Improving gel properties of purified Chlorella protein extract by alkali and TGase modifications combined with Ca2+: A study on the multidimensional regulatory mechanisms of gel properties.
Abstract
The textural properties of food colloidal systems are highly dependent on the gelling characteristics of animal-derived proteins (such as egg protein, EP) and polysaccharides (such as starch, pectin, and gums). The development of plant-based protein alternatives faces challenges such as insufficient gel strength and poor structural stability. This study focused on purified Chlorella protein extract (PCPE). To address the insufficient gel performance of PCPE, a synergistic optimization strategy of "modification combined with calcium ion regulation" was proposed. Results revealed that alkali treatment strengthened ionic interactions while weakening hydrogen bonds and hydrophobic interactions, promoting protein molecular rearrangement and resulting in a narrower and more concentrated particle-size distribution. This increased the initial storage modulus to 136 Pa, comparable to that of EP. TGase treatment catalyzed protein-protein and protein-polysaccharide covalent cross-linking, forming a dense network structure and significantly increasing gel hardness to approximately 1.5 times that of EP. Furthermore, the addition of calcium ions synergistically enhanced gel strength via salt bridge formation, further elevating the initial storage modulus to 297 Pa. However, a high calcium concentration (25 mM) led to an approximately 20% reduction in water-holding capacity for TGase-treated PCPE gels. This study elucidates the multidimensional regulatory mechanisms underlying enhanced plant-protein gelation and provides a strategy for developing sustainable plant-based gelled foods.