Widely Targeted Metabolomics Analysis Reveals Great Changes in Nonvolatile Metabolites of Oolong Teas during Long-Term Storage

Abstract

As a semifermented tea, oolong is exceedingly popular worldwide for its elegant, flowery aroma and mellow, rich taste. However, recent marketing trends for old oolong teas and their chemical quality largely remain unexplored. In this study, we applied widely targeted metabolomics using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with multivariate analysis to investigate the chemical change of oolong teas in the aging process. With the increasing of store time, most nongalloylated catechins; tannins, including TFs and proanthocyanidins; flavonols and glycosylated flavonols; amino acids and their derivatives; nucleotides and their derivatives; and lots of alkaloids and phospholipids declined, while most fatty acids and organic acids increased, and galloylated catechins, GA, and caffeine were almost stable. The result also suggested that approximately seven years (but not an infinite extension) was a special period for oolong tea storage, which brings about excellent taste.

Aged oolong tea alleviates dextran sulfate sodium-induced colitis in mice by modulating the gut microbiota and its metabolites

“…Polysaccharides and flavonoids have been shown to alleviate colitis by inhibiting the expression of inflammatory factors and modulating the gut microbiota (F. Huang et al, 2016 ). For AOT stored for 20 to 30 years, the comparison revealed that the complex and diverse water-soluble polysaccharides and flavonoids in AOT tended to increase year by year as the storage time increased, which is consistent with the study of Hong ( Hong et al, 2021 ) et al . and Peng ( Peng et al, 2022 ) et al .…”

“…Further comprehensive analysis of the results of inflammatory factors, tight junction proteins, oxidative stress factors and gut microbiota showed that AOT from different storage periods provided different degrees of relief in DSS-induced colitis mice. This is an intriguing finding, as the phytochemical makeup of AOT varies according to storage duration ( Hong et al, 2021 , Peng et al, 2022 ). The phytoactive components of AOT were analyzed at four different storage periods.…”

“…Oolong tea, a famous traditional Chinese tea, is semifermented. In recent years, AOT has become increasingly popular in the consumer market, and there exists a commonly accepted belief among consumers in China that the longer tea is stored and oxidized, the better the flavor and greater the health benefits ( Hong et al, 2021 ). Long-term use in folk medicine also shows that AOT regulates gastrointestinal discomfort, exhibits antioxidant and anti-inflammatory effects and relieves diarrhea.…”

Optimizing Processing Techniques of Oolong Tea Balancing between High Retention of Catechins and Sensory Quality

“…The content of catechins in oolong tea gradually decreases with an increase in the degree of roasting [11]. During long-term storage of oolong tea, the content of non-gallated catechins gradually decreases, while the content of gallated catechins remains relatively stable [12].…”

Widely targeted metabolomics analysis reveals the formation of nonvolatile flavor qualities during oolong tea manufacturing: a case study of Jinguanyin

“…Generally, the formation of the characteristic flavor is a consequence of multiple stresses in the postharvest manufacturing of oolong tea ( 6 ). While many studies have been centered on using different tea varieties to understand and investigate the characteristic flavor and formation mechanism in each manufacturing process of oolong tea, such as Tieguanyin after roasting ( 7 ), Shuixian tea after long-term storage ( 8 ), Wuyi rock tea produced with four tea cultivars (including Rougui, Dahongpao, Qizhong and Shuixian) at three roasting levels (low, moderate and sufficient) ( 9 ) and oolong tea processed with Chin-Hsin-Dah-Pang and Chin-Hsin-Gan-Tzu two cultivars at the turning-over stage ( 10 ). Meanwhile, nonvolatile compounds linked to tea taste have been categorized according to five tasting properties, namely, bitterness, astringency, umami, sweetness, and sourness ( 11 ), and the characteristic flavor of oolong tea has an important correlation with both their contents and types.…”