Changes in the Composition of Olive Pomace after Fermentation: A Preliminary Study

Because olive pomace (the main by-product of olive oil production) is phytotoxic, new applications must be investigated to minimize its negative environmental impact. In this work, olive pomace was fermented for 4 and 32 days at room temperature, having in view its valorization as a novel food, thereby creating opportunities for the food industry and addressing a challenge of the olive oil sector. The chemical and microbiological modifications that occurred along the fermentation were followed. The results showed no significant differences (p > 0.05) in total protein between the control and the fermented samples; however, the latter exhibited higher levels of essential amino acids. The major nonessential and essential amino acids were glutamic acid and leucine in all samples. There was a significant increase in the total fat of the 32-day sample and the main fatty acid was oleic acid in all samples. There were considerable reductions in total vitamin E, phenolics, and antioxidant activity values post-fermentation. Hydroxytyrosol replaced oleacein as the main phenolic in the 32-day sample. A sharp increase in total microorganisms occurred (2.20 x 102 to 3.00 x 104-2.01 x 107 colony forming units/mL) but no pathogenic microorganisms were detected. Overall, olive pomace fermentation creates novel products for the food industry with a balanced nutritional composition.