An apparatus to determine physiological effects of heat flux with a cryogenic substance applied to an organism, includes a heat flux sensor 12, a cryogen delivery apparatus (e.g. a spray nozzle 18) spaced apart a distance D1 from the heat flux sensor 12； and an organism culture 28 supported on the heat flux sensor 12 in the path of delivery of the cryogenic substance from the cryogen delivery apparatus 18. A related method is also provided to determine physiological effects of cryogen on an organism, and includes testing a live organism culture for heat flux with a cryogenic substance； and establishing an amount of heat transfer required at the organism for achieving maximum destruction of said organism. The cryogenic substance may be liquid nitrogen, liquid oxygen or liquid argon, and the organism culture may comprise Campylobacter. The effects of the treatment on the micro-organisms may be determined by measuring the leakage of ATP from the cells.
