We often see or hear about pesticide residues in crops. We even heard that a certain kind of tea cannot be exported because of excessive pesticide residues. Pesticides have toxic, teratogenic and carcinogenic side effects, thus causing people to fear and doubt. So, how to eliminate pesticide residues on vegetables and fruits in daily life? Now I will introduce you to several simple methods:

Peeling method: The pesticide residues in vegetables and fruits are mainly concentrated on the surface. Peeling is a better way to remove residual pesticides. Don’t be too troublesome or afraid of losing nutrients. Peel apples, pears, kiwis, carrots, winter melons, pumpkins, zucchini, eggplants, radishes, etc. if you can.

Alkaline water soaking method: The types of pesticides that contaminate vegetables are mainly organophosphorus pesticides that are difficult to dissolve in water, but decompose quickly in an alkaline environment, so this method is one of the effective measures to remove pesticide pollution. 1. It can be used for all kinds of vegetables and fruits. The method is to rinse the surface dirt first, soak it in alkaline water (500 ml of water plus 5-10 grams of edible alkaline noodles) for 5-15 minutes, and then rinse with clean water 3-5 times.

Water soaking and washing method: This method is the most basic and commonly used method to remove dirt and residual pesticides on vegetables and fruits. It is mainly used for leafy vegetables, such as spinach, daylily, leek flowers, Lettuce, Chinese cabbage, etc. Generally, rinse the surface dirt with water first, and then soak it in clean water for no less than 10 minutes. Fruit and vegetable cleaning agent can promote the dissolution of pesticides, so you can add a small amount of fruit and vegetable cleaning agent when soaking. After soaking, rinse with running water 2-3 times.

Storage method: Pesticides can slowly decompose into substances harmless to the human body over time in the air, so vegetables and fruits that are easy to preserve, such as apples, kiwis, winter melons, etc., can be stored for a period of time to Reduce pesticide residues. Generally stored for more than 15 days, it is recommended that you do not eat newly picked unpeeled fruits immediately.

Heating method: Carbamate pesticides can decompose faster as the temperature rises, so some vegetables and fruits that are difficult to treat by other methods can be heated to remove part of the pesticides. Commonly used for celery, spinach, Chinese cabbage, cabbage, green peppers, cauliflower, beans, etc. First wash the surface dirt with clean water, put it in boiling water for 2-5 minutes, remove it, and then rinse 1-2 times with clean water.

Ozone disinfection method: Connect the ozone generator to tap water, and use ozone-treated water to wash vegetables and fruits to remove residual pesticides.

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How to identify tea

Author: Unknown Time: February 16, 2005 Source: Fake and shoddy goods identification manual Font size: Large, Medium, Small

The tea tree belongs to the Theaceae family, and tea leaves are divided into five categories: red, green, flower, pressed, and oolong. The main components of tea include tannic acid, caffeine, protein, aromatic oils, enzymes, pectin, vitamins, carbohydrates, minerals, organic acids, etc. Because of these ingredients, people can appreciate the delicious taste of tea and enjoy the nutrition of tea. Fake and inferior tea does not have these ingredients and can also harm people's health.

my country is a major tea-producing country in the world. Half of the 29 provinces and cities in the country produce tea in various varieties. Among them, the famous West Lake Longjing tea is famous for its unique shape, superior color, aroma and taste. Its origin is limited to Shifeng Mountain, Meijiawu, Wengjiashan, Yunqi, Hupao and other places around Longjing Village in West Lake, Hangzhou. In 1988, Shifeng brand's premium Longjing tea won the highest award, the Palme d'Or, at the 27th World Quality Food Awards held in Athens, Greece. Longjing tea picked before Qingming is usually called Mingqian tea, which has the best quality; Longjing tea picked before Guyu is called Yuqian tea, which is also of good quality. Those that pick only one bud are called "Lotus Heart"; those that pick one bud and one leaf, the leaf is shaped like a flag, and the bud is shaped like a gun are called "Flag Gun"; those that pick one bud and two leaves are just unfolding, and the leaves are curled like a bird's tongue. It's called "tongue". Premium Longjing tea is standard and complete with one bud and one leaf. The frying technology of Longjing tea is extremely demanding. After frying, the tea leaves need to be stored for half a month to a month, so that the aroma will be more fragrant and fragrant, and the taste will be more fresh and delicious. This is the unique feature of Longjing tea.

