Phenolic extracts obtained from thermally treated secondary varieties of dates: Antimicrobial and antioxidant properties

- Phenolic extracts (E140 and E160) were obtained from palm dates thermally treated.
- The extract obtained at 160 °C showed higher antioxidant and antimicrobial activity.
- The oxidative stability of sunflower oil was increased by four-fold using E160.
- Promising values of inhibition against plant pathogens were found using E160.
- Thermal treatment of dates produces bioactive extracts for food formulation.

Palm dates are an important source of natural bioactive compounds and their application in the food industry could valorize secondary cultivars at risk of disappearing. Secondary palm date varieties were thermally treated by direct steam at two temperatures (140 and 160 °C) during 30 min. The liquid was extracted by organic solvent, obtaining two extracts, PE140 and PE160, with high concentrations of sugar degradation products, mainly hydroxymethylfurfural and phenolic compounds like tyrosol or gallic and protocatechuic acids. The use of the higher temperature produced 22 g of extract/Kg of fresh dates with antioxidant activities in the aqueous matrix (EC50 value of 2.72 mg/L for DPPH and TEAC value of 0.05 mmol Trolox®/g of extract) and remarkable protection against lipid oxidation in oils, increasing the stability of sunflower oil by the Rancimat method by four-fold. Promising values of inhibition against plant pathogens were found with values of MIC of 3.13 mg/mL. Therefore, thermal treatment of dates was effective for obtaining bioactive phenolic extracts suitable for food formulation.