Quality and Antioxidant Property of Three Types of Tea Infusions

Insights on the Nutraceutical Properties of Different Specialty Teas Grown and Processed in a German Tea Garden

European countries have recently started experimenting with growing and producing their own teas in small quantities, mainly for the specialty tea sector. To characterize European teas, this study investigated a set of five tea types obtained from different Camellia sinensis varieties/cultivars, representing various oxidation grades (green, white, yellow, oolong, black), all grown and processed in the only tea garden in Europe (in Germany) that focuses on all five types. Hot and cold brews were studied by measuring the total phenolic (TPC) and flavonoid contents (TFC), the antioxidant capacity and UV-Vis spectra, also with the objective of discriminating between the different tea types and the different plant varieties. The dried leaves were analyzed to measure the content of essential and toxic elements and by ATR-FTIR spectroscopy to determine a chemical fingerprint for identifying the tea varieties and types. The average levels of TPC (hot brew = 5.82 ± 2.06; cold brew = 5.4 ± 2.46 mM GAEq), TFC (hot brew = 0.87 ± 0.309; cold brew = 0.87 ± 0.413 mM CAEq), and antioxidant capacity (ORAC assay-hot brew = 20.9 ± 605; cold brew = 21.8 ± 8.0 mM TXEq, ABTS assay-hot brew = 15.2 ± 5.09; cold brew = 15.1 ± 5.8 mM TXEq, FRAP assay-hot brew = 9.2 ± 3.84; cold brew = 10.4 ± 5.23 mM AAEq) observed compared well with those from other parts of the world such as China, Africa, and Taiwan. The hazard quotient <1 and the hazard index of 0.14 indicate that there is no non-carcinogenic risk from consumption of these teas. The obtained information is essential for elucidating the characteristics and the impact of tea processing and tea variety on the health benefits of these tea products coming from a single European tea garden. This multifaceted approach would help tea growers in Europe increase their knowledge on the health attributes of the teas they grow, ultimately leading to optimization of the nutraceutical properties of these teas.

Comparative Analysis of Hot and Cold Brews from Single-Estate Teas (Camellia sinensis) Grown across Europe: An Emerging Specialty Product

Tea is grown around the world under extremely diverse geographic and climatic conditions, namely, in China, India, the Far East and Africa. However, recently, growing tea also appears to be feasible in many regions of Europe, from where high-quality, chemical-free, organic, single-estate teas have been obtained. Hence, the aim of this study was to characterize the health-promoting properties in terms of the antioxidant capacity of traditional hot brews as well as cold brews of black, green and white teas produced across the European territory using a panel of antioxidant assays. Total polyphenol/flavonoid contents and metal chelating activity were also determined. For differentiating the characteristics of the different tea brews, ultraviolet-visible (UV-Vis) spectroscopy and ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry were employed. Overall, our findings demonstrate for the first time that teas grown in Europe are good quality teas that are endowed with levels of health-promoting polyphenols and flavonoids and that have an antioxidant capacity similar to those grown in other parts of the world. This research is a vital contribution to the characterization of European teas, providing essential and important information for both European tea growers and consumers, and could be of guidance and support for the selection of teas grown in the old continent, along with having the best brewing conditions for maximizing the health benefits of tea.

Dynamic Analysis of the Bacterial Community and Determination of Antioxidant Capacity during the Fermentation of Sour Tea

