Influence of steeping conditions (time, temperature, and particle size) on antioxidant properties and sensory attributes of some white and green teas

Antibacterial efficacy of berry juices against Bacillus cereus relative to their phytochemical composition and antioxidant properties

Ensuring the safety and stability of minimally processed foods using natural preservatives is of great scientific and commercial interest in modern biotechnology. Berry juice supplementation is increasingly recognized within this field. This study investigated the effectiveness of juices from four berry species Aronia melanocarpa, Ribes nigrum, Vaccinium macrocarpon, and Sambucus nigra, against the food pathogen Bacillus cereus. Overall, the antibacterial potency of juice supplements (up to 10% v/v in tryptic soy broth) followed the order of chokeberry > blackcurrant > cranberry > elderberry, with the latter showing no inhibitory effects. Notably, chokeberry and elderberry juices presented lower acidity and significantly greater phenolic contents (p < 0.05) than blackcurrant and cranberry juices did, suggesting that B. cereus susceptibility is not strictly dependent upon low extracellular pH or elevated anthocyanin levels. Instead, it is inferred to correlate with pro-oxidative effects induced directly at the intracellular level. Accordingly, this paper discusses the antioxidative, acidic, and lipophilic attributes of juices and their constituent fractions, including anthocyanins, to elucidate their biopreservative potential. The results of this study increase our understanding of the antibacterial susceptibility of B. cereus.

Continuous step-wise temperature extraction improves the flavanol content of tea beverages

BACKGROUND

Tea is the second most consumed beverage worldwide and its health benefits have been extensively studied because of its rich flavanol content. This study aims to evaluate the efficacy of a novel continuous step-wise temperature extraction process in maximising antioxidant activity, total phenolic content and flavanol concentration of different tea beverages.

RESULTS

Continuous step-wise temperature extraction produced the highest absolute antioxidant capacity, total phenolic content and concentration of major tea flavanols in Yuhua tea compared to the other tea types at all extraction points. Despite having the lowest baseline concentration of tea flavanols, Lapsang Souchong tea showed the greatest increase in catechin and epigallocatechin-3-gallate levels with the continuous step-down temperature process, by over 500% and 300%, respectively. In addition, Moonlight White tea showed the greatest percentage change in total antioxidant capacity and phenolic content at the end of the process compared to the baseline. Furthermore, the continuous step-wise temperature extraction showed a moderate increase in caffeine concentration in all the tea samples.

CONCLUSION

Our findings revealed a beneficial impact of continuous step-wise temperature extraction on the antioxidant capacity, phenolic content and flavanol profile in different types of tea, which may be valuable in the production of added-value tea beverages. © 2024 Society of Chemical Industry.

Quality and antioxidant activity of dandelion root infusions as affected by cold plasma pretreatment

Ground and unground dandelion roots were subjected to dielectric barrier discharge cold plasma (DBDCP) at 40 kV for 0 (control), 10, or 20 min. Then, infusions of the pretreated dandelion roots in water were prepared, and the changes in color, total phenolic content (TPC), antioxidant activity, and sensory properties were investigated. The 20-min pretreatment increased the b* value, TPC, antioxidant activity, and sage odor of the ground dandelion root infusions compared with the control, whereas decreases in the TPC, antioxidant activity, and sage odor were noted in the 10-min pretreated infusions of the unground roots. DBDCP pretreatment did not affect the overall likeliness of infusions of ground and unground roots. In addition, the TPC, antioxidant activity, and overall likeliness of infusions of the ground dandelion roots were higher than those of the unground samples. In conclusion, it can be said that the DBDCP pretreatment can be utilized to improve the TPC and antioxidant activity of ground dandelion roots.

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.

