An apparatus for providing a thermal treatment to a product, such as food, is described. One embodiment of the apparatus includes lime and water contained separately within a sealed reaction vessel. The reaction vessel includes a flexible wall portion that is adjacent to a perforator that can puncture a membrane separating the lime and water. In one embodiment, the perforator is separate from and fee-floating within the water. In another embodiment, the reaction vessel is substantially surrounded by the product. The reaction vessel is hermetically sealed against underpressure or overpressure, permitting use with pressurized food. The reaction vessel can be incorporated into a variety of containers and the reaction vessel and container can be sterilized for packaging food.