Boiling food in vacuum-sealed bags, a process known as sous vide cooking, is a safe method of food preparation as long as the food is cooked to an appropriate internal temperature and proper cooking methods are used. Bags marked for food preparation do not contain any unsafe components and are designed to withstand high heat.
Following the correct time and temperature recommendations for sous vide dishes decreases the likelihood that pathogens or bacteria are found in the dish. When the food is done, it needs to be served immediately or quickly cooled to prevent the growth of bacteria.
Food products that are prepared in a vacuum-sealed bags should not be thicker than 2 inches. Items that are too thick take too long to cook and grow spores quicker.