Abstract

Olive oil production in Chile has increased 900% in the last 10 years, resulting in a concomitant increase in waste products that need to be managed. In this study, drying assays were conducted in a convective hot-air dryer on Arbequina olive waste cakes between 40 and 90 degrees C and a constant airflow of 2m/s. Proximate composition, dietary fiber, minerals, fatty acids, tocopherols, phytochemicals as well as antioxidant activity as DPPH, FRAP and ORAC values were determined. These six drying temperatures were found to have variable effects on general composition of the residues. Fatty acids were found in high concentration at low temperatures where oleic acid was the most abundant and -tocopherol was the most prevalent form of vitamin E. The phytochemical content (total phenolics, flavonoids and flavanols) represented an average of 20.7% of the waste cake. Fresh cake showed the highest polyphenols and flavonoids content whereas flavanols content was higher at all drying temperatures. 3-Hydroxytyrosol was the most abundant phenolic compound, and found in higher abundance in samples dried at 90 degrees C. The antioxidant capacity measured by FRAP and DPPH assays decreased with drying or remained unchanged when measured by ORAC assay. Given the nutritional and commercial potential of waste cakes, a drying technology for the preservation of bioactive compounds from waste products is discussed.