Quality Changes of Different Tea Beverages during Storage

The quality changes of tea beverages including color stability, turbidity and nutritional component stability were analyzed in this article. Four kinds of tea beverages, namely high-acid green tea, low-acid green tea, high-acid black tea and low-acid black tea drinks, were stored under different storage conditions. The impact of different storage temperature and storage periods on the quality of tea beverages was investigated by the measurements of soluble solid contents, transmittance, turbidity, color difference, catechin and epigallocatechin gallate (EGCG) contents. The results showed that, there was no significant difference in the transmittance of tea beverages during different storage conditions; Under the storage condition of 4 ℃ and 25 ℃, turbidities of high-acid green tea product were increased significantly. To 180 days, the turbidity increased by 52.04% and 34.12% under 4 ℃ and 25 ℃, respectively; There was no significant difference in the turbidities of black tea product. During storage, the brightness values(L^*) of different tea beverages decreased significantly, and the red value (a^*) and blue value (b^*) increased significantly. When stored at 25 ℃ for 180 d, the brightness values (L^*) of four tea products (high-acid green tea, low-acid green tea, high-acid black tea and low-acid black tea drinks) were decreased by 31.86%, 39.98%, 30.22% and 37.73%. The content of tea polyphenol and EGCG decreased significantly with the extension of storage time. When stored at 55 ℃ for 15 days, the contents of catechins in high-acid green tea, low-acid green tea, high-acid black tea and low-acid black tea products were dropped by 9.08%, 10.28%, 13.39%, 18.63%, the contents of EGCG were dropped by 35.32%, 42.18%, 49.03%, 47.22%, respectively.