Extrusion Moisture Content Research Articles

Unlocking the potential of pasting properties to predict extrudate characteristics of corn grits blends with high amylose corn starch, potato starch, or rice flour.

The development of new production lines of extruded ready-to-eat (RTE) snacks often results in high losses of edible food due to the trial-and-error approach in industry. Being able to predict extrudate characteristics of new formulations before having to run trials on industrial scale would be beneficial for reducing waste and having a more efficient development process. With this study, the correlation between pasting properties of seven blends of flours/starches and extrudate characteristics was investigated (100% corn grits, 25% and 50% replacement of corn grits with high amylose starch, potato starch, and rice flour). The predictive power of pasting characteristics on extrudate's moisture content, water absorption and solubility index, sectional expansion index (SEI) and hardness was studied. Results indicated the potential of predicting SEI, water solubility index (WSI), and water absorption index (WAI) of RTE-snacks. WSI and WAI were, respectively, negatively correlated with peak temperature (R2 =0.897), and positively with peak temperature and positively with trough viscosity (R2 =0.855). One can conclude that the rheometer can be a useful tool to gain insight into the characteristics of the extrudate, although further research with enlargement of the dataset is necessary to make the rheometer effectively deployable for potentially other extrudate characteristics.

Protein digestibility of textured-wheat-protein (TWP) -based meat analogues: (I) Effects of fibrous structure

This study aimed to investigate the effects of fibrous structure under different moistures during extrusion on the protein digestibility of textured-wheat-protein (TWP) -based meat analogues. Three TWPs (TWP-1, TWP-2, TWP-3) were prepared under an extrusion moisture content of 26.5%, 29.3% and 32.0%. The fibrous structure was analysed through determining the texture properties, degree of texturisation, microstructure of TWPs, and chemical bonds of proteins. When the extrusion moisture increased from 26.5% to 32.0%, the hardness, and degree of texturisation of TWP increased from 2067.1 ± 606.7 g and 2.16 ± 0.13 to 2681.8 ± 359.7 g and 3.55 ± 0.22, respectively, while the cohesiveness decreased from 0.581 ± 0.061 to 0.394 ± 0.033 with less compact fibers. Changes in the particle size and distribution, SDS-PAGE, soluble nitrogen content, and free amino acids of digesta were determined during digestion. It was found that the TWP prepared under a lower extrusion moisture content had a bigger particle size of both gastric and small intestinal digesta. The combination of the results of SDS-PAGE, the soluble nitrogen content, and free amino acids of digesta showed the digestion of protein in TWPs was greater than that in the control sample, and the breakdown rate and proteolysis degree in TWPs increased with the increase in the degree of texturisation of TWP. After the small intestinal digestion, the release of free amino acids in the TWP-1, TWP-2, TWP-3, and the control sample were 375.1 ± 1.4, 489.5 ± 0.8, 475.0 ± 1.6, and 262.3 ± 0.8 mg/10 g digesta. The lower degree of proteolysis in the TWPs prepared under a lower moisture content may be due to its smaller gaps between fibers with greater cohesiveness.

Linking Expansion Behaviour of Extruded Potato Starch/Rapeseed Press Cake Blends to Rheological and Technofunctional Properties

In order to valorise food by-products into healthy and sustainable products, extrusion technology can be used. Thereby, a high expansion rate is often a targeted product property. Rapeseed press cake (RPC) is a protein- and fibre-rich side product of oil pressing. Although there is detailed knowledge about the expansion mechanism of starch, only a few studies describe the influence of press cake addition on the expansion and the physical quality of the extruded products. This study assessed the effect of RPC inclusion on the physical and technofunctional properties of starch-containing directly expanded products. The effect of starch type (native and waxy), RPC level (10, 40, 70 g/100 g), extrusion moisture content (24, 29 g/100 g) and barrel temperature (20–140 °C) on expansion, hardness, water absorption, and solubility of the extrudates and extruder response was evaluated. At temperatures above 120 °C, 70 g/100 g of RPC increased the sectional and volumetric expansion of extrudates, irrespective of starch type. Since expansion correlates with the rheological properties of the melt, RPC and RPC/starch blends were investigated pre- and postextrusion in a closed cavity rheometer at extrusion-like conditions. It was shown that with increasing RPC level the complex viscosity |ƞ*| of extruded starch/RPC blends increased, which could be linked to expansion behaviour.