Harvest Stage and Brewing Conditions Impact Mineral Content, Phenolic Compounds, and Antioxidant Capacity of Lemon Balm (Melissa officinalis L.) Herbal Tea

Lemon balm (Melissa officinalis L.) is commonly consumed as an herbal tea for its antioxidant health benefits. Young seedlings known as microgreens are popular for their distinct flavors and can contain higher mineral content on a dry weight basis compared to their adult counterparts. However, the use of microgreens for herbal teas has not been previously investigated. In this study, lemon balm was grown to adult and microgreen harvest stages and prepared as herbal teas by brewing with boiled (100 °C) water for 5 minutes and room temperature water (22 °C) for 2 hours. The effects of harvest time and brewing method on the mineral content, phenolic compounds, and antioxidant capacity of lemon balm herbal teas were assessed. Results showed that adult lemon balm tea contained higher total phenolics, total flavonoids, rosmarinic acid, and antioxidant capacity than microgreen teas, with hot preparations containing the highest amounts (p ≤ 0.05). In contrast, microgreen lemon balm teas contained higher amounts of minerals (p ≤ 0.05), including calcium, potassium, magnesium, sodium, phosphorus, copper, and zinc. In general, brewing conditions did not impact the content of most minerals. Overall, the results support the potential of using dried microgreens as herbal teas. Microgreen lemon balm teas prepared hot and cold offer antioxidant compounds and are richer sources of minerals than adult teas. The ease of growth for microgreens offers consumers the opportunity for home preparation of a novel herbal tea beverage.

On the relative extraction rates of colour compounds and caffeine during brewing, an investigation of tea over time and temperature

Various beliefs are common about the extraction of soluble compounds from leaf tea, suggesting that cold brewed tea or tea brewed for a shorter time than usual may contain a higher polyphenol-to-caffeine ratio, a selling point due to the potential health benefits of polyphenolic compounds. To test these beliefs, we investigated the effect of brewing time and temperature on the colour intensity and caffeine content of the extract of one type of black tea. Results showed that the extraction of the two components of interest had different half-lives, with an initial large variation of the ratio between them rapidly reaching a quite constant value. At different temperatures, a significantly different ratio between caffeine and colour compounds was observed. Although the difference in relative concentration was small, the range of brewing temperatures tested was only 20 Kelvin, so it seems possible to increase this difference. A difference in total extraction efficiency of both components together was noted too. To effectively change the ratio of the components using the extraction time would require using accurate times of less than 3 minutes and accurate temperatures unusual in a home environment.

Evaluation of the Brewing Characteristics, Digestion Profiles, and Neuroprotective Effects of Two Typical Se-Enriched Green Teas

As a functional beverage, selenium (Se)-enriched green tea (Se-GT) has gained increasing popularity for its superior properties in promoting health. In this study, we compared the brewing characteristics, in vitro digestion profiles, and protective effects on neurotoxicity induced through the amyloid-beta (Aβ) peptide of two typical Se-GTs (Enshi Yulu (ESYL) and Ziyang Maojian (ZYMJ), representing the typical low-Se green tea and high-Se green tea, respectively). ESYL and ZYMJ showed similar chemical component leaching properties with the different brewing methods, and the optimized brewing conditions were 5 min, 90 °C, 50 mL/g, and first brewing. The antioxidant activities of the tea infusions had the strongest positive correlation with the tea polyphenols among all of the leaching substances. The tea infusions of ESYL and ZYMJ showed similar digestive behaviors, and the tea polyphenols in the tea infusions were almost totally degraded or transferred after 150 min of dynamic digestion. Studies conducted in a cell model of Alzheimer’s disease (AD) showed that the extract from the high-Se green tea was more effective for neuroprotection compared with the low-Se green tea. Overall, our results revealed the best brewing conditions and digestion behaviors of Se-GT and the great potential of Se-GT or Se-enriched green extract (Se-GTE) to be used as promising AD-preventive beverages or food ingredients.

Comparison of the Fungal Community, Chemical Composition, Antioxidant Activity, and Taste Characteristics of Fu Brick Tea in Different Regions of China

