Optimum Extrusion Conditions Research Articles

Response Surface Methodology for Optimizing Twin‐Screw Prepared Cistanche deserticola‐Potato Composite Rice

AbstractIn order to find the best extrusion conditions which can not only satisfy the taste of the public, but also retain echinacoside to the greatest extent, response surface methodology is used to design the reported experiment. Broken rice, potato flakes, and Cistanche deserticola are used as main raw materials to prepare C. deserticola‐potato composite rice by twin‐screw extruder in this study. Hardness, springiness, content of echinacoside, and sensory score are determined for optimization. The optimum extrusion conditions are obtained as follows: the screw speed is 139 rpm, barrel temperature is 115 °C, and the moisture content is 29%. It is found that C. deserticola‐potato composite rice with 0.7% of C. deserticola has the most acceptable quality and there are 93.45 mg of echinacoside in every 100 g of rice. The development strategy of potato staple food can be realized better by using potato flakes instead of some rice flour (30%) to recombine rice grains. With the improvement of utilization rate of broken rice, sustainable development can be achieved.

Effects of extrusion operating conditions and blend proportion on the physicochemical and sensory properties of teff-rice blend extruded products

The effects of extrusion conditions, teff-to-rice blend ratio (25-100%), feed moisture content (21-25%) and barrel temperature (130- 150°C) on the physico-chemical properties and the sensory attributes of extruded product from teff-rice blend was investigated. The physico-chemical properties (specific length, bulk density, expansion, water absorption index (WAI), water solubility index (WSI) and hardness), and sensory acceptability (flavor, color, texture and overall acceptability) were significantly (p<0.05) influenced by the extrusion conditions. Increasing barrel temperature resulted in higher expansion, lower density, reduced hardness and higher WAI, and WSI. Increase in the proportion of teff resulted in increased density, hardness, and WSI whereas increase in teff proportion brought about a decrease in expansion and WAI. Increasing feed moisture content resulted in higher density, lower expansion, higher WAI, lower WSI, higher hardness and lower crispness. The sensory scores reduced with increase in the proportion teff. The numerical optimization revealed that the optimal extrusion conditions for the best result were extrusion temperature of 150°C, feed moisture content of 21.2% and blending ratio of 40% teff with a desirability value of 0.901. The graphical optimization revealed that the best results were found between 140 to 150°C, 21 to 22% feed moisture and 25 to 46% of teff proportion.

Development of thiamine-rich snacks from brown rice using extrusion technology

PurposeSnack industry is one of the fastest growing food sectors globally, and people are nowadays conscious about intake of healthy snacks on regular basis. There is enormous variety of ready-to-snacks available in the market. Brown rice though highly nutritious in comparison to polished rice is consumed meagerly by masses. Each raw material/ingredient used in extrusion cooking requires specific control of processing variables to meet acceptable product characteristics and consumer demands, which in turn necessitates the need to optimize the conditions for development of brown-rice-based snacks. The aim of this study was to optimize the extrusion cooking conditions for development of brown-rice-based extrudates.Design/methodology/approachExtrusion conditions were optimized through design expert using central composite rotatable design (CCRD) experimental design. The effect of feed moisture (10–22%), screw speed (215–385 rpm) and barrel temperature (95–160 °C) on specific mechanical energy (SME), bulk density (BD), water absorption index (WAI), water solubility index (WSI), expansion ratio (ER), breaking strength (BS) and instrumental color (L*, a*, b*) was evaluated.FindingsAll the system and product responses were significantly (p < 0.01) affected by independent variables. Regression models obtained were highly significant with high coefficient of determination (R2 = 0.992). The optimum extrusion conditions obtained by numerical optimization for development of snacks were moisture content of 12%, screw speed of 350 rpm and temperature of 133 °C. The vitamin B1 content of brown-rice-based snacks was 0.45 mg/100 (50% of RDA) whereas no vitamin B1 was detected in white-rice-based snacks used as control.Practical implicationsThe developed snacks contain 0.45 mg/100 g of vitamin B1. If a person on an average consumes 150 g of snacks in a day, 50% of RDA (1.2 mg/day) for vitamin B1 can be sufficed. Therefore, developed snacks can prove to be a viable vehicle to reduce the vitamin B1 deficiency burden among the target population. Large-scale production and consumption of such type of snacks could improve the nutritional status of vitamin B1 deficient people. Furthermore, it can also provide a good opportunity for snack industry to develop nutritious snacks through utilization of brown rice.Originality/valueBrown rice flour contains nutrients such as iron, calcium, zinc, sodium and vitamin B1 in appreciable portions and was thus explored for development of nutritious snacks. Moreover, developed snacks recorded an overall acceptability of 4.70 out of 5, which depicts it is acceptable for mass production and consumption.

