A method for judging tea grade based on carbon quantum dots
A technology of carbon quantum dots and grades, applied in measuring devices, material excitation analysis, fluorescence/phosphorescence, etc., can solve problems such as lack of comparability, unscientific formulation of sensory indicators, unobjective review and scoring characterization, and achieve discrimination accuracy High, improve stability and accuracy, and objectively judge the effect
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Embodiment 1
[0034] The specific process of this embodiment is as follows:
[0035] (1) Preparation of carbon quantum dots by hydration method:
[0036] Take 0.42mmol thiourea, 1.26mmol urea and 0.28mmol sodium citrate dissolved in 30mL ultrapure water, stir for 15min to fully dissolve. The mixed solution was transferred to a polytetrafluoroethylene-lined reaction kettle with a volume of 50 mL, and heated in an oven at a reaction temperature of 185° C. for a reaction time of 6 h. After the reaction is completed, cool to room temperature and pass through a 0.22 μm filter membrane to obtain a yellowish-brown liquid that is the carbon quantum dot solution, which is set aside;
[0037] (2) Weigh 0.2g of 120 samples of Yunnan black tea of different grades (special grade, first grade, second grade, third grade, fourth grade, fifth grade, sixth grade and extra grade) to be tested, add 8mL of 70% ethanol, and conduct ultrasound for 45min For leaching, the ultrasonic temperature is 70°C, and th...
Embodiment 2
[0073] In order to examine the feasibility of this method, cross-validation was carried out on the observed values of the known discrimination results of different grades of Dianhong tea. In cross-validation, each observation is classified according to a function derived from all observations other than that observation, and the classification results are shown in Table 3. The results in Table 3 show that 95% of the cross-validation groups are correctly classified, and the classification accuracy is P 特级 =100%, P 一级 =86.7%, P 二级 =100%, P 三级 =100%, P 四级 =93.3%, P 五级 =86.7%, P 六级 = 93.3% and P 级外 = 100%. It shows that the grade discriminant method of Dianhong based on carbon quantum dot nanomaterials combined with principal component analysis and Bayesian discriminant method is feasible.
[0074] Table 3 Classification and verification results of Bayesian discriminant for different grades of Dianhong tea
[0075]
[0076] The invention judges by detecting the carbo...
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