An industrial approach for the selective recovery of biophenols from agro-food wastes

Several phenolic compounds play a key role in the non-ligninic cell wall structures and constitute as much as the 0.6% of the weight into the main agro-food wastes. These wastes contain different type of phenols which are characteristics of the different vegetables used for the food production. On the basis these wastes can then constitute important industrial source of biophenols. The industrial recovery of the biophenols is however limited by some prominent problems to be solved: 1) the distant location and the recovery of wastes on the territory; 2) the low concentration of bio-phenols in comparison to the large amount of wastes to be treated; 3) the management of a large amount of wastes to be transported to the extraction plant and the relative costs; 4) the large amount of wastes to be treated in time due to the scarce stability of the wastes and their seasonality; 5) the high-costs for the special disposal of the exhausted waste after solvent extraction. Furthermore, the biophenols are mainly water soluble, water soluble-esterified and insoluble-bound covalently linked to the polysaccharidic backbones of the vegetable cell wall. In this communication we demonstrate the possibility to perform an extraction of the phenolic fraction from different agro-food wastes throughout a patented adsorption/desorption process using the weak ion exchange after an enzymatic pre-treatment which was developed in order to hydrolyse the vegetable cell wall structures and to release the covalently linked phenolics. The bio-catalytic treatment was used instead of the typical acidic/basic hydrolysis because of the possibility of a easier scale up of the process. The hydrolytic step allowed to solubilise the 50% of the phenolic content, yield comparable to those of chemical hydrolysis. This technology allowed to recover the 25-54% of the solubilised phenols such as hydroxityrosol, ferulic acid and resveratrol in concentrated extracts (3-5 g/liter) from three different agro-food wastes hydrolysate. We report and discuss the results of a 1 cubic meter per day pilot scale plant for the recovery of biophenols from olive milling waste waters carried out in an European Project FAIR CT 97 3039 “Natural antioxidants from olive milling process”. The agro-food wastes can then constitute the main economical industrial source of biophenols as chemical building blocks for the near future.