Effect of extrusion temperature, moisture content and screw speed on the functional properties of aquaculture balanced feed

The aim of this study is to analyze the effect of feed moisture content, temperature, and screw velocity on the functional properties of extruded feeds for aquaculture with a bean flour and soy protein base. Fishmeal was substituted at different concentrations of bean flour or soy protein. Later, the diets were extruded and the expansion index, apparent density, and the extrusion sinking velocity were analyzed and an optimization of the process was carried out. The extrusion moisture content has an effect (p < 0.05) on the extrusion expansion index. The extrusion conditions were optimized with 93, 186 and 279 g/kg of bean flour or soy protein. The diets with soy protein require a higher amount of moisture, higher temperature, and a higher screw velocity than diets with bean flour, to obtain diets that are within range of the physical characteristics similar to commercial diets.

Twin-Screw Extrusion Processing of Rainbow trout (Oncorhynchus mykiss) Feeds Using Graded Levels of High Protein Corn-Based Distillers Dried Grains (HP-DDG) and Conventional Distillers Dried Grains with Solubles (DDGS)

&lt;p&gt;Twin-screw extrusion cooking trials were performed to investigate the differential effects of conventional DDGS (DDGS) and HP-DDG inclusion, as fishmeal replacers, on physical properties (moisture content, water activity, thermal properties, expansion ratio, unit density, bulk density, water absorption, solubility and pellet durability indices, and color) of Rainbow trout (Oncorhynchus mykiss) feed. Four ingredient blends were formulated with 20 and 40% C- DDGS, and 20 and 40% HP-DDG, along with other required dietary ingredients. Each diet was extruded using two replications; a fishmeal based diet acted as the control diet. The highest and the lowest extrudate moisture content and water activity were observed for the diets containing 20% DDGS and 40% HP-DDG, respectively. Compared to the control diet, increasing HP-DDG content from 20 to 40% had no effect on the bulk density of the products, while increasing DDGS content from 20-40% led to a considerable rise in bulk density of the extrudates by 14.2 and 6%, respectively. Also, extrudates with the lowest brightness, greenness, and yellowness values were obtained from the diet containing 20% DDGS, whereas the most color intensity values were observed for the diets containing 40% DDGS and 20% HP-DDG. Increasing DDGS and HP-DDG from 0-40% caused a remarkable increase in water absorption index, by 72 and 30%, respectively. Likewise, the water solubility index increased, but in a considerably lesser order of magnitude. High pellet durability index of more than 99% was achieved with inclusion of either DDGS or HP-DDG. None of the diets impacted the thermal properties of the extrudates. Inclusion of 20 and 40% DDGS resulted in the extrudates with the largest and the smallest unit density values of nearly 887 and 750 kg/m&lt;sup&gt;3&lt;/sup&gt;, respectively. As was expected, expansion ratio decreased with increasing unit density. Increasing inclusion levels of HP-DDG did not show any effect on unit density or expansion ratio of the products. Future research should concentrate on investigating the effects of both extrusion processing and graded levels of different types of DDGS on Rainbow trout feeds.&lt;/p&gt;

Changes in Moisture, Protein, and Fat Content of Fish and Rice Flour Coextrudates during Single-Screw Extrusion Cooking

