A growing demand for alternative sources of texturized vegetable protein (TVP) has resulted from various factors including plant allergies, perceived health risks associated with genetically modified organisms (GMO), animal welfare beliefs, and lifestyle choices. Soy and wheat have been the primary ingredients in TVP over the past few decades, but desires for clean label ingredients (especially non-GMO and nonallergenic) have led to demand for alternative plant protein ingredients such as pea protein. To understand the capabilities of pea protein to create meat-like texture with additions of another protein source that also contributes starch, this study focused on extruding pea protein with increasing amounts of chickpea flour (CPF). Six treatments, with inclusions of CPF ranging from 0 to 50%, were processed on a twinscrew extruder to determine the optimal ratio of pea protein isolate to CPF. Bulk density was the greatest with 20% CPF (272 g/L) and resulted in the lowest water holding capacity (55.5%). Texture profile analysis (TPA) hardness, springiness, and chewiness showed optimum results for the 10 and 20% CPF (674 to 1024 g, 72.1 to 80.7%, 400 to 439, respectively). With no CPF addition, protein interactions created a strong network exhibiting extreme springiness (91.3%). Addition of CPF greater than 20% resulted in a detrimental decrease in hardness by 38 to 84% and chewiness by 73 to 92%. Phase transition analysis and specific mechanical energy data provided a greater understanding of the degree of texturization during extrusion. Inclusion of CPF between 10 and 20% led to the optimum protein to starch ratio, allowing adequate protein texturization and creating product characteristics that could potentially mimic meat.

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Four commercial pea protein isolates were analyzed for their physico-chemical properties including water absorption capacity (WAC), least gelation concentration (LGC), rapid visco analyzer (RVA) pasting, differential scanning calorimetry (DSC)-based heat-induced denaturation and phase transition (PTA) flow temperature. The proteins were also extruded using pilot-scale twin-screw extrusion with relatively low process moisture to create texturized plant-based meat analog products. Wheat-gluten- and soy-protein-based formulations were similarly analyzed, with the intent to study difference between protein types (pea, wheat and soy). Proteins with a high WAC also had cold-swelling properties, high LGC, low PTA flow temperature and were most soluble in non-reducing SDS-PAGE. These proteins had the highest cross-linking potential, required the least specific mechanical energy during extrusion and led to a porous and less layered texturized internal structure. The formulation containing soy protein isolate and most pea proteins were in this category, although there were notable differences within the latter depending on the commercial source. On the other hand, soy-protein-concentrate- and wheat-gluten-based formulations had almost contrary functional properties and extrusion characteristics, with a dense, layered extrudate structure due to their heat-swelling and/or low cold-swelling characteristics. The textural properties (hardness, chewiness and springiness) of the hydrated ground product and patties also varied depending on protein functionality. With a plethora of plant protein options for texturization, understanding and relating the differences in raw material properties to the corresponding extruded product quality can help tailor formulations and accelerate the development and design of plant-based meat with the desired textural qualities.

The overall objective of this study was to understand texturization of pea protein isolate (PPI) using low moisture extrusion, and investigate protein interactions, functionality, and cross-linking with the inclusion of different levels of pea fiber (5-15%) and different types of starch-containing legume flours (20% chickpea flour or pea flour). PPI/ legume flour raw formulations had 18-27% lower water absorption capacity (WAC) as compared to the PPI control. However, WAC increased by 8-16% with the addition of pea fiber to a PPI/ legume flour control. Rapid Visco Analysis trends mirrored these results with peak viscosity shifting to higher temperatures with the addition of legume flour and lower temperatures with the addition of pea fiber. The role of starch in interfering with protein hydrophilic interactions and that of fiber in decoupling this effect were discussed. These interactions determined extruded textured protein properties, with more layering and denser products (174-229% higher bulk density as compared to control) observed with the addition of legume flours leading to lower water hydration capacity (WHC), as opposed to more cellular and porous microstructure (55-58% lower bulk density as compared to control) with the addition of fiber. Bulk density and WHC trends due to these porosity and layering effects impacted the instrumental texture characteristics of ground hydrated product, including hardness that increased from 475 g to 837-2334 g with the higher layering caused by starch, but decreased from 1295 g to 534-1050 g due to the porosity induced by fiber. To summarize, the use of legume flours and fiber can allow flexibility in targeting specific qualities while reducing costs and increasing sustainability of plant-based meats.