To understand the process to be optimised and its overall applicability to larger scales there was a need to characterise the properties of WOP in presence of water. As a first approach, the moisture content and solid particle percentage was determined in all studied citrus peels (Table 1). The moisture content in citrus varied considerably (78.6–87.1%) not only between different citrus, but also between different varieties of oranges. Satsumas and grapefruits were the fruits in which the measured water content was the highest. The reason behind this observation might be linked to the juicing step, in which the processing for these two fruits was not as efficient as for the rest of the samples due to their size (grapefruits were too large for the machine to appropriately handle them whilst the satsumas were too small).