Effect of Ferrous Ion on Heat-Induced Aroma Deterioration of Green Tea Infusion

Flavor evolution of unsweetened green tea beverage during actual storage: Insights from multi-omics analysis

The flavor evolution of unsweetened green tea beverage (USGTB) under actual storage is critical for quality control yet remains unclear. Unlike previous studies conducted by accelerated shelf-life testing, this research investigated sensory-chemical changes in naturally stored USGTB (0-7 months) through multi-omics integrating metabolomics and sensomics. Results identified the 5-month as a critical point for flavor preservation. The EC-EGCG dimer emerged as a novel aging marker, contrasting with freshness indicators (ascorbic acid and other antioxidants). Protocatechuic acid and 2-furoic acid served as multi-flavor contributors (yellowish, sweetness and astringency), whereas L-tartaric acid and malic acid enhanced sourness. Concurrently, aroma deterioration was driven by the diminished (E)-β-ionone and accumulated methyl salicylate. Mechanistically, oxidations of ascorbic acid, catechins, and fresh aroma-related volatiles, flavonoid glycosylation, and oligosaccharides hydrolysis collectively drove color darkening, astringency enhancement, sweetness intensification, and cooked-off flavor development. These findings provided targeted quality control points for USGTB during actual shelf-life.

Exploring the sensory acceptance, physicochemical properties, and phenolamide leaching characteristics of rose tea

The consumption of rose tea has gained popularity due to its unique flavor and health benefits. In particular, previous data exemplified the protective role of N1, N5, N10-(E)-tri-p-coumaroylspermidine (ETCS; a phenolamide) against alcohol-induced hepatic injuries. This study evaluated the customer acceptance and physicochemical properties of eight rose tea varieties that available in the market. In general, Qianye rose (Rosa centifolia) exhibits better flavor and taste, while Hetian rose (Rosa damascena Mill.) has the highest ETCS level. Moreover, a negative correlation between ETCS content and both vitamin C and anthocyanins content in rose is observed. Additionally, the optimal brewing conditions for rose tea is 95 °C mineral water for 5 min in a thermos bottle, based on ETCS level in the infusion. And rose tea can be brewed for at least three times. Collectively, our findings provide valuable insights for rose tea drinkers and individuals interested in the dietary hepatic-protective benefits.

Effect of the type of brewing water on the sensory and physicochemical properties of light-scented and strong-scented Tieguanyin oolong teas

Variations in the quality of brewing water profoundly impact tea flavor. This study systematically investigated the effects of four common water sources, including pure water (PW), mountain spring water (MSW), mineral water (MW) and natural water (NW) on the flavor of Tieguanyin tea infusion. Brewing with MW resulted in a flat taste and turbid aroma, mainly due to the low leaching of tea flavor components and complex interactions with mineral ions (mainly Ca2+, Mg2+). Tea infusions brewed with NW exhibited the highest relative contents of total volatile compounds, while those brewed with PW had the lowest. NW and MSW, with moderate mineralization, were conducive to improving the aroma quality of tea infusion and were more suitable for brewing both aroma types of Tieguanyin. These findings offer valuable insights into the effect of brewing water on the sensory and physicochemical properties of oolong teas.

Effects of brewing water on the volatile composition of tea infusions

There is a huge demand for brewing water in tea consumption, and the sensory flavor of tea infusion is significantly affected by the water used for brewing. To investigate the impact of brewing water on the aroma of tea infusions made from Camelia senensis, the three tea infusions of green, oolong and black tea brewed by six different drinking waters were analyzed by sensory evaluation, solid-phase microextraction, gas chromatography-mass spectrometry, and chemometrics. Brewing water with high pH values (>8.10) and high TDS content (>140 ppm) resulted in a lower overall aroma acceptability for tea infusion, where HCO3-, Ca2+ and Mg2+ were key influencing ions. A total of 86, 106, and 131 volatiles were identified in green, oolong and black tea infusions, respectively, which were strongly influenced by six different brands of waters. Decanal, dimethyl sulfide, β-ionone and linalool were potent volatiles in tea aroma changes caused by brewing water.

The types of brewing water affect tea infusion flavor by changing the tea mineral dissolution

The effects of different brewing water samples, including natural drinking water (NDW), pure water (PW), mineral water (MW), distilled water (DW), and tap water (TW) on flavor and quality of green tea infusion were investigated. The results showed the dissolution rate of mineral substances varied greatly depend on the type of water used. Notably, the tea infusion brewed with MW showed the highest taste response and darker but higher brightness in color. Furthermore, the content of volatile compounds was highest in tea infusion brewed with NDW and lowest in tea infusion brewed with MW. The mineral substances content and pH were the main factors affecting volatile compounds in green tea infusion. Thereinto, Ca²⁺ and Fe³⁺ remarkably affected the content of alcohols and aldehydes in volatile compounds. These results suggested that water with a neutral pH value and lower mineral substance content is more conducive for brewing green tea.

Effects of Hydrogen Peroxide Produced by Catechins on the Aroma of Tea Beverages

Hydrogen peroxide has a significant effect on the flavor of tea beverages. In this study, the yield of hydrogen peroxide in (-)-epigallocatechin gallate (EGCG) solution was first investigated and found to be significantly enhanced under specific conditions, and the above phenomenon was amplified by the addition of linalool. Then, an aqueous hydrogen peroxide solution was added to a linalool solution and it was found that the concentration of linalool was significantly reduced in the above-reconstituted system. These findings were verified by extending the study system to the whole green tea infusions. The results suggested that the production of hydrogen peroxide in tea beverages may be dominated by catechins, with multiple factors acting synergistically, thereby leading to aroma deterioration and affecting the quality of tea beverages. The above results provided a feasible explanation for the deterioration of flavor quality of green tea beverages with shelf life.