Steam explosion modification on tea waste to enhance bioactive compounds' extractability and antioxidant capacity of extracts

In this work, steam explosion (SE) was introduced to modify physicochemical features of tea waste to intensify bioactive compounds' extraction and antioxidant capacity of extracts. Modification effects of SE on chemical composition, multi-scale structure and solubilization of tea waste were investigated to confirm that cell wall composition and porous network of tea waste were destroyed and restructured, resulting in the increased solubility after SE. Effects of SE on distribution and diffusion rules of four typical bioactive compounds in tea extracts revealed that SE enhanced their extraction efficiency by raising the maximum extraction yield and diffusion coefficient. After SE treatment, the extraction yields of tea polyphenols, caffeine, saponin and water soluble sugars were maximally increased by 15.5%, 14.1%, 28.8% and 74.8%, respectively. Most of them experienced a balance of dissolution and degradation during SE, showing a firstly increasing and then decreasing tendency with increasing SE severity. The availability of tea waste facilitated by SE led to at least 20% improvement of antioxidant capacity including Ferric reducing antioxidant power (FRAP) and center dot OH, O-2 center dot(-) radical scavenging activity of tea extracts.