Teach you some scientific methods to identify tea
identification of tea with sensory and physical and chemical identification of two methods. Sensory evaluation, also referred to as review, the first shape, is the appearance of identification. Sensory evaluation can be divided into four aspects: one is the cable, the different bands and presenting different requirements, such as elastic, straight, flat, thickness, weight, whole pieces. In line with the normal condition of the variety. Two is the color is dull or smooth, also should tally with the requirements of the varieties, such as Black Tea is red brown, Green Tea is a new green, brown green tea. Three is cleanliness, should be clean, no block, block, piece, end does not exceed the limit, can not contain non tea inclusions. Four is the tenderness, the same varieties of tea in the bud tip pekoe preferable, the cable is slightly thick, but tender moist translucent.
Identification of the tea can be divided into aroma, taste, soup color, leaf bottom. First, the aroma, nose smell fresh, strong pure as good, weak impure for the next, stuffy coke coarse acerbity more times, bad smell is bad. All kinds of tea are normally should have their own unique aroma, such as Jasmine Tea with jasmine aroma, Magnolia, Magnolia, stephanandra Chloranthus tea with aroma. Two, taste, taste with tongue taste, mellow mellow, fresh and pure as the best, astringent, bitter, coarse, fermented, light as the next, mildew, spicy, raw grass flavor is bad. Three is soup color, in the hot tea, observe the depth of light and shade. The general shallow is better, dark times, but Black Tea Tangshaibi Green Tea deep, tea soup color to dark. Four is the bottom of the leaf, tasting the wet tea, hand pressing, soft and elastic, belong to the delicate, hard board, no flexibility for coarse old. The identification method is mainly to distinguish the superior, inferior and inferior. All things are from quantitative change to qualitative change, fake tea is often found in this sense of identification.
There is no tea in the whole process and expressed in words of quality standards, now only tea origin purchase standard, namely 6 and 18, and the international GB/T91721988 "tea" standard grade parison. Among them, only national standard GB9679— 1988 "tea hygiene standard" is mandatory. Sensory indicators: the tea should have the normal shape and solid color fragrance, can not mix with heterogeneous plants, leaves shall not contain straw substances, no odor, no odor, no mildew. Physicochemical index: lead content of not more than 2mg per kg (3mg tea), copper and antimony is less than 60mg, not more than 0.2mg (0.4mg tea).
Water index: water content is too high, the faster the deterioration of tea; less moisture, tea is not easy to deteriorate, but the water is too low, tea quality will decline. The water content of tea is about 3%.
Ash index: inorganic compounds in tea are called ash. The content of ash is phosphorus and potassium, followed by calcium, magnesium, iron, manganese, aluminum, sulfur and so on, and the total amount should not exceed 7%.
There are 4 items in the physical identification of tea:
1: take a little leaf blade test after boiling water, with a magnifying glass, if the leaf color is dark green, glossy above, hairy abaxially, oval shaped leaves, leaf end short rounded, serrated leaf margin ciliate, serrated, can be judged as true tea. The leaves which do not conform to the above characteristics are adulterated tea.
2 of tea inspection incorporation has soaked: suspicious leaves, made of powder, placed on the surface plate, the other on the upper end and covering a surface plate, electric control, use small fire to bake for 5 ~ 10min, on the surface of the dish covered with microscopic examination, if visible, many very fine oil the droplets, and there are many fine needle like crystals for caffeine, that is pure tea. Otherwise, caffeine has been dissolved without storage, can be judged to have been soaked tea. According to the method to determine the proportion of extract, tea extract proportion has been soaked in 1.0023 to 1.0057, far from 1.0098 to 1.0145 the proportion of tea extract is combined with the use of the above two methods, a more accurate judgment.
3 of tea mixed with the pigment of the test: take tea powder on the white paper, rubbing, as in the paper on the left shows the various color streaks, colorants. A little tea may be mixed with chloroform, oscillation, such as chloroform appear blue or green, shows that tea mixed with indigo or turmeric colorant etc..
4 inspection of wax incorporation in tea: take a little tea stalls in rough white, with an electric iron, such as the white paper has obvious traces of oil, that tea mixed with beeswax or paraffin.
Chemical identification of tea:
If the suspect leaves do not contain caffeine and manganese, it has proved that it is not tea, but if the detection of caffeine and manganese, it can not be sure that the suspicious leaves are tea. Therefore, it is necessary to test whether there is theanine or not according to the method stipulated by the national standard to determine the true or false of tea.
The market spot checks found that the bulk tea does not match the general price, Zhicijiegao; packaging tea there are many unscrupulous traders forged “ &rdquo, “ Monkey King; JINGWAH ” other famous trademarks, packaging, yijiachongzhen, shoddy, and quejinduanliang. Take “ JINGWAH ” brand as an example, its trademarks, longevity word patterns and packaging patterns have been registered, protected by the state law. Packaging fixed-point printing, exquisite and exquisite, the vast number of consumers in the purchase of packaged tea should be carefully identified, pay attention to comparison, to avoid being fooled.
