鉴别铁观音茶叶的方法

鉴别铁观音茶有感官和理化鉴定两个方法。感官鉴定，也叫审评，第一形状，属外观鉴定。感官鉴定又可分为四项：一是条索，条的种类不同，条索的要求与呈现各异，如松紧、曲直、粗细、扁圆、整碎、轻重等。要与该品种正常情况相符。二是色泽，是枯燥还是光润，还应与该品种要求相符，如红茶是红褐色，绿茶是崭新绿色，花茶为褐绿色。三是净度，应洁净无梗，块、片、末不超过限度，不能含有非茶类夹杂物。四是嫩度，同一品种茶叶以芽尖白毫多者为佳，条索虽稍粗壮，但嫩润半透明。

鉴别茶的内质，可分香气、滋味、汤色、叶底。一是香气，鼻嗅新鲜，浓厚纯正为好，淡薄不纯为次，闷焦粗涩者更次，有异味者为劣。各种花茶均应有自己独特的正常香气，如茉莉花茶应具茉莉香气，玉兰、珠兰花茶应具玉兰、珠兰香气。二是滋味，用舌部味蕾感觉，甘醇浓郁，鲜嫩纯正为优，涩、苦、粗、酵、淡为次，霉、辣、生草味为劣。三是汤色，在茶汤热时，观察明暗深浅。一般明浅为佳，暗深者次，但红茶汤色比绿茶深，紧压茶汤色要暗。四是叶底，品尝沏过的湿茶叶，用手按，柔软有弹性属于细嫩，板硬无弹性为粗老。上述鉴别方法主要是区分优、次、劣。一切事物都是由量变到质变，伪劣茶叶也就往往是在这种感官鉴别中发现。

铁观音茶叶尚无全方位、全过程用文字表述的质量标准，现只有产地收购毛茶标准，即6级18等，和国际GB/T9172-1988《花茶级型坯》标准。其中只有国标GB9679—1988《茶叶卫生标准》具有强制性。感官指标：具有该茶正常应有的外形及固有色香味，不能混有异种植物，叶不得含草类物质，无异味，无异臭，无霉变。理化指标：每kg铅含量不超过2mg(紧压茶为3mg)，铜不超过60mg，锑不多于0.2mg(紧压茶为0.4mg)。

水分指标：含水量太高，茶叶变质越快;水份越少，茶叶不易劣变，但水份过低，茶叶品质会下降。一般茶叶含水量在3%左右为最佳。

灰分指标：茶叶中的无机化合物称为灰分，灰分中含量较多的是磷、钾，其次是钙、镁、铁、锰、铝、硫等，总量不得超过7%。

茶叶的物理鉴别有4项内容：

1叶片检验：取少许开水冲泡后的叶片，用放大镜观察，如果叶片的颜色为深绿色，上面光滑，背面有茸毛，叶片呈椭圆形，叶端短小钝圆，叶缘呈锯齿状，锯齿上有纤毛，即可判断为真茶。不符合以上特征的叶片即为掺假茶。

2对掺入已浸泡过的铁观音茶叶检验：取可疑茶叶片，制成粉末，置于表面皿中后，另于其上端再加盖一表面皿，控制电炉，用小火烘烤5～10min，在覆盖的表面皿上，用镜检，如果可见许多极细的油滴状物，并有许多细针状结晶者为咖啡碱，表明是纯茶。否则说明咖啡碱早已溶解无存，可以判为是已经浸泡过的茶叶。还可以根据浸出液比重法来确定，已经浸泡过的茶叶浸出液比重为1.0023～1.0057，与新茶浸出液比重1.0098～1.0145相差甚远，上述两种方法结合使用，更能准确判断。

3对茶叶中掺入了色素的检验：取茶碎末放在白纸上，反复摩擦，如在纸上留下了各种颜色条痕，说明有着色剂存在。还可取茶少许加入三氯甲烷，振荡后，如三氯甲烷呈现蓝色或绿色者，表明茶叶掺入了蓝靛或姜黄等着色剂。

4对茶叶中掺入蜡质的检验：取少许茶叶摊于粗糙白纸上，用电熨斗烫之，如在白纸上有明显油迹存在，说明茶叶中掺入了蜂蜡或石蜡。

茶叶的化学鉴别：

如果可疑叶片不含咖啡碱和锰，已能证明不是茶叶，但若检出咖啡碱与锰，也还不能肯定可疑叶片就是茶叶。因此，还需要根据国家标准规定的方法，作有无茶氨酸的检验，来最终判定茶叶的真假。

市场抽查发现，散装茶普遍质价不符，质次价高;包装茶中有不少不法商贩伪造“猴王”、“京华”等名牌商标、包装，以假充真，以次充好，而且缺斤短两。以“京华”牌为例，其商标、寿字图案和包装袋图案都进行了注册，受国家法律保护。包装定点印刷，细致精美，广大消费者在购买包装茶时应仔细辨认，注意比较，避免上当。

There are two methods to identify tea: sensory and physicochemical. Sensory identification, also called review, the first shape, belongs to appearance identification. The sensory identification can be divided into four items: one is the rope, the types of the rope are different, and the requirements and presentation of the rope are different, such as tightness, straightness, thickness, oblate, whole broken, weight and so on. To be consistent with the normal conditions of the breed. The second is color, whether it is dull or smooth, and it should also be in line with the requirements of the variety, such as black tea is reddish brown, green tea is brand new green, and scented tea is brownish green. The third is the clarity. It should be clean and stalkless, and the pieces, slices, and ends should not exceed the limit, and should not contain non-tea inclusions. The fourth is tenderness. For the same variety of tea, it is better to have more bud tips and pekoe. Although the cord is slightly thick, it is tender and translucent.

