Recovery of Added-Value Compounds from Orange and Spinach Processing Residues: Green Extraction of Phenolic Compounds and Evaluation of Antioxidant Activity.

María Fernanda Montenegro-Landívar,Xanel Vecino,César Valderrama,Paulina Tapia-Quirós,Mònica Reig,Javier Saurina,Mercè Granados,José Luis Cortina

doi:10.3390/antiox10111800

Abstract

Phenolic compounds recovery by mechanical stirring extraction (MSE) was studied from orange and spinach wastes using water as a solvent. The statistical analysis showed that the highest total polyphenol content (TPC) yield was obtained using 15 min, 70 °C, 1:100 (w/v) solid/solvent ratio and pH 4 for orange; and 5 min, 50 °C, 1:50 (w/v) solid/solvent ratio and pH 6 for spinach. Under these conditions, the TPC was 1 mg gallic acid equivalent (GAE) g−1 fresh weight (fw) and 0.8 mg GAE g−1 fw for orange and spinach, respectively. MSE substantially increased the phenolic compounds yields (1-fold for orange and 2-fold for spinach) compared with ultrasound-assisted extraction. Furthermore, the antioxidant activity of orange and spinach extracts was evaluated using DPPH, FRAP and ABTS. The obtained results pointed out that the evaluated orange and spinach residues provided extracts with antioxidant activity (2.27 mg TE g−1 and 0.04 mg TE g−1, respectively).

Highlights

Fruits and vegetables are a rich source of phenolic compounds that provide the plant with protection against harmful ultraviolet radiation and pathogens, among other abiotic and biotic stresses [1,2,3,4]
Temperature and time were simultaneously studied according to our previous experience in the phenolic compounds extraction from fruit matrices, and taking into account the data reported in literature for similar systems [15,17,26]
Thermo-mePolyphenol extraction from fruit and vegetable wastes was performed using mechanical stirring as as aa cost-effective cost-effective technique where water water is used used as aa solvent

Summary

Introduction

Fruits and vegetables are a rich source of phenolic compounds that provide the plant with protection against harmful ultraviolet radiation and pathogens, among other abiotic and biotic stresses [1,2,3,4]. Phenolic compounds are secondary metabolites produced by plants. Natural antioxidants have been used to replace the synthetic antioxidants additives (e.g., butylated hydroxytoluene (BTH) or butylated hydroxyanisole (BHA)) used in food products [9,10,11], since their toxicity has been proven [12,13]. Another source of phenolic compounds is the agri-food processing industries that generate large amounts of by-products and/or wastes

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