Study on the Correlation between Huiguo Technology and Sensory Quality of Hakka Fried Green Tea

: Hakka roasted green tea is a characteristic product of Hakka region in Guangdong Province, but the research on the key technology of traditional Hakka green tea has not been in-depth. This study systematically studied the temperature and time of the pot in the pot process, and conducted experiments through the national standard sensory evaluation method. The pot time of 5h, 3H and 1H was set for different experimental groups at 100 ℃, 80 ℃, 60 ℃ and 40 ℃, respectively, to study the effect of the pot process on the sensory quality of Hakka green tea, strive to improve the aroma quality of Hakka green tea and directional control provides reference data.


Brief overview of Hakka fried green tea
Hakka stir fried green tea is one of the traditional tea varieties in Guangdong. It is mainly distributed in Meizhou, Heyuan, Jieyang, Shanwei, Huizhou, Shaoguan and other places in Guangdong. It is locally known as "Hakka stir fried green tea", "Hakka stir fried tea", and "stir fried baby". The main cultivated varieties are Meizhan, Jinxuan, Huang Guanyin, and Jin Guanyin, mainly with medium and small leaves. The traditional technology of Hakka stir fried green tea mainly includes fresh leaves, withering, killing, rolling, drying Huiguo, etc., of which Huiguo technology determines the rate of moisture loss of tea, and also affects the thermophysical and chemical changes inside the tea, so it has an impact on the quality of Hakka fried green tea. Therefore, it plays a key role in the formation of special "fried rice flavor", "high fire flavor", "fried chestnut flavor", "high fire sweet flavor" and other aroma and gray green appearance quality characteristics in the quality of traditional fried green tea.

Research on the technology of Hakka fried green tea Zhonghui pot
At present, the research on the process of frying green tea in the frying pan mainly focuses on the process flow of the frying pan, the temperature of the frying pan and the time of the frying pan. For example, zhongxiaobing and other researchers proposed that the fried green tea under the combined drying and frying process has strong flavor and rich fried rice flavor, and the quality is due to the traditional Hakka fried green tea [1] ; It is pointed out in the research on the influence of pot temperature on the aroma of roasted green tea that there is no final conclusion on the optimal temperature of pot temperature at present. The general temperature is 100-110 ℃ at high temperature, 70-100 ℃ at medium temperature, and 40-70 ℃ at low temperature [2] ; At the same time, some researchers have studied the influence of different growth time on the quality of fried green tea at high temperature, such as 1H, 2h, 4h, 6h, and so on. It is concluded that four different flavor types of fried green tea can be prepared by high temperature long-time glow pot, mainly including honey flavor with fragrance, chestnut flavor with fragrance, honey flavor and honey chestnut flavor [3] . However, there is no research on the relationship between the cooking pot process and the sensory quality of Hakka roasted green tea in the previous research. This research will focus on the research on the cooking pot temperature and time in the key process of roasting green tea, and comprehensively and systematically study the sensory quality of Hakka roasted green tea treated by different cooking pot processes, so as to provide reference for the quality oriented control of Hakka roasted green tea.

Experimental method
In this experiment, the control variable method was used to set up two groups of experimental samples with different cooking temperature and cooking time for a total of 12 comparative experiments. In this group of experiments, the Hakka fried green tea operated by the conventional Hakka fried green tea pot was used as a reference. In the experiment, a total of 12 experiments were set, including the pot temperature of 100 ℃, 80 ℃, 60 ℃, 40 ℃, and the pot time of 5h, 3h, 1H. Among them, the samples with the frying temperature of 60 ℃ and the frying time of 3H were taken as the CK group. The experimental design is shown in Table 1 table of the experimental design of the glow pot process, and each treatment is repeated for 3 times.

Sample raw materials
Raw material production area: Qingliangshan tea production area, Meijiang district, Meizhou City, Guangdong Province, with an altitude of 500 meters, an average annual sunshine duration of 2009.9 hours, a spring temperature of 12 ℃ -23 ℃, and an average annual rainfall of 1479.9 mm.
Fresh leaves: at the same time, they were harvested in the Qingliang mountain of Meizhou in spring, and the tea varieties were local Meizhan varieties.

Main experimental instruments and equipment
Model 60 drum green killing machine, Model 55 tea rolling machine, dryer, hygrometer, thermometer, 150ml evaluation cup, 200ml evaluation bowl, evaluation disc, tray balance, etc.

