Twin-screw extrusion of barley–grape pomace blends: Extrudate characteristics and determination of optimum processing conditions

Health-Promoting Properties and the Use of Fruit Pomace in the Food Industry-A Review

Fruit pomace, a by-product of the fruit industry, includes the skins, seeds, and pulp most commonly left behind after juice extraction. It is produced in large quantities: apple residues alone generate approximately 4 million tons of waste annually, which is a serious problem for the processing industry but also creates opportunities for various applications. Due to, among other properties, their high content of dietary fiber and polyphenolic compounds, fruit residues are used to design food with functional features, improving the nutritional value and health-promoting, technological, and sensory properties of food products. This article presents the health-promoting (antioxidant, antidiabetic, anti-inflammatory, and antibacterial) properties of fruit pomace. Moreover, the possibilities of their use in the food industry are characterized, with particular emphasis on bread, sweet snack products, and extruded snacks. Attention is paid to the impact of waste products from the fruit industry on the nutritional value and technological and sensory characteristics of these products. Fruit pomace is a valuable by-product whose use in the food industry can provide a sustainable solution for waste management and contribute to the development of functional food products with targeted health-promoting properties.

Effect of extrusion process conditions on extrudates enriched with carotenoids encapsulated by different methods using gum arabic and vegetable fat as carriers

Bioactive compounds into extruded foods enhance their nutritional value but they are heat and shear labile and prone to oxidation. This study was aimed to examine the impacts of distinct encapsulation methods on the stability of carotenoids under typical extrusion conditions. The study presents innovative encapsulation methods and investigates the protection efficacy of carotenoids degradation, as well as the effects on the physicochemical characteristics of carotenoid-rich products. Thus, spray drying, spray chilling, and their combination were compared based on their ability to protect carotenoids. Processing temperatures were 110 °C and 140 °C, and shear rates 500 and 2000 1/s. Carotenoid retention was determined, β- and α-carotene retention ranged from 17 to 44 % and 18 to 48 %, respectively. Upon storage at room temperature, the carotenoid content was stable for 15 days, followed by a marked reduction after 30 days. Extrudates enriched microparticles produced by spray chilling and the combined methods exhibited higher carotenoid protection during storage. They also showed better quality attributes, notably bulk density, high water absorption index, color properties, and carotenoid retention. These findings suggest that encapsulation can protect carotenoids during extrusion, and the protection can be tailored to optimize the attributes of the final products.

Fabrication of textured functional ingredient based on apple: Sesame by-product

The search for new sources of fortified components from low-cost and sustainable sources has become a trend in the last decade. Food byproducts containing valuable bioactive compounds such as dietary fiber, protein, and phytochemicals are being used as substrates for obtaining beneficial components that can promote health. Extrusion is an efficient technology for converting food by-products into nutrient-rich food ingredients. The objective of this work was to optimize the extrusion process to obtain the best combination of moisture content (14, 18 and 22%) and screw speed (SS) (120,150 and180 rpm), apple pomace (AP): semi-defatted sesame cake (SDSC) blends (25:75, 50:50 and 75:25 w/w) to fabricate textured functional ingredients (TFI) with high values of expansion ratio (ER), water absorption index (WAI), brightness level, total phenolic compounds (TPC) and antioxidant activity (AA) and lower hardness based on a central composite design. The optimal treatment was determined at 176 rpm SS, 18% moisture content and a ratio of (75:25) AP: SDSC. The desirability value has indicated an appropriate match between the predicted and the observed response. TFI exhibited higher soluble dietary fiber fraction (WAI) values and lower plate count values during 30 days of storage compared to the unprocessed by-product, suggesting that TFI could be successfully used for the manufacture of innovative, high quality products such as porridge, beverages, cookies, soups and others that could provide health benefits based on the values obtained.

