. >> reporter: a heotel in the north central prefecture serves meals featuring aged ingredients. the steak for the main dish and the potatoes in the rich sweet soup are aged using a special method. >> translator: very delicious. >> reporter: all kinds of foods are aged in cellars in the mountains. this part of japan gets heavy snowfall each year. food placed in the facilities doesn't melt even in the summer. local people call them snow rooms. there are about 40 of them in the prefecture. people have long stored summer vegetables inside the cellars, but they have been found to be useful for another purpose. >> these days the snow rooms are used not just for keeping things cool but to age foods to improve their quality. >> reporter: the secret is maintaining the humidity rate of more than 90%. and temperatures that stay around freezing. temperatures in refrigerators fluctuate and cause food cells to go bad over time. in contrast, temperatures in snow rooms are stable. researchers think this is why food becomes more tasty with aging. 26 small and mid sized companies have teamed up t