Changes in proximate composition of fish and rice flour coextrudates like moisture, protein, and fat content were studied with respect to extrusion process variables like barrel temperature, x 1 (100–200 °C); screw speed, x 2 (70–110 rpm); fish content of the feed, x 3 (5–45%); and feed moisture content, x 4 (20–60%). Experiments were conducted at five levels of the process variables based on rotatable experimental design. Response surface models (RSM) were developed that adequately described the changes in moisture, protein, and fat content of the extrudates based on the coefficient of determination (R 2) values of 0.95, 0.99, and 0.94. ANOVA analysis indicated that extrudate moisture content was influenced by x 4, protein content by x 1 and x 3, and fat content by x 3 and x 4 at P < 0.001. Trends based on response surface plots indicated that the x 1 of about 200 °C, x 2 of about 90 rpm, x 3 of about 25%, and x 4 of about 20% minimized the moisture in the extrudates. Protein content was maximized at x 1 of 100 °C, x 2 > 80 rpm, x 3 of about 45%, and x 4 > 50%, and fat content was minimized at x 1 of about 200 °C, x 2 of about 85–95 rpm, x 3 < 15%, and x 4 of about >50%. Optimized process variables based on a genetic algorithm (GA) for minimum moisture and fat content and maximum protein content were x 1 = 199.86, x 2 = 109.86, x 3 = 32.45, x 4 = 20.03; x 1 = 199.71, x 2 = 90.09, x 3 = 15.27, x 4 = 58.47; and x 1 = 102.97, x 2 = 107.67, x 3 = 44.56, x 4 = 59.54. The predicted values were 17.52%, 0.57%, and 46.65%. Based on the RSM and GA analysis, extrudate moisture and protein content was influenced by x 1, x 3, and x 4 and fat content by x 2, x 3, and x 4.

Physical properties, molecular structures, and protein quality of texturized whey protein isolate: Effect of extrusion moisture content

To explore the complex relationship between processing conditions and functional and nutritional properties of food products containing whey protein isolate (WPI), we investigated the effect of extrusion texturization at various temperatures (50, 75, and 100°C) and varying moisture levels of the feed (20, 30, 40, and 50%) on changes in the composition, molecular structure, and protein quality of the extrudates. Bradford assay methods were used to determine protein solubility of the extruded WPI as a function of changing level of moisture. Protein compositional changes as a function of extrusion conditions were quantitatively characterized and analyzed by sodium dodecyl sulfate-PAGE and reversed-phase-HPLC techniques. We showed that at a given temperature, increasing the extrusion moisture content resulted in a slight increase in the overall protein water solubility (at 50 and 75°C), averaging approximately 5% per 10% increase in moisture content. A reduction in β-lactoglobulin content was observed at 50°C with increasing moisture content, indicative of the sensitive nature of β-lactoglobulin to extrusion treatment, whereas the amount of α-lactalbumin remained unchanged at all moisture contents used at a set temperature. The protein quality of the extruded WPI, determined chemically by available sulfhydryl and primary and secondary amines, remained relatively unchanged as a function of moisture level. Circular dichroism and intrinsic tryptophan fluorescence spectroscopic studies revealed considerable structural changes, both at the secondary structural level and the tertiary contacts as a function of increasing temperature, and higher moisture levels can slightly preserve secondary structures but not the tertiary contacts of the protein molecules. Atomic force microscopy provided direct visualization of the fine difference of the protein particles caused by changing extrusion moisture contents, which is in close agreement with the results obtained using other techniques in this work.

EFFECTS OF STARCH, LIPID AND MOISTURE CONTENTS ON EXTRUSION BEHAVIOR AND EXTRUDATE CHARACTERISTICS OF RICE‐BASED BLENDS PREPARED WITH A VERY‐LOW‐COST EXTRUDER

ABSTRACT Response surface methodology with a 3 × 3 factorial plan design was used to investigate the effects of starch content (60–70 g/100 g dry matter [DM]), lipid content (6.2–10.2 g/100 g DM) and moisture content (10–16 g/100 g wet matter [WM]) on extrusion behavior of rice‐based blends, on the physicochemical properties of extrudates, and the apparent viscosity of resulting gruels. The increase in starch content increased the loss of lipid, the expansion ratio, the degree of gelatinization (DG) of starch, and the water absorption index (WAI). Increasing lipid content resulted in higher loss of lipids and a lower WAI and water solubility index (WSI). Water content had the most influence. Increasing water content resulted in increased loss of lipids, higher moisture content of extrudates, and in lower die temperature, expansion ratio, DG, WAI and WSI. The high DG (≥91%) of all extrudates demonstrated that the very‐low‐cost extruder manufactured in Vietnam is suitable for the production of ready‐to‐eat infant flour.PRACTICAL APPLICATIONSThis work tested and optimized the effect of blend composition on the characteristics of rice‐based extrudates obtained using a very‐low‐cost extruder (VLCE) manufactured in Vietnam and on derived gruels. Our results enable prediction of the characteristics of extruded products, when the starch, lipid and water contents of the blends are known. Thus, VLCE users will be able to choose the nature and relative proportion of ingredients to obtain extrudates with specific targeted characteristics. In addition, this study demonstrated that serious loss of lipids occurs during extrusion of blends with high lipid contents. To obtain the lipid content recommended for complementary food, it is thus preferable to add ingredients with high lipid content after extrusion. We conclude that this kind of VLCE manufactured in Vietnam is suitable for low‐cost production of instant flour with all the required characteristics for use as complementary foods for infants and young children after the age of 6 months.