Reduction of Alternaria Toxins via the Extrusion Processing of Whole-Grain Red Sorghum Flour

This study delved into the impact of two extrusion processing parameters-screw speed (SS at 400, 600, 800 RPM) and material moisture content in the extruder barrel (M at 12, 15, 18%) at constant feed rate (50 kg/h)-on reducing the content of alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA), and tentoxin (TEN) in whole-grain red sorghum flour. Ultra-performance liquid chromatography combined with a triple-quadrupole mass spectrometer (UPLC-MS/MS) was employed for the determination of Alternaria toxin levels. The extruder die temperature fluctuated between 136 and 177 °C, with die pressures ranging from 0.16 to 6.23 MPa. The specific mechanical energy spanned from 83.5 to 152.3 kWh/t, the torque varied between 88 and 162.8 Nm, and the average material retention time in the barrel ranged from 5.6 to 13 s. The optimal parameters for reducing the concentration of all Alternaria toxins with a satisfactory quality of the sorghum snacks were: SS = 400 RPM, M = 12%, with a reduction of 61.4, 76.4, 12.1, and 50.8% for AOH, AME, TeA, and TEN, respectively.

Exploring modified rice flour and supplementation approach to enhance resistant starch content: Visco thermal and structural characterization

Supplementation of rice flour with Apple Pomace Powder (APP) and Synthetic Vinegar (SV) was investigated to reduce the glycemic potential of ready-to-eat snacks using extrusion cooking. The aim of the study was to compare the increase in resistant starch and decrease in glycemic index of modified rice flour based extrudates after supplementing the Modified rice flour with synthetic vinegar and apple pomace. The effects of independent variables-SV (3-6.5 %) and APP (2-23 %) were evaluated on resistant starch, predicted glycemic index, glycemic load, L*, a*, b*, ΔE and overall acceptability of supplemented extrudates. Design expert predicted 6 % SV and 10 % APP as desirable conditions for enhancement of resistant starch and reduction of glycemic index. Resistant Starch (RS) of supplemented extrudates increased by 88 % while as pGI and GL was decreased by 12 % and 66 % respectively as compared to un-supplemented extrudates. L* value increased from 39.11 to 46.78, a* value increased from 11.85 to 22.55, b* value increased from 10.10 to 26.22 and Δ E increased from 7.24 to 17.93 respectively in supplemented extrudates. The results suggested that apple pomace and vinegar can act in synergy to reduce the in-vitro digestibility of rice based snacks, while maintaining the sensory acceptance of the developed product. The significant (p < 0.001) decrease in the glycemic index was achieved as the supplementation level increased. The increase in RS correlates with the decrease in glycemic index and glycemic load.

Corn Extrudates Enriched with Health-Promoting Ingredients: Physicochemical, Nutritional, and Functional Characteristics

The objective of this study was to evaluate the effects of different types of powder additions on the properties of corn extrudates. The following ingredients, which are good sources of bioactive compounds, were used to substitute corn flour: legume protein sources (2% pea, 5% broccoli, and 5% lucerne), plants (15% beetroot and 15% rosehip), and condiments (2% chili, 2% turmeric, 2% paprika, and 2% basil). The total polyphenolic content (TPC) and antioxidant activity (AA) increased when the corn flour was replaced with the different types of ingredients. The highest TPC was found for rosehip followed by the beet, basil, and broccoli additions. Compared to the raw formulations, all the extrudates, except the rosehip extrudate, showed a decrease in the TPC ranging from 11 to 41%, with the smallest loss (11%) occurring for basil and the highest loss (41%) occurring for the control extrudate, respectively. The same observation was recorded for the AA. For the extrudate enriched with rosehip, the TPC and AA increased by 20% and 16%, respectively. The highest level of protein digestibility was in the corn extrudate with the pea addition followed by broccoli and lucerne. The extruded corn samples with condiment additions had a lower glycemic index than the control extrudate. This study demonstrated the potential for the production of gluten-free corn extrudates enriched with ingredients from different sources with improved nutritional properties, conferring also a natural color in the final extrudates.

