How to identify whether there are pesticides in tea?
The truly effective way is to rely on the tea quality inspection department to use physical or chemical methods to identify whether tea contains pesticides.
There are two methods for identifying tea: sensory and physical and chemical identification. Sensory evaluation, also called evaluation, is the first appearance evaluation. Sensory identification can be divided into four items: First, cords. Different types of cords have different requirements and presentations, such as tightness, straightness, thickness, oblateness, wholeness, weight, etc. It must be consistent with the normal conditions of the breed. The second is the color, whether it is dull or smooth, it should also conform to the requirements of the variety. For example, black tea is reddish brown, green tea is brand new green, and scented tea is brownish green. The third is purity, which should be clean and stemless, with lumps, slices and powder not exceeding the limit, and should not contain non-tea inclusions. The fourth is tenderness. Tea leaves of the same variety are better if they have more white hairs on the bud tip. Although the cords are slightly thicker, they are tender and translucent.
Identify the inner quality of tea, which can be divided into aroma, taste, soup color and leaf bottom. The first is the aroma, which smells fresh to the nose. It is better if it is thick and pure. It is inferior if it is light and impure. It is inferior if it is burnt, thick and astringent. It is inferior if it has an odor. All kinds of scented tea should have their own unique normal aroma. For example, jasmine tea should have the aroma of jasmine, and magnolia and pearl orchid tea should have the aroma of magnolia and pearl orchid. The second is the taste, which can be felt by the taste buds on the tongue. Glycol, richness, freshness and purity are the best, astringent, bitter, thick, yeasty and bland are the second best, and moldy, spicy and herbaceous taste are the worst. The third is the color of the soup. When the tea soup is hot, observe the light and dark depth. Generally speaking, light and light are better, followed by dark and dark. However, the color of black tea soup is darker than that of green tea, and the color of pressed tea soup is darker. The fourth is the bottom of the leaves. Taste the brewed wet tea leaves and press them with your hands. If they are soft and elastic, they are tender, and if they are hard and inelastic, they are thick and old. The above identification methods mainly distinguish between excellent, inferior and inferior. Everything changes from quantity to quality, and fake and inferior tea is often discovered during this sensory identification.
There is no comprehensive and whole-process quality standard for tea. Currently, there are only standards for purchasing raw tea from the place of origin, namely Grade 6 and Grade 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. It cannot be mixed with foreign plants. The leaves must not contain herbaceous substances. There is no peculiar smell, no odor, and no mildew. Physical and chemical indicators: lead content per kg shall not exceed 2 mg (3 mg for compressed tea), copper shall not exceed 60 mg, and antimony shall not exceed 0.2 mg (0.4 mg for compressed tea).
Organochlorine and organic mercury Pesticide residue indicators, the content of 666 and DDT shall not exceed 0.2 mg/kg.
Moisture index: If the water content is too high, the tea will deteriorate faster; the less water, the tea will be less likely to deteriorate, but water content If the proportion is too low, the quality of the tea will decline. Generally, the optimal moisture content of tea is about 3%.
Ash index: The inorganic compound in tea is called ash. The most abundant ash content is phosphorus and potassium, followed by calcium, magnesium, iron, manganese, aluminum, sulfur, etc. The total amount should not exceed 7 %.
The physical and chemical identification of tea is divided into physical identification and chemical identification.
There are 4 items in the physical identification of tea leaves:
1 Leaf inspection: Take a leaf after brewing with a little boiling water and observe it with a magnifying glass. If the color of the leaf is dark green and the top is smooth, , there are hairs on the back, the leaves are oval, the leaf ends are short and blunt, the leaf edges are serrated, and there are cilia on the serrations, it can be judged as real tea. Leaves that do not meet the above characteristics are adulterated tea.
2 Test for mixed tea leaves: Take the suspected tea leaves, make them into powder, place them in a watch glass, cover the upper end with a watch glass, control the electric stove, and use a small Bake over fire for 5 to 10 minutes. Check under a microscope on a covered watch glass. If you can see 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 long been dissolved, and it can be regarded as tea that has been soaked. It can also be determined based on the specific gravity method of the infusion. The specific gravity of the tea infusion that has been soaked is 1.0023 to 1.0057, which is far from the specific gravity of the new tea infusion, which is 1.0098 to 1.0145. The above two methods can be used in combination to make a more accurate judgment.
3. Inspection of pigments incorporated into tea leaves: Place the broken tea on white paper and rub it repeatedly. If streaks of various colors are left on the paper, it indicates the presence of colorants. You can also add a small amount of chloroform to the tea. After shaking, if the chloroform turns blue or green, it indicates that the tea has been mixed with coloring agents such as indigo or turmeric.