EFFECT OF BARREL TEMPERATURE ON REHYDRATION KINETICS OF DIRECT‐EXPANDED TEF FLOUR BREAKFAST CEREAL

ABSTRACT The effect of barrel temperature (110, 130 and 150C) on the rehydration kinetics of tef flour extrudates was investigated. Rehydration was conducted in distilled water for 300–420 min using a constant‐temperature water bath at 25C (±1C). Water absorption rate was high at the early stages (60–90 min) of hydration, decreased subsequently and finally approached an equilibrium. Three models, namely, Peleg's equation, first‐order kinetic and normalized Weibull model, were fitted to the rehydration data. The three models described the rehydration characteristics adequately (R2 = 0.95–0.99). The water absorption rate and equilibrium moisture content were found to be barrel temperature‐dependent (P &lt; 0.05). Extrudates processed at a barrel temperature of 150C exhibited a high water absorption rate, followed by those extruded at 130 and 110C, respectively. The equilibrium moisture content of extrudates processed at 150 and 130C was significantly (P &lt; 0.05) higher than those extruded at 110C. In view of the values of the shape parameter βof the normalized Weibull model, the mechanism of water absorption appeared to be by diffusion for extrudates processed at 130C (β = 0.67), whereas in extrudates processed at 110 (β = 0.89) and 150C (β = 1.03), external resistance to mass transfer and relaxation phenomena, respectively, were found to be the water absorption mechanisms. In comparison, the normalized Weibull model described the rehydration characteristics relatively better, resulting in smaller RMSE value.PRACTICAL APPLICATIONSSome extruded food products, like breakfast cereals, are consumed after being rehydrated (e.g., in milk). The rehydration characteristics, in turn, are influenced by the extrusion operating conditions. Fast rehydration without much change in the crispiness is a required attribute of breakfast cereals. Describing and modeling the kinetics of moisture uptake as a function of the operating conditions could lead to a better understanding and control over the mechanisms underlying the sorption process and the ability of the product to rehydrate. Such information is vital in process and quality optimization.

Extrusion Studies of Aquaculture Feed using Distillers Dried Grains with Solubles and Whey

Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% distiller-dried grains with solubles (DDGS) along with 5% whey were prepared with a net protein content adjusted to 28% (wet basis [wb]). Other ingredients in the blends included soy flour, corn flour, fish meal, vitamin, and mineral mix. These blends were extruded in a single-screw extruder at 15, 20, and 25% (wb) moisture content and at 130 and 160 rpm screw speeds. Compared to previous research, the durability and unit density of the extrudates in this study were found to increase substantially by the addition of whey to the blends. Increasing the DDGS content from 20 to 40% resulted in a 5.8 and 16.8% increase in extrudate moisture content and redness, respectively, but produced a decrease of 11.2% in brightness and 3.6% in yellowness of the extrudates. Increasing the moisture content of the ingredient blends from 15 to 25% resulted in an increase of 16.1, 8.7, and 9.3% in moisture content, durability, and redness, respectively, but a decrease of 9.8 and 5.6%, respectively, in brightness and yellowness of the extrudates. Neither DDGS level nor screw speed significantly affected extrudate durability or unit density. In fact, changing the screw speed had no significant effect on many of the properties of the extrudates studied, except for moisture content, redness, and yellowness. As demonstrated in this study, ingredient moisture content and screw speed are critical considerations when producing extrudates with feed blends containing DDGS; further work is needed to optimize processing conditions and to produce floating feeds.