Multi-response surface optimisation of extrusion cooking to increase soluble dietary fibre and polyphenols in lupin seed coat

The seed coat of the legume lupin which is rich in insoluble dietary fibre is a major by-product in human food applications. Extrusion cooking has been demonstrated to increase desirable soluble dietary fibre in the Australian sweet lupin seed coat. In this study, processing condition of twin-screw extrusion cooking was optimised using a central composite rotatable design to increase soluble dietary fibre in lupin seed coat from 44.17 g/kg up to 113.69 g/kg dry basis. The high levels of polyphenols in the seed coat were retained. The optimal extrusion conditions which achieved maximum levels of soluble dietary fibre, total free phenolic content and total free individual phenolic content simultaneously were identified and validated. The extrusion cooking largely had no or slight effects on bioaccessibility and bioavailability of the selected minerals and individual polyphenols. The extrusion cooked lupin seed coat could be a natural antioxidant dietary fibre source for human consumption.

Optimization of an extrusion process for the development of a fiber‐rich, ready‐to‐eat snack from pineapple by‐products and sweet whey protein based on corn starch

AbstractThe aim of the present study was optimized extrusion cooking process for the development of a fiber‐rich, ready‐to‐eat snack from pineapple by‐products and sweet whey protein based on corn starch. The variables studied were the extrusion temperature (ET = 120–180°C), feed moisture content (FMC = 18–25 g/100 g), proportion of sweet whey powder/corn starch (SWP/CS = 0–59.5 g/100 g), and proportion of pineapple by‐product powder (PBP = 0–30 g/100 g), (PBP + [SWP + CS] = 100 g). Analysis of the standardized effects revealed that the SWP/CS proportion had the most significant importance among all the variables, followed by the PBP content. The optimal extrusion conditions were ET = 160.00°C, FMC = 23.04 g/100 g, SWP/CS = 52.08 g/100 g, and PBP =22.50 g/100 g. These results represent an alternative to add value to these raw materials of low commercial value while also avoiding the generation of waste and environmental pollution.Practical applicationsThese results represent an alternative to add value to these raw materials of low commercial value, as well as avoiding the generation of waste and environmental pollution.

Optimization, modeling, and characterization study for the physicochemical properties of raw banana and defatted soy composite extrudates

Novel raw banana and defatted soy composite extrudates were formulated to combat celiac enteropathy. The influence of four independent parameters viz. barrel temperature (BT: 60–80 °C), screw speed (SS: 200–300 rpm), moisture content (MC: 10–20%, wb), and defatted soy flour content (SFC: 0–32%) on physicochemical properties of extrudates were evaluated. Response surface methodology (RSM) identified the optimum extrusion conditions (80 °C BT, 200 rpm SS, 10% MC, and 32% SFC). Compared to RSM (R2:0.379–0.918), artificial neural network (R2:0.909–0.991) proved as a better tool for response prediction. Scanning electron microscopy confirmed the antagonistic effect of SFC addition on extrudate porosity. The addition of SFC decreased the crystallinity of the starch granules (71 to 49%), whereas, storage time had a positive effect (49 to 53%) on crystallinity of the composite extrudates. Fourier transform infrared spectroscopy analysis elucidated the secondary structures of protein in the composite flour which were degraded during the extrusion cooking.

Optimization of Extrusion Conditions for Production of Instant Millet-Soybean Blended Flour

This study developed an optimized protocol for production of instant millet-soybean flour with high solubility. Response surface methodology was used to determine optimal processing conditions for desired water absorption index (WAI) and water solubility index (WSI). Three levels of extrusion temperature (130, 150 and 180 °C) and feed moisture (15, 20 and 25%) were used. Nutritional composition, consumer acceptability and shelf stability of millet-soybean blend produced using optimal extrusion conditions were determined. Analysis of variance showed that the contribution of a quadratic model was significant for WAI and WSI, with high correlation coefficients (R2 = 0.80 and 0.75, respectively). Response surface plots showed that increase in temperature significantly increased both WAI and WSI, while increase in feed moisture significantly increased WAI and decreased WSI. The optimal extrusion conditions were found to be: barrel temperature 159 °C and feed moisture of 25% with product predicted WAI of 2.124 g H2O/g and WSI of 51.30%. Experimental values for responses of products made using optimized conditions were in agreement with the predicted values. Gruels made using the extruded millet-soybean flour were acceptable but with lower consumer acceptability (p &lt; 0.05) scores than the commercially available and extruded millet only flour. Yeasts and molds as well as coliforms were not detected. Total plate count results ranged from 1.35 to 2.9 log cfu/g within one month of storage. This study provides information on the conditions that are suitable for processing an acceptable highly soluble instant millet-soybean flour.