Structure and Texture Characteristics of Novel Snacks Expanded by Various Methods

The aim of this work was to evaluate the structure of novel potato-based snack foods supplemented with various levels of fresh carrot pulp by using X-ray micro-computed tomography, texture profile, and sensory analysis. Three different methods of extruded snack pellets expansion were used to obtain ready-to-eat crisps: deep-fat frying, microwave, and hot-air toasting. The obtained results revealed that the pellets expansion method affected the porosity, size of pores and wall thickness, texture properties, and notes of sensory analyses of the obtained crisps. Deep-fat frying had a similar influence to microwave heating on ready-to-eat crisps properties, and both methods were significantly different in comparison to hot-air toasting. Crisps based on snack pellets supplemented with the addition of fresh carrot pulp in the amount of 10 to 30% expansion through hot-air heating showed unsatisfactory expansion and texture, but it is highly advisable to use deep-fat frying and microwave heating to achieve attractive potato-carrot crisps.

Development of Extruded Noodles Incorporated with Dried Vegetables and the Evaluation of Quality Characteristics

In this study, extruded noodles incorporated with dried green bean, tomato, and okra seed powder was produced using an extruder at 80 °C and 100 °C barrel temperatures. Vegetable powder was blended with wheat flour at weight ratios of 0:100, 4:96, 8:92, and 12:88 to formulate composite flour. Quality characteristics, such as cooking properties, color, and textural properties together with antioxidant activities, total phenolic contents, sensory properties, and microstructures of the products were determined. In addition, the lycopene and β-carotene contents in noodles enriched with tomato powder were determined. The increase in the ratio of vegetable powder caused a decrease in the cooking time and water absorption capacity. The noodle products exhibited low cooking loss (less than 4%) and cooking time (less than 6 min). The L*, a*, and b*values of noodles varied from 53.76-78.30, 2.29-15.23, and 14.52-28.85, respectively. The β-carotene and lycopene contents increased with the increase of the tomato powder ratio. The antioxidant activity and the total phenolic content increased as the ratio of the vegetable powder used in all enriched noodle products increased. The noodles enriched with green bean and tomato powder gave the highest score of 7.40 in terms of the overall acceptance.

Effect of extrusion processing on techno-functional, textural and bioactive properties of whole grain corn flour-based breakfast cereals sweetened with honey

The present study investigated the effect of honey and extrusion processing parameters on techno-functional and bioactive properties of wholegrain corn flour breakfast cereals. The central composite rotatable design (CCRD) was used to plan the experiments using feed moisture (FM), extrusion temperature (ET), and honey level as process variables and sectional expansion ratio (SER), bulk density (BD), water absorption index (WAI), water solubility index (WSI), and textural hardness as response variables. The feed containing honey and wholegrain corn flour was extruded through a twin-screw extruder according to CCRD. The data were fit in the appropriate regression models based on model significance and insignificant lack-of-fit. The selected experiments from CCRD were considered for studying the bioactive properties and the effect of ET and honey level on bioactive properties was determined. The results of the study indicated that FM and honey adversely affected the SER, BD, and textural hardness while ET augmented these properties of breakfast cereals. The WAI decreased with an increase in honey level and ET during extrusion. The incremental addition of honey in the mix as well extrusion at elevated temperature led to higher WSI. The whole grain corn flour added with 10.22% honey and extruded at 16.06% FM, and 138.07 ^o C ET produced optimum quality breakfast cereals with 0.70 desirability. The total phenolic content of breakfast cereals decreased and antioxidant activity, and hydroxymethylfurfural content increased upon extrusion at the higher temperatures. Honey addition lowers the loss of phenolic content during extrusion and improved the antioxidant activity of breakfast cereals. This article is protected by copyright. All rights reserved.

