Although the meat will become soft under high temperatures and long-term heating, the resulting duck color is not popular with consumers, and sous-vide cooking can make food have beautiful appearance and attractive color. Since sous-vide cooking can precisely control the temperature and time, many chefs will use this feature to control the meat to have the doneness and color they want. Color and appearance are often used as indicators of the doneness of the meat. The muscle of the cooked meat shrinks, and is grayish-white and dry on the surface. The uncooked meat is usually pink and moist. Most color measurements show that a value decreases with increasing temperature between 50 and 65°C, such as pork and lamb.
It is generally accepted that most of the volatile aromatic compounds that contribute to the acceptability of cooked meat are formed at temperatures above 70°C. Therefore, a pleasant flavor may be generated cooked by sous-vide cooking at 50°C to 60°C. The flavor of the meat is produced through a series of complex chemical reactions between precursors, intermediate reaction products and degradation products in heating. The content of most volatile compounds from lipid oxidation showed a decreasing trend, and that of volatile compounds from amino acid and thiamine degradation showed a trend of increasing. The characteristic flavor of cooked meat is derived from the heat-induced reactions during heating, mainly Maillard reaction and lipid degradation. Both types of reactions involve complex reaction pathways leading to the production of multiple species, which is why many volatile compounds are also found in cooked meat in a vacuum bag sealed by a vacuum sealer. Prolonged heating time in sous-vide cooking also increased its amino acid and thiamine degradation products, such as carbon disulfide, dimethyl disulfide, 2-methyl shphene, 2-pentaneshphene, and benzosiazole. These compounds have low odor thresholds and provide meaty, salty, grilled, and stewed flavors associated with stewed flavor. Most studies have shown that the flavor attributes produced by sous-vide cooked meat products is lower than that of meat cooked at higher temperatures due to the lack of products of the Maillard reaction. Therefore, it is common practice to roast the meat at high temperatures (130 to 150°C) for a few minutes to obtain a more appealing appearance (caramel surfaces) and flavor.