4 Test for wax mixed with tea leaves: Spread a small amount of tea leaves on rough white paper and iron it with an electric iron. If there are obvious oil stains on the white paper, it means that the tea leaves are mixed with wax. of beeswax or paraffin.
Chemical identification of tea leaves:
If the suspect leaves do not contain caffeine and manganese, it can be proved that they are not tea leaves. However, if caffeine and manganese are detected, it is not certain that the suspect leaves are tea leaves. . Therefore, it is necessary to test the presence or absence of theanine according to the methods stipulated in national standards to ultimately determine the authenticity of the tea.
Spot checks on the market found that loose tea generally has inconsistent quality and price, with low quality and high prices; in packaged tea, many unscrupulous traders forge the trademarks and packaging of famous brands such as "Monkey King" and "Jinghua", passing them off as genuine. Shoddy goods are shoddy, and they are worth a lot of money. Take the "Jinghua" brand as an example. Its trademark, longevity pattern and packaging bag pattern have all been registered and are protected by national laws. The packaging is printed at fixed points and is meticulous and exquisite. Consumers should carefully identify and compare when purchasing packaged tea to avoid being deceived.
The results of the national quality supervision and inspection of jasmine tea in the fourth quarter of 1999 showed that 4.29% of the pesticide residues exceeded the limit specified by the national standard. Our country’s tea production area is vast and there are many varieties. Most of the tea gardens are located in high mountains. The water and soil are pure and there is little pollution. However, in tea gardens located in hilly areas, there are many diseases and insect pests in the summer and autumn tea seasons. Tea farmers neglect the correct use of pesticides, resulting in excessive pesticide residues in tea. During the processing and blending of tea, raw materials are mixed with each other, which expands the scope of pesticide residue contamination and seriously affects the reputation of tea, domestic sales, and foreign trade exports. The new inspection standards implemented by the European Union from July 1, 2000 have greatly reduced the pesticide residue limit indicators for tea. As a major tea producer and exporter, my country faces severe challenges. Beijing, Tianjin, and Shanghai have formulated strict tea quality standards. . How to remove pesticides in tea
First, we advocate washing tea. The method of "washing tea" is to pour boiling water into the tea leaves, gently shake the tea and water in the pot several times, and pour out the tea immediately. , it can not only wash dust and sand, but also remove some pesticide residues and heavy metal substances that are easily soluble in hot water, so that the toxic substances that are originally dissolved in the tea soup can be removed. Especially the method of drinking with boiling water will greatly reduce lead. intake.
Second, avoid long-term brewing. For example, the lead in tea leaves is almost insoluble in the tea soup during brewing. As long as it is brewed within two hours, most of the residual pesticide ingredients contained in the brewed tea leaves will be dissolved. Not coming out. Therefore, when drinking tea, you can pay attention to two points: "Don't chew the tea leaves" and "Don't brew a cup of tea from morning to night."
How do pesticides attach to tea leaves?
Tea farmers grow tea, just like vegetable farmers grow vegetables. They do not use pesticides, chemical fertilizers and insecticides. The key is the amount of residues. Generally speaking, tea before Qingming Festival is relatively safe. After spring tea, there is a high incidence of insect pests, which occurs every ten days. At this time, the tea trees need to be sprayed with pesticides. Therefore, the pesticide residues in summer and autumn tea are relatively high. More.
It is almost impossible to tell whether tea contains pesticides by just looking at its shape, color, and smell. It can only be tested by experts from the Quality Supervision Bureau. However, it is normal for most teas to contain pesticides. As long as the pesticide residues are controlled within national standards, it is a safe product for the human body. In addition, some pesticide ingredients, such as lead in tea, are almost insoluble in the tea soup during normal brewing, and most of the residual pesticide ingredients contained in tea brewed with ordinary water cannot be brewed within two hours. come out.
Therefore, there are two points to remember: one is not to chew tea leaves, and the other is not to brew a cup of tea from morning to night without changing the tea leaves. Drinking tea this way is relatively safe.
And according to the relevant testing report of a certain city, 43 tea varieties were randomly inspected (testing items included labels, heavy metal indicators, colorant indicators and pesticide residues). After inspection, 35 types of tea products were qualified, with a sampling pass rate of 81.4%. Three types of tea were found to contain fenvalerate exceeding the standard, and 5 types of tea were found to contain dicofol. Dicofol is a low-toxic organochlorine acaricide with very stable properties and is not easily degraded under natural conditions. The use of dicofol on tea trees is prohibited in my country; fenvalerate is a pyrethroid insecticide that degrades slowly under natural conditions. . It is normal for most tea leaves to contain pesticides, which generally do not cause acute poisoning in the human body. However, the chronic poisoning caused by the accumulation of pesticide residues in the human body should not be underestimated.