Extruder Screw Speed Research Articles

Extrusion of a Curcuminoid-Enriched Oat Fiber-Corn-Based Snack Product.

Extruded snack products were made from an oat fiber-corn flour matrix fortified with 1.5% (w/w) curcuminoids (750mg curcuminoids/100 g) to improve the solubility and stability of curcuminoids. The effects of extruder feed moisture content (21%, 28%, and 35%) and screw speed (200 and 300 rpm) on the extrusion parameters and physical properties of final snacks were investigated. Curcuminoids lost during extrusion and curcuminoids loss during subsequent drying of extrudates were analyzed, to separate the losses occurring in each unit process. Drying post extrusion (at 50°C for 4hr) was essential to obtain a crunchy shelf stable product (5% moisture). Curcuminoids loss during extrusion was from 17% to 84%, with high loss for the extrusion with low feed moisture content (21%). A further curcuminoids loss of 4% to 44% occurred during drying, with much higher loss for the extrudate with high moisture content. Total curcuminoids retained after extrusion and drying was 12% to 41% (59% to 88% loss), equivalent to 180 to 616 mg curcuminoids retained per 100 g snack, levels within recommended daily dose. Curcuminoids retained after drying was stable during 80 days of storage at 25°C. The results highlighted the importance of understanding the impact of each unit process separately (for example, extrusion and drying) on the stability of curcuminoids for the development of healthier extruded snacks. PRACTICAL APPLICATION: Extruded snacks products were developed by fortifying the snacks with oat fiber and curcuminoids in order to address the need for a healthy ready to eat food products. Some extrusion characteristics were selected to produce snack products which have favorable properties in terms of consumer acceptance.

Disruption of lignocellulosic biomass along the length of the screws with different screw elements in a twin-screw extruder

Proper screw design is crucial for effectively pre-treating wood fibers, to assist in the downstream enzymatic conversion of the cellulose into fermentable sugars. Initially, the impact of extruder barrel temperature (50, 100, and 150 °C) and screw speed (25, 50, and 75 rpm) were studied to arrive at the optimum conditions for sugar yield. Lower temperatures and screw speeds resulted in increased sugar yields. To examine the influence of shear imparted by the screws, the residuals samples were recovered from different zones along the screws and evaluated. Sugar yield, crystallinity index, and the particle size distribution of the material collected at different zones were determined. Glucose yield and xylose/mannose yields of the material along the screws, ranged from 23.25 to 42.88% and from 11.95 to 20.54%, respectively. The importance of the screw design was highlighted.

The effect of polyester recycled tire fibers mixed with ground tire rubber on polyethylene composites. Part II

This work reports on the mechanical (tension, flexion, and impact) and physical (density and hardness) properties of polyester recycled tire fibers (RTFs) mixed with ground tire rubber and linear low-density polyethylene with and without styrene–ethylene–butylene–styrene grafted maleic anhydride as a compatibilizer. In particular, the effect of RTF content (10, 25, and 50 wt%), extruder screw speed (110, 180, and 250 r/min), and temperature profiles (extrusion and injection molding) was studied. The results showed that the best properties were obtained at the highest RTF content (50%) and extruder screw speed (250 r/min) combined with the lowest temperature profile in both extrusion and injection molding when the compatibilizer was added.

Rheological characterization of polyethylene/polyester recycled tire fibers/ground tire rubber composites

ABSTRACTThe rheological behavior of polyester recycled tire fibers (RTF) mixed with ground tire rubber and linear low density polyethylene (LLDPE) with and without styrene–ethylene–butylene–styrene grafted maleic anhydride (SEBS‐g‐MA) as a compatibilizer was investigated in the melt (small amplitude oscillatory shear) and solid (dynamic mechanical analysis) states. In particular, the effect of RTF content (10, 25, and 50 wt %), extrusion screw speed (110, 180, and 250 rpm), and temperature profiles (extrusion and injection molding) was studied. In general, it was found that the rheological properties in the melt state (modulus and viscosity) of the uncompatibilized samples increased with RTF content, but higher values were obtained when SEBS‐g‐MA was added due to better interfacial coupling. Although similar results were obtained in the solid state, it was shown that melt rheology can better explain the variations as the measurements are more sensitive to the interface quality since the matrix contribution is less important. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46563.

