Effect of freezing treatment in tea preparation using Camellia sinensis leaves

This study was conducted to examine the effect of freezing in the tea preparation using Camellia sinensis leaves in order to develop new technology for improving tea quality. Effects of single and combined treatments of freezing (F: - 20 °C, 15 days), steaming (S: 100 °C, 3 min), and hot-air drying (HD: 50 °C, 12 h) on the physicochemical characteristics of tea (powder and hot-water leachate) prepared from treated Camellia sinensis leaves were investigated. The L* , b* , and C* values of the powder were the highest in SHD-treated leaves, followed by HD-, SFHD-, and FHD-treated leaves. Redness (+a* value) was only seen in FHD-treated leaves and greenness (- a* value) was the highest in SHD-treated leaves. Browning index of the leachate was significantly lower in SHD- and SFHD-treated leaves than in FHD-treated leaves (p < 0.05). Soluble solids, acidity, and phenolic compounds of FHD-treated leaves were significantly lower than in SHD- and SFHD-treated leaves (p < 0.05). Sucrose was highest in SHD-treated leaves and glucose was highest in FHD-treated leaves. Sensory preference was better evaluated in FHD-treated leaves than in SHD- and SFHD-treated leaves. These results suggest that freezing treatment in tea processing promotes browning and component decomposition and enhances sensual preference. Therefore, freezing has a potential application in the tea manufacturing.