Changes in profiles of volatile compounds and prediction of the storage year of organic green tea during the long-term storage

Analysis of changes in volatile metabolites of pickled radish in different years using GC-MS, OAV and multivariate statistics

Pickled radish is a local specialty fermented food, loved for its unique flavor. In this study, the volatile components of pickled radish from different years were identified and analyzed, and 82 volatile metabolites were finally identified and 39 volatile differential metabolites were screened out, which showed that the contents of γ-butyrolactone, 3-furaldehyde and ethyl lactate showed an increasing trend. Odor activity value (OAV) analysis showed that 3-furaldehyde, dimethyl tetrasulphide and linolenic acid were important aroma components in pickled radish. In addition, the potential pathways for the formation of volatile metabolites in pickled radish were preliminarily constructed based on the KEGG database, in which alcohols, aldehydes and acids contributed to the formation of the unique flavor of pickled radish. The present study reveals the systematic changes of volatile metabolites in pickled radish and provides a new perspective to understand the changes of its flavor characteristics.

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.

Underlying characteristic aroma of white tea from diverse geographical origins and its prediction

BACKGROUND

White tea, an agriculturally distinctive product, exhibits significant aroma variations across different regions. Nevertheless, the mechanisms driving these differences, and distinguishing methods suitable for specific origins, have been scarcely reported. In this study, we analyzed the aroma characteristics and volatile components of 100 white tea samples from ten regions, utilizing sensory evaluation, headspace solid-phase microextraction-gas chromatography-mass spectrometry and chemometrics, then established a discrimination model.

RESULTS

A total of 66 volatile compounds were identified, with alcohols and esters being the most important. Linalool and geranyl alcohol were common and relatively abundant volatile compounds across all ten regions, significantly contributing to the aroma characteristics of white tea. The relative content of volatile compounds differed notably across regions, where 33 key compounds, including (E)-2-phenylbut-2-enal and methyl 2,5-octadecadiynoate, were crucial for regional prediction. Employing machine learning algorithms, such as random forest and support vector machine for regional prediction, yielded accuracies of 93.33% and 90.00%, respectively.

CONCLUSION

This study unveils new insights into aroma variation in white tea across different origins, proposing an innovative way of origin determination. © 2025 Society of Chemical Industry.

Flowering in aged white tea: Recovering umami taste and amplifying of stale aroma

Throughout the natural aging process from new to aged white tea, the flavor evolves into a 'stale flavor', despite the initial umami diminishes. The flowering process, inoculation of Eurotium cristatum to white tea, improves the flavor. The impact on sensory qualities and underlying chemical basis of flowering in aged white tea warrant investigation. Sensory analysis, non-targeted metabolomics and volatilomics together deciphered flavor modifications of flowering in aged white tea from different aging years (FAWTs). Findings indicate the flowering process can recover the umami of aged white tea, enhancing the 'stale flavor'. These changes primarily stem from oxidations of catechins and free amino acids, enrichments of flavonols and soluble sugars, and 16 pivotal aroma compounds from degradations of lipids and glycosides. Additionally, 15 volatile and 39 non-volatile compounds were identified as potential biomarkers for FAWTs. These findings offer a viable strategy to improving the quality of aged white tea.

Temporal analysis of non-targeted flavor component variation in green tea storage and rapid prediction of storage duration

The precise changes in the flavor quality of green tea before and after the optimal consumption period remain elusive. This study used HS-SPME-GC-MS to carefully examine the volatile compounds of green tea samples from multiple storage periods and simultaneously detected changes in taste and color during tea infusion. Notably, 16 compounds with VIP > 1.5 were identified, highlighting their significance in the overall analysis profile. Among these components, nonanoic acid, octanoic acid and hexanal were identified as potential contributors to off-flavors and rancid oil flavors in tea after storage. The color of the tea broth becomes darker. Bitter flavor is associated with increased amino acid content. The PSO-SVM model showed excellent accuracy for predicting the storage duration of green tea. These findings provide critical theoretical understandings of green tea manufacturing and quality control.

Monitoring quality changes in green tea during storage: A hyperspectral imaging method

The quality of green tea deteriorates the longer it is stored. However, there is a lack of accurate and rapid methods for determining the storage period of tea. In this study, hyperspectral imaging (HSI) was used to determine the storage period of green teas stored at 4 °C (set 1) and 25 °C (set 2), and to quantify and visualize the main chemical components (e.g. catechins). In this study, three prediction algorithms were compared, in which partial least squares discriminant analysis outperformed the other models in qualitative discrimination, with 98% and 96% correct discrimination for two sets, respectively. Moreover, quantitative models for ester catechins, simple catechins, and total catechins were developed with Rp > 0.90 and RPD > 1.0, indicating that the models were reliable. Further, a more intuitive visualization of catechin content was achieved. In conclusion, the HSI provides a rapid, non-destructive method to determine the freshness of stored green tea.

Brewing method-dependent changes of volatile aroma constituents of green tea (Camellia sinensis L.)

