Optimization of storage conditions for Zhenghe white tea: Effects of temperature and humidity on sensory and physiochemical qualities over one-year storage

To provide scientific basis for finding the best storage technology of white tea, different temperature (15°C, 25°C, and 35°C) and humidity (40%, 50%, and 60%) were employed in the storage of five white tea samples, and sensory quality and physicochemical composition were analyzed, with the production practical condition of Natural Temperature, Relative Humidity≤60% (NT, RH≤60%) as a contrast. The physicochemical results showed that the water content of some samples exceeded 8.5% when stored for 12 months under both high humidity and control conditions. The water extracts of all samples met the regulations of the China National Standards (GB/T 22291-2017), which requires at least 30%. The sensory evaluation indicated that the changes of five samples were small from 3 months to 6 months and large from 6 months to 12 months under different storage conditions. The influence of temperature on Baimudan was greater than that of humidity, but unobvious to Shoumei. Correlation analysis indicated that temperature and humidity were inversely correlated with water content, and storage time exhibited positive correlations with water, free amino acids, tea polyphenols, catechins, caffeine, and ester catechins content, and negative correlations with water extracts and non-ester catechins content. The result of PCA showed that appearance, leaves, overall sensory scores, aroma, taste, ester catechins, catechins, and tea polyphenols content were key indicators that could be affected by storage conditions. Thus, for Baimudan, the condition of 25°C, 40% is better for storage, under which the grass odor and bitter taste were faded or weakened, and the sweetness appeared. For Shoumei, the condition of 25°C, 60% is suitable, under which the grass odor and astringent taste disappeared, and the bitter taste was weakened. • High humidity (60%) made some white tea exceed water content during the storage. • The quality of Baimudan was more affected by temperature than that of Shoumei. • PCA was used to simplify the indicators of white tea under different conditions. • With production condition as contrast, the results are practical and instructive.