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Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops

Location: Healthy Processed Foods Research

Title: Membrane-filtered olive mill wastewater: Quality assessment of the dried phenolic-rich fraction

Author
item Sedej, Ivana - University Of California
item Milczarek, Rebecca
item Wang, Selina - University Of California
item Sheng, Runqi - University Of California
item Avena Bustillos, Roberto
item Takeoka, Gary
item Dao, Lan

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2016
Publication Date: 3/14/2016
Citation: Sedej, I., Milczarek, R.R., Wang, S., Sheng, R., Avena Bustillos, R.D., Takeoka, G.R., Dao, L.T. 2016. Membrane-filtered olive mill wastewater: Quality assessment of the dried phenolic-rich fraction. Journal of Food Science. 81:E889–E896. doi: 10.1111/1750-3841.13267.

Interpretive Summary: A current trend in olive mill wastewater (OMWW) management is to not only decrease environmental pollution but also utilize valuable co-products. Recovery of phenolics from OMWW could help olive oil processors add value to their co-product, increasing the sustainability of olive oil production.The objectives of this study were to explore different techniques for drying a phenolic-rich membrane filtration fraction of OMWW and compare the techniques in terms of the dried product quality and feasibility of the process. We found that drying of the filtered OMWW is possible only with addition of 10% maltodextrin as a carrier, due to the low solids content. The highest recovery for OMWW from 2 different olive production processes was achieved with freeze-drying. Findings from this study show that drying of the membrane filtration stream of OMWW, especially spray drying, results in a powder which contains phenolics. Further characterization of the dried material is needed for its possible applications in nutraceutical, feed or food industries. Processing the OMWW in this way will help olive oil processors add value to their co-product OMWW stream.

Technical Abstract: A current trend in olive mill wastewater (OMWW) management is to not only decrease environmental pollution but also extract and utilize valuable by-products. Therefore, the objectives of this study were to explore different techniques for drying a phenolic-rich membrane filtration fraction of OMWW and compare the techniques in terms of the dried product quality and feasibility of the process. The OMWW from two (3-phase and 2-phase) California mills was subjected to a two-step membrane filtration process using a novel vibratory system. The reverse osmosis retentate (RO-R) is a phenolic-rich co-product stream, and the reverse osmosis permeate is a near-pure water stream that could be recycled into the milling process. Spray-, freeze-, and infrared-drying were applied to obtain solid material from the RO-R. Drying of the RO-R was possible only with addition of 10% maltodextrin as a carrier. The total soluble phenolics in dried RO-R were in the range 0.15–0.58 mg gallic acid equivalents/g of dry weight for 2-phase RO-R, and 1.38–2.17 mg gallic acid equivalents/g of dry weight for the 3-phase RO-R. Spray-dried RO-R from 3-phase OMWW showed remarkable antioxidant activity. Tyrosol, vanillic acid, and p-coumaric acid were quantified in all dried RO-R, whereas 3-hydroxytyrosol was found in 3-phase dried RO-R. Findings from this study show that drying of the membrane filtration stream of OMWW, especially spray drying, results in a powder that contains phenolics. This combination of separation and drying technologies helps to add value to an olive oil by-product and increase sustainability of its production.