In this study, the fungal community structure, metabolites, antioxidant ability, and taste characteristics of five Fu brick tea (FBT) from different regions of China were determined and compared. A total of 69 operational taxonomic units (OTUs) were identified and assigned into 5 phyla and 27 genera, with Eurotium as the predominant genus in all samples. Hunan (HN) sample had the strongest fungal diversity and richness, followed by Guangxi (GX) sample, and Zhejiang (ZJ) sample had the lowest. GX sample had higher amounts of gallic acid (GA), total catechins, gallocatechin (GC), and epicatechin gallate (ECG) as well as antioxidant activity than the other samples. The levels of total phenolics, total flavonoids, epigallocatechin (EGC), catechin, epicatechin (EC), thearubigins (TRs), and theaflavins (TFs) were the highest in the ZJ sample. Guizhou (GZ) and Shaanxi (SX) samples contained the highest contents of epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG), respectively. Total phenolics, GA, EC, CG, and TFs were positively associated with most of fungal genera. Total phenolic content (TPC), total flavonoid content (TFC), and most of catechins contributed to the antioxidant activities of FBT. HN sample had the strongest sourness and sweetness, ZJ sample had the strongest saltiness, SX sample had the strongest umami, and GZ sample had the strongest astringency, which was ascribed to the varied metabolites. This work reveals that FBT in different regions vary greatly in fungal community, metabolites, antioxidant activity, and taste characteristics, and provides new insight into the quality characteristics formation of FBT in different regions.

Effect of brewing time and temperature on the physical properties, antioxidant activities and sensory of the kenaf leaves tea

Kenaf (Hibiscus cannabinus L.), an annual herbaceous plant in the Malvaceae family, has become a multifunctional crop in Malaysia due to its large number of industrial applications for its fibrous stem. Recently, its kenaf leaves that have high antioxidant properties are getting more attention to be developed into tea. Therefore, this research aims to determine the best brewing time and temperature based on the physical properties, antioxidant activities and sensory of kenaf leaves tea (KLT). The kenaf leaves powder which was infused in hot (80 °C or 100 °C; 5 min or 10 min) or cold water (room temperature; 60 min or 120 min) were analysed. Results demonstrated that the KLT brewed at 80 °C for 10 min and 100 °C for 10 min showed the highest antioxidant activities in most of the antioxidant analysis conducted. Moreover, the colour of cold-brewed KLT was much lighter than the hot-brewed KLT and the cold-brewed KLT (room temperature; 120 min) can likely be a new trend for the consumer since it contained high antioxidising capabilities. However, the pH, greenness, yellowness, sensory results in KLT were not affected significantly by both brewing time and temperature (p > 0.05). The antioxidant test was correlated positively with the phytochemical contents but insignificant relationship with most of the colour parameters. Overall, the optimum temperature and time for brewing KLT was 80 °C at 10 min because it saved energy and extracted the highest amount of antioxidants while retaining similar sensory taste with other brewing conditions.

In Vitro Evaluation of Antioxidant and Anticancer Activity of Lemongrass (Cymbopogon citratus (D.C.) Stapf)

Cancer is considered a multifactorial disease and its development could be associated with several factors, for example, rotenone exposition. Unfortunately, many cancers are resistant to chemotherapy, as cervical cancer. Regarding this, lemongrass is a remarkable natural product that presents antioxidant and anticancer activities, which could show therapeutic action against rotenone and cervical cancer. Thus, this study aimed to investigate the antioxidant and anticancer action of lemongrass. An in vitro study was conducted using VERO (kidney cells) and SiHa cell lines (cervical cancer cells). VERO cells were exposed to rotenone and lemongrass extract for 24 and 72 h. While SiHa cells were exposed to lemongrass isolated and associated to chemotherapy, 5-fluorouracil, during 24 and 48 h. After, levels of viability, proliferation, and oxidative metabolism were determined. The results showed that lemongrass presents antioxidant activity on VERO cells by increasing cell viability and proliferation and decreasing oxidative stress caused by rotenone. Moreover, lemongrass showed anticancer activity by decreasing cell viability and increasing oxidative stress parameters on SiHa. Besides, lemongrass had no alteration in the chemotherapy activity. Therefore, this study revealed that lemongrass presents antioxidant and anticancer activity since it can protect against the cytotoxicity of rotenone and reduce the cell viability of cervical cancer.