The quality of tea is related to climate, light, and growth environment. High mountain tea is better than low mountain tea, Yangshan tea is better than Yinshan tea, and first-pass tea is better than second-pass tea. For the same kind of tea, tea leaves from high mountains are pointed and tea leaves from low mountains are round; tea leaves from Yangshan mountains are thick and tea leaves from Yinshan mountains are thin; tea leaves from the first time have round stems and tea leaves from the second time have flat stems.

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 kilogram 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).

As for organochlorine and organomercury pesticide residue indicators, the contents of 666 and DDT shall not exceed 0.2mg/kg.

Moisture index: If the moisture content is too high, the tea will deteriorate faster; if the moisture content is too low, the tea will be less likely to deteriorate, but if the moisture content is too low, the quality of the tea will decline. Generally, the optimal moisture content of tea is around 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 5~10 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 1.0023~1.0057, which is far from the specific gravity of the new tea infusion, which is 1.0098~1.0145. 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 tea leaves.

Spot inspections on the market found that the quality and price of loose tea generally do not match, and the quality is inferior and the price is high; in packaged tea, many unscrupulous traders forge the trademarks and packaging of famous brands such as "Monkey King" and "Jinghua" and pass 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. China's tea production area is vast and there are many varieties. Most tea gardens are located in high mountains, with pure water and soil and 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 pollution 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. .

The following introduces the key points for identifying new tea:

Looking at the appearance, all varieties of tea should be tightly knotted, the peaks should be heavy and round, the stems should be short and tender, the color should be smooth, and the leaves should be slightly rounded. Those that are flat, curly, and uniform in thickness are of high quality; those that are fluffy and light, with short and broken leaves and many tea stems are of poor quality.

Look at the color. Green tea should be green and fresh, while dark green, dark yellow, burnt yellow or brownish red is the worst. Black tea should be reddish-brown or jet-black, with fine buds. Golden color is the top grade, while black, greenish brown or dark red is the inferior grade. For various scented teas, pure green and matte ones are better.

The better the aroma and quality of the tea, the more fragrant and fragrant it will be. When chewed or brewed, green tea has a fresh aroma first, followed by astringency; black tea has a sweet aroma first, followed by sourness; scented tea has both a tea aroma and a floral aroma. If there is no tea aroma or a grassy smell, it is fake tea. , if there is a pesticide smell, moldy smell and other odors, it is a poor quality product.

Distinguish the color and flavor of tea soup. Take a small amount of sample and brew it for observation. The soup of high-quality green tea is green and clear. The tea is bitter at first, then has a strong aroma and is sweet and has a chestnut aroma. The soup of high-quality black tea is bright red in color and has a strong aroma. , mellow, fresh and refreshing; the color of scented tea soup is yellow, bright and transparent.

The following introduces the identification methods of the top ten famous teas

1 West Lake Longjing is produced in Xihu District, Hangzhou. The tea leaves are flat and straight in shape, smooth to the touch, delicate leaves, neat strips, consistent width, and color. Emerald green or green yellow, one bud and one leaf or two leaves, the bud is longer than the leaf, generally less than 3cm long, the buds and leaves are evenly formed into flowers, without pedicles or fragments, the leaf shape is relatively thin, easy to break and fragile, and the water content is below 6 . Soaked in the soup, the buds grow into flowers, one flag and one shot, intertwined with each other, the fragrance is sweet and mellow, and the fragrance lingers for a long time. The West Lake Longjing tea should be picked early, tender and diligent. Frying requires three manual processes. Each 500g of first-grade West Lake Longjing requires about 36,000 Mingqian tea buds.

The fake "Zhejiang Longjing" that is faked as "West Lake Longjing" is yellow in color, with wider leaves, a strong appearance, and a strong aroma. Other fake Longjing teas have a grassy smell, more pedicles, a rough texture, and no fragrance of Longjing tea.

2 Biluochun is produced in Biluofeng of Dongting Mountain on the shore of Taihu Lake in Wuxian County, Jiangsu Province. The silver buds are exposed, one bud and one leaf. The total length of the tea leaves is 1.5cm. The cords are slender and curled into snails. The buds are covered with hairs. It has a pekoe curly shape, the leaves are curly green, the bottom of the leaves is tender, uniform and bright, the soup is clear and bright green, and the taste is meaningful and fragrant. 500g of Biluochun requires 60,000 buds to make, so it is known as "craft tea".

