Integrated metabolic phenotypes and gene expression profiles revealed the effect of spreading on aroma volatiles formation in postharvest leaves of green tea

Chen

et al. 2022

Foods

Fatty acids (FAs) are important precursors of oolong tea volatile substances, and their famous derivatives have been shown to be the key aroma components. However, the relationship between fatty acids and their derivatives during oolong tea production remains unclear. In this study, fresh Tieguanyin leaves were manufactured into oolong tea and green tea (control), and fatty acids and fatty acid-derived volatiles (FADV) were extracted from processed samples by the sulfuric acid–methanol method and solvent-assisted flavor evaporation (SAFE), respectively. The results showed that unsaturated fatty acids were more abundant than saturated fatty acids in fresh leaves and decreased significantly during tea making. Relative to that in green tea, fatty acids showed larger variations in oolong tea, especially at the green-making stage. Unlike fatty acids, the FADV content first increased and then decreased. During oolong tea manufacture, FADV contents were significantly and negatively correlated with total fatty acids; during the green-making stage, methyl jasmonate (MeJA) content was significantly and negatively correlated with abundant fatty acids except steric acid. Our data suggest that the aroma quality of oolong tea can be improved by manipulating fatty acid transformation.

Section: Resultsmentioning

confidence: 99%

Variations in Fatty Acids Affected Their Derivative Volatiles during Tieguanyin Tea Processing

Chen

et al. 2022

Foods

“…Because of the large number of volatiles, we focused on 16 major volatiles that play key roles in tea fragrance [ 7 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] ( Figure 3 B). There was no significant change in the contents of ten aroma volatiles, namely, β-myrcene, D-limonene, terpineol, geraniol, phytol, neophytadiene, linalool oxide, methyl salicylate, methyl hexadecanoate, and dibutyl phthalate, between PTL and UTL.…”

Section: Resultsmentioning

confidence: 99%

“…The water contents of UTL decreased more than PTL after 24 h (75.77% vs. 77.15%, respectively), and the difference between the two groups was significant ( p < 0.05). A previous study showed that, after 6 h, the water content of tea leaves decreased to 63.8–68.1% [ 17 ]. The relatively high water content in UTL from this study might have been caused by the storage method: we kept fresh leaves in a basket without spreading, which probably slowed down water loss.…”

Section: Discussionmentioning

confidence: 99%

“…Head-space solid-phase micro extraction/gas chromatography–mass spectrometry (HS-SPME/GC-MS) was used to analyze volatile compounds [ 17 ]. Briefly, 0.2 g FTL powders spiked with 10 µL internal standard solution (8.64 µg/mL ethyl decanoate in dichloromethane) was added to a 2 mL NaCl saturated solution in a 15 mL head-space vial (Agilent, MA, USA).…”

Section: Methodsmentioning

confidence: 99%

“…d Aroma description found in references [ 14 , 18 ], the Flavornet database ( , accessed on 5 December 2021), and PubChem ( , accessed on 5 December 2021). e Aroma volatile compounds identified from references [ 7 , 13 , 14 , 17 , 18 , 19 , 20 ], the Flavornet database ( , accessed on 5 December 2021), PubChem ( , accessed on 5 December 2021), the Flavor Library ( , accessed on 5 December 2021), and Ichemistry ( , accessed on 5 December 2021). ‘—’, no aroma description information was found in the literature.…”

Section: Figurementioning

confidence: 99%

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The Physiology of Postharvest Tea (Camellia sinensis) Leaves, According to Metabolic Phenotypes and Gene Expression Analysis

Mei

Zheng

et al. 2022

Molecules

Proper postharvest storage preserves horticultural products, including tea, until they can be processed. However, few studies have focused on the physiology of ripening and senescence during postharvest storage, which affects the flavor and quality of tea. In this study, physiological and biochemical indexes of the leaves of tea cultivar ‘Yinghong 9′ preserved at a low temperature and high relative humidity (15–18 °C and 85–95%, PTL) were compared to those of leaves stored at ambient conditions (24 ± 2 °C and relative humidity of 65% ± 5%, UTL). Water content, chromatism, chlorophyll fluorescence, and key metabolites (caffeine, theanine, and catechins) were analyzed over a period of 24 h, and volatilized compounds were determined after 24 h. In addition, the expression of key biosynthesis genes for catechin, caffeine, theanine, and terpene were quantified. The results showed that water content, chromatism, and chlorophyll fluorescence of preserved leaves were more similar to fresh tea leaves than unpreserved tea leaves. After 24 h, the content of aroma volatiles and caffeine significantly increased, while theanine decreased in both groups. Multiple catechin monomers showed distinct changes within 24 h, and EGCG was significantly higher in preserved tea. The expression levels of CsFAS and CsTSI were consistent with the content of farnesene and theanine, respectively, but TCS1 and TCS2 expression did not correlate with caffeine content. Principal component analysis considered results from multiple indexes and suggested that the freshness of PTL was superior to that of UTL. Taken together, preservation conditions in postharvest storage caused a series of physiological and metabolic variations of tea leaves, which were different from those of unpreserved tea leaves. Comprehensive evaluation showed that the preservation conditions used in this study were effective at maintaining the freshness of tea leaves for 2–6 h. This study illustrates the metabolic changes that occur in postharvest tea leaves, which will provide a foundation for improvements to postharvest practices for tea leaves.

Food Science & Nutrition

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

Göksu Sürücü,

Tolun,

Halisçelik

et al. 2024

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.