Sous-vide comes from French, the English term is slow-cooking, which is based on scientific research to find out the temperature range of the protein cells of each ingredient when they are heated and calculate how long it takes to heat the protein cells within the blasting temperature. The slow-cooking technology appeared in the 18th century, and was officially used in the preparing food in restaurants in France in the 1970s. With the booming of molecular gastronomy, this cooking method has become popular again in the international gastronomy world, and has become a favorite among many Michelin chefs. The low-temperature slow-cooking technology is to put the food into a vacuum bag and seal it, and then slowly cook it at a low temperature of 45 to 80°C, which not only prevents the collagen fibers inside the food from being damaged, but also makes the food release the most sodium glutamate at the most suitable temperature, retaining the most tender taste and nutrition.
 
1. Advantages of sous-vide
Food cooked by traditional methods will reduce the weight by 15% to 20%, most of which is the water in the food. Experiments have shown that the ingredients processed by slow cooking at a low temperature can guarantee that internal moisture not lose to the greatest extent. Sous-vide can retain the original taste and nutrition of food, and also helps to ensure the taste of ingredients, especially meat and seafood. Vitamins can be retained more than steaming and boiling. For example, cooking a piece of ordinary beef at 59°C for 12 hours at a low temperature can make the beef very tender, because this temperature is just enough to dissolve the fiber in the beef without adding any additives. For buffalo with tough meat, the traditional method is to marinate, and the baking soda or meat tenderizer added during marinating are all chemical additives. Molecular cuisine is a scientific way of cooking. It has strict standards for the amount of various ingredients, and the control of temperature and time is also very particular. Therefore, apart from using some special kitchen utensils, tools and auxiliary materials, no additives are used in the production process. Such molecular cuisine is very good for keeping in good health.
 
2. Temperature control
Different ingredients use different low temperatures during slow cooking. Generally speaking, the cooking temperature for white meat such as chicken is between 60 and 75°C; for seafood, the cooking temperature is between 43 and 55°C; for vegetables, the cooking temperature is generally lower than 40°C; for red meat, the temperature is above 50°C. Generally speaking, the lower the density of the ingredients, the lower the required temperature becomes.
 
3. The selection of ingredients
Sous-vide is to cook food at a low temperature below 70°C, which is more suitable for ingredients with higher requirements for taste, such as foie gras, salmon, and high-grade beef. Low-temperature slow cooking can be used for all ingredients, but is especially suitable for seafood and red meat. The fiber of red meat is thick and easy to be cooked. After using the low-temperature slow-cooking, the connective tissue of the ingredients has a sufficient melting time, and the effective control of low temperature can prevent the meat from being cooked for too long. As a result, the red meat will be more tender than that cooked by normal cooking methods, and the gravy will be preserved more. When cooking slow-cooked steak, the chef will use the sirloin part of the beef. The optimal low-temperature slow-cooking temperature for this part is 60°C. The steak is pre-cut into 4 to 6 pieces, sealed in a bag, and slow-cooked for about 25 minutes. After taking out the steak, apply a small amount of butter on the surface; put it on the griddle at temperatures between 230 to 250℃ and bake until the surface is slightly juicy and burned and the steak is tender. For red meat rich in collagen, the cooking time will be longer, because this will ensure the meat is tender and juicy. After removing the fascia of the lamb knee, fry it in a pan until there is fragrant, then seal the red wine, rosemary together with the meat in the bag; put it into the water at 68°C and cook for 8 hours. It will be tender and juicy.
 
Among seafood, marine fish with rich fish oil is also suitable for low temperature slow cooking methods, such as tuna, cod and salmon. The tuna has a lot of fish oil. After marinating it with salt, vegetable water, bay leaves, onions, rosemary and thyme for 1 hour, then soaking at a temperature of 63.8℃ for 3.5 hours, the meat looks like a living fish when served. When cooking silver cod at low temperatures, choose the middle part close to the spine of the fish, with a little belly meat, and much oil, which is suitable for long-term cooking. Marinate the silver cod, and then immerse the silver cod at a low temperature below 50℃ for 10 minutes, which can keep the meat tender to the greatest extent. When slow-cook salmon at low temperatures, first take out the spine and its flash. Marinate for 45 minutes, then cut into thin slices; slow-cook at a temperature of 55°C for 3 minutes. The salmon will be tender. Foie gras is an important ingredient in western food. It can also be slow-cooked at low temperatures. First, marinate the foie gras with red wine, onion, celery, dried baby bamboos, black pepper and bay leaves for two weeks, and then cook it at a temperature of 78°C. Soak it for 90 minutes, so that the moisture and oil of the foie gras can be retained.
 
4. Marinades
When slow-cooking at low temperatures is adopted, do not use seasonings containing high concentration of alcohol to marinate and season food before cooking, because the seasonings with high concentration of alcohol will seriously damage the protein composition of meat at a constant temperature, and even cause meat to lose its original taste and texture.
 
When using the low-temperature slow-cooking, the ingredients are slowly cooked together with the marinade in a vacuum bag. The sauce can fully penetrate into the interior of the ingredients due to the long cooking time. Therefore, the sauce used for slow cooking at a low temperature will be slightly lighter than ordinary sauces to prevent the original flavor of the ingredients from being suppressed. In addition, avoid high-concentration spirits such as brandy.