Polyphenol oxidase (PPO) is an important metalloenzyme in the tea plant (Camellia sinensis). However, there has recently been a lack of comprehensive reviews on Camellia sinensis PPO. In this study, the methods for extracting PPO from Camellia sinensis, including acetone extraction, buffer extraction, and surfactant extraction, are compared in detail. The main purification methods for Camellia sinensis PPO, such as ammonium sulfate precipitation, three-phase partitioning, dialysis, ultrafiltration, ion exchange chromatography, gel filtration chromatography, and affinity chromatography, are summarized. PPOs from different sources of tea plants are characterized and systematically compared in terms of optimal pH, optimal temperature, molecular weight, substrate specificity, and activators and inhibitors. In addition, the applications of PPO in tea processing and the in vitro synthesis of theaflavins are outlined. In this review, detailed research regarding the extraction, purification, properties, and application of Camellia sinensis PPO is summarized to provide a reference for further research on PPO.

Tannase, as a type of tannin−degrading enzyme, can catalyze the hydrolysis of ester and depside bonds in gallotannins, thereby releasing gallic acid and glucose. Based on this reaction mechanism, Tannase can effectively improve the problems of bitter taste, weak aroma, and tea cheese in tea infusion, and is therefore widely used in the tea industry. However, due to high production costs, difficulties in purification and recovery, and insufficient understanding of Tannase properties, the large−scale application of Tannase is severely limited. Therefore, the sources of Tannase and the effects of fermentation temperature, pH, stirring speed, time, carbon, and nitrogen sources on the preparation of Tannase are described in this study. The advantages and disadvantages of various methods for measuring Tannase activity and their enzymatic characterization are summarized, and the concentration and purification methods of Tannase are emphasized. Finally, the application of Tannase to reduce the formation of tea precipitate, enhance antioxidant capacity, increase the extraction rate of active ingredients, and improve the flavor of the tea infusion is described. This study systematically reviews the production, characterization, purification, and application of Tannase to provide a reference for further research and application of Tannase.

Hops provide the characteristic bitter taste and attractive aroma to beer; in this study, hops were replaced by jasmine tea extract (JTE) during late-hopping. The addition of JTE improved the beer foam stability 1.52-fold, and increased the polyphenol and organic acid contents. Linalool was the most important aroma compound in hopped (HOPB) and jasmine tea beer (JTB), but other flavor components were markedly different, including dimeric catechins, flavone/flavonol glycosides, and bitter acids and derivatives. Sensory evaluation indicated that addition of JTE increased the floral and fresh-scent aromas, reduced bitterness and improved the organoleptic quality of the beer. The antioxidant capacity of JTB was much higher than that of HOPB. The inhibition of amylase activity by JTB was 30.5% higher than that of HOPB. Functional properties to beer were added by substituting jasmine tea extract for hops during late hopping.

Tea polyphenol oxidase (CsPPO) is a crucial enzyme involved in the production of tea and tea products. However, the recombinant expression of CsPPO in microorganisms is often hindered by challenges such as inclusion body formation and extremely low enzyme activity. In this study, the CsPPO gene (1800 bp) from Camellia sinensis cv. Yihongzao was cloned and 14.5% of its codons were optimized for Pichia pastoris expression. Compared to pre-optimization, codon optimization significantly enhanced CsPPO production in P. pastoris KM71, yielding a 42.89-fold increase in enzyme activity (1286.67 U/mL). The optimal temperature and pH for recombinant CsPPO were determined to be 40 °C and 5.5, respectively. This study demonstrates that codon optimization effectively improves the expression of plant-derived enzymes such as CsPPO in eukaryotic expression systems. Future research should explore the long-term stability of recombinant CsPPO and its potential applications in tea fermentation processes and functional food development.