The Effect of Brewing Process Parameters on Antioxidant Activity and Caffeine Content in Infusions of Roasted and Unroasted Arabica Coffee Beans Originated from Different Countries

Coffee is one of the most often consumed beverages almost all over the world. The multiplicity of beans, as well as the methods and parameters used to brew, encourages the optimization of the brewing process. The study aimed to analyze the effect of roasting beans, the brewing technique, and its parameters (time and water temperature) on antioxidant activity (determined using several in vitro methods), total polyphenols, flavonoids, and caffeine content. The infusions of unroasted and roasted Arabica beans from Brazil, Colombia, India, Peru, and Rwanda were analyzed. In general, infusions prepared from roasted beans had higher antioxidant activity and the content of above-mentioned compounds. The hot brew method was used to obtain infusions with a higher antioxidant activity, while the cold brew with higher caffeine content. The phenolic compound content in infusions prepared using both techniques depended on the roasting process. Moreover, the bean’s origin, roasting process, and brewing technique had a significant effect on the tested properties, in contrary to brewing time and water temperature (below and above 90 °C), which had less impact. The results confirm the importance of coffee brewing optimization.

Aroma and catechin profile and in vitro antioxidant activity of green tea infusion as affected by submerged fermentation with Wolfiporia cocos (Fu Ling)

In response to the increasing interest of western consumers in high antioxidant activity of green tea but their low acceptance of its green odor, we employed a new starter culture, Wolfiporia cocos to tune flavor of green tea infusion. After submerged fermentation for 17 h, W. cocos changed the characteristic green odor to an attractive floral, jasmine-like, and slightly citrus-like flavor while preserving most of in vitro antioxidant activity. By application of mSBSE-GC-MS-O combined with sensorial tests, the formed pleasant aroma was mainly attributed to methyl anthranilate (OAV 802), linalool (OAV 190), 2-phenylethanol (OAV165), and geraniol (OAV 118). Concurrently, the catechin profile determined by UHPLC-MS showed diverse reduction rates (10-50%) for the individual catechins after fermentation. Nevertheless, up to 80% of in vitro antioxidant activity in DPPH assay was preserved. Overall, our findings provide an innovative approach to naturally flavor green tea while retaining the antioxidant activity.

Effects of soaking treatment on the acrylamide and inulin contents of Jerusalem artichoke tea and its antioxidant activity

There are several studies that show that large amounts of acrylamide are detected in Jerusalem artichoke (Helianthus tuberosus L.) tea. This study examined acrylamide, inulin content and antioxidant properties of Jerusalem artichoke tea brewed in different conditions. Uniformly sliced Jerusalem artichokes were soaked in different salt and acidic solutions for 60 min at 20 °C and extracted with hot or cold water. The acrylamide content was analyzed by high-performance liquid chromatography-tandem mass spectrometry. The Inulin content and antioxidant activity were analyzed by spectrophotometer. Soaking significantly reduced acrylamide levels (p < 0.05) with the largest decrease observed for acetic acid, whereas the effects of all soaking treatments on inulin content were similar. Teas brewed using small-particle-size samples and hot water exhibited the highest acrylamide/inulin levels and antioxidant activity. Consequently, The most suitable treatment for Jerusalem Artichoke tea preparation was 1-h soaking in 1% acetic acid at 20 °C.

Chitosan Activated with Genipin: A Nontoxic Natural Carrier for Tannase Immobilization and Its Application in Enhancing Biological Activities of Tea Extract

In this work, a non-toxic chitosan-based carrier was constructed via genipin activation and applied for the immobilization of tannase. The immobilization carriers and immobilized tannase were characterized using Fourier transform infrared spectroscopy and thermogravimetric analysis. Activation conditions (genipin concentration, activation temperature, activation pH and activation time) and immobilizations conditions (enzyme amount, immobilization time, immobilization temperature, immobilization pH, and shaking speed) were optimized. The activity and activity recovery rate of the immobilized tannase prepared using optimal activation and immobilization conditions reached 29.2 U/g and 53.6%, respectively. The immobilized tannase exhibited better environmental adaptability and stability. The immobilized tannase retained 20.1% of the initial activity after 12 cycles and retained 81.12% of residual activity after 30 days storage. The catechins composition analysis of tea extract indicated that the concentration of non-ester-type catechins, EGC and EC, were increased by 1758% and 807% after enzymatic treatment. Biological activity studies of tea extract revealed that tea extract treated with the immobilized tannase possessed higher antioxidant activity, higher inhibitory effect on α-amylase, and lower inhibitory effect on α-glucosidase. Our results demonstrate that chitosan activated with genipin could be an effective non-toxic carrier for tannase immobilization and enhancing biological activities of tea extract.