Effect of Extrusion Processing Conditions on the Phenolic Compound Content and Antioxidant Capacity of Sorghum (Sorghum bicolor (L.) Moench) Bran.

Sorghum is a cereal with little use in human diet; however, this grain can provide several nutrients and, additionally, has a high content of phenolic compounds concentrated in bran, which could be beneficial to human health due to its high antioxidant capacity. However, these bioactive compounds are bound within the cell wall matrix; it is necessary to release these compounds to take advantage of their antioxidant properties. The extrusion process increases the accessibility of bound phenolic compounds, breaking their bonds from the bran matrix. The aim of this study was to determine the optimal extrusion conditions for maximizing the phenolic compound content and antioxidant capacity of sorghum bran extrudate. The extrusion process factors evaluated were feed moisture (FM) from 25 to 35% and the fourth extrusion zone temperature (T) in the range of 140-180°C. Analysis of variance and response surface analysis were used in the evaluation. The prediction coefficient, (FM)2, (T)2 and their interaction (FM)(T) significantly affected the free total phenolic compounds. The antioxidant capacity of the free total phenolic compounds was significantly affected by (FM)2 and (T)2. The optimal extrusion conditions were FM = 30% and T = 160°C, which provided free total phenolic compounds with a value of 7428.95μg GAE/g (predicted value: 7810.90μg GAE/g) and antioxidant capacity with a value of 14.12μmol TE/g (predicted value: 14.85μmol TE/g). Results confirmed that extrusion process optimization was useful to increase the content of phenolic compounds and improved the antioxidant capacity of sorghum bran.

Development of a third-generation snack with type 4 resistant sorghum starch: Physicochemical and sensorial properties

Extruded third-generation fiber enriched snacks can be made using type 4 resistant starch. The present study aimed to evaluate and optimize some extrusion conditions, namely the transition or intermediate barrel temperature and the feed moisture in the direct formation of third-generation snacks with type 4 resistant starch using the phosphorylation of sorghum starch. The physicochemical and sensory properties of the optimal snack were investigated. An increase in barrel temperature resulted in an increase in the resistant starch (13.1 ± 0.5 g/100 g) and the expansion index values, as long as the feed moisture was maintained above 28%. The optimal conditions with a desirability value of 0.932 were a barrel temperature of 136 °C and a feed moisture of 28.5%. The optimal third-generation snack had 17.1 ± 0.2 g/100 g of resistant starch and a desirable expansion index of 5.7 ± 0.4, as well as general sensory acceptability (“I like moderately”). Phosphorylated resistant starch of the optimal snack showed a degree of substitution and a percentage of phosphorus (0.02 ± 0.00 and 0.35 ± 0.15%, respectively) within the limits allowed in foods. This study showed that using optimal extrusion conditions, phosphorylation of sorghum starch was possible to produce resistant starch and simultaneously to obtain an extruded snack with acceptable physical and sensorial properties. Additionally, it showed that sorghum is a good alternative source of starch for the formulation of extruded snacks.

Physicochemical and functional properties of extruded dietary fiber from mushroom Lentinula edodes residues

Dietary fiber from Lentinula edodes (LEDF) residues were obtained using various extrusion conditions and their physicochemical and functional properties, such as glucose adsorption capacity (GAC), water holding capacity, oil holding capacity, glucose retardation (GRI) and bile acid retardation index (BRI) were measured. Based on principal component analysis, the optimal extrusion conditions were determined, i.e., extrusion temperature 130 °C, moisture content 40% and screw speed 125 r/min. The dietary fiber contained 3.6% soluble and 88% insoluble dietary fiber and the major components were cellulose (26%) and hemicellulose (42%). Compared with untreated fibers, GAC and BRI of LEDF with optimal extrusion conditions increased 0.46 mg/mg and 28%, respectively. Regression analysis suggested that GRI and hemicellulose showed a significant positive correlation (p≤0.05). Overall, it could be suggested that the LEDF obtained with the optimized extrusion condition might be used as a potential ingredient in functional foods.

