Effects of different LED lights during withering process on the aroma quality of Gongmei white tea

【Objective】 The study aimed to clarify the effects of different LED lights withering on the aroma components of Gongmei white tea, which could provide reference for all-weather and standardized light withering production of white tea.【Method】 With no light withering as a control, effects of withering of red light (630 nm), yellow light (570 nm), blue light(430 nm) and sunligh on Gongmei white tea aroma compounds were analyzed by sensory evaluation and headspace solid phase micro-extraction combined with gas chromato graphy-mass spectrometry(HS-SPME-GC-MS) and odor activity value(OAV) in this study.【Result】 The aroma scores of Gongmei white tea in the four kinds of lights withering were all higher than those without light withered. Among them, the yellow light treatment had the highest aroma score (89.1), showing floral fragrance, and the other three light treatments were mainly clear fragrance. A total of 68 aroma components were detected in the tested samples including 16 aldehydes, 17 alcohols, 10 esters, 11 ketones, 10 hydrocarbon and others, of which 58 components were in each treatment. The four light qualities could increase the total aroma contents of Gongmei white tea samples. Among them, Gongmei white tea had the highest total aroma components(279.736 μg/L) under yellow light withering, and aldehydes (46.787 μg/L), alcohols (173.163 μg/L), ketones (16.889 μg/L), heterooxy-gen compounds(6.823 μg/L), ethers(12.574 μg/L), sulfur(0.388 μg/L) and sulphocompound(3.608 μg/L) contents were all higher than other lights and control. Cis-linalool oxide, trans-linalool oxide, cis-linalool oxide(furan type), trans-linalool oxide(pyran type), benzaldehyde, phenylacetaldehyde, decanal, β-cyclocitral, cis-citral, butyl ether, dimethyl sulfide that were beneficial to the aroma quality of white tea, all had the highest contents in the yellow light group. A total of five aroma components with relatively high OAV were obtained, followed by β-ionone, linalool, nonanal, dimethyl sulfide, and dimethyl sulfide, which made a greater contribution to the aroma formation of the tested samples.【Conclusion】 Yellow LED light withering is the most beneficial for improving aroma factor, increasing total content of aroma components and forming good aroma quality characteristics of Gongmei white tea, and can be prioritized as a compensation light source for all-weather processing of white tea.