The improved rehydration property, flavor characteristics and nutritional quality of freeze-dried instant rice supplemented with tea powder products

Given the high nutritional value, the research of tea in foods has attracted increasing attention. The instant green tea (IGT), instant black tea (IBT) and match (Mat) were added to improve the qualities of freeze-dried instant rice (FDIR) and the rehydration property, flavor characteristics and nutritional quality were investigated in this paper. The results showed that the addition of three tea powders made FIDR achieve a higher rehydration rate and a better texture in the shortest rehydration time, as well as richer flavor components and higher antioxidant capacity. Moreover, the content of resistant starch was increased and the degree of starch hydrolysis was decreased. In comparison, IBT was the best improvement. Furthermore, the thermal property and XRD spectroscopy revealed that the crystal structure made regular feedback under the action of tea powders. The contact angle and surface energies, SEM and CLSM analysis showed that the changes in outer morphology of rice grains induced by tea powders were considerable. Moreover, FTIR and Raman spectroscopy confirmed that the hydrogen bonding between tea powder and starch made a more stable short-range structure. These all suggested that it is feasible to produce FDIR with tea powders as a novel instant rice with superior quality.