Valorisation of waste olive pomace: Laboratory and pilot scale processing to extract dietary fibre

•Presence of 10% soluble dietary fibre remaining in olive pomace.•Higher soluble dietary fibre obtained with high shear mixing.•Water and oil holding properties of insoluble dietary fibre affected by pH.•Development of process to commercially valorise olive pomace without defatting. The olive oil industry generates large quantities of waste pomace which has the potential to be used in a range of applications, including as a source of dietary fibre in the food ingredients sector. This study determined that hexane extracted olive pomace still retained 10.6% soluble dietary fibre (SDF) although the total sugar content of 27% was low. The lower and upper yields from single trials on freeze dried olive pomace (10 g) for hexane extracted IDF (insoluble dietary fibre) and SDF were 41–53% and 0.5–2.5%, respectively. These results tentatively indicated that pH and homogenization (high shear mixing) were important factors that affect IDF and SDF yields. The pilot scale processing of 36 kg (wet weight) frozen olive pomace, equivalent to 5.65 kg (dry weight), focused on recovery yield of SDF using an alkaline treatment approach combined with wet milling (2 h). There was no increase in microbial contamination during the trial. While a relatively high yield of SDF (5.6%) was obtained, the monosaccharide content was low, and this fraction did not exhibit gelation properties which is one of the key indicators for functionality in the food ingredients sector. A lower-than-expected IDF yield (13.6%) was obtained during the pilot trial compared with initial laboratory results (41.3–53.0%). However, this process enriched the fibre content from 40% to more than 70% in the majority of the IDF samples collected during the pilot trial. It was determined that the highest water and oil holding capacities in these samples were 6.9 and 4.1, respectively, which were associated with IDF extracted at pH 4.5. This study revealed that SDF could be recovered from olive pomace and the recovery of IDF could be scaled up, where physical disruption and pH conditions caused apparent changes in the yields, and the water and oil holding capacities of dietary fibre fractions. [Display omitted]