Effects of process parameters on thermal properties of glass fiber reinforced polyamide 6 composites throughout the direct long‐fiber‐reinforced thermoplastics process

The direct long‐fiber‐reinforced thermoplastic (D‐LFT) process is an efficient, one‐stop manufacturing process starting from raw materials to a final product, and includes various types of equipment. Tandem twin‐screw extruders are the main components of the D‐LFT process, and their control dictates productivity and properties of products. This study investigates the effects of extruder temperature and screw speed on molecular weight and thermal properties of glass fiber‐reinforced polyamide 6 (PA6) composites throughout the D‐LFT process. Viscosity number measurements, thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC) analyses were performed on samples taken from different locations along the D‐LFT process. It was found that viscosity number, which is a measure of molecular weight of the PA6 base resin, decreased with increasing extruder temperature and decreasing screw speed. In contrast, TGA results showed that the low screw speed of the extruders increased apparent activation energy of the final product. Non‐isothermal DSC crystallization analysis revealed no substantial changes to the material's degree of crystallinity with the variations in extruder temperature and screw speed; however, isothermal DSC crystallization analysis showed that the low screw speed of the extruders increased crystallization half‐time of the final material. POLYM. ENG. SCI., 58:E114–E123, 2018. © 2017 Society of Plastics Engineers

Instrumental and sensory properties of pea protein-fortified extruded rice snacks

Characteristic attributes of pea-protein fortified, extruded rice snacks were evaluated by mechanical, acoustic and descriptive sensory analysis. The addition of pea protein isolate (0 to 45% (w/w)) to rice flour and extruder screw speed strongly affected the expansion behaviour and therefore, textural attributes of extruded snack products. The sensory panel described the texture of highly expanded extrudates as crisp, while low expanded extrudates were perceived as hard, crunchy and non-crisp. Results of the instrumental and sensory analysis were compared and showed a high correlation between mechanical and sensory hardness (r=0.98), as well as acoustic and sensory crispness (r=0.88). However, poor and/or negative correlations between acoustic and sensory hardness and crunchiness were observed (r=−0.35 and −0.84, respectively).

Extrusion Processing of Amaranth and Quinoa into Gluten-Free Snack Foods for Celiac and Gluten-Free Diets

Because of the growth of gluten intolerance and Celiac disease, there is growing interest in development of gluten-free foods. Beyond just being gluten-free, such foods can also have other positive nutritional benefits to human health. Extrusion processing is commonly used to produce a wide variety of human food products. Gluten-free grains can be a processing challenge, however, due to lack of proper binding, which can lead to poor quality food products. This research explores how extrusion parameters impacted the quality of amaranth- and quinoa-based extrudates. The specific objectives of this project included extruding each of the grains, then measuring extrudate properties, such as color, unit density, expansion ratio, and durability. Both the quinoa and amaranth were extruded as raw grain, as well as ground to 2mm and 1mm particle sizes. Other experimental conditions included moisture contents of 20% and 40% (d.b.), and extruder screw speeds of 50 rpm and 100 rpm. All treatments were successfully extruded, and all extrudates had high quality attributes, making this the first time either quinoa or amaranth was extruded without any binding ingredients. This study provides information useful for commercial scale-up.

Pea protein-fortified extruded snacks: Linking melt viscosity and glass transition temperature with expansion behaviour

The addition of proteins to extrusion feed formulations can strongly affect the expansion behaviour of the melt and often results in limited expansion of the final product. Therefore, the aim of this study was to investigate the impact of pea protein isolate (PPI) content (0–30%) and extruder screw speed (300–700 rpm) on the (i) initial and final expansion, (ii) melt viscosities and (iii) glass transition temperatures of rice starch-based, extruded snacks. Highest initial expansion was observed at 30% PPI content, but significant (p < 0.05) shrinkage occurred at screw speeds of 500 and 700 rpm. Melts containing 30% PPI exhibited higher viscosities than those without PPI. Furthermore, addition of PPI reduced the glass transition temperature and broadened its temperature transition range. Addition of 30% PPI possibly delayed melt solidification, which resulted in shrinkage and non-uniform final extrudate structures. Extrudates containing 20% PPI exhibited the highest final expansion and no significant shrinkage was observed.

