Innovations in food extrusion technologies: Applications, advances, and future prospects-a review

Contemporary dining habits have spurred a shift in ready-to-eat (RTE) snack production, with mushrooms offering a nutritional boost due to their protein, carbohydrate, fibre and vitamin content. Proximate composition data aid in creating snacks with balanced nutrition. Mushrooms also contribute antioxidants and antimicrobial compounds, adding a health dimension. Extrusion cooking, known for adaptability and energy efficiency, improves texture, nutrition and shelf life. Though concerns exist about oil intake, frying remains popular for taste and consistency enhancement, requiring careful management. Baking extends shelf life and preserves flavour while enhancing nutrient availability. Various studies highlight the potential of these techniques to meet consumer preferences for convenient, appealing and health-conscious snacks by incorporating ingredients like legume protein isolates, nuts and seeds, etc. The RTE snack industry evolves to provide healthier options driven by technological innovations and sustainability practices, with personalised and functional snacks on the horizon. The study aims to explore and highlight the nutritional benefits of incorporating mushrooms into RTE snacks and discusses the unique advantages of extrusion, frying and baking in snack production.

Extrusion technology is gaining increasing popularity in the global agro-food processing industry, which employs mixing, forming, texturing and cooking to develop a novel food product. Extrusion cooking is a high-temperature short-time (HTST) process which inactivates enzymes and reduces microbial contamination. Extrusion cooking is mostly preferred, as it has high productivity and significant nutrient retention as compared to conventional cooking. The extrusion technology has become an important technique in food processing industries with its numerous advantages over other processing methods. It is one of the cost effective method and offers a platform for processing of different products from various food groups by modifying minor or major ingredients and processing conditions. Extrusion technology is applied in food processing industry for the development of variety of snacks, pasta, breakfast cereals, pet foods, supplementary foods and other textured foods. It is an economical technology for incorporating food processing by-products and residue back into the food stream. The versatility of extrusion technology makes it convenient for development of nutritionally rich fortified products and value added products with combination of different inexpensive raw materials. Extruded products have less moisture content, longer shelf life and are microbiologically safe. The variability of the product and high quality, productivity of the new foods and minimal processing time are the advantages of this technology.

The fundamental principles of extrusion, as applied to food processing, are described. Basic extrusion theory, hardware, various commercial uses, and role of process and design parameters in specific food applications are provided. Innovations in food extrusion technology are enabling its rapid expansion and applicability in diverse areas related to bioprocessing and value addition. Ongoing research spans various cutting edge areas including nutrition and nanotechnology. As an example of ongoing extrusion research that aligns with the main theme of this book, a recent study is described that relates raw material particulate rheology to the granular flow regime in a single screw food extruder. Corn meal and corn flour were used as model particulate systems for the study. Various particulate-scale characteristics and flow parameters of these two materials were determined using a powder rheometer, which is a promising new off-line tool. Properties such as basic flow energy (10.3 mJ/g for corn flour versus 8.7 mJ/g for corn meal), specific energy (7.1 mJ/g versus 4.4 mJ/g), cohesion (1.9 kPa versus 0.8 kPa) and flow function (3.4 versus 10.2) were good indicators of flowability in an extruder. These results were validated in a particulate flow study involving the two model systems in a pilot-scale single screw extruder. Visualization data, obtained using a transparent Plexiglas window, confirmed that corn flour exhibited much higher flow impedance as compared to corn meal during extrusion. It was concluded that powder rheometry is a potentially valuable tool for design of screw metallurgy and geometry, although further studies are needed in this area.

The extrusion technique, which combines mixing, shaping, texturing, and heating to create a unique food product, is gaining popularity in the worldwide agro-food processing sector. Extrusion cooking is a high-temperature, short-time (HTST) method that kills bacteria and inactivates enzymes. Compared to conventional cooking, extrusion cooking is favored because of its high productivity and substantial nutrient retention. Extrusion technology has become an essential tool in the food processing industry with its various benefits over other processing methods. It is a low-cost approach that provides a platform for processing a variety of items from several food categories by altering major or minor components and processing conditions. Extrusion technique is used in the food sector to create a wide range of supplemental foods, pet foods, morning cereals, pasta, snacks, and other textured foods. It's a low-cost method of reintroducing food processing waste and by-products into the food supply. Extrusion technology's flexibility allows for the production of value-added products and nutritionally dense fortified goods using various low-cost raw ingredients. Extruded goods are microbiologically safe, have a longer shelf life, and have less moisture content. This technology's advantages include product diversity and excellent quality and new food productivity and low processing time.

