Preparation of Cold Brew Tea by Explosion Puffing Drying at Variable Temperature and Pressure

Cold brew tea was prepared using explosion puffing drying at variable temperature and pressure. The influences of moisture content of predried tea leaves, freezing pretreatment times at −18°C, and puffing temperature on water extracts content of cold brew tea were studied according to the orthogonal experiments of processing of cold brew tea based on single factors. The biochemistry ingredients of cold brew tea and hot air–dried green tea were determined and compared. The optimum processing conditions of cold brew tea were obtained as follows: predried tea leaf moisture content 50%, freezing pretreatment three times, puffing temperature 105°C. Under these optimized processing conditions, cold brew tea was obtained. When cold brew tea was soaked in cold water for 30 min at 20°C, the water extracts content, caffeine, tea polyphenols, and free amino acids of cold brew tea reached 18.21, 0.88, 11.86, and 1.02%, respectively. High-performance liquid chromatography (HPLC) analysis showed that the amount of tea catechins in cold brew tea and hot air–dried green tea were 11.74 and 11.47%, respectively. The caffeine in cold brew tea was 3.06%, equal to that in hot air–dried green tea. Experimental results showed that biochemistry ingredients of cold brew tea prepared by explosion puffing drying at variable temperature and pressure difference were easy to extract by low-temperature water. This research provides theory and technical support for industrialized production of cold brew tea.