The effect of gelatin inclusion in high protein extruded pet food on kibble physical properties

Pet food is a $23 billion industry that continues to grow. Owners continue to humanize their pets and their dietary needs, thus the pet food industry tends to mirror human dietary trends. Currently, pet food is trending towards higher levels of protein, thus lower levels of starch. Decreasing starch, one of the main structure forming ingredients in extruded foods, creates issues of lower rates of expansion and decreased kibble durability. Consumers tend to dislike ingredients that do not serve a nutritional purpose; therefore, gelatin may be a plausible binding ingredient for high protein pet foods. Gelatin is a pure protein derived from collagen and is sold as a dry, odorless, tasteless powder. High-bloom gelatins find numerous uses in human food as a stabilizer, foaming agent, and capsule base among other uses. Low-bloom gelatin may find a value-added opportunity as a nutritional binder in pet food. Four extrusion experiments were performed to test this hypothesis. Experiment 1 compared gelatin at 0, 50, 100, and 150g/kg inclusion and 150g/kg gelatin at 3 different extruder screw speeds. Results showed a decrease in expansion but an increase in hardness and pellet durability index (PDI); however, there may have been inadequate preconditioning. It was unclear whether the decrease in expansion or presence of gelatin improved product durability. Experiment 2 analyzed two levels of gelatin, 0 and 100g/kg, under two extruder screw speeds, 300rpm and 500rpm, and two hydration ratios, 170 and 280g/kg. In this experiment, there were no differences in density, expansion, hardness, or PDI. This indicated preconditioning was more ideal and may indicate gelatin does not decrease product expansion. Experiment 3 analyzed two levels of gelatin, 0 and 100g/kg, at two target densities, low and high. Results indicated that gelatin created a more expanded product when processed under similar conditions as a control formula. Experiment 4 analyzed different strengths of gelatin to determine if the low-bloom gelatin experiments were repeatable with more conventional strength gelatins. Treatments were a control with no gelatin, and a 100, 175, and 250 bloom gelatins. Results showed increased gelatin strength increased product expansion, likely through a foaming effect. However, durability declined with mid- and high-bloom gelatins; thus, low-bloom gelatin may be the most promising to improve product characteristics and preserve durability. Based on these experiments, low-bloom gelatin may find use as a nutritional binder in high protein pet foods.

Effect of Germination and Extrusion on Physicochemical Properties and Nutritional Qualities of Extrudates and Tortilla from Wheat.

Wheat is the most common grain in the temperate region. Modifying its constituent through food processing improves its functionality and nutrient access. In this study, the combined effect of germination and extrusion on physicochemical properties and nutritional qualities of extrudates and tortilla from wheat was evaluated. Results showed that germination significantly increased (P <0.05) the γ-aminobutyric acid content in germinated whole wheat (GW) and extruded germinated whole wheat (EGW) as compared to the control of whole wheat (WW). Germination also significantly increased the protein content, reducing sugar and total soluble sugar content in GW, while extrusion had much increasing impact on reducing sugar content in extruded samples. Specific mechanical energy during extrusion was reduced as feed moisture content increased from 20 to 30%. Higher extruder screw speed (350rpm) led to better expansion ratio at low moisture content (20%) as compared to low screw speed (200rpm). Extrusion significantly increased the starch digestibility but decreased the protein digestibility in extrudates. Tortilla made from 100% WW had about the same physical characteristics, namely color and rollability, with tortilla made from 85% WW with 15% GW, 85% WW with 15% extruded whole wheat (EW), and 85% WW with 15% EGW. Tortilla made from 85% WW with 15% GW showed the largest diameter, thinnest thickness and least extensibility. A 15% extruded germinated wheat (350rpm) addition in 85% WW showed significant increase of γ-aminobutyric acid content in tortilla compared to the control (100% WW).

