Abstract

   To explore the taste characteristics and flavor characteristics of
   Baiyun 0492 white tea, Fuyun 6 was used as a comparison to describe and
   analyze the taste of the tea by the standard tea sensory evaluation
   method and quantitative descriptive analysis. A total of 1083
   nonvolatile metabolites were identified by ultrahigh-performance liquid
   chromatography and mass spectrometry (UPLC–MS–MS). N-Feruloyl tyramine,
   with strong biological activity, may be the specific metabolite of
   Baiyun 0492 white tea, and 3,4,5-tricaffeoylquinic acid, with a bitter
   taste, may be the specific metabolite of Fuyun 6 white tea. Most of the
   different metabolite contents were negatively correlated with the
   Baiyun 0492 and Fuyun 6 white tea grades. KEGG metabolic pathway
   analysis showed that Baiyun 0492 and Fuyun 6 white teas had higher
   enrichment levels of flavonoids, caffeine, amino acids and
   carbohydrate-related metabolic pathways. Correlation analysis using
   widely targeted metabolomics and quantitative taste description showed
   that most flavonoid differences and some amino acid and phenolic acid
   differences were significantly positively correlated with bitterness
   and astringency, including quercetin-3-o-rhamnoside (quercetin),
   L-arginine, 3,4,5-tricaffioylquinic acid, and neochlorogenic acid. Some
   soluble sugars were positively correlated with sweetness, including
   D-maltose and D-sucrose, which were the key taste components of Baiyun
   0492 and Fuyun 6. These metabolites may be responsible for the taste
   characteristics of Baiyun 0492, which is characterized as sweet and
   mellow, while the taste of Fuyun 6 is mainly mellow. In this study, a
   wide range of targeted metabolomics techniques were used to screen out
   different metabolites related to the quality of Baiyun 0492 and Fuyun 6
   white teas, providing a reference for clarifying the quality
   characteristics of Baiyun 0492.

   Keywords: new tea tree stain, taste characteristics, flavor
   characteristics, metabolomics

1. Introduction

   White tea, one of six kinds of traditional tea in China, is mainly
   produced in the northeast of Fujian Province. Based on the different
   tenderness levels of fresh tea leaves, white tea can generally be
   classified into Baihaoyinzhen (bud only), Baimudan (one or two leaves
   with buds), Gongmei (more than two leaves with buds) and Shoumei (more
   than two leaves without buds) [[38]1]. In recent years, white tea has
   received increasing attention worldwide, owing to its desirable flavors
   and various health benefits, which has led to studies of suitable
   cultivars of white tea and innovation in floral white tea products
   using highly aromatic cultivars [[39]2]. The types, contents and
   proportions of nonvolatile compounds, including flavonoids, amino
   acids, phenolic acids and their derivatives, alkaloids, lipids, sugars
   and pigment substances in white tea directly affect the tea color,
   aroma, taste and other sensory qualities. Theanine, aspartic acid,
   asparagine and adenosine monophosphate are positively correlated with
   the umami taste of white tea, and flavan-3-ols (EGCG, ECG, GCG, and
   epigallocatechin 3-coumaroate), theasinensins (asinensin A and
   theasinensin F), procyanidin B3 and theobromine have strong
   correlations with bitterness and astringent tastes [[40]3]. In
   addition, different production areas, different tea cultivars and
   tenderness levels of fresh leaves influence the different qualities of
   the taste and aroma of white tea [[41]4,[42]5]. Therefore, it is
   significant and valuable to study the taste and quality characteristics
   of white teas of different varieties. The sour, bitter, umami, salty
   and sweet taste of Fuding white tea are the highest among three
   production regions, while the astringency value of Yunnan white tea is
   significantly higher than that of Fuding and Xinyang white tea [[43]4].
   In different grades of white tea, the total contents of catechins,
   hydrolyzed tannins, phenolic acids, theanine and caffeine decrease with
   reducing grades, and theaflavins and flavonols in longevity plum and
   White Peony are higher than other grades [[44]5,[45]6].

   Baiyun 0492 (also known as Baiyuntezao), a new cultivar of tea plant
   selected by individual plant selection in the Tea Research Institute of
   Fujian Academy of Agricultural Sciences in Wuqu Town, Shouning County,
   Fujian Province, has the characteristics of early spring shoot
   germination, and it is suitable for making white tea and green tea. The
   white tea manufactured from this plant exhibits superior quality
   compared to that from Fuding Dabai tea, suggesting its potential for
   being selected and bred into a distinctive elite cultivar of white tea.
   This study aims to analyze the differences in non-volatile substances
   between Baiyun 0492 and Fuyun No. 6 from the perspectives of sensory
   evaluation scores and physicochemical component contents based on
   widely-targeted metabolomics. It also explores the differential
   metabolites, their metabolic pathways, and the relationships between
   metabolites and the umami and bitterness of white tea. By doing so, it
   analyzes the main reasons that may cause the differences in the taste
   quality of white tea, with the expectation of clarifying the taste
   quality characteristics of Baiyun 0492 white tea and providing
   references for the research and development of Baiyun 0492