Agri-food Waste: Recovery of Bioactive Compounds from Dried Fruits Hard Shells for Nutraceutical Applications

Nowadays, climate change, an increase in pollution, resource scarcity and the remarkable amount of agricultural and food waste produced by industries all over the world have become environmental severe priorities. In this framework, the circular bio-economy concept underlines the necessity of transforming by-products into new value-added resources to minimize waste generation.1 Agri-food waste with low economic value are still rich in bioactive compounds, especially polyphenols, which can be recovered and used for several potential industrial and nutraceutical applications. Dried fruit hard shells are the primary waste obtained from Pistacia vera, Prunus dulcis and Corylus avellana industrial manufacturing but are even a potential source of natural antioxidants.2 In this study, we decided to optimize the operating extraction conditions for the recovery of polyphenols from dried fruit hard shells. Microwave-assisted extraction (MAE) technique was chosen as a green extraction method.3 Single-factor experiment was initially performed to define the preliminary range of the major extraction variables. The effects of ethanol concentration, irradiation power, extraction time and solventto- solid ratio on the total phenolic content (TPC) and on the antioxidant capacity (using DPPH, ABTS and FRAP values) were investigated by mean of the response surface methodology (RSM; Figure 1). RSM was applied with Box-Behnken design (BBD) to establish a mathematical model and obtain the optimal MAE conditions for maximum recovery of TPC and antioxidant activity. Identification of bioactive compounds was carried out through HPLC/MS and NMR. The results highlighted that the proposed methodology can be an effective way to recover bioactive phenolic compounds from fruit hard shells, making these by-products a promising source of compounds with potential applications in food and healthcare sectors.