Search Results (8)

Tea, one of the world’s most consumed beverages, has a rich variety of sensory qualities such as appearance, aroma, mouthfeel and flavor. This review paper summarizes the chemical and volatile compositions and sensory qualities of different tea infusions including black, green, oolong, dark, yellow, and white teas based on published data over the past 4 years (between 2021 and 2024), largely focusing on the methodologies. This review highlights the relationships among the different processing methods of tea and their resulting chemical and sensory profiles. Environmental and handling factors during processing, such as fermentation, roasting, and drying are known to play pivotal roles in shaping the unique flavors and aromas of different types of tea, each containing a wide variety of compounds enhancing specific sensory characteristics like umami, astringency, sweetness, and fruity or floral notes, which may correlate with certain groups of chemical compositions. The integration of advanced analytical methods, such as high-performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC–MS), with traditional sensory analysis techniques was found to be essential in the evaluation of the chemical composition and sensory attributes of teas. Additionally, emerging approaches like near-infrared spectroscopy (NIRS) and electronic sensory methods show potential in modern tea evaluation. The complexity of tea sensory characteristics necessitates the development of combined approaches using both analytical methods and human sensory analysis for a comprehensive and better understanding of tea quality. Full article

Yellow tea (YT), a slightly fermented tea with a unique yellowing process and mellow taste, is becoming widely popular. Currently, the YT includes bud yellow tea (BYT), small-leaf yellow tea (SYT), and large-leaf yellow tea (LYT) based on maturity of raw materials. Previous studies have shown that YT has outstanding potential in preventing metabolic syndrome. However, the distinct effects and mechanisms of different types of YT on ulcerative colitis (UC) are still unclear. This study investigated the effects and mechanisms of continuous or intermittent intervention of three yellow tea water extracts (YTEs) on dextran sulfate sodium (DSS)-induced ulcerative colitis in CD-1 mice. The results showed that YTE intervention significantly improves the syndrome of DSS-induced UC in mice. Mechanistic studies reveal that YTEs increase the expression levels of tight junction (TJ) proteins and reduce the levels of pro-inflammatory cytokines in the colon by inactivating TLR4/NF-κB/NLRP3. YTE treatment protected intestinal barrier integrity and reduced serum lipopolysaccharide (LPS) levels. Interestingly, our results indicate that large-leaf yellow tea (LYT) has a better alleviating effect than BYT and SYT. YTE intervention before DSS administration has a certain degree of preventive effect on ulcerative colitis, while continuous YTE intervention after DSS induction has a significant reversing effect on the damage caused by DSS. Our results indicated that drinking YT may have preventive and therapeutic effect on UC, especially drinking LYT. Full article

Foods containing tea could be widely utilized due to the addition of good tea ingredients, especially large-leaf yellow tea, which is rich with a good flavor. Applying this change to bread containing tea would improve its product quality. In this research, large-leaf yellow tea bread (LYB), possessing a special flavor, was developed using ultrafine large-leaf yellow tea powder and flour as the main raw materials. The amount of ultrafine large-leaf yellow tea powder added to bread was optimized using texture, sensation, and specific volume as comprehensive evaluation indicators. At the optimal dosage, the free amino acids, volatile flavor compounds, antioxidant activity, and in vitro starch digestibility of LYB were measured. Response surface optimization experimental results showed that the comprehensive score of bread was highest when the added amount of ultrafine large-leaf yellow tea powder was 3%. In particular, compared to blank bread (BB), adding ultrafine large-leaf yellow tea powder into bread could effectively increase its amino acid composition, enhance its volatile flavor compounds, improve the antioxidant capacity, and reduce the digestibility of starch. Full article

Leaf color variations in tea plants were widely considered due to their attractive phenotypes and characteristic flavors. The molecular mechanism of color formation was extensively investigated. But few studies focused on the transformation process of leaf color change. In this study, four strains of ‘Baijiguan’ F1 half-sib generation with similar genetic backgrounds but different colors were used as materials, including Green (G), Yellow-Green (Y-G), Yellow (Y), and Yellow-Red (Y-R). The results of broadly targeted metabolomics showed that 47 metabolites were differentially accumulated in etiolated leaves (Y-G, Y, and Y-R) as compared with G. Among them, lipids were the main downregulated primary metabolites in etiolated leaves, which were closely linked with the thylakoid membrane and chloroplast structure. Flavones and flavonols were the dominant upregulated secondary metabolites in etiolated leaves, which might be a repair strategy for reducing the negative effects of dysfunctional chloroplasts. Further integrated analysis with the transcriptome indicated different variation mechanisms of leaf phenotype in Y-G, Y, and Y-R. The leaf color formation of Y-G and Y was largely determined by the increased content of eriodictyol-7-O-neohesperidoside and the enhanced activities of its modification process, while the color formation of Y-R depended on the increased contents of apigenin derivates and the vigorous processes of their transportation and transcription factor regulation. The key candidate genes, including UDPG, HCT, CsGSTF1, AN1/CsMYB75, and bHLH62, might play important roles in the flavonoid pathway. Full article

