In gas steam cooking, what is used as the primary heat source?

In gas steam cooking, steam serves as the primary heat source because it is an efficient medium for transferring heat. The process relies on the high latent heat of vaporization of water, meaning that steam can transfer a significant amount of heat energy to the food being cooked, ensuring even cooking and moisture retention. This method is particularly advantageous for cooking foods like vegetables, seafood, and rice, as it helps preserve their flavors, textures, and nutritional value.

Other heat sources mentioned in the choices play different roles in cooking but do not serve the same function in steam cooking. Direct fire involves flame that directly heats the cooking surface and may dry out food. Electricity can be used for cooking, but in this context, it would typically relate to electric steamers rather than gas steam cooking. Hot air is primarily associated with dry heat cooking methods, such as baking or roasting, which are not ideal for applications requiring moist heat. Thus, steam is uniquely suited as the heat source for gas steam cooking, facilitating a distinct cooking method.