The fake ones have one bud and two leaves. The buds and leaves are uneven in length and yellow in color.

3 Xinyang Maojian is produced in Cheyun Mountain in Xinyang, Henan Province. It has a tight, thin, round, smooth, straight appearance, and a clear black color. It usually has one bud and one leaf or one bud and two leaves. After drinking it, the taste is sweet, the cheeks and teeth are stimulated, and the taste is like sugar-roasted chestnuts.

The leaves of fake products are curled and yellowed.

4 Junshan Silver Needle is produced in Junshan, Yueyang, Hunan. Made from the fat, unexpanded bud heads. The bud heads are fat, straight, even, and covered with hairs. They are golden in color, fresh in aroma, light in color, and sweet in taste. When brewing, the bud tips rush to the water surface, stand upright in the air, and then slowly sink to the bottom of the cup, forming the shape of a group of buds. When the bamboo shoots are unearthed, they stand upright like silver knives.

Fake products often have a grassy smell, and the silver needles cannot stand upright after brewing.

5 Lu'an Guapian is produced in Qiyun Mountain in Lu'an and Jinzhai counties in Anhui. Its shape is flat, with no buds or stems on each piece. The leaves are green and glossy, slightly overlapping upwards, and resemble melon seeds. When brewed, they have a sweet aroma, the soup is green in color, and the taste is sweet. The bottom of the leaves is thick and bright.

Fake products taste bitter and are yellow in color.

6 Huangshan Maofeng is produced in Huangshan, Anhui. The buds and leaves of the tea tree are thick and hairy. The shape of the mature tea is tender and slightly curled, with many peaks. The buds are fat and even, and the color is green and oily. When brewed, the aroma is fresh, mist surrounds the top, the soup is clear, apricot yellow, and has a mellow taste. , the fragrance is long-lasting and sweet, and the leaf buds at the bottom of the leaves are thick and bright.

The fake ones are earthy in color, bitter in taste, and have no flowers at the bottom of the leaves.

7 Keemun black tea is produced in Qimen County, Anhui. The color of the tea is brown-red, cut into 06-08cm pieces, and has a rich, strong, mellow and fresh taste.

Fake products generally contain artificial colorings, taste bitter and thin, and have uneven leaves and shapes.

8 Duyun Maojian is produced in the Buyi and Miao Autonomous Region of Duyun County, Guizhou. It is made from the tender buds of tea trees picked before the Qingming Festival. The tea leaves are uniformly green, small and thin, with one bud and one leaf unfolding. It is shaped like a bird's tongue, 2-25cm long, with tight and thin strips, curled and exposed vellus hairs, and the bottom of the leaves is light green. , after brewing, the fragrance is long-lasting, mellow and sweet.

Fake products have uneven leaf bases and a bitter taste.

9 Tieguanyin is produced in Anxi County, Fujian Province. The leaves are as heavy as iron and as beautiful as Guanyin. They are mostly spiral-shaped, sandy green in color, smooth and green in color, and have a natural orchid fragrance. After brewing, the soup is clear and golden in color, with a mellow and sweet taste. It is slightly bitter in the mouth and turns sweet immediately. It is resistant to brewing. The bottom of the leaves is spread, with green and red edges, thick and bright, and each tea has tea branches.

The fake leaves are long and thin, with thicker cords and no green and red edges. The leaves lose their fragrance after being soaked three times.

10 Wuyi Rock Tea is produced in Wuyi Mountain, Chong'an County, Fujian Province. The shape of the tree is thick, tight, even, with twisted strips, commonly known as "dragonfly head", and frog skin-like sand grains are raised on the back of the leaves, commonly known as "toad's back". When brewed, the taste is mellow and bitter, smooth and refreshing, the soup is clear yellow, the brew is bright, the bottom of the leaves is evenly bright, the edges are vermilion or red spots, the central leaf mesophyll is yellow-green, the veins are light yellow, and it can withstand more than 6-8 times of soaking.

Fake products have dull appearance, weak brewing taste and lack of flavor.