The imbalance of the redox state caused by extra reactive oxygen species is closely related to many diseases. Therefore, it is necessary for people to ingest antioxidants through food. The safety of some synthetic antioxidants has been questioned. In this context, it is worth exploring natural and safe antioxidants from biological sources. Tea has good antioxidant activity, and the antioxidant activity of fermented sour tea is better than that of other types. It is necessary to clarify the antioxidant capacity of sour tea during fermentation, as well as the microbial community and its sources. Nonculture and culture-dependent methods were adopted to track the changes in the microbial population and community structure during the fermentation of sour tea. Sequence analysis of 16S rRNA gene amplification revealed significant differences in community complexity and structure at different fermentation times. The highest proportion of operational taxonomic units (OTU s) in all samples was Latilactobacillus, which was determined to be Lactiplantibacillus plantarum by further analysis. The second highest proportion of OTUs was Enterobacter. With the fermentation of sour tea, the antioxidant capacity increased, and all isolated Lb. plantarum had good DPPH clearance rates. Our findings suggest that Lb. plantarum plays a crucial role in the fermentation process of sour tea. The possibility of discovering new antioxidants was provided by the determination of the antioxidant capacity and bacterial community during the fermentation of sour tea.

Quality characteristics of green Tea's infusion as influenced by brands and types of brewing water

The influences of four types of brewing waters including tap water (TAP), alkaline ionized water (ALK), magnetized water (MAG) and mineral water (MIN), and two brands of commercial green tea (L and T) on quality characteristics of tea infusions were studied. The Oxidation Reduction Potential (ORP) values of the brewing waters was TAP > MAG, MIN > ALK. After brewing, all infusions showed a significant drop (p < 0.05) in pH values. The pH of original brewing waters of ALK (8.64) was the highest as compared to other waters, whereas L-MIN (pH 6.63) and T-MIN (pH 5.82) showed the highest pH values after brewing. Overall, the quality characteristics of green tea infusions were influenced by the brands of tea and the types of brewing water used. MAG was the most superior brewing water in extracting the green tea. Evidenced by total phenolic and flavonoids contents, both L-MAG and T-MAG infusions were superior in extracting antioxidative compounds as compared to other tea infusions. In addition, T-MAG infusion was the least astringent (P < 0.05) and scored the highest (P < 0.05) overall acceptability ( 5.40 ) by sensory panelists.

Effect of fixation methods and various clones of Camellia sinensis var. sinensis (L) properties and antioxidant activity of Indonesian green tea

Fixation is essential in green tea processing to inactivate the polyphenol oxidase enzyme. In Indonesia, green tea is made from the Assam variety and produced using the panning method. Few studies are reported on green tea made from Indonesian clones of the Sinensis variety. This study aims to identify chemical characteristics, antioxidant activity, and sensory evaluation of green tea from local clones of the Sinensis variety (GMBS 2, GMBS 4, and GMBS 5) with different fixation methods (panning and steaming). The results show that the caffeine content of green tea products ranged from 2.51-2.59% and 2.67-2.74% for panning and steaming methods. The panning method produced green tea with higher total polyphenol and flavonoid content than the steaming method. Green tea with the panning method has an IC50 value of 14.45; 14.41; and 17.41 mg/L for GMBS 2, GMBS 4, and GMBS 5, respectively. The panning method resulted in a smaller IC50 value than the steaming method for GMBS 2 and GMBS 4 clones. The steaming method produced green tea with a higher taste, aroma, and total score than those the panning method. However, different fixation methods did not significantly affect the appearance, liquor color, and leaf infusion. In conclusion, different fixation methods on GMBS 2, GMB 4, and GMB 5 produced green tea products that met the Indonesian National Standard 3945:2016. Further research is needed to determine the role of the plucking period/season and the characteristics of volatile compounds of green tea from GMBS clones with different fixation methods.