Impacts of Cellulose Fiber Particle Size and Starch Type on Expansion During Extrusion Processing.

Objective of this study was to understand the impacts of cellulose fiber with different particle size distributions, and starches with different molecular weights, on the expansion of direct expanded products. Fiber with 3 different particle size distributions (<125, 150 to 250, 300 to 425 μm) and 4 types of starches representing different amylose contents (0%, 23%, 50%, and 70%) were investigated. Feed moisture content (18 ± 0.5 % w.b) and extruder temperature (140 °C) were kept constant and only the extruder screw speed was varied (100, 175, and 250 rpm) to achieve different specific mechanical energy inputs. Fiber particle size and starch type significantly influenced the various product parameters. In general, the smaller fiber particle size resulted in extrudate with higher expansion ratio. Starch with an amylose: amylopectin ratio of 23:77 resulted in highest expansion compared to the other starches, when no fiber was added. Interestingly, starch with 50:50, amylose: amylopectin ratio in combination with smaller fiber particles resulted in product with significantly greater expansion than the control starch extrudates. Aggregation of fiber and shrinkage of surface was observed in the Scanning Electron Microscope images at 10% fiber level. The results suggest the presence of active interactions between the cellulose fiber particles and corn starch molecules during the expansion process. A better understanding of these interactions can help in the development of high fiber extruded products with better expansion.

Impact of protein content on physical and microstructural properties of extruded rice starch-pea protein snacks

The physical and microstructural properties of pea protein-fortified, expanded snacks were examined after extrusion at various moisture contents, temperatures, screw speeds and pea protein isolate (PPI) contents of up to 50% (w/w). The highest expansion and, thus, the lowest bulk density and hardness were recorded at a PPI content of 10% (w/w). An increase of extruder screw speed from 400 to 600 rpm resulted in enhanced expansion of extrudates, while increasing die temperature (from 130 to 150 °C) or moisture content (from 23 to 26%) did not significantly change expansion of different extruded blends. X-ray micro-computed tomography images indicated internal structural differences between extruded blends. Most prominent was the non-uniform structure of extrudates with a PPI content of 30% (w/w). This can be attributed to the decreased glass transition temperature as result of increasing PPI content resulting in delayed material solidification after exiting the extruder die. Extrudates with a PPI content of 50% (w/w) showed poor expansion and were significantly (p < 0.05) harder than extrudates with lower PPI contents.

Process optimization of functionalized MWCNT/polyetherimide nanocomposites for aerospace application

Polyetherimide (PEI) is a high performance thermoplastic polymer that retains its properties at elevated and cryogenic temperatures. Nanofiller reinforced PEI used in aerospace structures will substantially reduce the payload. This study attempts to optimize nanofiller content and process parameter for melt compounding of PEI/acid (COOH) functionalized MWCNTs (Multi-walled Carbon Nanotube) nanocomposite using Response surface methodology (RSM). Face Centered Central Composite Design (FCCD) with two factors viz. MWCNT content and extrusion screw speed at three levels each is used to model and optimize nanocomposite properties relevant to aerospace applications. FTIR spectrum confirmed the functionalization of MWCNTs while morphological analysis confirmed the dispersion of MWCNTs. COOH-MWCNTs reinforced composite showed enhanced thermal and mechanical properties along with better retention of properties upon exposure to gamma irradiation and atomic oxygen. These properties were modeled with non-linear quadratic equations using regression analysis and verified by validation experiments. Optimization for performance of nanocomposites for aerospace application has been revealed by overlapping the contour plots within the practical constraints to recognize the combination of factor ranges.

