[4] While this cooking process used to be accomplished by bringing the wine or grape juice to a boil, recent technological advances have allowed for flash pasteurization to substitute for this procedure.
[citation needed] It is debated whether this is a subjective temperature for which different individuals may determine their own personal yad soledet bo.
Rabbi Joshua Falk doubts that yad soledet bo can be anything but that which would objectively scald an infant's abdomen because the temperature at which people will instinctively withdraw their hand from a heat source is not universal.
This deduction is further supported by more objective criteria such as the Weber-Fechner law which describes how humans (and other animals) respond to physical stimuli.
Rabbi Yaakov Chaim Sofer[8] quotes Rabbi Yosef Chaim's work Ben Ish Chai[9] as stating that one can know if something is not yad soledet bo if one can put it in one's mouth without exceeding the normal limitations of the food being too hot for one to eat or drink.