Chloroplast thylakoid extract modulates protein aggregation and gelation in yoghurt: A timing-dependent mechanistic...

This study examined the effects of chlorophyll-rich thylakoid extract (CE) on yoghurt gelation, emphasizing the timing of its incorporation. CE was added either before (Pre-L) or after (Post-L) fermentation, and outcomes were evaluated using physicochemical, rheological, and structural analyses during 21 days of storage at 4 °C. CE moderated acidification, maintaining pH above 4.2 compared with 3.9 in the control. Post-L addition improved water-holding capacity (+24.8%) and reduced syneresis (-18.6%). FTIR revealed increased β-sheet content (39.6% vs. 23.3% in control) and reduced α-helix levels, while Pre-L showed intermediate values. Surface hydrophobicity and sulfhydryl profiles indicated that Pre-L promoted hydrogen bonding and disulfide bridging during fermentation, whereas Post-L primarily strengthened the pre-formed gel through hydrophobic aggregation and electrostatic stabilization. Computational docking confirmed thylakoid-milk protein interactions at hydrophobic and hydrogen bonding sites. Overall, CE timing governs protein assembly and texture, with Post-L providing the greatest improvements in structure and stability.