Effects of chitosan oligosaccharide and hyriopsis cumingii polysaccharide on the quality of wheat flour and extruded flour products

Abstract

Effects of chitosan oligosaccharide (COS) and hyriopsis cumingii polysaccharide (HCP) on the quality of wheat flour and corresponding extruded flour products were investigated in this work. The results showed that both COS and HCP are conducive to the improvement of dough quality. Moreover, compared to control group samples, the moisture content, expansion ratio and oil absorption rate of the samples were increased and the hardness were decreased with the addition of COS. These phenomena indicate the quality of extruded flour products became better in the presence of COS as well. However, HCP has little or no effect on the quality of extruded flour products may be due to its degradation under high temperature and pressure extrusion. COS with higher stability exhibited better improvement effects on the quality of extruded flour products and showed a promising prospect for application in extruded food industry.

Graphical Abstract

Evaluation of nutritional characteristics and consumers’ acceptance of gluten-free sweet biscuits made from rice-based pregelatinized composite flours containing orange pomace and soy protein isolate

Gluten-free bakery products are usually deficient in dietary fiber and inferior sources of protein. Studies that have assessed sensory characterization of products prepared with orange pomace are scarce. This study evaluated the employment of 30% of rice-based pregelatinized composite flours (containing 15, 25 or 35% orange pomace blended with 5% soy protein isolate) on gluten-free biscuits. The target was the investigation of the nutritional profile and consumer’s acceptance of three short dough sweet biscuit samples. Thermoplastic extrusion was an efficient unit operation for the elaboration of a new gluten-free ingredient in which a by-product rich in total dietary fiber and a component with a high level of protein were employed. All pregelatinized composite flours in this study can be labeled as protein sources and can be claimed as high in total dietary fiber content, as well as two biscuit samples that can be labeled as total dietary fiber source. Also, all pregelatinized composite flours and biscuits presented low moisture and water activity, being microbiologically stable to room temperature (25 ± 2 °C). Complementarily, the results of the microbiological evaluations [(coagulase-positive Staphylococcus, thermotolerant coliform (45 °C) and Salmonella sp. (absence in 25 g)] of the biscuits and their comparison with the Brazilian microbiological standards legislation attested their safety. Concerning the sensory analysis, adults’ results showed that the flavor attribute might be responsible for increasing the overall impression score of a sample. In contrast, children’s results showed that they did not distinguish (p ≥ 0.05) two of three samples of biscuits analyzed.

Utilization of Food Processing By-products in Extrusion Processing: A Review

The processing of agricultural products into value-added food products yields numerous by-products or waste streams such as pomace (fruit and vegetable processing), hull/bran (grain milling), meal/cake (oil extraction), bagasse (sugar processing), brewer's spent grain (brewing), cottonseed meal (cotton processing), among others. In the past, significant work in exploring the possibility of the utilization of these by-products has been performed. Most by-products are highly nutritious and can be excellent low-cost sources of dietary fiber, proteins, and bioactive compounds such as polyphenols, antioxidants, and vitamins. The amount of energy utilized for the disposal of these materials is far less than the energy required for the purification of these materials for valorization. Thus, in many cases, these materials go to waste or landfill. Studies have been conducted to incorporate the by-products into different foods in order to promote their utilization and tackle their environmental impacts. Extrusion processing can be an excellent avenue for the utilization of these by-products in foods. Extrusion is a widely used thermo-mechanical process due to its versatility, flexibility, high production rate, low cost, and energy efficiency. Extruded products such as direct-expanded products, breakfast cereals, and pasta have been developed by researchers using agricultural by-products. The different by-products have a wide range of characteristics in terms of chemical composition and functional properties, affecting the final products in extrusion processing. For the practical applications of these by-products in extrusion, it is crucial to understand their impacts on the qualities of raw material blends and extruded products. This review summarizes the general differences in the properties of food by-products from different sources (proximate compositions, physicochemical properties, and functional properties) and how these properties and the extrusion processing conditions influence the product characteristics. The discussion of the by-product properties and their impacts on the extrudates and their nutritional profile can be useful for food manufacturers and researchers to expand their applications. The gaps in the literature have been highlighted for further research and better utilization of by-products with extrusion processing.

