Deterioration of Tea Quality Caused by Tea White Scab Disease Disease

Tea is a popular daily beverage worldwide, especially in China. Tea white scab disease affects tea quality is poorly understood. In the current study, we aimed determine whether tea quality will variation. we collected green tea samples from ve samples (with varying morbidity from CK to (cid:0) on Baiyun Mountain in Hunan Province. Results showed that tea quality are obviously decreased as infected by tea white scab disease . Results showed that an increase in incidence rate decreased total tea polyphenols (TP) , water extract and caffeine but increased amino acids (AA) , Nonetheless, the constituents of polyphenolic compounds were differentially altered. Additionally, the percentage of (−)-epicatechin (EC) and (−)-epicatechin-3-gallate (ECG) increased with increasing morbidity. (−)-epigallocatechin (EGC) and (−)-epigallocatechin-3-gallate(EGCG) just the opposite. The constituents of AA, especially Alanine, γ-aminobutyric acid, serine and phenylalanine increased with increasing elevational gradients. Proline, and theanine were reduce along with morbidity level. As a whole. This observation demands development of effective measures for sustaining green tea quality in the face of tea white scab disease.


Introduction
Tea, which made from the fresh leaves of tea plant (Camellia sinensis), is one of the mostly used daily beverage throughout the world, especially in China. It is estimated that more than 3 billion cups of tea are consumed every day (L. Chen & Zhou, 2005; Z. Chen, 1994). Tea also is associated with many physiological and pharmacological health bene ts (Singh, Shankar, & Srivastava, 2011). Back to 2737 B.C., China is the earliest country for cultivation and utilization of tea plan, and South China are the main area (Hasimoto M, 1978;Yamanishi, 1995). As vital economic crop in South China,tea white scab could attach enough importance.
Tea white scab diseasse, which are important to susceptible tea cultivars are grown in humid areas, can cause tea leaves blemishes. This disease not only can reduce the quality of tea for the market, but also cause tea yield losses. Fungal pathogens Elsinoe leucospila are initiated when spores attach to host surfaces and germinate (Hématy, Cherk, & Somerville, 2009;Underwood, 2012;Zhou, et al., 2020). Then the spores breach external and internal barriers with altering host defence mechanisms and establish biotrophic interactions (Tucker & Talbot, 2001), and usually cause external blemishes, tea white scab disease. This organism can affects the leaves and twigs on many susceptible cultivars, such as lemons, grapefruit, and many tangerines (K. R. Chung, 2011; Paudyal, Hyun, & Hwang, 2017). For infecting tea leaves, there were no report in South China.
As health bene ts drink, the basic components of tea like catechins, alkaloids, proteins and carbohydrate were potential health bene ts (Banerjee & Chatterjee, 2015). At the same time, the function of the tea is also largely attributed to the abundant secondary metabolites (Hamiltonmiller, 2001;. For example, avonols, anthocyanins, saponin, and aroma precursors (Lv, Dai, et

Sample Collection
From January 2015 to January 2019, Sampling was conducted from ve levels with varying morbidity including CK (morbidity: 0), (morbidity: 11-40%), (morbidity: 41-50%), (morbidity: 51-80%), (morbidity: 81-100%),which were leaves of fuding white tea variety of 17 years With the same management from the cities of changde in Hunan in China.All the samples were split into two, one batch was Baked sample immediately and the other batch left to pan-red for different durations.

Determination of sensory quality evaluation
According to the national standard (GB/T 23776 − 2009). the samples of pan-red tea were put into 90℃ water with the proportion by tea and water is 1:50, appearance(a), aroma(b), Liquor color(c), taste(d) and Infused leaves(e). The scoring factors and coe cients are shown in Table 1.The total score of each factor is 100 points, Sensory evaluation = a×25%+b×10%+c×25%+d×30%+e×10%.

Determination of basic biochemical component test
We detected water extract of tea, free amino acids, caffeine, tea polyphenols, and avonoids. Ethanol was used as a solvent to extract phenolic compounds from dried fresh tea samples. The extraction was performed at temperature of 40, 50, and 60℃ which was maintained using a water bath. Folin-Ciocalteu's reagent was used to detennine the total phenolic content spectrophotometrically and gallic acid was used as the calibrant (Komes, et al., 2010). Brie y, the diluted sample extract (1.0 ml) was transferred to tubes in duplicate, where each tube contained 5.0 ml of a 1/10 dilution of Folin-Ciocalteu's reagent in water.

Determination of catechin and monomer content
We carried out further phytochemical analysis to determine concentrations of individual catechins and free amino acid compounds from a sub-sample of tea samples. An HPLC method (GB/T 8313 − 2008) was used to quantify concen trations of catechins as described by (Wei, et al., 2011).The individual catechins we measured include: epigallocatechin-3-gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC) and epicatechin (EC).

