Enhancing the Phenolic Value of Polyphenol-Rich Extra Virgin Olive Oils Through Optimized Water Extraction, Macroporous Resin Recovery and Spray Drying

Olive oil polyphenols are well-established for their health-promoting properties. A recently emerged polyphenol-rich extra virgin olive oil (EVOO) was subjected to a water extraction process, optimized using response surface methodology (RSM). The effects of salt content and the water-to-oil ratio on the total phenolics were initially evaluated. Maximal phenolic yield was obtained by a water/EVOO ratio of 9.6:1 (v:v) and 0% added salt, although the addition of 3% salt provided an oil-free extract with a satisfactory phenolic yield compared to the optimized extract. Further, the phenolics of the optimized water extract were recovered using macroporous XAD resins. XAD-7HP resin and 75% ethanol/water eluent were selected based on comparatively improved adsorption/desorption and recovery data. Recovered phenolics were then encapsulated using spray drying and a maltodextrin carrier; the resulting powder was evaluated for physical and phenolic release properties. Phenolic composition was measured in all stages using 1H-NMR, revealing a phenolic yield of 39% in the extraction step, which was reduced through recovery and encapsulation to 25%; oleocanthal and oleacein were partitioned from olive oil to water extract by 55–50% while oleuropein and ligstroside aglycones only by 14.5–31.7%. The compositional pattern of water-extracted phenolics remained the same throughout recovery and encapsulation. These findings contribute to a moderately efficient, green procedure in developing innovative nutraceutical supplements/functional food ingredients.