The influence of the extrusion process on the nutritional composition, physical properties and storage stability of black chokeberry pomaces

The study examined the influence of the process of extrusion on the physical properties and nutritional composition of black chokeberry pomaces. It has been determined that the extrusion process resulted in a reduction of the content of anthocyanins and fibre, but an increase of the contribution of simple sugars. In order to assess the phase transitions occurring in the products, a state diagram was utilized, which was constructed using the freezing and vitrification curve and values characterizing the conditions of maximum cryoconcentration. The determined values of critical water activity (based on water activity concepts) indicate that pomaces and extrudates retain crispiness in storage under moderate environmental relative humidity conditions. However, in the case of the glass transition concept, the determined values of water activity indicate that products stored in room temperature must be protected against the influence of humidity.

Production of high fiber ready-to-eat expanded snack from barley flour and carrot pomace using extrusion cooking technology

The effects of feed moisture content (14, 17 and 20% db), die temperature (120, 145 and 170 °C) and carrot pomace content (10, 17.5 and 25%) on the sectional expansion index, hardness, porosity, micro and macro structure and sensory properties of high fiber expanded barley-carrot pomace snack were investigated using a central composite design. Results showed that with increasing the moisture content the hardness of the extruded snacks increased while their expansion ratio decreased. The hardness decreased with increasing the die temperature, but the expansion ratio increased with increasing the die temperatures to up to 145 °C and decreased afterwards. An increase in carrot pomace content decreased the expansion ratio and cell average size while the hardness and cell wall thickness increased. The optimum condition for production of expanded barley-carrot pomace snack was 10% carrot pomace content, 142.7 °C die temperature and 14.02% moisture content. During extrusion cooking, the soluble dietary fiber of barley-carrot pomace snack increased, but no change on the total dietary fiber content was observed. Therefore, the extruded snacks prepared from barley flour and carrot pomace had high nutritional value.

Application of extrusion technology in plant food processing byproducts: An overview

The food processing industry generates an immense amount of waste, which leads to major concerns for its environmental impact. However, most of these wastes, such as plant-derived byproducts, are still nutritionally adequate for use in food manufacturing. Extrusion is one of the most versatile and commercially successful processing technologies, with its widespread applications in the production of pasta, snacks, crackers, and meat analogues. It allows a high degree of user control over the processing parameters that significantly alters the quality of final products. This review features the past research on manufacture of extruded foods with integration of various plant food processing byproducts. The impact of extrusion parameters and adding various byproducts on the nutritional, physicochemical, sensory, and microbiological properties of food products are comprehensively discussed. This paper also provides fundamental knowledge and practical techniques for food manufacturers and researchers on the extrusion processing of plant food byproducts, which may increase economical return to the industry and reduce the environmental impact.

In Vitro Antioxidant Activity Optimization of Nut Shell (Carya illinoinensis) by Extrusion Using Response Surface Methods

The pecan (Carya illinoinensis) nut shell is an important byproduct of the food processing industry that has not been previously explored as an antioxidant compound. This work aims to study the effect of the extrusion temperature and screw speed on the moisture content, water and oil absorption index, water solubility index, color, phenolic compounds, condensed tannin compounds, and antioxidant activity of pecan nut shell extrudates. Extrusion variables were adjusted using a response surface methodology. Extrusion, performed at 70 °C and 150 rpm, almost doubled the concentration of polyphenols in the non-extruded shell and significantly increased radical scavenging activity. Compounds in extrudates, performed at 70 °C and 150 rpm, were quantified by high-performance liquid chromatography (HPLC) with a diode-array detector (DAD) and identified by liquid chromatography coupled with time-of-flight mass spectrometry (LC-MSD-TOF). Extrusion significantly increased most phenolic acid compounds, including gallic acid, ellagic acid pentose, ellagic acid, dimethyl ellagic acid rhamnoside, and dimethyl ellagic acid. The soluble fiber in extrudates was more than three-fold higher than in the control. Therefore, extrusion at 70 °C and 150 rpm increased the concentration of phenolic compounds, antioxidant activity, and total dietary and soluble fiber. Our findings support the notion that extruded pecan nut shell can be used in clean-label products and improve their nutraceutical value.

