Is frying possible in space?

Abstract

Dietary nutrition and uptake of earth-like foods are extremely important aspects for the health and performance of astronauts, especially during future planned long-term space missions. Despite the major progress in studying and designing systems for crop cultivation in microgravity conditions in the last years, there hasn't been equal interest in food preparation processes and cooking. There are several reasons for this but it is chiefly because at present astronauts stay in space for a few months at most, so there is no serious nutritional or psychological need for earth-like food habits. This, however, will change drastically in long-term missions, e.g., to Moon and Mars. French fries are a very popular food commodity across many cultural backgrounds on earth and as such they may be appreciated by long-term space travelers of different origin. The process of frying in hot oil is associated with complex heat and mass transfer along with the growth and detachment of water vapor bubbles. These phenomena are strongly affected by buoyancy and gravitational acceleration making the study of frying at space conditions a challenging task. The present work examines potato frying in hot oil during the short duration low gravity conditions achieved in a Parabolic Flight Campaign organized by the European Space Agency. An innovative device has been constructed, allowing the simultaneous observation of bubbles dynamics above the potato surface and the thermal behavior inside the potato flesh. It is seen that even in the absence of buoyancy i.e., during parabolas, vapor bubbles still detach and depart from the surface of potato permitting hot oil to maintain contact with the potato surface and leading eventually to a fried product. Instantaneous overpressure inside potato pores due to vapor formation upon boiling of potato water is suggested as the mechanism generating the force for bubbles detachment and departure. Moreover, the amount of produced vapor is comparable among the examined values of gravitational acceleration, including the low gravity conditions during parabolas. All in all, the results of the present study provide primary experimental evidence that frying can occur in space.