329: Ca2+ Inhibition of Intermolecular ß-Sheet Formation in Extruded Pea Protein Isolate (PPI): Impact on Texturization and Physicochemical Properties

Introduction

Calcium chloride is a key fortifier and cross-linking agent in food products, crucial for enhancing gel strength, texture, and stability in protein and dairy systems. While calcium's effects on food gels are well-studied, this research investigates its impact on β-sheet formation in extruded pea protein isolate and the resulting changes in mechanical properties, water-holding capacity, and anisotropic swelling behavior.

Methods

The Young’s Modulus was measured using a Texture Analyzer (TA), which provides insights into various physicochemical properties such as hardness, cohesiveness, and springiness. Extrudates were soaked in water overnight to evaluate how much water the extrudates could retain, allowing for the assessment of changes in water-holding capacity. Additionally, Fourier-transform infrared (FTIR) spectroscopy was used to identify the intermolecular β-sheet of proteins.

Results

Calcium concentration significantly affected the properties of the extruded protein matrix. Young’s modulus increased, while swelling strain and water-holding capacity (WHC) decreased with higher calcium levels. At low calcium concentrations, anisotropic swelling was prominent in the extrusion direction, but it became isotropic at higher levels.

FTIR analysis showed β-sheet formation was extended during extrusion at low calcium concentrations, as indicated by a red-shift from 1625 cm⁻¹ to 1621 cm⁻¹. In contrast, high calcium concentrations inhibited β-sheet formation and fiber development, with minimal peak shifts observed. These results demonstrate calcium's role in modulating the mechanical properties, WHC, and molecular structure of extruded proteins.

Significance

This research reveals the correlation between calcium concentration and texture properties, physicochemical properties, improving the understanding of the effect of calcium on the structure of meat analogues and aiding manufacturers in producing meat analogues with desired properties.

Authors: Haoyu Wang, Hiroshi Nakagawa and Job Ubbink