Stir frying (cy=cháau) is a cooking technique in which ingredients are fried in a small amount of very hot oil while being stirred or tossed in a wok. The technique originated in China and in recent centuries has spread into other parts of Asia and the West. It is similar to sautéing in Western cooking technique.
Wok frying may have been used as early as the Han dynasty (206 BC – 220 AD) for drying grain, not for cooking. It was not until the Ming dynasty (1368–1644) that the wok reached its modern shape and allowed quick cooking in hot oil. However, there is research indicating that metal woks and stir-frying of dishes were already popular in the Song dynasty (960–1279), and stir-frying as a cooking technique is mentioned in the 6th-century AD Qimin Yaoshu. Stir frying has been recommended as a healthy and appealing method of preparing vegetables, meats, and fish, provided calories are kept at a reasonable level.Foreword, Paul Dudley White in
The English-language term "stir-fry" was coined and introduced in Buwei Yang Chao's How to Cook and Eat in Chinese, first published in 1945, as her translation of the Chinese word chǎo 炒. Although using "stir-fry" as a noun is commonplace in English, in Chinese, chǎo is used as a verb or adjective only.
The term initially appears in the sense of "stir frying" in the Qimin Yaoshu (齊民要術), a sixth-century agricultural manual, including in a recipe for
/ref> In sources from the Tang dynasty (618–907), chao refers not to a cooking technique, but to a method for Tea processing. It reappears as a cooking method in a dozen recipes from the Song dynasty (960–1279). The Song period is when the Chinese started to use vegetable oil for frying instead of . Until then, vegetable oil had been used chiefly in lamps.
Historically, stir frying was not as important a technique as boiling or steaming, since the oil needed for stir frying was expensive. The technique became increasingly popular in the late Ming dynasty (1368–1644), in part because the wood and charcoal used to fire stoves were becoming increasingly expensive near urban centers, and stir-frying could cook food quickly without wasting fuel. "The increasingly commercial nature of city life" in the late Ming and Qing dynasty (1644–1912) periods also favored speedy methods. But even as stir frying became an important method in Chinese cuisine, it did not replace other cooking techniques. For instance, "only five or six of over 100 recipes recorded in the sixteenth-century novel Jin Ping Mei are stir fry recipes and wok dishes accounted for only 16 percent of the recipes in the most famous eighteenth century recipe book, the Suiyuan shidan".
By the late Qing, most Chinese kitchens were equipped with a wok range ( chaozao 炒灶 or paotai zao 炮臺灶) convenient for stir-frying because it had a large hole in the middle to insert the bottom of a wok into the flames.
The term "stir fry" as a translation for "chao" was coined in the 1945 book How To Cook and Eat in Chinese, by Buwei Yang Chao. The book told the reader:
Although using the term "stir-fry" as a noun is commonplace in English, in Chinese, the word 炒 (chǎo) is used as a verb or adjective only. In the West, stir frying spread from Chinese family and restaurant kitchens into general use. One popular cookbook noted that in the "health-conscious 1970s" suddenly it seemed that "everyone was buying a wok, and stir frying remained popular because it was quick." Many families had difficulty fitting a family dinner into their crowded schedules but found that stir-fried dishes could be prepared in as little as fifteen minutes.
First the wok is heated to a high temperature, and just as or before it smokes, a small amount of cooking oil is added down the side of the wok (a traditional expression is 热锅冷油 "hot wok, cold oil") followed by dry seasonings such as ginger, garlic, , or . The seasonings are tossed with a spatula until they are fragrant, then other ingredients are added, beginning with the ones taking the longest to cook, such as meat or tofu. When the meat and vegetables are nearly cooked, combinations of soy sauce, vinegar, wine, salt, or sugar may be added, along with thickeners such as cornstarch, water chestnut flour, or arrowroot.
A single ingredient, especially a vegetable, may be stir-fried without the step of adding another ingredient, or two or more ingredients may be stir-fried to make a single dish. Although large leaf vegetables, such as cabbage or spinach, do not need to be cut into small pieces, for dishes which combine ingredients, they should all be cut to roughly the same size and shape.
When read in Mandarin, the second character is transliterated as qi ( ch'i according to its Wade-Giles romanization, so wok hei is sometimes rendered as wok chi in Western cookbooks) is the flavour, , and "essence" imparted by a hot wok on food during stir frying. Out of the Eight Culinary Traditions of China, wok hei is encountered the most in Cantonese cuisine, whereas it may not even be an accepted concept in some of the others.
To impart wok hei the traditional way, the food is cooked in a seasoned wok over a high flame while being stirred and tossed quickly. The distinct taste of wok hei is partially imbued into the metal of the wok itself from previous cooking sessions and brought out again when cooking over high heat. In practical terms, the flavour imparted by chemical compounds results from caramelization, Maillard reactions, and the partial combustion of oil that come from charring and searing of the food at very high heat in excess of . Aside from flavour, wok hei also manifests itself in the texture and smell of the cooked items.
A larger amount of cooking fat with a high smoke point, such as refined plant oils, is often used in bao. The main ingredients are usually cut into smaller pieces to aid in cooking.
Another study examined the nutritional value of broccoli after five common cooking techniques: steaming, boiling, microwaving, stir-frying and stir-frying followed by deep frying. The study found that the two most common methods of home cooking in China, stir-frying and stir-frying combined with deep frying in soybean oil, resulted in a much greater loss of chlorophyll, soluble protein, soluble sugar and vitamin C. The method which affected these values the least was steaming. Stir frying for five minutes and stir frying combined with boiling caused the highest loss of , which according to this study are best preserved by steaming. A study performed by the Spanish National Research Counsel stir-fried the broccoli for only three minutes and thirty seconds and found that nutritional value of these broccoli samples varied depending on which cooking oil was used. Comparing these results to an uncooked sample, the study found that phenolics and vitamin C were reduced more than glucosinolates and minerals. Stir-frying with soybean, peanut, safflower or extra virgin olive oil did not reduce glucosinolates, and broccoli stir-fried with extra virgin olive oil or sunflower oil had vitamin C levels similar to uncooked broccoli. These levels were significantly lower with other edible .
Stir frying is not without health . Recent studies show that heterocyclic amines and polycyclic aromatic hydrocarbons are formed by stir frying meat at very high . These chemicals may cause DNA changes that may contribute to increased risk of cancer.
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