Physicochemical Parameters, Mineral Composition, and Nutraceutical Properties of Ready-to-Drink Flavored-Colored Commercial Teas

The physicochemical parameters, mineral composition, and nutraceutical properties of ready-to-drink flavored-colored commercial teas were analyzed in the present study. The pH of samples was slightly acidic (3.72 to 4.11), titratable acidity was low (0.092 to 0.174%), and color parameters were wide variable (pink, yellow, brown, and red). Citrus-flavored tea obtained the highest content of manganese (0.281 mg·L−1), zinc (0.069 mg·L−1), magnesium (2.92 mg·L−1), potassium (62.65 mg·L−1), and sodium (271.74 mg·L−1), while lemon-, peach-, and blueberry-flavored teas obtained the highest levels of copper (0.035 mg·L−1), iron (0.246 mg·L−1), and calcium (18.21 mg·L−1), respectively. Citrus, lemon-, sangria-, and rose petal-flavored teas obtained the highest content in total phenols (211.56 mg·L−1), total flavonoids (65.46 mg·L−1), total catechins (640.79 mg·L−1), and total anthocyanins (640.79 mg·L−1), respectively. Lemon- and rose petal-flavored teas showed the highest and lowest antioxidant capacity levels in DPPH (1096.00 to 118.77 μmolTE·L−1), ABTS (1048.84 to 232.00 μmolTE·L−1), and FRAP (1269.20 to 147.70 μmolTE·L−1) assays. The levels of sodium reported in labels of all samples were lower than data obtained in our analysis. Also the levels observed for total phenols in blueberry-, citrus-, and rose petal-flavored teas were lower than our analysis, but total phenols of lemon-, peach-, and sangria-flavored teas were higher than the content reported in their labels. The results obtained in the present work give information to consumers for choosing flavored-colored ready-to-drink tea based on the physicochemical, nutritional, and nutraceutical properties.

Diversity of lactic acid bacteria from Miang, a traditional fermented tea leaf in northern Thailand and their tannin-tolerant ability in tea extract

The microbiota of lactic acid bacteria (LAB) in thirty-five samples of Miang, a traditional fermented tea leaf product, collected from twenty-two different regions of eight provinces in upper northern Thailand was revealed through the culture-dependent technique. A total of 311 presumptive LAB strains were isolated and subjected to clustering analysis based on repetitive genomic element-PCR (rep-PCR) fingerprinting profiles. The majority of the strains belonged to the Lactobacillus genera with an overwhelming predominance of the Lb. plantarum group. Further studies of species-specific PCR showed that 201 of 252 isolates in the Lb. plantarum group were Lb. plantarum which were thus considered as the predominant LAB in Miang, while the other 51 isolates belonged to Lb. pentosus. In contrast to Lb. plantarum, there is a lack of information on the tannase gene and the tea tannin-tolerant ability of Lb. pentosus. Of the 51 Lb. pentosus isolates, 33 were found to harbor the genes encoding tannase and shared 93-99% amino acid identity with tannase obtained from Lb. pentosus ATCC 8041^T. Among 33 tannase gene-positive isolates, 23 isolates exhibited high tannin- tolerant capabilities when cultivated on de Man Rogosa and Sharpe agar-containing bromocresol purple (0.02 g/L, MRS-BCP) supplemented with 20% (v/v) crude tea extract, which corresponded to 2.5% (w/v) tannins. These Lb. pentosus isolates with high tannin-tolerant capacity are expected to be the high potential strains for functional tannase production involved in Miang fermentation as they will bring about certain benefits and could be used to improve the fermentation of tea products.

Effects of alternative steeping methods on composition, antioxidant property and colour of green, black and oolong tea infusions

Cold water steeping is reported to maximise tea health benefits, but requires long infusion time. In this work, the employment of a brief hot infusion step followed by ice addition was evaluated. The comparison of this innovative method with hot and cold steeping was investigated on green, black and oolong teas. Catechins, xanthines and gallic acid content, antioxidant power, total phenolics and colour analysis were evaluated. Hot infusion shown rapid extractive power, but relevant compound degradation. On the contrary, cold infusion extracted higher level of healthy molecules with slow kinetic. The innovative method achieved in short time similar properties of cold infusion in terms of antioxidant power. As for bioactive compounds, such as gallic acid and epigallocatechin gallate, highest values, about double than in hot infusion, were recorded for green and black teas. This steeping method may represent an alternative approach for industrial beverage preparation.