Evaluation of Antioxidant Activity of Cudrania tricuspidata (CT) Leaves, Fruit Powder and CT Fruit in Pork Patties during Storage

The objective of this study was to assess antioxidant activities of leaves and fruit powder of Cudrania tricuspidata (CT) with different particle sizes (crude, 500 μm, 150 μm), and determine the physicochemical properties and microbial counts of pork patties with various levels of CT fruit powder (CTFP) during refrigerated storage. Total phenolic content of crude leaves had the highest value of 3.54 g/100 g (p<0.05). Overall, CT leaves (CTLP) had higher total phenolic content than CTFP (p<0.05). 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of CTFP was higher than that of CTLP (p<0.05), which showed higher iron chelating ability and reducing power than CTFP (p<0.05). After pork patties were manufactured with 0.5% and 1.0% of CTFP at 500 μm, pH, color values, thiobarbituric acid reactive substance (TBARS), and peroxide values (POV) were then measured. The addition of CTFP into pork patties significantly (p<0.05) increased redness and yellowness values of patties. TBARS values of pork patties containing CTFP were lower (p<0.05) than those of CTFP-0 patties after 10 days of storage. Pork patties added with CTFP showed no significant (p>0.05) difference TBARS values among different storage periods. POV values of pork patties containing CTFP were lower than those of the control from 3 days up to the end of refrigerated storage (p<0.05). These results suggest that CTFP could be used as a natural antioxidant to retard lipid oxidation in meat products during refrigerated storage.

Effect of microwave-drying on the quality and antioxidant properties of Ganoderma lucidum fermented sea-buckthorn tea

Effects of microwave power on the sensory properties (taste and aroma), chemical composition (catechins, caffeine, crude protein, and amino acid), active composition (flavones, triterpene, polysaccharide, and ergosterol) and antioxidant properties (superoxide free radical and hydroxyl radical scavenging abilities, reducing power) of Ganoderma lucidum fermented sea-buckthorn tea were investigated. G. lucidum fermented sea-buckthorn tea was dehydrated using microwaves at three power settings: 125, 250, and 500. After microwave treatment, a statistically significant difference in the chemical composition, active composition and antioxidant capacity (p < 0.05) of teas dried at different power settings was found. These results indicate that 250 W microwave treatments could effectively release and activate active components, improving the antioxidant activity of fermented tea.

Changes of antioxidant activity and active compounds content in selected teas

Our study tested 45 tea infusions classified into five groups (white, green, red, black, and other teas) for the content of total polyphenols and flavonoids, as well as antioxidant properties, by the FRAP and DPPH methods. We examined these parameters after prolongation of the brewing time from 10 to 30 min and overnight storage. The results showed that the capacity of the teas to bind free radicals was differentiated and the amount of anti-oxidant compounds depended on their nature. In terms of antioxidant activity and total polyphenol content, the tested tea types were ranked in the following order: white > green > black > red > other teas (yerba mate > rooibos). Our experiment demonstrated a positive correlation between the polyphenol content and antioxidant activity of the analyzed teas. Also, the DPPH antiradical efficiency was comparable to their ability to reduce ferric ions. The extended brewing time had a significant effect on the antioxidant activity of the infusions and the polyphenolic compounds analyzed therein. In contrast, storage of the infusions for 24 h at room temperature changed their antioxidant activity and affected the total polyphenol content.

Thermostable Tannase from Aspergillus Niger and Its Application in the Enzymatic Extraction of Green Tea

Tannase is widely used in tea beverage processing because of its ability to catalyze the hydrolysis of hydrolysable tannins or gallic acid esters and effectively improve the quality of tea extracts through enzymatic extraction. A new thermophilic tannase was cloned from Aspergillus niger FJ0118 and characterized. The tannase exhibited an optimal reaction temperature of 80 °C and retained 89.6% of the initial activity after incubation at 60 °C for 2 h. The enzymatic extraction of green tea at high temperature (70 °C) for a short time (40 min) was devised on the basis of the superior thermal stability of tannase. The enzymatic reaction significantly increased the total polyphenol content of green tea extract from 137 g·kg⁻¹ to 291 g·kg⁻¹. The enzymatic reaction effectively degraded the ester catechins into non-ester catechins compared with the water extraction method. Results suggested that the thermally stable tannase exhibited potential applications in the enzymatic extraction of green tea beverage.

