Journal of Tea Science Research, 2024, Vol.14, No.1, 19-43 http://hortherbpublisher.com/index.php/jtsr 21 small or broken leaves; Longevity Eyebrow is made from ground tea leaves (Pan et al., 2018). Moreover, new white tea can be processed into the compressed aged white tea, which has lower amounts of amino acids, soluble sugar, tea polyphenols, ester catechin, and gallic acid, but the umami and astringency tastes are less intense (Chen et al., 2020a). In general, the main constituents of white tea are proteins, polysaccharides, phenolic compounds, amino acids, and methylxanthines (Dias et al., 2019), among which phenolics, amino acids, and methylxanthines are the three most important tea quality determinants (Hinojosa-Nogueira et al., 2021). Tea catechins and their derivatives can account for up to 30% of the dry weight of the leaf, the most important being gallocatechin (GC), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), gallocatechin gallate (GCG), and epigallocatechin gallate (EGCG). Among them, EGCG is the most abundant (about 59% of total catechins) and the most studied. The other two important functional components, theanine and caffeine, represent around 4% and 2%-5% of the dry weight of tea, respectively (Dias et al., 2019, Paiva et al., 2021) (Table 2). The content of bioactive compounds in white tea is determined by both tea sub-types and grades. The contents of EGCG, theanine, and caffeine in hot tea infusions prepared from three types of Fuding white tea followed the order silver needle < longevity eyebrow < white peony (Pan et al., 2018). Similar results were reported with white pony water extract containing higher total catechin content up to 8 times than the silver needle white tea from the same company (Unachukwu et al., 2010). However, there was variation among teas from different companies with a wide range from 14.40 to 369.60 mg/g of dry plant material. In another study, the chemical content of EGCG and caffeine in white tea leaves followed the order silver needle > white peony > longevity eyebrow, while silver needle and white peony had similar and higher theanine content than the longevity eyebrow (Yang et al., 2018). Within the same subtype, the component quality can still vary between different grades. When the metabolites in super, first, second, and third grade white peony were analyzed and compared, a gradual decrease was observed in the flavonoids including EGCG across four different grades of white tea (Yue et al., 2019). Similar results were also reported in another study where the contents of total catechins and caffeine decreased as the grade level decreased (Ning et al., 2016). Table 1 Representative subvarieties and properties of white tea White tea Grade and pluck standards Characteristics Major cultivar Silver Needle (Yin Zhen) First grade. Only top buds leaf shoots) of the Camellia sinensis Generally whiter appearance and a lighter body with shorter withering time than Zhenghe (Fuding) China Longer withering process, deeper color and a fuller body than Fuding (Zhenghe) White Peony (Bai Mu Dan) Second grade. One leaf shoot and two immediate young leaves one bud two leaf ratio) Fuller flavor and greater potency than silver needle (Sanlier et al., 2018) Tribute Eyebrow (Gong Mei) Third grade. One bud with two or three leaves Processed more than silver needle and white peony teas, offering a dark brew with an earthy taste (Ahmed and Stepp, 2013) Longevity Eyebrow (ShouMei) Fourth grade. More than two leaves, with or without bud By-product of silver needle tea production, darker in color, making a darker brew with more depth Darjeeling Unfurled buds with two or three soft leaves Similar to silver needle, the high elevation and low temperatures results in its unique flavor development India Ceylon Slightly curved and unopened buds A very light coppery brew with pine and honey flavor Sri Lanka
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