Impacts of the Particle Sizes and Levels of Inclusions of Cherry Pomace on the Physical and Structural Properties of Direct Expanded Corn Starch

An effort was made to understand the impacts of dried cherry pomace (by-product of cherry juice processing) inclusion into corn starch extrudates on their direct expansion characteristics. The effect of pomace particle sizes (whole unfractionated ( 500 μm), 500 μm) and levels of pomace inclusion (0, 5. and 15% (w/w)) were specifically investigated. Feed moisture content of 15.5 ± 0.5% (w.b.) and the extruder barrel temperature of 140 °C were kept constant with varying extruder screw speed (150, 200, and 250 rpm). The radial expansion ratio (ER) increased with 5% pomace level of inclusion compared with control but decreased significantly (p < 0.05) at 15% inclusion. Particle sizes significantly affected ER (p < 0.05) with smaller particle sizes resulting in increased ER at all levels of pomace. Adding cherry pomace significantly decreased water absorption index (WAI) and water solubility index (WSI) with smaller particles leading to higher WSI. Extrusion process did not reduce the total phenolic content (gallic acid equivalents). Inclusion of the smallest particle size (<125 μm) cherry pomace at 5% level of inclusion yielded extrudates with the highest expansion ratio among all treatments, including the control. The scanning electron images suggested improvements in the extrudate surface and the internal cell structures. The results indicated the presence of active interactions between the cherry pomace and starch during the expansion process which is not present as an inert material.

Automatic extruder for processing recycled polymers with ultrasound and temperature control system

Melt viscosity is one of the main factors affecting product quality in extrusion processes particularly with regard to recycled polymers. However, due to wide variability in the physical properties of recycled feedstock, it is difficult to maintain the melt viscosity during extrusion of polymer blends and obtain good quality product without generating scrap. This research investigates the application of ultrasound and temperature control in an automatic extruder controller, which has ability to maintain constant melt viscosity from variable recycled polymer feedstock during extrusion processing. An ultrasonic modulation system has been developed and fitted to the extruder prior to the die to convey ultrasonic energy from a high power ultrasonic generator to the polymer melt. Two separate control loops have been developed to run simultaneously in one controller: the first loop controls the ultrasonic energy or temperature to maintain constant die pressure, the second loop is used to control extruder screw speed to maintain constant throughput at the extruder die. Time response and energy consumption of the control methods in real-time experiments are also investigated and reported this paper.

Physico-Chemical Properties of Extruded Copolymer Film

The aim of this study was to investigate the properties of copolymer films made from cassava starch and jellyfish gelatine with glycerol or sorbitol as a plasticizer. The concentrations of gelatine used were 1 and 3% (wt/vol). The prepared copolymer of cassava starch solution (5%) and gelatine solution (1:1 (vol/vol)) was mixed with glycerol or sorbitol (30%) prior to extrusion. The feeding rate of solution was 1 kg/h and the extruder screw speed was 30 rpm. The films were dried by an infared dryer. All extruded films had the thickness of 0.10–0.30 mm. At 1% jellyfish gelatine, the glycerol plasticized copolymer film yielded higher tensile strength, water vapor transmission rate, oxygen transmission rate and %solubility than the sorbitol plasticized film. As the concentration of jellyfish gelatine increased to 3%, the elongation of glycerol plasticized film increased approximately five times compared to two times for sorbitol plasticized films. Practical Applications Gelatine, a denatured form of collagen protein, can be derived from pig, beef or fisheries products such as fish, squid and jellyfish. The application of gelatine is widely used for food and biomedical aspect. The film copolymer of cassava starch and gelatine can be formed by a single screw extruder with glycerol or sorbitol as a plasticizer. The copolymer film with glycerol showed noticeable elongation property, which could be benefit for the development of edible film.

Defatted flaxseed meal incorporated corn-rice flour blend based extruded product by response surface methodology.

Considering the evidence of flaxseed and its defatted flaxseed meal (DFM) for human health benefits, response surface methodology (RSM) based on three level four factor central composite rotatable design (CCRD) was employed for the development of DFM incorporated corn - rice flour blend based extruded snack. The effect of DFM fortification (7.5-20%), moisture content of feed (14-20%, wb), extruder barrel temperature (115-135°C) and screw speed (300-330 RPM) on expansion ratio (ER), breaking strength (BS), overall acceptability (OAA) score and water solubility index (WSI) of extrudates were investigated using central composite rotatable design (CCRD). Significant regression models explained the effect of considered variables on all responses. DFM incorporation level was found to be most significant independent variable affecting on extrudates characteristics followed by extruder barrel temperature and then screw rpm. Feed moisture content did not affect extrudates characteristics. As DFM level increased (7.5% to 20%), ER and OAA value decreased. However, BS and WSI values were found to increase with increase in DFM level. Based on the defined criteria for numerical optimization, the combination for the production of DFM incorporated extruded snack with desired sensory attributes was achieved by incorporating 10% DFM (replacing rice flour in flour blend) and by keeping 20% moisture content, 312 screw rpm and 125°C barrel temperature.

