Effects of rapid depressurisation on the structural integrity of common foodstuffs

In preparation for the eventual manufacture and storage of food in space, we conducted a set of experiments to determine the effect of a rapid catastrophic depressurisation on a range of common foodstuffs. The experiment tested the hypothesis that rapid depressurisation would cause explosive destruction or boiling of stored foodstuffs. We tested 18 types of fruit, 18 types of vegetables, 4 types of nuts, 4 types of fish, 10 types of raw and prepared meat, chicken eggs, 9 types of cheese and 8 other foods including rice and lentils. They were exposed to depressurisation from atmospheric pressure to 6 mb in 5.67 min to simulate a rapid depressurisation event on Mars. We found most of the tested produce to be robust against depressurisation. No explosive rupture or failure was observed in any of the tested items. Introduction of cuts into the produce resulted in localised bubbling, for example in tomatoes, and bubbling was observed at the site of bruising, for example in bananas and pears. At pressures greater than similar to 30 mb we attribute this to outgassing and below this pressure to a combination of outgassing and boiling and we present a general model to describe these findings. Raw meat (such as ham), fish (such as salmon) and some cheeses (such as Mozzarella) bubbled at their surfaces, causing the surface to dry. The most profound changes were observed in sausages, haggis and chicken in which air expanded beneath the skins, stretching the skin and causing wrinkling when repressurisation occurred, although the overall integrity of the food was not altered. We conclude that a rapid depressurisation event in a food storage unit would not cause catastrophic physical disruption of food. However, secondary protection inside closed containers is advisable for fish, raw and prepared meats, fruits and vegetables with observable bruising or damage, to protect against drying during a depressurisation event. Our data show the potential for low pressure storage of food.