The determination of optimal levels of green tea amount and brewing time would have a crucial role in the accumulation of desired aromatic volatile compounds to meet worldwide market demand. Aroma is the most important factor influencing tea consumers' choices along with taste, price, and brand. This study aims to determine how the brewing time and amount of green tea affect the aroma profile of green tea infusion. The effect of the amount of Turkish green tea (5-10 g) and brewing time (5-60 min) on aromatic volatile compounds was evaluated using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) technique. The SPME/GC-MS analysis identified 57 components in the aroma profile of green tea infusions including 13 esters, 12 alkanes, 7 unknowns, 6 ketones, 3 alcohols, 2 terpenes, 2 terpenoids, 1 alkaloid, 1 phenolic compound, 1 lactone, 1 pyrazine, and 1 norisoprenoid. The green tea amount and brewing time had significant effects on the number of chemical compounds. A total of 42, 47, and 36 aromatic volatile compounds were determined by brewing 5, 7.5, and 10 g of green tea. The most abundant constituents in green tea infusions were phytone, 2-decenal, lauric acid, unknown 1, methoxy-1-methylethyl pyrazine, α-ionone, β-ionone, and diethyl phthalate (DEP). With this study, the aroma structures of green tea infusion have been revealed for the first time depending on the brewing time and quantity.

The enhancement of flowery-like aroma in green tea under optimized processing conditions by sensory-directed flavor analysis

Flowery-like aroma are positive contributors to green tea. Here, the optimal processing conditions for green tea with flowery-like aroma were designed using spreading time, fixation time and drying temperature as three factors designed by response surface methodology (RSM), and the response value of aroma sensory evaluation score. The volatiles in batches of tea samples were analyzed by GC-MS. The optimal quality was obtained with a flowery-like aroma by RSM under a spreading time of 8.97 h, fixation time of 162.3 s, and drying temperature of 103.32 °C. GC-O and odor activity values further revealed floral-like volatiles, including decanal, linalool oxide, β-lonone, geraniol, (Z)-jasmone, linalool, nonanal, and benzeneacetaldehyde. The recombination of these floral volatiles confirmed the consistency with the floral green tea. Furthermore, the extending spreading duration (8-10 h), reducing fixation duration (160-190 s), and increasing drying temperature (100-115 °C) promote their accumulation in green tea. This study provides new perspectives for the precise enhancement of floral odorants for green tea.

Exploring tea and herbal infusions consumption patterns and behaviours: The case of Portuguese consumers

Consumption of tea and herbal infusions (THIs) have a long history in traditional medicine and cultural practices. The health-promoting benefits attributed to THIs are considered influential factors in consumer choices. However, there is limited data on consumer choices and attitudes that might interfere with the positive effects associated with THIs consumption. The aim of this study was to investigate the consumption pattern and behavior of THIs consumers in Portugal, assessing the influence of socio-demographic factors on the selection of THIs products and consumer practices related to these beverages. An online survey was conducted, and from the collected data, 720 responses met the aim of the study and were further analyzed. Most of the respondents were female, 74.4%, belonging to the 40-60 age group (40.6%) and were medium consumers of THIs (47.2%). Green tea was the most consumed type among participants, and its consumption was associated not only with age but also with the pattern of THIs consumption. Despite that, participants preferred herbal infusions, with citronella, chamomile, and lemon verbena being the most consumed types. For certain types of herbal infusions, consumption was associated with age, while other types were preferred by moderate or heavy consumers. Most participants purchased THIs in supermarkets, registered trademark and brand stores, in the form of THIs bag. Light consumers use only bag, while medium/heavy consumers indicated the use of other forms. Almost half of the respondents admitted to not reading the information on product labels before consumption and using THIs after the expiry date, while only one-third of them declared paying attention to the label instructions. This study revealed the impact of socio-demographic factors as age on the consumption patterns and preferences of THIs of consumers. Of concern is the neglect of label usage among Portuguese consumers. This emphasizes the urgency of implementing interventions to guide proper label use and promote good consumption practices to ensure the quality of THIs products.

The Flavor Characteristics, Antioxidant Capability, and Storage Year Discrimination Based on Backpropagation Neural Network of Organic Green Tea (Camellia sinensis) during Long-Term Storage

The storage period of tea is a major factor affecting tea quality. However, the effect of storage years on the non-volatile major functional components and quality of green tea remains largely unknown. In this study, a comparative analysis of organic green teas with varying storage years (1-16 years) was conducted by quantifying 47 functional components, using electronic tongue and chromatic aberration technology, alongside an evaluation of antioxidative capacity. The results indicated a significant negative correlation between the storage years and levels of tea polyphenols, total amino acids, soluble sugars, two phenolic acids, four flavonols, three tea pigments, umami amino acids, and sweet amino acids. The multivariate statistical analysis revealed that 10 functional components were identified as effective in distinguishing organic green teas with different storage years. Electronic tongue technology categorized organic green teas with different storage years into three classes. The backpropagation neural network (BPNN) analysis demonstrated that the classification predictive ability of the model based on the electronic tongue was superior to the one based on color difference values and 10 functional components. The combined analysis of antioxidative activity and functional components suggested that organic green teas with shorter storage periods exhibited stronger abilities to suppress superoxide anion radicals and hydroxyl radicals and reduce iron ions due to the higher content of eight components. Long-term-stored organic green teas, with a higher content of substances like L-serine and theabrownins, demonstrated stronger antioxidative capabilities in clearing both lipid-soluble and water-soluble free radicals. Therefore, this study provided a theoretical basis for the quality assessment of green tea and prediction of green tea storage periods.