Hydroxytyrosol and Oleuropein-Enriched Extracts Obtained from Olive Oil Wastes and By-Products as Active Antioxidant Ingredients for Poly (Vinyl Alcohol)-Based Films.

Francesca Luzi,Annalisa Romani,Luigi Torre,Mariangela Clemente,Silvia Urciuoli,Debora Puglia,Edoardo Grande,Roberta Bernini,Elisa Pannucci,Luca Santi

doi:10.3390/molecules26072104

Abstract

Oxidative stability of food is one of the most important parameters affecting integrity and consequently nutritional properties of dietary constituents. Antioxidants are widely used to avoid deterioration during transformation, packaging, and storage of food. In this paper, novel poly (vinyl alcohol) (PVA)-based films were prepared by solvent casting method adding an hydroxytyrosol-enriched extract (HTyrE) or an oleuropein-enriched extract (OleE) in different percentages (5, 10 and 20% w/w) and a combination of both at 5% w/w. Both extracts were obtained from olive oil wastes and by-products using a sustainable process based on membrane technologies. Qualitative and quantitative analysis of each sample carried out by high performance liquid chromatography (HPLC) and nuclear resonance magnetic spectroscopy (NMR) proved that the main components were hydroxytyrosol (HTyr) and oleuropein (Ole), respectively, two well-known antioxidant bioactive compounds found in Olea europaea L. All novel formulations were characterized investigating their morphological, optical and antioxidant properties. The promising performances suggest a potential use in active food packaging to preserve oxidative-sensitive food products. Moreover, this research represents a valuable example of reuse and valorization of agro-industrial wastes and by-products according to the circular economy model.

Highlights

In the last few years, there has been an increasing demand for antioxidant compounds able to prevent or delay damages caused by free radicals, highly reactive and unstable species
Fractions were purified by chromatography to obtain the final products (HTyrE and oleuropein-enriched extract (OleE), respectively) which were characterized by high performance liquid chromatography (HPLC)-DAD and 1H- and 13C-nuclear resonance magnetic spectroscopy (NMR) analysis
In the case of films containing hydroxytyrosolenriched extract (HTyrE) up to 10%wt, the additive was effective in enhancing tensile strength, while in terms of the deformation at break, a lower limit was detected for the concentration of 5%wt

Summary

Introduction

In the last few years, there has been an increasing demand for antioxidant compounds able to prevent or delay damages caused by free radicals, highly reactive and unstable species. They include reactive oxygen species (ROS) as superoxide radical (O2−·), hydroxyl radical (HO·), hydrogen peroxide (H2O2), hypochlorous acid (HClO), and reactive nitrogen species (RNS) such as nitric oxide (NO·) and peroxynitrite (ONOO−) [1]. Oxidative processes represent one of the main causes of food spoilage. Spoilage processes affect taste, color, texture, and shelf life of food. Research is involved in finding strategies to extend the shelf life of food, as often they are not consumed immediately after their production but require long transport and storage times [2]

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Conclusion