Gelation of tamarind seed polysaccharide induced by tea polyphenols: Screening, gelling kinetics, and properties

The gelling kinetics and properties of different tea polyphenol-induced gelation of TSP were investigated by rheological and texture techniques. Results showed that epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and gallic acid (GA) were the key factors of tea polyphenols to induce gelation of TSP at different concentration ranges. Sol-gel transition temperatures were determined as 28.8, 15.7, 26.2, and 22.9 °C for TSP/EGCG, TSP/EGC, TSP/ECG, and TSP/GA, respectively from temperature ramp during cooling process. Structure developing rate (SDR) analysis indicated that TSP/EGCG possessed the highest SDR to form gel structure. Non-isothermal kinetic studies demonstrated that all samples needed to overcome high energy barrier at the initial gelling preparation stage during cooling, but much lower Ea at the gel strengthening stage. Besides, a gel aging stage was designated to TSP/EGCG system from 17.72 to 4.00 °C with the lowest Ea (70.16 kJ/mol). These results revealed that gallate and galloyl moieties were the critical structure features of tea polyphenols to promote gelation of TSP, and EGCG showed the strongest ability. Texture tests further found that low temperature and acidic pH were favorable to enhance the mechanical strength of TSP/EGCG gel, but alkaline environment and high content of sucrose weakened the gel structure. This study illustrated the key factors and gelling properties of tea polyphenol-induced gelation of TSP, laying a theoretical foundation to explore polyphenol-response hydrogels in food and biomedicine fields.