Black tea and green tea are the second most common beverages after drinking water. Recently, Dutch researchers found that drinking tea (with or without milk) can improve the overall level of antioxidants in the blood. Previous studies have found that antioxidants help prevent heart disease.
A recent research report published in the European Journal of Clinical Nutrition shows that phytochemicals in the form of flavonoids in tea (represented by catechuic acid in green tea and theaflavins in black tea) are effective antioxidants.
Chris Rothenblum, a nutritionist with the American Dietetic Association, said that researchers are trying to find some other healthy substance properties in food. At present, except for the known fiber and vitamins, the whole field of phytochemistry is still blank. There may be many beneficial substances in tea.
Dr. Rianne glover ne, who works in Anyilifulnutrition center in Vladin, and his colleagues observed the effect of drinking tea in 265,438+0 volunteers. The age of these volunteers is between 18 and 70 years old, among which 1 1 is female. None of them smoke. Except for the hectic night before the start of the study, the daily activities and diet of these volunteers remained normal at other times.
In the experiment, each volunteer drank three cups of tea every day for six days. Four kinds of tea were used in the experiment: green tea, green tea with whole milk, black tea and black tea with whole milk. As a control group, some volunteers drank placebos such as mineral water or mineral water with milk. After the volunteers drank it, the researchers took blood samples every 30 minutes for 2 hours. The researchers measured the content of plasma antioxidants at every interval to see if the content of plasma antioxidants increased after drinking these teas.
Dr. flax and his colleagues found that no matter whether milk is added or not, any kind of tea can significantly improve the level of antioxidants, and the increase of green tea is 1.5 times that of black tea. In particular, green tea significantly increased plasma catechuic acid, which was more than 5 times that of black tea. As far as drinking tea is concerned, Americans and Europeans drink black tea more often, while drinking green tea is more common in some countries in Asia and the Middle East.
"I have a new batch of tea drinks, but its raw material is not green tea, but tea powder. Is there any difference between the two? " Ms. Lu, who runs a convenience store, looked at the two kinds of tea drinks in her hand and wondered, "Some customers are more careful and ask me a question, but I can't answer it."
Summer is here, and it's time for tea drinks to show their talents. Then, how many kinds of tea drinks are there on the market, what raw materials are they made of, and what's the difference? The reporter made a consumption survey in the market yesterday.
survey
Ten kinds of tea drinks and ten kinds of raw materials
With the increase of temperature, tea drinks are gradually popularized in the market. The reporter noticed that tea drinks occupy the most eye-catching position in shelves and freezers, whether in supermarkets, supermarkets or convenience stores. Because of the similar tastes and prices, several major brands have also launched a propaganda war. "mainly rely on special tastes and health concepts to compete."
But a closer look at the formula table of these tea drinks shows that although they are all "tea", the raw materials are different. Among the ten kinds of tea drinks purchased by the reporter, none of the raw materials are the same.
For example, Master Kong's "Jinliang" black tea uses "black tea powder", the same series of green tea uses "tea powder", ordinary green tea drinks say "green tea", and jasmine tea is a complex "selected jasmine tea (green tea blank)";
Wahaha green tea and black tea drinks are directly labeled as "green tea and black tea"; On the peasant barley tea, there are "tea leaves" and on the jasmine tea, there are "jasmine tea and jasmine extract".
Quality Supervision: At present, there is no unified appraisal standard.
Similar tea drinks have so many different raw materials. Is the manufacturer playing tricks or is the processing technology really different?
The staff of Hangzhou Quality Supervision Bureau said that tea drinks have industry standards and enterprise standards, and the raw material directly marked on the packaging is "green tea", and tea extract is generally used. Different labeling is mainly due to the different processing degree of raw materials purchased by enterprises. For example, if the raw material directly purchased is tea powder, it will be marked as "tea powder"; If the enterprise buys and grinds its own tea, it will write "tea". "As long as the most basic raw material is tea, how to express it is up to the enterprise itself."
In this regard, Lou Liqun, director of the Food Supervision Department of the Municipal Quality Supervision Bureau, said: "The state stipulates that according to the nature of the product, the ingredients are clearly stated on the packaging in proportion. In this way, beverage companies have not violated regulations. "
Manufacturer: The ingredients of raw materials are really different.
"Whether it is a green tea drink or a black tea drink, our raw material is tea." Wahaha staff said, "If the formula is labeled as green tea and black tea, there is no problem."