Improvement of nutritional and nutraceutical value of nixtamalized maize tortillas by addition of extruded chia flour

In this work the objectives were: (1) To optimize the extrusion conditions of defatted chia seeds maximizing antioxidant activity (AoxA), total phenolic content (TPC) and in vitro protein digestibility (IVPD), and (2) To evaluate the nutritional, nutraceutical, and sensory (acceptability) properties of tortillas formulated with commercial nixtamalized maize flour (MASECAMR) and optimized extruded defatted chia flour. Response surface methodology was applied as an optimization tool. A central composite rotatable design with two factors [Extrusion temperature (ET=50-160°C), screw speed (SS=50-240 rpm)] in five levels were used. The extruded from each treatment (13) were dried and ground to obtain extruded defatted chia flours (EDCF). The desirability function was applied as optimization technique. The prediction models for each response variable were adequate and reproducible. The optimal extrusion conditions to obtain optimized extruded defatted chia flour (OEDCF) were ET=147°C/SS=237 rpm; a high global desirability (D=0.815) was associated with these optimal conditions. The tortillas elaborated with MASECATM flour + OEDCF had higher IVPD, C-PER, TPC and AoxA, and better antihypertensive potential than elaborated with only MASECATM flour. The addition of OEDCF to MASECATM flour increased the nutritional and nutraceutical value of the tortillas.

Response surface methodology for evaluation of the effects of screw speed, feed moisture and xanthan gum level on functional and physical properties of corn half products

Effects of screw speed (100–300 rpm), feed moisture (37–47%) and xanthan gum (XG) level (0–1%) on the functional and physical properties of corn half products were investigated and optimized by using three-factor and three-level Box-Behnken design (BBD) under response surface methodology (RSM). Response variables are water absorption index (WAI), water solubility index (WSI), degree of gelatinization (DG), water activity (aw), specific volume and color properties of extrudates. Increased screw speed decreased WAI and aw values and increased WSI values significantly. Specific volume of half products was low for all extrusion combinations and negative correlated with screw speed, feed moisture and XG level. Lightness and yellowness of half products were increased with increases in screw speed, feed moisture and XG level. Low DG for all half products was obtained (46.33–63.36%) because of temperature under 100 °C in last two zones in extruder. Desirability function approach was used to find the optimum extrusion conditions. The optimized combinations of extrusion conditions were found 300 rpm screw speed, 47% feed moisture and 0.44% XG content with a desirability value of 0.991. No significant difference was found between experimental data and predicted values.

Use of response surface methodology (RSM) for composite blends of low grade broken rice fractions and full-fat soybean flour by a twin-screw extrusion cooking process

In this study, seventeen (17) composite blends of broken rice fractions and full-fat soybean, formulated using response surface methodology and central composite design within a range of barrel temperatures (100-140 °C), initial feed moisture content (15-25%) and soybean composition (8-24%), were extruded with a twin-screw extruder and the expansion and color indices were optimized. The results indicated a significant (p<0.05) effect of extrusion conditions on the responses. Fitted predictive models had coefficients of 88.9%, 95.7%, 97.3%, 95.4% and 95.2%, respectively, for expansion index, bulk density, lightness, redness and yellowness. The p-value and lack-of-fit tests of the models could well explain the observed variability and therefore could be used to establish production setting for the twin-screw extruder. The optimum extrusion conditions were found to be 130 °C (barrel temperature), 20% (feed moisture level) and 23% feed soybean composition and optimum responses in terms of bulk density, expansion index, lightness, redness and yellowness chroma indices were 0.21 g cm -3 , 128.9%, 17.1, 3.13 and 24.5 respectively. This indicates that optimum conditions can be established in twin-screw extrusion cooking of broken rice fractions and full-fat soybean composite blends that can result in product of low bulk and maximum expansion with a satisfactory light yellow product color that can be used to produce products that valorize broken rice and reduce qualitative postharvest loss.