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To identify the inner quality of tea, it can be divided into aroma, taste, soup color and leaf bottom. The first is the aroma, the nose smells fresh, the thick and pure is good, the weak and impure are the second, the stuffy and coarse are the worst, and the peculiar smell is inferior. All kinds of scented tea should have their own unique normal aroma, such as jasmine tea should have the aroma of jasmine, magnolia and Zhulan flower tea should have the aroma of magnolia and Zhulan. The second is the taste, which can be felt by the taste buds of the tongue. It is rich in glycol, fresh and pure is superior, astringent, bitter, coarse, fermented, and mild are inferior, and mildew, spicy, and grassy are inferior. The third is the color of the soup. When the tea soup is hot, observe the light and shade. Generally, light and light are better, and dark is the second. However, the color of black tea is darker than that of green tea, and the color of pressed tea is darker. The fourth is the bottom of the leaves. Taste the wet tea leaves that have been brewed and press them with your hands. Soft and elastic are tender, and hard and inelastic are rough and old. The above identification methods are mainly to distinguish the superior, inferior and inferior. Everything changes from quantity to quality, and fake tea leaves are often found in this sensory identification.

There is no comprehensive and whole-process quality standard for tea. Currently, there are only the standard of raw tea purchased from the origin, that is, grade 6 and 18, and the international GB/T9172-1988 "scented tea grade parison" standard. Among them, only the national standard GB9679-1988 "Tea Hygiene Standard" is mandatory. Sensory indicators: It has the normal appearance and inherent color and aroma of the tea, can not be mixed with different plants, leaves must not contain grass substances, no peculiar smell, no peculiar smell, no mildew. Physical and chemical indicators: the lead content per kg is not more than 2mg (3mg for compressed tea), copper is not more than 60mg, and antimony is not more than 0.2mg (0.4mg for compressed tea).

Moisture index: If the water content is too high, the tea will deteriorate faster; the less water, the tea will not easily deteriorate, but if the water content is too low, the quality of the tea will decline. Generally, the moisture content of tea leaves is about 3%.

Ash content index: The inorganic compounds in tea are called ash content. The content of ash content is mostly phosphorus and potassium, followed by calcium, magnesium, iron, manganese, aluminum, sulfur, etc. The total amount should not exceed 7%.

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There are 4 items in the physical identification of tea:

1 Leaf inspection: Take a little leaf after brewing with boiling water and observe it with a magnifying glass. If the color of the leaf is dark green, the top is smooth, the back is hairy, the leaf is oval, the end of the leaf is short and blunt, and the edge of the leaf is serrated and serrated. If there are cilia on it, it can be judged as real tea. Leaves that do not meet the above characteristics are adulterated teas.

2. Inspection of the tea leaves that have been soaked: Take suspicious tea leaves, make powder, put them in a watch glass, and cover the upper end with a watch glass. On the covered watch glass, microscopic examination, if there are many very fine oil droplets and many fine needle-like crystals, it is caffeine, indicating that it is pure tea. Otherwise, it means that the caffeine has already been dissolved, and it can be judged as the tea that has been soaked. It can also be determined according to the specific gravity method of the extract. The specific gravity of the tea extract that has been soaked is 1.0023 to 1.0057, which is far from the specific gravity of the new tea extract of 1.0098 to 1.0145. The combination of the above two methods can be more accurate.

3. Inspection of tea mixed with pigments: Take tea powder and put it on white paper and rub it repeatedly. If there are streaks of various colors on the paper, it means that there are colorants. You can also add a little chloroform to the tea. After shaking, if the chloroform appears blue or green, it means that the tea leaves are mixed with colorants such as indigo or turmeric.

4. Inspection of the inclusion of wax in tea: Take a little tea and spread it on rough white paper and iron it with an electric iron. If there are obvious oil marks on the white paper, it means that the tea is mixed with beeswax or paraffin.

Chemical identification of tea:

If the suspected leaf does not contain caffeine and manganese, it can be proved that it is not tea, but if caffeine and manganese are detected, it is not sure that the suspicious leaf is tea. Therefore, it is also necessary to test the presence or absence of theanine according to the method specified by the national standard to finally determine the authenticity of the tea.

Market spot checks found that bulk tea generally does not match the quality and price, and the quality and inferior price are high; many unscrupulous traders in packaged tea forge famous brand trademarks and packaging such as "Monkey King" and "Jinghua", pretending to be fake and shoddy. Jin is short. Taking the "Jinghua" brand as an example, its trademark, longevity character pattern and packaging bag pattern are all registered and protected by national laws. The packaging is fixed-point printing, meticulous and exquisite, and consumers should carefully identify and compare when purchasing packaged tea to avoid being deceived.