Currently, about 5% of the earth's population suffers from gluten-related disorders. Modern technologies for gluten-free diets and filling the protein deficit are aimed at manufacturing gluten-free (GF) pasta products using non-conventional plant raw materials with high biological value. GF grains and crops (rice, corn, buckwheat, amaranth, quinoa, etc.) are used to produce GF pasta products. However, there is a scarcity of studies that comprehensively understand GF flour addition on the nutritive, sensory and cooking properties. Therefore, the scope of this literature review covers the main types of non-conventional raw materials for GF pasta products and summarizes the research on pasta products made from them. Results indicate that the rheological and sensory attributes of pasta made from pure GF flours such as rice or corn still requires a deeper study of technological processes in producing GF pasta. Incorporating nutrient-dense ingredients such as amaranth, quinoa, sorghum, and chia flours not only enhances the nutritional profile of gluten-free pasta but also offers opportunities for diverse culinary applications. The improvement of sensory attributes in rice-, corn-, buckwheat-based pasta, coupled with the effective use of cooking enhancers like xanthan gum, transglutaminases, inulin, and alternative starches, paves the way for creating more palatable gluten-free options. As techniques such as high-temperature treatment, extrusion cooking, and starch pregelatinization become more refined, future developments may focus on optimizing these processes to further improve the texture, taste, and overall quality of gluten-free pasta. Continued research and innovation in ingredient selection and processing technologies will be crucial for meeting the growing demand for gluten-free products that do not compromise on culinary experience or nutritional value.

The aim of this paper was to review the different definitions of extrusion cooking of food available in literature. Extrusion cooking of food entails different unit operations in a single process whereby different food ingredients are uniformly mixed and forcefully passed through a die. It has been used in producing various shapes and sizes of food products. Extrusion technology is mostly applied in the manufacture of snacks, breakfast cereals and ready-to-eat food products and the more modern 3D breakfast cereals and snacks. Extrusion cooking involves a high temperature short time process and is very useful in producing low-fat snacks. Extrusion cooking of food entails different unit operations in a single process. An extruder has five major components, pre-conditioner, barrel, screw, die (usually with cutter) and the feeding system. It originated in the metallurgical industry. Food extruder may be classified thermally, geometrically or conveying mechanism based on applications, design and configurations. Extruders have the same operating principles, basically, a screw extruder is made up of a rotating screw in a fixed barrel and a die at the exit. Different types ofextruders have advantages and limitations. Different researchers have used a variety of raw material for extrusion cooking ranging from flours of cassava, maize, wheat, corn, millet and soybean. Pasta and breakfast cereals are the commonest extruded cereal-based food products.

Today's computational capacity enables the use of advanced statistical algorithms to identify relationships between features in high-dimensional data. Additive manufacturing methods are typically complex processes with many variables in both printing parameters and material properties. Consequently, machine learning offers opportunities for process optimization, quality assurance, and innovation in both Material Extrusion and Powder Bed Fusion technologies. The paper reviews the recent findings in machine learning applications for these additive manufacturing techniques, focusing on areas like defect detection, process control, and material property prediction. Key trends reveal that, while machine learning offers promising enhancements for additive manufacturing, challenges remain in data scarcity, model generalization, real-time adaptability. Our findings underscore the potential of machine learning to improve the overall quality of additive manufacturing processes by predicting optimal manufacturing parameters.

Extrusion technology is used widely in the manufacture of a range of breakfast cereals and snacks for human consumption and animal feeds. To minimise consumer exposure to mycotoxins, the levels of deoxynivalenol (DON) and zearalenone (ZON) in cereals/cereal products and fumonisins B1 and B2 (FB1 and FB2) in maize are controlled by European Union legislation. Relatively few studies, however, have examined the loss of Fusarium mycotoxins during processing. The behaviour of FB1, FB2 and fumonisin B3 (FB3), DON and ZON during extrusion of naturally contaminated maize flour and maize grits is examined using pilot-scale equipment. DON and ZON are relatively stable during extrusion cooking but the fumonisins are lost to varying degrees. There is some loss of ZON when present in low concentrations and extruded at higher moisture contents. The presence of additives, such as reducing sugars and sodium chloride, can also affect mycotoxin levels. Moisture content of the cereal feed during extrusion is important and has a greater effect than temperature, particularly on the loss of fumonisins at the lower moistures. The effects are complex and not easy to explain, although more energy input to the extruder is required for drier materials. However, on the basis of these studies, the relationship between the concentration of Fusarium toxins in the raw and finished product is toxin- and process-dependent.

In order to improve the edible quality of hybrid indica rice (Type 9718) in China, extrusion technology might be considered to create the so-called "reformed rice." Effects of extrusion parameters such as feed water content, barrel temperature and extruder screw speed on physicochemical properties of rice extrudates were investigated. Water-soluble carbohydrates and enzyme sensitivity (α-amylase) of extrudates were basically higher than those of parboiled rice. Water absorption index of all extrudates was lower than that of parboiled rice (4.95 g/g), which indicated that extrusion cooking was not only a heating procedure but also a process with shear force, degradation of rice starch. Through statistical analysis, it was found that both barrel temperature and feed water content could positively be correlated with physicochemical properties of extrudates excluding bulk density. Texture studies indicated that hardness of all hybrid indica rice (Type 9718) extrudates was lower than that of cooked raw rice and parboiled rice. The scanning electron microscope images demonstrated that there was indeed a granular gel network formed within the rice extrudates. PRACTICAL APPLICATIONS Extrusion cooking technology is used for cereal and protein processing in the food. In the present study, this technology was employed to investigate the effects of feed water content, barrel temperature and extruder screw speed on the physicochemical properties of hybrid indica rice (Type 9718) extrudates. It was found that extrusion cooking was not only a heating procedure but also a process with shear force and pressure, destruction and degradation of rice starch, the most important constituent which could affect physicochemical properties in rice extrudates. Textural studies had shown that under proper extrusion parameters, the texture of hybrid indica rice (Type 9718) extrudates was in fact much better than that of cooked raw rice and parboiled rice.

