Tuber respiration
The potato tuber is a living organism and therefore it respires. In respiration, oxygen is absorbed from the surrounding air and together with carbohydrate (sugar) from the tuber, converted into carbon dioxide and water.
Heat is produced during this process. The respiration rate and thus the production of CO2 and heat depends mainly on the storage temperature of the tuber.
Maturity, wounding, the sugar content and sprout growth
Other factors which affect the respiration rate are: maturity of the tuber, wounding of tubers, the sugar content and sprout growth.
Tubers which are immature, damaged or starting to sprout have a considerably higher respiration rate than mature tubers.
The heat production of mature tubers at 5-10 oC a few weeks after harvest is about 40 J/kg per hour, at 20 oC this rises to 100 J/kg per hour.
The respiration rate of immature tubers soon after harvest is much higher than of mature tubers.
The heat production of freshly harvested immature tubers can be more than 400 J/kg per hour at 20 oC.
After some time of storage the level of respiration of these immature tubers will reach the respiration rate of mature tubers.
When tubers start to sprout the respiration rate rises again.