Sensory quality test method
GB/T 23776-2018 tea sensory evaluation method national standard method was used to evaluate the five evaluation factors of sample tea, namely, the five factors of appearance (strip, color, uniformity, cleanliness), soup color, aroma, taste and leaf bottom.
Evaluation method: take 3g representative tea samples, place them in 150ml evaluation cup after warm scalding, fill it with boiling water, soak it for 4min, and evaluate the appearance, soup color, aroma, taste and leaf bottom with the percentage evaluation method according to the factor score coefficient of 25%, 10%, 25%, 30% and 10% respectively.

Results and analysis
According to the national standard method for the evaluation of Hakka fried green tea processed by different pot treatments, the results are shown in Table 2 table of sensory quality results of Hakka fried green tea processed by different pot treatments.
The Hakka fried green tea processed in different saucepans was evaluated by the percentile tea evaluation method. See Table 3 for the results of the percentile tea evaluation method of Hakka fried green tea processed in different saucepans.
According to the sensory evaluation results of Hakka fried green tea with different pot processes, only the comprehensive evaluation of samples 6, 10 and 11 was lower than that of the control group, and the other treatment effects were higher than that of the control group, of which samples 1, 2, 4 and 7 were significantly higher than that of the control group. The experimental data showed that the temperature (40-60 ℃) or short-term (1h-3h) boiling temperature and boiling time were not conducive to the aroma and taste of Hakka green tea, while the aroma and taste of high temperature (100 ℃) and long-term (5H) were significantly higher than those of the control group, mainly manifested as "fried rice flavor", "high fire flavor" and "fried chestnut flavor", and the taste was thick and mellow. The comprehensive results showed that the comprehensive performance of 100 ℃ experimental group was better than that of 80 ℃, The 80 ℃ experimental group was slightly better than the 60 ℃ experimental group, and the comprehensive performance of the 40 ℃ experimental group was poor.

Effect of different cooking processes on the quality of Hakka fried green tea
At present, some studies have shown that the processing technology is the key factor for the formation of different aroma types of green tea. The appropriate cooking temperature and time are conducive to the formation of the quality of Hakka roasted green tea. Through the high-temperature and long-time cooking process, tea polyphenols are further oxidized, polysaccharides are further decomposed, the phenol ammonia ratio is reduced, and the bitter taste is reduced. At the same time, it is conducive to the formation of volatile organic compounds, including aldehydes, hydrocarbons, ketones, alcohols. The lipid content was significantly improved [4] . At the same time, in the hightemperature and long-term cooking process, the aroma was concentrated and the taste was thick and mellow. In the high-temperature and long-term cooking process, researchers such as Hu Die pointed out that the formation and content of 17 key aroma types in the cooking process were significantly affected by temperature factors, time factors and temperature time interaction factors, among which the formation and content of fried rice flavor α-Limonene and δ-The content of dusonene was significantly affected by time and temperature time interaction factors, forming high fire aroma α-The content of cyclamene is significantly affected only by temperature [5] .
The results of this study showed that different cooking processes had significant effects on Hakka fried green tea. After high temperature and long-term cooking process, the tea polyphenols in tea were effectively removed, the aroma of traditional Hakka fried green tea was promoted, and the alcohol concentration of tea soup was improved. At the same time, with the reduction of cooking temperature and time, the aroma showed a change trend of "fried rice aroma -high fire aroma -fried chestnut aroma -fragrance", which was roughly consistent with the previous research results.

Next improvement measures
This experiment explored the effects of different cooking processes on the sensory quality of Hakka fried green tea. The experimental materials were all spring tea raw materials. In order to further systematically and deeply study the relevant change laws in different seasons and regions, the next stage of research will select Hakka fried green tea raw materials in different seasons and regions for further research, and increase the dimension of different tenderness, Further enrich and improve the comprehensiveness of the research, and increase the research on the content and aroma components. The research on the content and aroma formation mechanism of Huiguo technology is also the focus of the next step.

Conclusion
The experimental results showed that no matter which treatment method of the Huiguo process experimental group, it had a positive significance for the improvement of the quality of Hakka roasted green tea, especially for the formation of high aroma. To a certain extent, the Huiguo process reduced the bitter taste of green tea, and improved the concentration of taste and aroma components.
Among them, the treatment method of 100 ℃ and 5 hours was the best. The comprehensive evaluation score was 92.45 points, which was significantly higher than that of CK group. The treatment effect of shape and 80 ℃ on the bottom of leaves and 5 hours on the bottom of leaves was the best. The overall performance was more curly, dark green with gray, uniform and clean, and the bottom of leaves was softer and brighter than yellow green; The color, aroma and taste of the soup were the best when the cooking temperature was 100 ℃ and the cooking time was 5h, which showed that it was yellow green and bright, the aroma of fried rice was rich, and the taste was thick, mellow and sweet. Therefore, high temperature for a long time is conducive to improving the quality of Hakka fried green tea.