Extrusion cooking is one of the most relevant innovations of the 20th century and has been extensively used for the production of savory snacks. These technologies have gradually gained acceptance because they are a continuous process, energy-efficient, environmentally friendly, and save labor as well as industrial floor space. The main advantage of extrusion technologies is their versatility. Extrusion cooking technologies are widely used for production of many grain-based snacks. There are basically two major categories of extrusion processes: direct extrusion, which yields second-generation expanded puffs, and production of half products or pellets for the manufacturing of third-generation snacks. When the two processes are compared, the requirements of raw materials, formulations, tempering or conditioning, and processing conditions are quite different. Direct extruded puffs are produced with a single or twin extruder and are usually baked or fried after extrusion and then flavored with liquid or powdered seasonings. On the other hand, most pellets or half-products are obtained after two sequential extrusion stages named cooking and forming, where two separate extruders are employed, however, novel units can perform both steps. The resulting pellets are carefully dehydrated and then expanded by frying, high-temperature, or microwave baking. The two main novel extrusion technologies are coextrusion and supercritical CO2 extrusion (SCFX). The first one allows the production of extrudates with two different materials, yielding snacks with inner fillings, whereas the SCFX technology produces expanded extrudates with unique texture at lower operational temperatures, preserving nutritional and functional compounds.

Chapter 6 - Extrusion Technology and Glass Transition

Innovations in food extrusion technology are enabling its rapid expansion and applicability in diverse areas related to bioprocessing and value addition. This study relates raw material particulate rheology to the granular flow in a single screw food extruder. Raw materials based on corn (i.e., meal, flour, and starch), wheat (i.e., farina, flour, and starch), and sucrose (i.e., granulated, superfine, and powdered) were used as model particulate systems for the study. Various particulate-scale characteristics and flow parameters of these nine materials were determined using a powder rheometer, a promising new offline tool. Properties such as basic flow energy, specific energy, cohesion, stability index, flow function, and effective angle of internal friction were good indicators of flowability in an extruder. Corn meal exhibited lower energy requirements and a higher propensity for flow than corn flour (6.7 mJ/g versus 10.7 mJ/g, and “free-flowing” versus “cohesive,” according to Flow Function classifications), with wheat farina showing similar results when compared to wheat flour (5.8 mJ/g versus 7.9 mJ/g, and “highly free-flowing versus “cohesive,” according to Flow Function classifications), although both wheat systems showed comparatively lower energy requirements than their comparable corn systems. Sugar, being of a different base material and particle shape, behaved differently than these starch-based materials—flow energy decreased and propensity to flow increased (51.7 mJ/g versus 8.0 mJ/g, and “free-flowing” versus “highly free-flowing”). This large energy requirement for coarse sugar particles may be attributed more to particle shape than composition, as the sharp edges of sugar can interlock and increase restriction to movement through the sample. The starch-based results were validated in a particulate flow study involving the above model systems (corn meal, corn flour, wheat farina, and wheat flour) in a pilot-scale single screw extruder. Visualization data, obtained using a transparent plexiglass window during extrusion, confirmed that the flours exhibited higher flow energy requirements and a lower flow factor when compared to the coarser-particle size corn meal during extrusion, seen by the increased peak heights and barrel fill.

Assessment of taurine bioavailability in pelleted and extruded diets with red drum Sciaenops ocellatus

Chapter 13 - Role of Extrusion in Food Processing

Modification of rice protein by extrusion technology can broaden the range of processing and applications for food and feed raw materials. In this study, rice protein was extruded at different screw speeds (100–250 rpm), extrusion temperatures (90–150 °C), and moisture contents (25–40%). Compared with an unextruded protein, the functional properties and structural properties of textured rice protein were evaluated. The results showed that, after extrusion, the solubility of protein was improved, by up to 19.76%, which was 45.23% higher than pre-extrusion; the water holding capacity of extruded rice protein was highest at 200 rpm, 130 °C, and 25%, which could be enhanced by 37.74%; the emulsion stability was enhanced by 152.82% at 200 rpm, 130 °C, and 35%. Under extrusion, the content of sulfhydryl and disulfide bonds of rice protein decreased significantly; the hydrogen bond content increased, and the ionic bond content decreased; the hydrophobic effect decrease, except at 200 rpm, 130 °C, and 40%. The microstructure changed significantly after extrusion, producing protein aggregates with a tight structure. No new characteristic peaks appeared after extrusion, but transformation occurred between the components of the secondary structure: β-sheet and β-turn angles to an α-helix structure toward the transformation, but β-sheet was still the main component. As a safe and efficient modification method, extrusion cooking can effectively improve the functional properties of rice protein to enrich the application of rice protein resources.