Effects of extrusion process parameters on cooking characteristics and physicochemical, textural, thermal, pasting, microstructure, and nutritional properties of millet‐based extruded products: A review

Abstract

In the current century, consumers are more concerned about the quality and safety of food. They are focusing more on high nutritional value, tasty, and visually appealing food items which are available at low cost. Food industries are making a consistent effort in developing such food products from nutrition‐rich ingredients such as millet using the new technology of food processing such as extrusion. Millet is rich sources of protein, fiber, antioxidants, polyphenols, and micronutrients which make it an excellent raw material for developing a variety of nutritious and value‐added extruded food products. In food industries extrusion technology is being used to develop a wide range of food products with better product quality. The study of the effects of extrusion processing parameters, namely feed moisture (FM), extruder screw speed (FM), and barrel temperature (BT), and co‐ingredients on product quality characteristics is an important concern for developing a food product with better quality. The review focuses on various studies that have been reported on the development of millet‐based extruded products. Emphasis has been given on effects of co‐ingredients and extrusion processing parameters on extruder operation parameters, namely mass flow rate, specific mechanical energy, average residence time, torque, and die pressure, and the cooking characteristics, physicochemical, pasting, textural, thermal, nutritional properties, and overall acceptability of the millet‐based extruded products. The extrusion process parameters widely influence the product characteristics. During extrusion cooking, starch gelatinization, protein denaturation, modification of lipid, Maillard reactions, and complex formation among starch, protein, and lipids lead to significant changes in chemical and physical characteristics of the extruded products. Extrusion cooking has a significant effect on the inactivation of enzymes, and reduction in anti‐nutritional factors. Extrusion processing at high BT with high FM increases the degree of starch gelatinization which leads to an increase in water absorption index and expansion of the product. An increased degree of starch gelatinization decreases the melt viscosity and thereby decreases the torque and specific mechanical energy. Proper control of extrusion conditions and proportion of co‐ingredients give a product with higher nutritional value, better texture, and better sensory characteristics with high overall consumers' acceptability. Practical Applications Ready‐to‐eat (RTE) snacks are in high demand among consumers in recent years, owing to their better texture quality, good sensory characteristics, and easy availability at low cost. Extruded snacks are valuable food products in terms of production, packaging, handling, transportation, storage, and shelf‐life. Food industries are highly capable of improving consumers' acceptability and nutritional value by altering the extrusion process parameters and co‐ingredients. Proper monitoring of extrusion process parameters and the pro...

Quinoa Snack Production at an Industrial Level: Effect of Extrusion and Baking on Digestibility, Bioactive, Rheological, and Physical Properties

“…In extrudates, the pasting temperature is lower than in crude, because the gelatinization and structural degradation of starch during the extrusion process generates a lower swelling capacity so that the starch granule gelatinizes earlier. Previous researchers [ 52 , 53 ] obtained a similar trend in millet-based extruded products.…”

Preparation of Low Glycemic Rice and Comparison of Its Physicochemical Properties, Cooking Characteristics, Starch Digestibility and Microstructure with Raw Rice (Swarna Cv)

“…The lower peak viscosity of LGR is associated with the pre-gelatinization and degradation of starch during extrusion. Yadav et al [36] have stated that gelatinization and structural degradation of starch during the extrusion process reduce the swelling capacity and thereby, result in lower viscosity. Similar results were reported by Dalbhagat & Mishra [25] for fortified rice kernels and Hagenimana et al [37] for extruded rice flour.…”

“…Moisture flashing during extrusion could have caused these cracks and voids in the LGR. During extrusion, a sudden flash of moisture causes expansion in the hot viscoelastic melt at the die opening, where bubbles grow and eventually rupture, resulting in a large number of voids [35,36]. The significantly shorter cooking time of LGR also reflects the formation of cracks and voids during extrusion process.…”

Kidney Bean Substitution Ameliorates the Nutritional Quality of Extruded Purple Sweet Potatoes: Evaluation of Chemical Composition, Glycemic Index, and Antioxidant Capacity

“…Extruded foods have been a topic of discussion in the food industry for many years and continue to be a popular and convenient food choice for many consumers. Some concerns have been raised regarding the nutritional quality and safety of extruded foods [ 8 , 9 ]. Extruded foods are made by processing a mixture of ingredients, such as grains and legumes, under high pressure and temperature to create a dough-like material that is then pushed through a die to give it a specific shape.…”

“…Extruded foods are made by processing a mixture of ingredients, such as grains and legumes, under high pressure and temperature to create a dough-like material that is then pushed through a die to give it a specific shape. One concern with extruded foods is that the high heat and pressure used during processing can cause a loss of nutrients, especially vitamins and bioactive compounds [ 8 , 9 ]. Additionally, some studies have suggested that certain compounds formed during the extrusion process may have negative health effects.…”