Prediction of suitable brewing cuppages of Dahongpao tea based on chemical composition, liquor colour and sensory quality in different brewing

Oolong tea is famous for its characteristic of durably brewing. To explore suitable brewing cuppages and the scientific methods to brew Oolong tea in multiple steeping process. Dahongpao tea (Zhengyan, Banyan and Zhouyan tea) is well known Oolong tea variety, brewed at 14 times and assessed its chemical composition, infusion colour and sensory quality in different brewing intervals. The results showed that Zhengyan tea (A3) had the best quality of steeping among the chosen tea. It could be brewed up to 10 cuppages with 80% sensory score. The chemical composition and tea infusion colour strength were higher in Zhengyan tea. Though, 70% caffeine leached within first three steeping. The Forest regression model revealed that the suitable brewing time ranges between 4 and 10 in the chosen Dahongpao tea variety. This study provides a scientific method and suitable steeping times for the drinking of different Dahongpao tea through dynamic analysis of quantity of chemical composition, infusion colour strength and sensory quality.

Morphological, Physicochemical and FTIR Spectroscopic Properties of Bee Pollen Loads from Different Botanical Origin

Bee pollen loads generally have a homogeneous and monospecific pollen content and assume a typical form and color, due to the typical bee foraging habits, thus having a typical composition related to the botanical origin. The present study aims to characterize bee pollen loads belonging to different botanical species using morphological, spectroscopic and color properties and to find relationships between these variables. IR spectra analysis allowed to have a reliable picture of the components present in the different samples; color and granulometry permits a visual identification of pollen load belonging to different species. Multivariate analysis enabled differentiation among the botanical origin of most of the bee pollen samples, grouping them according to the family and the genus and confirming the possibility to use IR and color measurements for the evaluative analysis and classification of bee pollen samples, to promote the consumption of this bee product as functional food.

Impact of Cold versus Hot Brewing on the Phenolic Profile and Antioxidant Capacity of Rooibos (Aspalathus linearis) Herbal Tea

Consumption of rooibos (Aspalathus linearis) as herbal tea is growing in popularity worldwide and its health-promoting attributes are mainly ascribed to its phenolic composition, which may be affected by the brewing conditions used. An aspect so far overlooked is the impact of cold brewing vs regular brewing and microwave boiling on the poly(phenolic) profile and in vitro antioxidant capacity of infusions prepared from red ('fermented', oxidized) and green ('unfermented', unoxidized) rooibos, the purpose of the present study. By using an untargeted metabolomics-based approach (UHPLC-QTOF mass spectrometry), 187 phenolic compounds were putatively annotated in both rooibos types, with flavonoids, tyrosols, and phenolic acids the most represented type of phenolic classes. Multivariate statistics (OPLS-DA) highlighted the phenolic classes most affected by the brewing conditions. Similar antioxidant capacities (ORAC and ABTS assays) were observed between cold- and regular-brewed green rooibos and boiled-brewed red rooibos. However, boiling green and red rooibos delivered infusions with the highest antioxidant capacities and total polyphenol content. The polyphenol content strongly correlated with the in vitro antioxidant capacities, especially for flavonoids and phenolic acids. These results contribute to a better understanding of the impact of the preparation method on the potential health benefits of rooibos tea.

A Comparative Study of Antioxidant Potential and Phenolic Content in White (Silver Needle), Green and Black Tea

Background:

White, green and black are the major tea types obtained from the same tea plant (Camellia sinensis). The differences in processing result in different types of tea, of which green tea (20%) and black tea (78%) are the most consumed worldwide and also white tea is gaining popularity due to its subtle taste and recent evidences about its health benefits. Silver needle is a sub type of white tea, made purely from buds whereas green tea is procured from leaves that are steamed or panfried, and to produce black tea, the tea leaves are withered, fully oxidized and then dried.

