Charge-dependent mechanisms of ionic polysaccharides modulating myofibrillar protein gelation: A dual-system...

Ionic polysaccharides improve gelation and hydration in meat systems, yet their structure-function relationships remain poorly defined. This study compared κ-carrageenan (CAR, anionic), agar (weakly anionic), curdlan (CUR, neutral), and chitosan (CHI, cationic) using a dual-system strategy integrating minced chicken gels with purified myofibrillar proteins. Concentration screening (1-2%) identified 1.75% as optimal for CAR, CUR, and CHI, and 1.25% for agar. At these levels, CAR and agar produced high gel strength (∼4.0 × 10³ g × mm) and storage modulus above 10 kPa, while CUR maximized water-holding capacity (∼68%). In contrast, CHI showed limited improvement due to charge incompatibility. To elucidate these differential outcomes, mechanistic analyses revealed charge-dependent effects across treatments: CAR maintained controlled protein aggregation (ζ-potential -29.45 mV) enabling organized networks, whereas agar preserved protein structure with highest β-sheet content (∼52%). Conversely, CUR induced spontaneous aggregation (particle size 2.3 μm), and CHI formed stable complexes preventing gelation (solubility ∼83%). Notably, molecular force analysis further demonstrated multi-modal interactions involving electrostatic, hydrophobic, and potentially hydrogen-bonding contributions varying by polysaccharide type. Overall, anionic polysaccharides, especially CAR, provided the most effective network formation. Collectively, these findings establish that charge compatibility is critical for protein gelation, thereby offering practical guidance for formulating structured meat products.