Diffusing wave spectroscopy for the study of emulsions on-ground and in microgravity

We review the approaches, both experimental and modelling, and the main results obtained recently in the investigation of emulsions by diffusing wave spectroscopy (DWS). DWS is a correlation spectroscopy based on the analysis of the time structure of the scattered light emerging from a laser illuminated opaque sample. Such a non-invasive technique is well suited to the investigation of drop size distribution and drop dynamic in emulsions. This dynamic determines the evolution, and finally the fate, of emulsions. Results obtained in laboratory are complemented by very recent results obtained in microgravity (the condition of absence of weight obtained in orbit) onboard the International Space Station ISS: mastering emulsions in such exotic conditions, not only offers new insight into the basic physical phenomena but may also provide new enabling technologies to ensure comfortable living environments and safe foods to the astronauts engaged in long space flights.