Objective:

The present study was undertaken to analyze and compare the antioxidant activity and phenolic composition of white (silver needle), green and black teas of same brand.

Method:

The radical scavenging ability of different tea types was measured using various antioxidant assays. The total phenolic content was also estimated using Folin-Ciocalteu’s method.

Results:

The white tea (silver needle) demonstrated highest radical scavenging activity followed by green and then black tea in various antioxidant assays performed. The total phenolic content of different types of tea exhibited the following order: white tea (133.30mg/g) > green tea (118.37mg/g) > black tea (101.8mg/g). A strong correlation was observed between the total phenolic content and antioxidant activity of different tea types, the correlation coefficient ranged from 0.87-0.97.

Conclusion:

White tea (silver needle) manifested highest antioxidant activity followed by green and least in black tea. The pronounced antioxidant ability of WT (silver needle) may be ascribed to the different parts of the plant (unopened buds) and the least processing it undergoes, followed by obtaining green tea and black tea from different parts of the plant (leaves), and variation in degree of processing.

Effect of Mongolian Herbal Tea on Growth of Candida albicans

Candida albicans, one of the main pathogens in the oral cavity, is involved in the development of oral candidiasis. Various components of tea, and especially polyphenols, are believed to be effective against the growth of yeast or bacteria. The purpose of this study was to investigate the effect of polyphenols in Mongolian herbal tea on growth of C. albicans. Tea extract was prepared from Mongolian herbal tea and diluted with distilled water (DW) at concentrations of 10, 20, 30, 40, or 50%. Distilled water was used as the control. Acidification of the medium was determined by measuring its pH; the presence of polyphenols by the Folin-Ciocalteau colorimetric method; and growth of C. albicans by absorbance at a wavelength of 630 nm at 0-, 6-, 12-, and 24-hr intervals. The pH of the medium was 5.2 to 5.27 in all experimental groups compared with 7.1 in the control group. Polyphenols were present in all experimental groups, and at significantly higher levels than in the control group. Growth of C. albicans showed a significant and time-dependent increase in the control and all experimental groups. Growth of C. albicans in all the experimental groups was higher than that in the control group. These results suggest that Mongolian herbal tea promotes the growth of C. albicans, despite the presence of polyphenols.

Effects of brewing conditions on the phytochemical composition, sensory qualities and antioxidant activity of green tea infusion: A study using response surface methodology

Green tea is a highly consumed beverage, and the phytochemical composition, sensory qualities, and antioxidant activity of tea infusion are significantly affected by brewing conditions. However, the simultaneous effects of brewing conditions on the infusion are unknown. This study aimed to model the effects of brewing conditions (temperature, time, water/tea ratio and particle size) on the phytochemical composition, sensory profiles and antioxidant activity of green tea infusion using response surface methodology. The regression models describing the brewing of detected indexes were significant (p ≤ 0.01) and reliable (R² ≥ 0.854). Particle size had the greatest negative effects on the phytochemical composition and antioxidant activities of tea infusion. Optimization of brewing conditions performed for five types of needs and preferences for consuming were verified to be credible. In particular, optimal conditions of overall acceptance were 82 °C (temperature), 5.7 min (time), 70 mL/g (water/tea ratio), and 1100 µm (particle size).

Influences of Product Temperature on Emotional Responses to, and Sensory Attributes of, Coffee and Green Tea Beverages