Effects of feed moisture and extruder screw speed and temperature on physical characteristics and antioxidant activity of extruded proso millet (Panicum miliaceum) flour

SummaryThe objective of this work was to determine the impact of extrusion variables [moisture (17–25%), screw speed (170–250 r.p.m.) and temperature (90–150 °C)] on the physical properties and antioxidant activity of proso millet extrudates. Extrusion variables were adjusted using an inscribed central composite rotatable design. Response variables were bulk density (BD), radial expansion ratio, water absorption index, water solubility index, hardness, colour (L*, a*, b*) and antioxidant activity. Moisture and screw speed were the most influential variables affecting millet extrusion: their linear, quadratic and interaction terms accounted for more than 50% of the variability in all responses except for b*. Expansion was greatest at severe conditions of low moisture and high screw speed. These conditions were also consistent with the highest antioxidant activity. This study demonstrated that high expansion and antioxidant activity can be obtained by extruding proso millet under low moisture and high screw speed conditions.

Functional and Structural Properties of Corn, Potato, and Cassava Starches as Affected by a Single-Screw Extruder

The aim of this study was to identify suitable starch sources that can improve the structural integrity of plant protein-based extruded feeds, specifically aquatic feeds. Extrusion trials were performed, using a single-screw extruder. Extruder temperature, screw speed, and moisture content were varied in a factorial design with a replicated central composite point. The effects of these variables on functional and structural properties of the extrudates were evaluated. Temperature had the dominant effect on all properties. Increasing extruder temperature resulted in notable increases in onset temperature of gelatinization and glass transition temperature of all extrudates. The lowest water absorption, alkaline viscosity, and the highest water solubility, in addition to the lowest Rapid Visco Analyzer profile were found for corn starch extrudates. The lowest thermal stability was observed for the potato extrudate. It is expected that cassava and potato starches can contribute better in the formation of a cohesive structure and the generation of more expanded extrudates, specifically in the production of aquafeed. The higher enthalpy transition of corn extrudates indicated the higher thermal stability of corn starch which can lead in production of more durable aquafeed extrudates.

Waxy Soft White Wheat: Extrusion Characteristics and Thermal and Rheological Properties

Waxy wheat flour was analyzed for its thermal and rheological properties and was extruded to evaluate its potential for extruded products. Normal soft white wheat flour was analyzed with the same methods and same extrusion conditions to directly compare differences between the two types of flour. Through DSC analysis, waxy wheat flour was found to have a higher gelatinization peak temperature of 66.4°C than normal wheat at 64.0°C, although the transition required 2.00 J/g less energy. Rapid visco‐analysis indicated that the waxy wheat flour pasted much more quickly and at lower temperatures than the normal wheat flour. Preliminary extrusion experiments were conducted to determine the optimal screw profile for waxy wheat with respect to maximum radial expansion. The optimum screw profile was used for extrusion trials with varying flour moisture (15–25% wb) and extruder screw speed (200–400 rpm) while monitoring process conditions including back pressure and specific mechanical energy. Physical properties of the extrudates were then studied. The radial expansion ratios of the waxy wheat extrudates exceeded those of the normal wheat extrudates by nearly twice as much, and it was observed that the waxy wheat flour took less energy in the form of fewer shear screw elements to expand. The waxy wheat extrudates also exhibited significantly higher water solubility and less water absorption than the normal wheat extrudates owing to solubilizing of the extrudates. The results of our study indicate that waxy wheat flour may be a viable ingredient for creating direct expanded products with less energy.