Single screw extrusion of apple pomace-enriched blends: Extrudate characteristics and determination of optimum processing conditions

Response surface methodology was used to investigate the single screw extrusion of apple pomace–defatted soy flour–corn grits blends and the product properties. Five different blends at a level of 0–20% w/w apple pomace were extrusion cooked with varied barrel and die temperature (100–140℃), screw speed (100–200 rpm), and feed moisture content (14–20% wet basis). Increasing apple pomace content in the blends significantly ( P < 0.05) increased the bulk density, the total phenolic content, and the antioxidant activity of the extrudates. The expansion ratio increased with pomace inclusion level of 5% but decreased significantly ( P < 0.05) at higher levels of pomace inclusion (10–20%). Moisture content had quadratic influence on water absorption and solubility indices. Optimal extrusion cooking conditions most likely to produce apple pomace-enriched extruded snack products were at 140℃ barrel and die temperature, 20% feed moisture content, and 200 rpm screw speed. The results indicated active interaction between apple pomace and starch during expansion process.

Development of functional extruded snacks by utilizing paste shrimp (Acetes spp.): process optimization and quality evaluation

BACKGROUND

Functional extruded snacks were prepared using paste shrimp powder (Acetes spp.), which is rich in protein. The process variables required for the preparation of extruded snacks was optimized using response surface methodology. Extrusion temperature (130-144 °C), level of Acetes powder (100-200 g kg^-1 ) and feed moisture (140-200 g kg^-1 ) were selected as design variables, and expansion ratio, porosity, hardness, crispness and thiobarbituric acid reactive substance value were taken as the response variables.

RESULTS

Extrusion temperature significantly influenced all the response variables, while Acetes inclusion influenced all variables except porosity. Feed moisture content showed a significant quadratic effect on all responses and an interactive effect on expansion ratio and hardness. Shrimp powder incorporation increased the protein and mineral content of the final product. The extruded snack made with the combination of extrusion temperature 144.59 °C, feed moisture 178.5 g kg^-1 and Acetes inclusion level 146.7 g kg^-1 was found to be the best one based on sensory evaluation.

CONCLUSION

The study suggests that use of Acetes species for the development of extruded snacks will serve as a means of utilization of Acetes as well as being a rich source of proteins for human consumption, which would otherwise remain unexploited as a by-catch. © 2017 Society of Chemical Industry.

Co-extrusion of food grains-banana pulp for nutritious snacks: optimization of process variables

Present study was undertaken to optimize the process conditions for development of food grains (maize, defatted soy flour, sesame seed)-banana based nutritious expanded snacks using extrusion processing. Experiments were designed using Box-Behnken design with banana pulp (8-24 g), screw speed (300-350 rpm) and feed moisture (14-16% w.b.). Seven responses viz. expansion ratio (ER), bulk density (BD), water absorption index (WAI), protein, minerals, iron and sensory acceptability were considered for optimizing independent parameters. ER, BD, WAI, protein content, total minerals, iron content, and overall acceptability ranged 2.69-3.36, 153.43-238.83 kg/m³, 4.56-4.88 g/g, 15.19-15.52%, 2.06-2.27%, 4.39-4.67 mg/100 g (w.b.) and 6.76-7.36, respectively. ER was significantly affected by all three process variables while BD was influenced by banana pulp and screw speed only. Studied process variables did not affected colour quality except 'a' value with banana pulp and screw speed. Banana pulp had positive correlation with water solubility index, total minerals and iron content and negative with WAI, protein and overall acceptability. Based upon multiple response analysis, optimized conditions were 8 g banana pulp, 350 rpm screw speed and 14% feed moisture indicating the protein, calorie, iron content and overall sensory acceptability in sample as 15.46%, 401 kcal/100 g, 4.48 mg/100 g and 7.6 respectively.

