Impact of extruder die temperature and nitrogen gas injection on the physical quality of soybean protein meat analogues
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The food sector is a major contributor to greenhouse gas emissions, and there is an urgent need to shift low-carbon footprint foods. Incorporating plant-based foods, such as meat analogues, in our diets can help mitigate the environmental impact of animal-based foods. Plant-based meat analogues are most commonly produced using high-moisture extrusion cooking, which transforms plant proteins (e.g., soy protein) into products that resemble the sensory characteristics of meat products. However, developing meat analogues with textural attributes similar to meat products is challenging due to the narrow operating range of extrusion process parameters that can provide texturized products with the desired layered and fibrous structure. This study used a novel gas-assisted high-moisture extrusion technique to explore the potential of this technique to improve the textural quality of soy protein-based meat analogues. The degree of texturization as well as the physical quality of meat analogues were studied as a function of long cooling die temperature (DT) and nitrogen gas injection pressure (GP). All extrusion operating parameters were kept constant except for DT (35, 50 and 65 °C) and GP (0, 1 and 2.5 bar). The texture analysis showed that different combinations of DT-GP led to a wide variation in the transversal cutting force (3.97-5.79 N), longitudinal cutting force (3.73-6.00 N), hardness (143.63-194.27 N), chewiness (106.01-150.49 N) and gumminess (115.15-161.85 N). The lowest density was observed for the meat analogues produced at the treatment combination of lowest DT and highest GP. The X-ray microtomography analyses of bubbles formed in the meat analogues produced at a pressure of 2.5 bar GP revealed that variation in DT impacted the properties of the gas volume fraction in the meat analogues. It was observed that an increase in DT led to an increased maximum structure thickness and sphericity while causing a decrease in the major diameter of the bubbles. These wide variations in textural and microstructural attributes indicate that gas-assisted high-moisture extrusion holds immense potential to improve the sensory properties of meat analogues.