Nanoemulsions of grape marc extract as a natural additives to impruve hazelnut paste shelf-life

In previous studies the authors obtained a phenolic freeze-dried extract from red-grape marc by hydroalcoholic extraction. Antioxidant properties of the extract could be maintained during long term storage, but the extract shows limited solubility both in aqueous and lipid systems. Since addition of the extract to hazelnut paste as natural additive to protect it against lipid oxidation improving its quality and shelf-life appears an interesting and profitable application, this study investigated the encapsulation of the extract into different nanoemulsion-based delivery systems. Three different delivery systems were fabricated at the nanoscale (around 200 nm) by high pressure homogenization for the encapsulation of the marc extracts. Formulation 1 was a sunflower-oil/water nanoemulsion with soy lecithin as emulsifier. Formulation 2 was a powder obtained by maltodextrin-assisted spray-drying of Formulation 1. Formulation 3 was an ethanol/solid-lipid nanoemulsion, produced by hot homogenization using soy lecithin as emulsifier. The original extract and its encapsulating formulations were homogenized into hazelnut paste at a concentration of 5000 ppm, resulting into different phenolics content, ranging from 1200 ppm for crude extract to less than 10 ppm for the delivery systems. An accelerated shelf-life test at 60°C was carried out and peroxides value (PV) of the lipid phase was periodically analyzed (until 100 days) to verify the protective effect of the extracts against oxidation. Results showed the efficiency of nanoemulsion formulation in improving solubility of the extract into the hazelnut paste. Addition of the extract could significantly improve the paste shelf-life by inhibiting its oxidation. Improved dispersion of nanoemulsion also increased the efficiency of the phenolic compounds, reducing the amount of extract required for the potential production of a natural preservative agent.