Characterization of Fibrous Protein Gel Network Properties in Brewer’s Yeast-Enhanced Meat Analogs Produced by High-Moisture Extrusion

The development of structured protein gel matrices with meat-like fibrous properties is a key challenge in the design of high-moisture meat analogs (HMMA). This study incorporated brewer’s yeast into a soy protein-wheat gluten-corn starch matrix and evaluated the stage-specific effects of moisture content (MC), barrel temperature (BT), and screw speed (SS) on the fibrous appearance, integrity index, nitrogen solubility index (NSI), texture, and cutting strength of yeast-enhanced meat analogs (Y-MA), alongside pasting, rheological, Fourier transform infrared spectroscopy (FTIR), and Raman analyses of pre-extrusion blends (0% and 10% yeast). Among the individual factors examined under their respective fixed processing conditions, moisture content produced the largest changes in several measured responses. Raising MC from 55% to 70% weakened the fibrous structure, reduced chewiness from 6211 to 867 g, and lowered cutting strength in both directions. Raising BT from 140 to 170 °C produced more distinct fibrous features, higher NSI, and greater firmness. Increasing SS from 150 to 300 rpm was associated with decreased chewiness. The 10% yeast blend showed lower pasting viscosities, a higher pasting temperature, and lower terminal G′ and G″ than the yeast-free blend, while FTIR and Raman spectra remained unchanged. These findings indicate that extrusion parameters influenced the fibrous appearance, matrix retention, and mechanical properties of Y-MA under the fixed conditions tested.