Sensory-directed isolation and identification of an intense salicin-like bitter compound in infected teas with bird's eye spot disease.

Teas infected with bird's eye spot disease generally exhibited a lingering and long-lasting, salicin-like bitter taste, which was unpalatable to consumers. Sensory-directed isolation processes have been performed in this study to investigate the salicin-like bitter compounds in infected teas. Results showed that infected teas were extracted using a 70% methanol aqueous solution to produce methanol extract, which was then further separated by sequential solvent extraction (SSE) to obtain dichloromethane extract, which contained the salicin-like bitter compounds. The dichloromethane extract was then isolated by flash chromatography to produce two salicin-like bitter fractions, eluted using 60% and 65% methanol aqueous solution. Finally, these two salicin-like bitter fractions were analyzed by RP-HPLC using 60-68% and 70-75% methanol aqueous solution, respectively, affording the location of the salicin-like bitter compounds in RP-HPLC chromatograms. Moreover, a new ursane-type triterpenoid, camellisin A methyl ester, was identified from infected teas. This study has provided preliminary isolation methods of salicin-like bitter compounds from the infected teas, which were essential to designing targeted debittering strategies for infected teas and improving the quality of the finished tea and the effective utilization of fresh tea leaves.

Characterization of triterpenoids as possible bitter-tasting compounds in teas infected with bird's eye spot disease.

Tea infected with bird's eye spot disease generally imparts a long-lasting bitter taste, which is unacceptable to most consumers. This study has comprehensively evaluated the taste profiles of infected and healthy teas and investigated their known bitter compounds previously reported in tea. Quantification analyses and calculation of dose-over-threshold (DoT) factors revealed that no obvious difference was visualized in catechins, caffeine, bitter amino acids, and flavonols and their glycosides between infected and healthy tea samples, which was also verified by principal component analysis (PCA) and hierarchical cluster analysis (HCA). Therefore, these known bitter compounds have been ruled out as critical contributors to the long-lasting bitterness of infected teas. Furthermore, Gel permeation chromatography, sensory analysis, and UPLC-Q-TOF-MS were employed and identified 13 substances from the target bitter fractions, including caffeine, ten triterpenoids, and two oxylipins. The higher triterpenoid levels were supposed to be the reason causing the long-lasting bitterness. This study has provided a research direction for the molecular basis of the long-lasting bitterness of infected tea leaves with bird's eye spot disease.

Lycopene, polyphenols and antioxidant activities of three characteristic tomato cultivars subjected to two drying methods.

The aim of this study was to evaluate the effects of freeze drying and oven drying on appearance, chemical components and antioxidant activities of three cultivars of tomatoes. This study showed cultivar 18,131 would provide the highest phenolic contents and ABTS radical scavenging activity, and cultivar 1862 provide the highest lycopene content after oven drying. On the basis of appearance and contents of polyphenols, freeze drying showed better results. However, oven drying was found superior in decreasing degradation of lycopene. The effects of drying on the polyphenol contents varied depending on the cultivars. In addition, there is no significant difference of antioxidant activities between freeze dried and oven dried tomatoes. These results also demonstrated that freeze drying is superior in maintaining physical structure and phenolic contents of tomato slices. However, oven drying is a viable option for drying tomatoes considering both costing and contents of lycopene.