팽연보조재 혼합에 따른 펄프압출물의 물리적 특성

Extrusion process and physical properties of extrudates of pulp powder (TMP, thermomechanical pulp fibers) mixed with expanding additives was evaluated to develop biodegradable packaging materials. To find out the optimum condition, the status of extrusion process, coefficient of elastic and expansion ratio of extrudates were tested on the composites (wheat flour, soluble starch, polyvinyl alcohol), blending conditions of composites and moisture contents of extrudates. In case of material composition, wheat flour played a key role to keep extrusion process irrespective of the added amounts of soluble starch and polyvinyl alcohol. The coefficient of elastic of extrudates was increased and the expansion ratio was reduced as the added amounts of wheat flour increased. Also, the coefficient of elastic of extrudates was decreased as the moisture content of extrudates increased. The lowest coefficient of elastic was 439.55 kPa under the condition, of pulp powder mixed with <TEX>$20\%$</TEX> of wheat flour based on pulp weight and <TEX>$10\%$</TEX> of soluble starch based on wheat flour weight and controlled <TEX>$20\%$</TEX>(wb) of moisture content.

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.

Rheological behaviour of different cereals using capillary rheometry

The rheological properties of wheat meal and wheat starch with and without added wheat germ oil (WGO) and of oat flour under low moisture conditions were investigated using a capillary rheometer and the flow behaviour described by the power law model. The consistency coefficient of wheat starch and wheat meal decreased with increase in moisture content from 21% to 28% (wet weight basis) and barrel temperature from 100°C to 125°C and with the addition of WGO to 8%. The flow behaviour index of wheat starch and wheat meal generally increased with this increase in extrusion moisture content and temperature and with the addition of WGO. Wheat starch showed the highest consistency coefficient and oat flour showed the lowest under identical set extrusion conditions of these temperatures and moistures. Both power law indices for oat flour showed a less well defined change for the same range of moisture and temperature. The effect of WGO addition to wheat starch or meal to the 8% level was to reduce their viscosities towards the value observed for oat flour. The power law indices varied with die diameter indicating possible wall slip.

EFFECT OF OPERATING CONDITIONS ON MELT RHEOLOGICAL CHARACTERISTICS DURING TWIN-SCREW FOOD EXTRUSION

Data on operating (feed rate, feed moisture content, screw speed, and temperature) and process variables(product/barrel/die temperatures, zone 4-5/die pressures, total power consumption) of a co-rotating twin-screw foodextruder, and extrudate moisture content were collected at 0.5 s intervals. The steady-state data were analyzed and themean residence time and average apparent viscosity of melted cornmeal determined. The average apparent viscosity wascalculated by using the total power consumption method and modeled as a function of the operating variables. Theaddition of two extra reverse paddles to the screw (configuration B) caused a decrease in fluid consistency coefficient(16.865 vs 20.130 kPasn) and an increase in shear-thinning behavior (0.22 vs 0.44) of the melt.

Extrusion‐Cooking of Sorghum Containing Different Amounts of Amylose

ABSTRACTThree sorghums containing different amounts of amylose (12.2, 21.5, and 26.7%) were decorticated, ground and extruded at three extrusion moisture levels (17, 32, and 45%). Highly expanded and brittle sorghum extrudates with high degrees of starch cooking were produced at 17% extrusion moisture content. All sorghum extrudates exhibited a V‐amylose x‐ray diffraction pattern. Functional characteristics, such as expansion, enzyme‐susceptible starch ratio, and water solubility, indicated that low amylose extrudates were more cooked than other varieties. Thin porridges prepared from extruded sorghums had an intermediate consistency, smooth texture, roasted flavor and white color. Thin porridges (atoles) from extrudates containing 21.5% amylose, were preferred by a sensory panel over those from extrudates containing 12.2 and 26.7% amylose.

A Physicochemical Model for Extrusion of Corn Starch

Corn starch extruded at 32.9, 29.2, 24.5, 22.5, 15.9 and 14.2% moisture was analyzed for expansion ratio, enzyme susceptibility, water solubility index, water absorption index, degree of gelatinization, paste viscosity and heat of gelatinization. A model system based on the combination of raw, gelatinized and dextrinized starch was used to represent the physicochemical properties of the extrudates. Reducing extrusion moisture content resulted in a progressive change from gelatinized-like to dextrinized-like properties. Maximum gelatinization was observed at about 28-29% moisture. Below 20% moisture, dextrinization becomes predominant during high- shear cooking-extrusion. Scanning electron micrographs also validate the assumptions of the model.