Use of response surface methodology (RSM) for composite blends of low grade broken rice fractions and full-fat soybean flour by a twin-screw extrusion cooking process

In this study, seventeen (17) composite blends of broken rice fractions and full-fat soybean, formulated using response surface methodology and central composite design within a range of barrel temperatures (100-140 °C), initial feed moisture content (15-25%) and soybean composition (8-24%), were extruded with a twin-screw extruder and the expansion and color indices were optimized. The results indicated a significant (p&lt;0.05) effect of extrusion conditions on the responses. Fitted predictive models had coefficients of 88.9%, 95.7%, 97.3%, 95.4% and 95.2%, respectively, for expansion index, bulk density, lightness, redness and yellowness. The p-value and lack-of-fit tests of the models could well explain the observed variability and therefore could be used to establish production setting for the twin-screw extruder. The optimum extrusion conditions were found to be 130 °C (barrel temperature), 20% (feed moisture level) and 23% feed soybean composition and optimum responses in terms of bulk density, expansion index, lightness, redness and yellowness chroma indices were 0.21 g cm-3, 128.9%, 17.1, 3.13 and 24.5 respectively. This indicates that optimum conditions can be established in twin-screw extrusion cooking of broken rice fractions and full-fat soybean composite blends that can result in product of low bulk and maximum expansion with a satisfactory light yellow product color that can be used to produce products that valorize broken rice and reduce qualitative postharvest loss.

Comparison of quality protein maize (QPM) and normal maize with respect to properties of instant porridge

The investigation was carried out to optimize the extrusion conditions for the development of normal maize and Quality Protein Maize (QPM) based instant porridge. The effect of 3 independent variables (moisture content (14–18%), barrel temperature (125–175 °C) and screw speed (400–550 rpm) on the dependent variables (carbohydrate solubility (CS), protein solubility (PS), hydration power (HP) and milk absorption capacity (MAC) was evaluated by using central composite design in response surface methodology (RSM). Feed moisture and barrel temperature exhibited significant affect (p ≤ 0.01; p ≤ 0.05) on PS, HP and MAC, while screw speed showed non-significant (p ≤ 0.01; p ≤ 0.05) affects on HP and CS. Increase in the moisture content and barrel temperature increases the CS and PS of normal as well as quality protein maize porridge. However, increase in screw speed results in decrease in protein solubility. Optimum extrusion conditions for QPM were 14.19–15.36% feed moisture (on dry basis), 411.61–466.50 rpm screw speed and 150ºC barrel temperature. Optimum extrusion conditions for NM were 14.02–14.17% feed moisture (on dry basis), 171.27–173.47 ºC barrel temperature and 404.05 rpm screw speed. Based on the results it was concluded that quality protein maize can be extruded into acceptable as well as nutritious breakfast food.

Effect of extrusion conditions on the physicochemical and phytochemical properties of red rice and passion fruit powder based extrudates.

The passion fruit powder blended rice flour based extrudate was developed and investigated in terms of physicochemical and phytochemical properties. The extrusion process was performed using a twin screw extruder and optimized using rotatable central composite design followed by response surface methodology. The effect of process parameters such as temperature (80-150°C), screw speed (200-400rpm), moisture content (20-30%) and passion fruit powder (0-15%) on product quality was investigated. The optimum extrusion conditions of temperature, screw speed, feed moisture content, and passion fruit powder were 97.50°C, 250rpm, 25.20% and 11.25%, respectively. At optimum condition, the predicted values of responses were expansion ratio 8.05, water absorption index 2.77, total phenolic content 129.492mg GAE/100g and DPPH scavenging activity 65.79%. A comparison between optimized and control extrudates revealed that thermal, crystallinity and morphological properties of extrudates differed significantly. The comparison was also conducted in terms of FT-IR, SEM-EDS and HPLC analysis. The phytochemical properties showed that β-carotene, cyanidin-3-glucoside, peonidin-3-D-glucoside chloride were higher in control whereas the optimized sample evinced more (±)-α-tocopherol and D-α-tocopherol.

Optimization and characterization of an extruded snack based on taro flour (Colocasia esculenta L.) enriched with mango pulp (Mangifera indica L.).

The aim of this study was to optimize and characterize an extruded snack made with taro flour and mango pulp. A central experimental design composed of the following three variables was used: mango pulp proportion (MPP = 0-10g/100g) in taro flour, feed moisture content (FMC = 16-30g/100g) and extrusion temperature (zone 4 of extruder) (T = 80-150°C) using a single-screw extruder with a compression screw ratio of 3:1. Increasing FMC values decreased the torque, pressure, specific mechanical energy (SME), expansion index (EI), water solubility index and pH values and increased the residence time, bulk density (BD), hardness and total colour difference. Increasing T values led to a decrease in the torque, pressure, BD and hardness values, while increasing MPP values only caused a significant increase in the hardness values and β-carotene content and a decrease in the pressure value. The optimal extrusion conditions were T = 135.81°C, FMC = 18.84g/100g and MPP = 7.97g/100g, with a desirability value of 0.772, to obtain a snack with EI = 1.52, BD = 0.66g/cm3, hardness = 24.48N, β-carotene content = 99.1μg/g and SME = 428.54J/g. The mango pulp is an available and economical source of β-carotene for the enrichment of extruded expanded taro snacks.