Determination of Amino acids composition
An automatic amino acid analyzer (Hitachi L-8900, Japan) was used to measure individual amino acids including Proline, Alanine, Methionine, Tyrosine β-alanine Tryptophan α-Aminobutyric acid Arginine Theanine Glutamic acid Phenylalanine Phosphoserine Taurine Phosphoethanolamine Urea Aspartic acid Threonine Serine Asparaginate Glycine Citrulline Valine Cystine Isoleucine Leucine β-Aminoisobutyric acid γ-Aminobutyric acid Histidine Ornithine Lysine α-Aminoadipicacid. Amino acids were measured by adding 5 ml of tea extract with 5 ml of sulfosalicylic acid and centrifuging the mixture at 13,000 rpm for 5 min to facilitate the reaction. The mixture was ltered through a 0.20-μm nylon lter membrane and run using the amino acid analyzer (Wang, et al., 2006).

Effect of tea white scab disease on Sensory quality evaluation
Tea made from increasingly severe tea white scab disease infected tea leave recorded a markedly progressive decline in appearance, aroma), Liquor color, taste and Infused leaves (Table 1). Along with the increase of morbidity (from CK to ), the appearance were from tight, green, smooth to coarse, yellowish green, and tea dust were increased. The aroma also with heavy smell. For liquor color, the CK were brilliant green, but turn into deep yellow green. The taste were obvious difference which changed from sweet and mellow to heavy bitter. At last, we had found densest spots on leave tea infused leaves.

Effect of tea white scab disease on Basic biochemical component
As four conventional index, water extract, caffeine and tea polyphenols were markedly decreased when the tea quality change. Free amino acids and avonoids were uctuate ( Table 2).

Effect of tea white scab disease on Catechin and monomer content
The variation of catechin and monomer content along with increase of tea morbidity (from CK to ) were shown in Table 3. Catechin was the most important functional composition in tea. Obviously, it was on a declining curve, but some its monomer content (EC, ECG) were up.

Effect of tea white scab disease on amino acid composition
It is known that many amino acids on tea and some were important for human. Our study revaled most amino acids variation in samples (Table 4). Among those amino acid, proline and theanine were reduce along with morbidity level. Alanine, γ-aminobutyric acid, serine, and phenylalanine were increased with increasing elevational gradients. To our interesting, tryptophan, asparagine, glutamic acid, and glycine were Page 6/12 increased abruptly on level (morbidity: 51-80%). Some amino acids such as α-aminobutyric acid, cystine had not been found on the tea severe infected by Elsinoe leucospila (level , ). The other amino acids also have some changes.

Discussion
Tea is a signi cant aquaculture species in China (Y. F. Li, et al., 2017). Tea white scab disease were found to occur at varying levels in tea. Consumer acceptability of tea greatly depends upon its sensory quality evaluation. Tea quality depends upon spatiotemporal variability of geographical origin, manufacturing process, which in turn highly in uence the chemical composition, and which are very critical in determining its quality. On the other hand, sensory quality evaluation factors like color, appearance, avor and taste also determines its commercial value (Bhattacharyya, et al., 2012;Bhondekar, et al., 2010). Qin et al (2017) compared the difference on sensory quality evaluation by human panel test and spectroscopy system, and revealed the variation on tea from different areas and variety. As shown in Table 1, tea white scab seases can strongly effect on the tea in sensory quality evaluation. The characteristic of high quality tea (CK) were green, smooth appearance; clean, high aroma; sweet, mellow taste, and fat, tender infused leaves. but the diseased one were quite another thing. Sensory quality evaluation, as rst tea standard of National Food  (2016) show difference thermal processing can cause variation in tea catechins. Our study also uncover the tea catechins content change along with tea white scab disease .Tea contain high levels of amino acids, the pro le of which bene cial health effects have also been proposed (Bryan, 2008). Good quality teas require high concentrations of amino acids principally contributing to mellowness and freshness, and an optimum ratio of amino acids for a balance of astringent to mellow tastes (Wang, Cheng, Yuchen, & Liu, 1988). It consistent with our results that many amino acids varied along with the increase of morbidity (from CK to ).
In conclusion, the present study showed the new pathogen (Elsinoe leucospila) of Tea white scab disease in tea from south China and comprehensive analysis the tea quality along with the increase of morbidity (from CK to ). In our study, sensory quality evaluation, basic biochemical component, catechin and monomer content and amino acid composition of tea are obvious change after infected by tea white scab disease.
Thus, the result will give advice to farm operators to understand and control Tea white scab disease in tea.