The manufacture of semi-fermented oolong tea is a skilled task requiring “sniffing indices” during processing. An experienced “sniffer” uses the appearance of grassy and floral fragrances to monitor the progress of fermentation. In the present work, semi-fermented oolong tea was sampled at 13 Stages of processing. At each stage, volatile compounds were collected by solid-phase micro-extraction and investigated by GC-MS analysis. It was found that C₆ aldehydes remained at constant levels throughout fermentation. Those volatiles responsible for the fragrance of oolong tea increased up to the end of fermentation. Trans- β-ocimene, α-farnesene, and 3-hexenyl hexanoate reached peak levels before heat fixation (“panning”). The fruity volatiles were C₁₀ or C₁₂ esters. Significant variations in trans- β-ocimene, linalool (and its oxides), 1H-indole, and α-farnesene accompanied the appearance of the floral fragrance. There was a 14.7% decrease in total catechins between the fresh tea shoots (Stage 1) and the end of fermentation (Stage 12). Epi-catechin, epi-gallocatechin, and epi-gallocatechin gallate decreased by 8%, 42%, and 5%, respectively, whereas epi-catechin gallate increased by 13% at the end of fermentation (Stage 12). Total catechin galate ester levels were raised significantly at the floral fragrance Stages (Stages 3, 4, 6, 8, 10, and 12).

Catechins belonging to polyhydroxylated polyphenols are the primary compounds found in green tea. They are associated with many physiological properties. Epicatechin (EC) is a non-gallate-type catechin with four phenolic hydroxyl groups attached. The changes in EC treated with color light illumination in an alkaline condition were investigated by chromatographic and mass analyses in this study. In particular, the superoxide anion radical (O2•−) was investigated during the EC photolytic process. EC is unstable under blue light illumination in an alkaline solution. When EC was treated with blue light illumination in an alkaline solution, O2•− was found to occur via a photosensitive redox reaction. In addition, the generation of monomeric, dimeric, and trimeric compounds is investigated. On the other hand, epigallocatechin gallate (EGCG), which is a gallate-type catechin, is stable under blue light illumination in an alkaline solution. Adding EGCG, during the blue light illumination treatment of EC decreased photolytic formation, suggesting that gallate-type catechins can suppress the photosensitive oxidation of EC. Gallate-type catechins are formed via the esterification of non-gallate-type catechins and gallic acid (GA). The carbonyl group on the gallate moiety of gallate-type catechins appears to exhibit its effect on the stability against the photosensitive oxidation caused by blue light illumination.

Catechin is a flavan-3-ol, a derivative of flavans, with four phenolic hydroxyl groups, which exhibits a wide range of physiological properties. Chromatographic analyses were employed to examine the effects of blue light irradiation on the changes of catechin hydrate in an alkaline condition. In particular, the detection of a superoxide anion radical (O₂•⁻), a reactive oxygen species (ROS), and the inactivation of Acinetobacter baumannii (A. baumannii)—including a carbapenem-resistant A. baumannii (CRAB)—was investigated during the photoreaction of catechin hydrate. Following basification with blue light irradiation, the transparent solution of catechin hydrate turned yellowish, and a chromogenic catechin dimer was separated and identified as a proanthocyanidin. Adding ascorbic acid during the photolytic treatment of catechin hydrate decreased the dimer formation, suggesting that ascorbic acid can suppress the photosensitive oxidation of catechin. When catechin hydrate was irradiated by blue light in an alkaline solution, O₂•⁻ was produced via photosensitized oxidation, enhancing the inactivation of A. baumannii and CRAB. The present findings on the photon-induced oxidation of catechin hydrate provides a safe practice for the inactivation of environmental microorganisms.

Diospyros blancoi A. DC. is an evergreen tree species of high-quality wood. Mabolo, the fruit of this plant, is popular among the natives in Taiwan, but its potential in economic use has not been fully explored. Mabolo has a rich aroma. Of the 39 different volatile compounds isolated, its intact fruit and peel were found to both contain 24 compounds, whereas the pulp contained 28 compounds. The most important aroma compounds were esters and α-farnesene. Our data show that mabolo is rich in dietary fiber (3.2%), and the contents of other nutrients such as malic acid, vitamin B2, vitamin B3, folic acid, pantothenic acid, and choline chloride were 227.1 mg/100 g, 0.075 mg/100 g, 0.157 mg/100 g, 0.623 mg/100 g, 0.19 mg/100 g, and 62.52 mg/100 g, respectively. Moreover, it is rich in calcium and zinc; the contents of which were found to be 42.8 mg/100 g and 3.6 mg/100 g, respectively. Our results show that D. blancoi has the potential to be bred for a novel fruit.

Tea is rich in catechins and aluminum. In this study, the process of catechin photolysis was applied as a model for examining the effects of aluminum chloride (AlCl₃) on the structural changes of catechin and the alteration of aluminum complexes under blue light irradiation (BLI) at pH 8 using liquid chromatography and mass spectrometry techniques. Additionally, the effects of anions on catechin upon the addition of AlCl₃ and treatment with BLI were also studied. In this study, when 1 mM catechin was treated with BLI, a superoxide anion radical (${\mathrm{O}}_2^{•-}$) was generated in an air-saturated aqueous solution, in addition to forming a dimeric catechin (proanthocyanidin) via a photon-induced redox reaction. The relative percentage of catechin was found to be 59.0 and 95.7 for catechin treated with BLI and catechin upon the addition of 1 mM AlCl₃ treated with BLI, respectively. It suggested that catechin treated with BLI could be suppressed by AlCl₃, while AlCl₃ did not form a complex with catechin in the photolytic system. However, under the same conditions, it was also found that the addition of AlCl₃ inhibited the photolytic formation of ${\mathrm{O}}_2^{•-},$ and reduced the generation of proanthocyanidin, suggesting that the disconnection of proanthocyanidin was achieved by AlCl₃ acting as a catalyst under treatment with BLI. The influence of 1 mM fluoride (${\mathrm{F}}^{-}$) and 1 mM oxalate (${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$) ions on the photolysis of 1 mM catechin upon the addition of 1 mM AlCl₃ and treatment with BLI was found to be insignificant, implying that, during the photolysis of catechin, the Al species were either neutral or negatively charged and the aluminum species did not form a complex with anions in the photolytic system. Therefore, aluminum, which is an amphoteric species, has an inherent potential to stabilize the photolysis of catechin in an alkaline conditions, while suppressing the ${\mathrm{O}}_2^{•-}$ and proanthocyanidin generation via aluminum ion catalysis in the catechin/Al system under treatment with BLI.