Use of Red Cactus Pear (Opuntia ficus-indica) Encapsulated Powder to Pigment Extruded Cereal

Encapsulated powder of the red cactus pear is a potential natural dye for the food industry and a known antioxidant. Although the use of this powder is possible, it is not clear how it alters food properties, thus ensuing commercial acceptability. The aim of this study was to evaluate the effect of encapsulated powder of the red cactus pear on the physicochemical properties of extruded cereals. The powder was mixed (2.5, 5.0, and 7.5% w/w) with maize grits and extruded (mix moisture 22%, temperature 100°C, and screw speed 325 rpm). The physical, chemical, and sensory characteristics of the extruded cereal were evaluated; extruded cereal without encapsulated powder was used as a control. All cereal extrudates pigmented with the encapsulated powder showed statistically significant differences (P<0.05) in expansion, water absorption, color, density, and texture compared to the control. The encapsulated powder had a positive effect on expansion and water absorption indices, as well as color parameters, but a negative effect on density and texture. Extruded cereal properties were significantly (P<0.05) correlated. Sensorially, consumers accepted the extruded cereal with a lower red cactus pear powder content (2.5% w/w), because this presented characteristics similar to extruded cereal lacking pigment.

Extrusion and Extruded Products: Changes in Quality Attributes as Affected by Extrusion Process Parameters: A Review

Extrusion of foods is an emerging technology for the food industries to process and market a large number of products of varying size, shape, texture, and taste. Extrusion cooking technology has led to production of wide variety of products like pasta, breakfast cereals, bread crumbs, biscuits, crackers, croutons, baby foods, snack foods, confectionery items, chewing gum, texturized vegetable protein (TVP), modified starch, pet foods, dried soups, dry beverage mixes etc. The functional properties of extruded foods plays an important role for their acceptability which include water absorption, water solubility, oil absorption indexes, expansion index, bulk density and viscosity of the dough. The aim of this review is to give the detailed outlines about the potential of extrusion technology in development of different types of products and the role of extrusion-operating conditions and their effect on product development resulting in quality changes i.e physical, chemical, and nutritional, experienced during the extrusion process.

The Effects of CO2 Injection and Barrel Temperatures on the Physiochemical and Antioxidant Properties of Extruded Cereals

The effects of CO₂ injection and barrel temperatures on the physiochemical and antioxidant properties of extruded cereals (sorghum, barley, oats, and millet) were studied. Extrusion was carried out using a twin-screw extruder at different barrel temperatures (80, 110, and 140°C), CO₂ injection (0 and 500 mL/min), screw speed of 200 rpm, and moisture content of 25%. Extrusion significantly increased the total flavonoid content (TFC) of extruded oats, and β-glucan and protein digestibility (PD) of extruded barley and oats. In contrast, there were significant reductions in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, PD of extruded sorghum and millet, as well as resistant starch (RS) of extruded sorghum and barley, and total phenolic content (TPC) of all extrudates, except extruded millet. At a barrel temperature of 140°C, TPC in extruded barley was significantly increased, and there was also an increase in DPPH and PD in extruded millet with or without CO₂ injection. In contrast, at a barrel temperature of 140°C, the TPC of extruded sorghum decreased, TFC of extruded oats decreased, and at a barrel temperature of 110°C, PD of extruded sorghum without CO₂ decreased. Some physical properties [expansion ratio (ER), specific length, piece density, color, and water absorption index] of the extrudates were significantly affected by the increase in barrel temperature. The CO₂ injection significantly affected some physical properties (ER, specific length, piece density, water solubility index, and water absorption index), TPC, DPPH, β-glucan, and PD. In conclusion, extruded barley and millet had higher potential for making value added cereal-based foods than the other cereals.