A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting

In this study, composites of aluminum alloy 6063 reinforced with 10 wt% boron carbide microparticles were successfully fabricated by a combination of spark plasma sintering and stir casting methods, followed by hot extrusion. A systematic study on the relationship between extrusion process variables (i.e. extrusion ratio, temperature, and punch speed) and porosity, particle refinement, particle distribution and consequently tensile properties and fracture behavior of the composites was performed. Extensive electron microscopy analysis and tensile testing of the composites revealed a multifactoral interdependency of microstructural evolution and mechanical properties on the extrusion process variables. For example, while increasing the extrusion ratio at higher temperatures led to moderate particle refinement, better densification of the composites, and improvement in mechanical properties, concurrent particle fragmentation and microvoid formation around the particles at lower temperatures had opposing effects on the mechanical behavior. We show that the dependency of mechanical properties on all such microstructural factors makes it difficult to predict optimum extrusion conditions in aluminum matrix composites. That is, unlike the common approach, extruding the composites at higher temperatures and achieving more reduction in area may not necessarily lead to the most favorable mechanical properties.

In Situ Salt Formation during Melt Extrusion for Improved Chemical Stability and Dissolution Performance of a Meloxicam-Copovidone Amorphous Solid Dispersion.

As the pipeline for poorly soluble compounds continues to grow, drug degradation during melt extrusion must be addressed. We present a novel method for stabilizing a thermally labile drug substance while preserving its physical stability and even improving its dissolution performance. In a previous study, we found that incorporating meglumine during extrusion of meloxicam results in chemical stabilization that cannot be achieved using process optimization alone. The purpose of this study is to understand the mechanism behind this stabilization and its impact on the performance of a meloxicam-Kollidon VA64 amorphous solid dispersion. The meloxicam concentration was maintained at 10% (w/w) for blends with and without meglumine. The optimal meglumine blend contained an equimolar amount of meloxicam to meglumine with the remainder consisting of Kollidon VA64. Both formulations were processed with optimized extrusion conditions and analyzed by HPLC for purity. Meglumine at a 1:1 molar ratio with meloxicam results in 100% purity of meloxicam after melt extrusion. Solid-state NMR revealed a proton transfer between the meloxicam and meglumine indicating an in situ salt formation. During non-sink dissolution, the meglumine ASD enables meloxicam to maintain supersaturatation (≅50 times more than meloxicam free acid) for >7.25 h. The ASD without meglumine began precipitating 2.25 h following the pH shift. The ASDs were placed at 40 °C/75% RH for 6 months, and their stability was assessed. No significant chemical degradation, recrystallization, or significant moisture uptake was observed after six months' storage at 40 °C/75% RH.

Improvement of beer flavour with extruded rice as adjunct

Extruded rice used as adjunct for beer fermentation was prepared using a single-screw extruder. Extrusion pretreatment facilitated the saccharification and gelatinization of the rice starch as well as the formation of a glassy cellular structure, which was evaluated through scanning electron microscopy analysis. The effects of different parameters, including barrel temperature, water content, nozzle diameter and screw speed, as well as their interactions with rice expansion rate, were evaluated by response surface methodology to determine the optimum extrusion conditions. Extruded rice was acquired using the optimum extrusion parameters (water content, barrel temperature, screw speed and nozzle diameter of 22.4%, 103°C, 8 mm and 191.6 rpm, respectively), and the expansion rate reached 275.1%. The effect of the extruded rice adjunct on beer flavour compounds was investigated by comparing flavour compounds with those of traditional rice-adjunct beer through sensitive static headspace–capillary gas chromatography spectrometry. The contents of esters, a highly important flavour group, in extruded-rice-adjunct beer (ethyl acetate, isoamyl acetate, ethyl hexanoate and ethyl caprylate at 11.6, 2.4, 0.2 and 0.3 mg L−1, respectively) were higher than those of the traditional rice-adjunct beer. The contents of high alcohols were lower in the traditional rice-adjunct beer than those in the extruded-rice-adjunct beer, but both levels satisfied the national standard for beer. Gas chromatography–mass spectrometry was employed to identify the flavour compounds of both beer samples through headspace–solid-phase microextraction. Copyright © 2017 The Institute of Brewing & Distilling