Mr. Jiang from the Quality Assurance Department of Hangzhou Food Co., Ltd., a subsidiary of Master Kong, explained that the same brand of tea drinks also use different raw materials because the raw materials themselves are different. "The raw material of iced black tea is imported from black tea powder; The raw material of ordinary green tea is the tea purchased by the enterprise itself from the tea farmers and then processed; The raw materials of jasmine tea have been atomized at the time of purchase. It is a tea extract similar to milk powder, so the logo on the package is different. "
expert
In fact, the composition has not changed.
Xu Hairong, deputy director of the Tea Department of Zhejiang University, said that in fact, no matter whether the raw material is tea or tea powder, the composition has not changed. "The spray drying process of tea leaves only removes water, and other nutrients are not lost much." He said, "In contrast, direct processing with tea leaves will be more fragrant, but tea powder is obviously more suitable for industrial production."
He prefers tea drinks with low sugar content to carbonated drinks. "Only beverages with tea polyphenols and caffeine content meeting the national standards can be called' tea drinks', so no matter what the raw materials are labeled, they are similar. Making tea has cultural significance, and tea drinks are more suitable for modern life. "
However, he believes that publicity such as "jasmine tea is healthier" is a kind of hype. "Jasmine tea has a relatively large market in China since ancient times, but its effect on the human body is not so magical."
Before the Tang Dynasty, the utilization and drinking of tea started from boiling soup or drying in the sun. Later, it was mostly made into cake tea by pounding leaves, or made into group tea by steaming leaves, so dry scattered tea and group cake tea appeared before the Tang Dynasty. In the early Tang Dynasty, steamed green tea has become the main tea species, and there are also sun-dried leaf teas (similar to modern white tea). Tang Lu Yu's "Six Drinks of Tea Classics" said: "Those who drink authentic (coarse) tea, loose tea, end tea and cake tea ..."? What's wrong with pens and coins? Cong zhi? Is there any trouble? What's wrong with planting? What's the matter with you? Br> Since the Song Dynasty, in addition to retaining the traditional steamed green group tea, a considerable number of steamed green loose tea have appeared. History of Song Dynasty: "There are two kinds of tea: Japanese tea and Japanese loose tea". Piece tea is cake tea, which is made by steaming tea leaves, mashing them into cakes and drying them in the sun. Loose tea is directly steamed and dried, showing a loose shape.
In the Yuan Dynasty, group tea was gradually eliminated and loose tea developed rapidly. The loose tea made at that time was divided into bud tea and leaf tea because of the different freshness and tenderness of fresh leaves. Bud tea takes young bud leaves as raw materials, such as Tanchun, Xianchun, Secondary Spring, Purple Bamboo Shoots and Bud Picking. Leaf tea is made of larger bud leaves, such as "before the rain". In the Ming Dynasty, in addition to steaming green tea, there were also fried green tea, black tea, yellow tea, black tea, and directly dried or dried white tea. So it can be said that green tea, yellow tea, black tea, white tea and black tea have all appeared. By the Qing Dynasty, in addition to the five major teas, oolong tea appeared again, and the tea-making techniques of various teas were also improved and improved. Many "famous teas" with extraordinary quality were appreciated by the imperial court and literati. At this point, the six major teas have been completed. With the export and trade activities of tea, many tea-making technologies have spread to many tea-producing countries, making different kinds and characteristics of tea available to consumers all over the world.
Classification of tea
At present, there is no unified method to classify tea in China. Some tea leaves are divided into six categories according to different production methods and quality: green tea, black tea, oolong tea (that is, green tea), white tea, yellow tea and black tea. Some teas are divided into seven categories according to the types of tea exported from China: green tea, black tea, oolong tea, white tea, scented tea, pressed tea and instant tea. According to the fact that tea processing in China is divided into two stages: primary processing and refined processing, some tea leaves are divided into two parts: crude tea, black tea, oolong tea, white tea and black tea, and yellow tea is classified as green tea. Finished tea includes refined green tea, black tea, oolong tea, white tea and reprocessed scented tea, pressed tea and instant tea.
Tea is divided into black tea and green tea, not because there are black tea and green tea before processing, but because there are black tea and green tea during processing.
Black tea is made by fermentation. After the fresh tea leaves were fermented by kneading, the chlorophyll in the tea leaves was destroyed and the green color disappeared, and the tannic acid contained in the tea leaves was oxidized to red by oxidase. This is why black tea is red.
Green tea is made without fermentation. People put fresh tea leaves in an iron pot and heat them quickly, so that only the water in the tea leaves is evaporated and chlorophyll is not completely destroyed.
Black tea and green tea taste different. Black tea is not as astringent as green tea because it solidifies tannic acid during fermentation. Green tea is more fragrant than black tea because it retains aromatic oil.