Coffee and green tea are popular beverages consumed at both hot and cold temperatures. When people consume hot beverages concurrently with other activities, they may experience at different temperatures over the period of consumption. However, there has been limited research investigating the effects of product temperatures on emotional responses and sensory attributes of beverages. This study aimed to determine whether emotional responses to, and sensory attributes of, brewed coffee and green tea vary as a function of sample temperature. Using a check-all-that-apply (CATA) method, 157 participants (79 for coffee and 78 for green tea) were asked to evaluate either coffee or green tea samples served at cold (5°C), ambient (25°C), and hot (65°C) temperatures with respect to emotional responses and sensory attributes. The results showed that sample temperature could have significant influences on emotional responses to, and sensory attributes of, coffee and green tea samples. More specifically, 6 and 18 sensory attributes of coffee and green tea samples, respectively, significantly differed with sample temperature. Beverage samples evaluated at 65°C were characterized, regardless of activation/arousal level, by positive emotional responses terms and favorable sensory attributes. While beverages evaluated at 25°C were associated more with negative emotional responses with low activation/arousal, those evaluated at 5°C were more frequently characterized as having negative emotional responses with high activation/arousal. Sensory and emotional drivers of liking for both coffee and green tea differed both with sample temperature and gender. While both emotional responses and sensory attributes were identified as drivers of liking among females, only emotional responses were identified as drivers of liking among males. In conclusion, this study provides empirical evidence that both emotional responses to, and sensory attributes of, coffee and green tea beverages can vary with sample temperatures. To provide a better understanding of product characteristics, emotional responses to, and sensory attributes of, coffee or green tea beverages should be tested over a wider range of product temperatures.

Effect of brewing time and temperature on antioxidant capacity and phenols of white tea: Relationship with sensory properties

White tea is highly consumed due to its sensory properties and health benefits, although most scientific reports don't include the analysis of both properties. Therefore, the objective of the present study was to unravel the best brewing conditions for optimal extraction of the bioactive compounds and antioxidant capacity, while realising the best sensory properties. Infusions of eighty commercial teas (sold in bags or leaves) were obtained at different time-temperature ratios, studying bioactive compounds (caffeine and individual catechins), antioxidant capacity and sensory analysis. Brewing at 98 °C for 7 min was the best condition to obtain a high content of antioxidant polyphenols and pleasant sensory properties. Those teas sold in bags give rise to tea brews with almost double antioxidant capacity. In conclusion, it is very important to link sensory and chemical data to obtain optimal sensorial quality and the highest healthy properties in white tea infusions.

Effect of brewing conditions on antioxidant properties of rosehip tea beverage: study by response surface methodology

The aim of this study was to investigate the effects of brewing conditions (infusion time and temperature) on the antioxidant properties of rosehip tea beverage. The ascorbic acid content, total phenolic content (TPC), and ferric reducing antioxidant power (FRAP) of rosehip tea beverage were analysed. A two-factor and three-level central composite design was applied to evaluate the effects of the variables on the responses. The best quadratic models were obtained for all responses. The generated models were validated under the optimal conditions. At the optimal conditions, the rosehip tea beverage had 3.15 mg 100 mL-1 of ascorbic acid, 61.44 mg 100 mL-1 of TPC, and 2591 µmol of FRAP. The best brewing conditions for the rosehip tea beverage were found to be an infusion time of 6-8 min at temperatures of 84-86 °C.

Influence of particle size and extraction solvent on antioxidant properties of extracts of tea, ginger, and tea-ginger blend

The influence of particle size and extraction solvent on the antioxidant properties of aqueous and ethanolic extracts of tea (Camellia sinensis), ginger (Zingiber officinale), and tea–ginger (2:1) blend was investigated. The powder sizes studied were 0.425, 0.710, and 1.180 mm. Extracts were analyzed for DPPH radical scavenging activity, ABTS radical scavenging activity, total phenol content (TPC), iron chelating activity, total flavonoid content, and peroxide scavenging activity. The powder with the lowest particle size of 0.425 mm tends to produce aqueous extracts of tea, ginger, and tea–ginger with highest antioxidant content. At this lowest particle size all the antioxidant properties assayed were maximized. The TPC of aqueous extracts obtained from the 0.425 mm tea, ginger, and tea–ginger powders were 685.44 ± 175, 283.58 ± 19, and 483.02 ± 176 mg gallic acid equivalent (GAE) L⁻¹, respectively. The TPC of aqueous extracts obtained from the 0.710 mm tea, ginger, and tea–ginger powders were 679.06 ± 169, 208.94 ± 147, and 400.10 ± 130 mg GAE L⁻¹, respectively. However, for the aqueous ethanolic and ethanolic extracts, the particle size that maximized the antioxidant extraction varied depending on the antioxidant property that was being assayed. The study suggests that particle size influences the extraction of antioxidants. Also, the optimum powder size that would maximize antioxidant extraction is dependent on the solvent used and the antioxidant property being measured.