Sterilize jars in advance over steam or using another sterilization method. Puree is subjected to short-term heat treatment, so the container must be completely sterile. Pour the mashed potatoes (just taken from the stove) into the jars, give a second of time to steam, then tighten the blanks tightly with the lids. It is better to use small jars in order to use mashed potatoes when opened at a time. Also, if suddenly one of the cans is not completely sterile, and the blank is fermented, the other jars of mashed potatoes will be good until winter.