EXTRUSION PROCESSING OF LOW-MOISTURE TEXTURIZED PLANT PROTEINS AS SCAFFOLDS FOR CELL CULTURE

Steven Verver

Extrusion technology is used to produce texturized plant proteins with a fibrous structure that remains stable when hydrated. While texturized vegetable proteins (TVP) have been utilized in the food industry for years as meat analogs, their potential applications go beyond that. Research into how extrusion processing parameters influence the physicochemical characteristics of TVP will enable optimization of the extrusion process for a variety of applications beyond meat analogs. This research explores modifications to the TVP extrusion process and how changes in physical characteristics affect the use of extrudates as scaffolds for cell culture. In the first study, a blend of 75% wheat protein and 25% wheat starch (w/w) was extruded at 25% moisture and a 70 g/min feed rate. The study focused on determining how changing the dimensions of the venturi insert in the die affected the physicochemical characteristics of the resulting texturized wheat protein (TWP). There were four venturi set-ups utilized, having different combinations of a 3.5 mm or 5 mm opening diameter and a 20 mm or 50 mm length. Additionally, samples were collected at four different screw speeds (200, 300, 400, and 500 rpm). Water holding capacity (WHC) and total soluble matter (TSM) were analyzed, along with the integrity index and texture profile analysis of the extrudates. The inclusion of a venturi increased the specific mechanical energy input at each screw speed compared with samples extruded without a venturi. Analyses demonstrated that the venturi decreased hardness while increasing the integrity, chewiness, and cohesiveness of the TWP without significantly influencing WHC and TSM. The venturi forced the proteins to form stronger fibers in the final extruded product. While venturi diameter had a greater impact on TWP quality than venturi length, the most important finding of the study was that the presence of a venturi led to greater changes in TWP quality than variations in venturi dimensions. The second study investigated the ability of texturized pea protein (TPP) scaffolds to support cell attachment and growth for use in a cultured meat (CM) application. A blend of 90% pea protein and 10% pea starch (w/w) was extruded at a constant feed rate of 60 g/min, but varying moisture contents (26%, 30%, and 34% w.b.) and screw speeds (400, 500, 600, and 700 rpm). These TPPs were evaluated for elastic modulus, tensile strength, texture profile analysis (TPA), and rehydration properties, as in the first study. Five combinations of extrusion conditions, selected based on elastic modulus, were seeded with C2C12 mouse myoblast cells and cultured for 14 days. Analyses of mechanical properties demonstrated maximum values at 500 rpm due to an interaction with the moisture content. The optimum energy input at that screw speed displayed better texturization characteristics, evaluated by rehydration properties. CM scaffolds prepared from TPP extruded at 34% moisture and a screw speed of 600 rpm showed the most promise based on cell attachment and the degree of myotube formation. This work showed promising results in the application of TPP scaffolds for CM without cytotoxic effects on cell growth. Further exploration of the influence of extrusion processing parameters on the physicochemical properties of texturized plant protein scaffolds will improve the quality of CM produced on these scaffolds.

EXTRUSION PROCESSING OF LOW-MOISTURE TEXTURIZED PLANT PROTEINS AS SCAFFOLDS FOR CELL CULTURE

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