Taishun County is located in the southwestern part of Wenzhou City, Zhejiang Province. It has extensive mountainous areas, distinct seasons, and abundant rainfall, providing superior natural resources and a favorable ecological environment that are conducive to tea plant growth. In recent years, Taishun County has attached great importance to the development of the tea industry. Currently, the total area of tea gardens in Taishun County is approximately 6,000 hectares, with the majority (about 60%) concentrated in the five towns of Shiyang, Yayang, Pengxi, Luoyang, and Bai Zhang. Sanbei Fragrant Green Tea is the main product in these towns, characterized by its high fragrance and rich flavor, as well as its lingering aroma after three infusions. It has won nearly one hundred awards, including the China Tea Cup, National Drink Cup, and International Famous Tea Gold Award. “Sanbei Fragrant” is the leading tea brand in Taishun County, with a comprehensive annual output value reaching 1.2 billion RMB. The tea industry has become a pillar industry in local ecological Agriculture, and tea income is one of the primary sources of income for local farmers.
01
Current Situation of Sanbei Fragrant Green Tea processing
The “Sanbei Fragrant” tea regional public brand has been vigorously cultivated by relevant departments in Taishun County, relying on local ecological and resource advantages to become the dominant brand of tea in Taishun County. However, during the process of brand construction, there are still many issues. The foundation of the tea industry remains relatively weak, with rather coarse tea production and lower technical levels in processing, resulting in a lack of market competitiveness for local tea products. Standardizing tea processing and improving tea processing technology have become key factors in accelerating the development of the local tea industry.
Through field research and tracking the traditional processing techniques of “Sanbei Fragrant” green tea, it was found that the quality of “Sanbei Fragrant” green tea products generally exhibits darker color, higher breakage rate, less compacted strips, and lower fragrance. The main reasons for these issues are believed to be:
(1) Insufficient rehumidification time after traditional wilting, uneven distribution of moisture between stems and leaves, which is not conducive to Rolling into strips and does not meet the tight and compact requirements of high-quality Sanbei Fragrant Green Tea;
(2) A simple rolling process, involving only one rolling. Due to the difference in dehydration rates across different parts of the fresh leaves, this results in uneven distribution of moisture between stems and leaves, making it difficult to roll into strips. To achieve strip formation, a long and heavy rolling method is adopted, leading to excessive cell breakage and the large outflow of tea juice, which accelerates the oxidation and decomposition of internal substances, causing the finished tea to appear darker and reduce in quality;
(3) During the initial rolling and frying process, the rolling temperature is low (equipment set at 125°C, leaf temperature around 60-80°C), under which thermal action is insufficient to develop and form adequate fragrance, leading to lower fragrance in the finished tea.
02
Materials and Methods
1. Experimental Materials
In late April 2023, fresh leaves from a group of tea plants, mainly consisting of one bud and three or four leaves, were picked at the tea garden base of Zhejiang Tailong Tea Manufacturing Co., Ltd. in Taishun County for processing experiments.
2. Instruments and Equipment
6CFS-80 Hot Air Tea Wilting Machine, 6CLHC-25 Cooling and Rehumidification Machine, 6CR-55 Tea Rolling Machine, 6CHD-80 Dynamic Strip Separating Machine, 6CHB-10 Chain Plate Tea Drying Machine, 6CCT-110 Tea Frying and Drying Machine are all from Zhejiang Zhufeng Machinery Co., Ltd.; DXCWS-15 Tea Microwave Wilting Machine is from Yixing Dingxin Microwave Equipment Co., Ltd.
3. Experimental Method
(1) Rehumidification Experiment
Fresh leaf materials of the same batch were uniformly spread out at a thickness of about 10 cm, for about 14 hours, until the moisture content reached 73% to 75%, then subjected to wilting treatment. First, they were subjected to hot air wilting (wilting temperature 330°C) until the moisture content reached 59% to 60%, then through microwave wilting until the moisture content was approximately 55%. After wilting operations, the treated leaves were divided into three equal parts, each undergoing different rehumidification times: 50 minutes (traditional process rehumidification time), 90 minutes, and 120 minutes. After rehumidification, they entered the 6CR-55 Tea Rolling Machine for 60 minutes with the same process parameters, followed by comparative analysis of the rolled leaves.
50-Minute Rehumidification
90-Minute Rehumidification
120-Minute Rehumidification
(2) Rolling Experiment
Fresh leaf materials of the same batch were divided into two equal parts, processed using the traditional process and new process shown in Figure 1, maintaining consistent moisture content in the finished product. Specific process parameters are shown in Table 1.
(3) Initial Rolling and Frying Experiment
Fresh leaf materials of the same batch were uniformly spread out, wilted, cooled and rehumidified, rolled, dynamically separated, and pre-dried, then divided into four equal parts. Each part was subjected to initial rolling and frying in machines set at different temperatures (125°C, 135°C, 145°C, 155°C). All samples were rolled and fried to 90% dryness, then further processed using the same process parameters for rolling and frying to enhance fragrance. Other process parameters are shown in Table 2.
4. Sensory Evaluation
Tea evaluators conducted sensory evaluations on the experimental samples subjected to different treatments according to the national standard GB/T 23776—2018 Method for Sensory Evaluation of Tea. Blind evaluation was used, repeated three times.
03
Results and Analysis
1. Influence of Different Rehumidification Times on the Shape of Tea Strips
The state of rolled tea strips after different rehumidification times is shown in Table 3. After 120 minutes of rehumidification, the shape of the rolled tea strips was optimal, with a 6.2% increase in strip formation rate, meeting the tightly compacted requirement for high-quality Sanbei Fragrant Green Tea. The main reason is likely due to the gradual even distribution of moisture