籼米(川种优3877)与粳米(隆两优534)为原料,利用响应面实验优化二级挤压工艺关键参数。结果表明,挤压参数能在一定范围内提高鲜湿方便米粉的品质。通过最佳二级挤压参数(进料水分41%、喂料速度0.50 kg/min、一级机筒温度179℃、二级机筒温度58℃、模板孔径1.0 mm)制作鲜湿方便米粉产品米香浓郁、富有弹性,综合品质较好。本研究可为鲜湿方便米粉连续化工业化生产提供参考。     

Physicochemical properties of extruded germinated wheat and barley as modified by CO2 injection and difference extrusion conditions

Germinated wheat and barley were extruded with a pilot‐scale corotating twin‐screw extruder under different barrel temperatures (100 and 120 °C), feed moisture content (30 and 35%) and CO₂ injection. The effect of germination, barrel temperature, feed moisture content and CO₂ injection on physical properties, proximate composition, γ‐aminobutyric acid, β‐glucan, phytic acid and protease activity was investigated. Results indicated that the barrel temperature, moisture content and CO₂ injection significantly affected water absorption index (WAI), water‐soluble solid index (WSI), specific length, expansion ratio, bulk density, mechanical properties and colour of all extruded products (P < 0.05). Extrusion process significantly decreased γ‐aminobutyric acid and protease activity in extruded germinated wheat (EGW) and barley (EGB) products (with and without CO₂ injection). However, extrusion process (with and without CO₂ injection) increased β‐glucan in EGB and decreased phytic acid in EGW. The content of proximate composition, γ‐aminobutyric acid, β‐glucan, phytic acid and protease activity was slightly affected by CO₂ injection.     

挤压碎米制备富锌强化大米

以粳米加工副产品碎米为原料,使用乳酸锌作为锌强化剂,通过挤压法制备富锌强化大米。将碎米粉碎成100?目,乳酸锌添加量2.0%,采用响应面法考察含水量、螺杆转速及机筒温度对富锌强化大米质构特性的影响。优化条件为含水量20%、螺杆转速80?r/min、机筒温度100?℃,制得富锌强化大米硬度为1?339.05?g,黏着性为0.75?mJ,弹性为0.79?mm,咀嚼性为967.42?mJ,锌含量为450.0?mg/kg。经X-射线衍射分析表明强化米中淀粉颗粒的结晶度较粳米明显减少,通过扫描电镜表征发现强化米淀粉颗粒外表面呈现不规则类似鳞片形状,并产生聚集现象,淀粉糊化温度由77.9?℃降低到56.2?℃,酶解反应完成后还原糖增加23.0%以上,有利于强化米淀粉颗粒的酶解作用。将其按1∶10的比例添加到粳米中,米饭口感、外观良好,锌含量为48.0?mg/kg。     

直接挤出制备米粉(线)工艺的优化

为了获得直接挤压制备米粉(线)的最适工艺参数,采用响应面(RSM)方法设计试验方案,对挤压机挤压制作米粉的工艺参数进行优化分析。研究原料含水量、机筒温度、螺杆转速对米粉糊化度的影响。结果表明:3个因素对糊化度影响大小依次为机筒Ⅲ区温度>螺杆转速>原料含水量。通过响应面分析得出挤压米粉最佳工艺:原料含水量35.1%,Ⅲ区温度102℃,螺杆转速117 r/min。在此条件下,米粉糊化度为92.1。与3种市售产品对比,自制米粉在硬度、糊化度、咀嚼性和感官品质方面达到了市售产品平均水平。