Harvesting seasons are crucial for the physicochemical qualities of large-leaf-variety black tea. To investigate the effect of harvesting seasons on physicochemical qualities, the color and sensory characteristics of black tea produced from “Yinghong 9” (Yh) and its mutant “Huangyu” (Hy) leaves were analyzed. The results demonstrated that Hy had better chemical qualities and sensory characteristics, on average, such as a higher content of tea polyphenols, free amino acids, caffeine, galloylated catechins (GaCs) and non-galloylated catechins (NGaCs), while the hue of the tea brew (ΔE*ab and Δb*) increased, which meant that the tea brew was yellower and redder. Moreover, the data showed that the physicochemical qualities of SpHy (Hy processed in spring) were superior to those of SuHy (Hy processed in summer) and AuHy (Hy processed in autumn), and 92.6% of the total variance in PCA score plots effectively explained the separation of the physicochemical qualities of Yh and Hy processed in different harvesting seasons. In summary, Hy processed in spring was superior in its physicochemical qualities. The current results will provide scientific guidance for the production of high-quality large-leaf-variety black tea in South China. Full article

Metabolic syndrome is a chronic metabolic disorder that has turned into a severe health problem worldwide. A previous study reported that large yellow tea exhibited better anti-diabetic and lipid-lowering effects than green tea. Nevertheless, the potential mechanisms are not yet understood. In this study, we examined the prevention effects and mechanisms of large yellow tea water extract (LWE) on metabolic syndrome using leptin receptor knockout (Lepr^−/−) rats. Seven-week-old male Lepr^−/− and wild type (WT) littermate rats were divided into Lepr^−/− control group (KO) (n = 5), Lepr^−/− with LWE-treated group (KL) (n = 5), WT control group (WT) (n = 6), and WT with LWE intervention group (WL) (n = 6). Then, the rats were administered water or LWE (700 mg/kg BW) daily by oral gavage for 24 weeks, respectively. The results showed that the administration of LWE significantly reduced the serum concentrations of random blood glucose, total cholesterol, triglyceride, and free fatty acids, and increased glucose tolerance in Lepr^−/− rats. Moreover, LWE remarkably reduced hepatic lipid accumulation and alleviated fatty liver formation in Lepr^−/− rats. A mechanistic study showed that LWE obviously activated SIRT6 and decreased the expression of key lipogenesis-related molecules SREBP1, FAS, and DGAT1 in the livers of Lepr^−/− rats. Furthermore, LWE significantly improved microbiota dysbiosis via an increase in gut microbiota diversity and an abundance of the microbiota that produce short chain fatty acids (SCFAs), such as Ruminococcaceae, Faecalibaculum, Intestinimonas, and Alistipes. Finally, LWE supplementation increased the concentrations of SCFAs in the feces of Lepr^−/− rats. These results revealed that LWE attenuated metabolic syndrome of Lepr^−/− rats via the reduction of hepatic lipid synthesis through the SIRT6/SREBP1 pathway and the modulation of gut microbiota. Full article

The yellow peach (Amygdalus persica), an important fruit in China, is highly susceptible to infection by Alternaria sp., leading to potential health risks and economic losses. In the current study, firstly, yellow peaches were artificially inoculated with Alternariaalternate. Then, the fruits were stored at 4 °C and 28 °C to simulate the current storage conditions that consumers use, and the Alternaria toxins (ATs) contents from different parts of the fruits were analyzed via ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The results showed that the growth of A. alternate and the ATs production were dramatically affected by the storage temperature. At 28 °C, the fungi grew rapidly and the lesion diameter reached about 4.0 cm within 15 days of inoculation, while, at 4 °C, the fungal growth was noticeably inhibited, with no significant change in the lesion diameter. To our surprise, high contents of ATs were produced under both storage conditions even though the fungal growth was suppressed. With an increase in the incubation time, the amounts of ATs showed a steady tendency to increase in most cases. Remarkably, alternariol monomethyl ether (AME), alternariol (AOH), and tenuazonic acid (TeA) were detected in the rotten tissue and also in the surrounding tissue, while a large amount of TeA could also be found in the healthy tissue. To the best of our knowledge, this is the first report regarding the production of ATs by the infection of Alternaria sp. in yellow peach fruits via artificial inoculation under regulated conditions, and, based on the evidence herein, it is recommended that ATs be included in monitoring and control programs of yellow peach management and food safety administration. Full article

Yellow tea has been widely recognized for its health benefits. However, its effects and mechanism are largely unknown. The current study investigated the mechanism of dietary supplements of large yellow tea and its effects on metabolic syndrome and the hepatic steatosis in male db/db mice. Our data showed that dietary supplements of large yellow tea and water extract significantly reduced water intake and food consumption, lowered the serum total and low-density lipoprotein cholesterol and triglyceride levels, and significantly reduced blood glucose level and increased glucose tolerance in db/db mice when compared to untreated db/db mice. In addition, the dietary supplement of large yellow tea prevented the fatty liver formation and restored the normal hepatic structure of db/db mice. Furthermore, the dietary supplement of large yellow tea obviously reduced the lipid synthesis related to gene fatty acid synthase, the sterol regulatory element-binding transcription factor 1 and acetyl-CoA carboxylase α, as well as fatty acid synthase and sterol response element-binding protein 1 expression, while the lipid catabolic genes were not altered in the liver of db/db mice. This study substantiated that the dietary supplement of large yellow tea has potential as a food additive for ameliorating type 2 diabetes-associated symptoms. Full article