Response surface methodology (RSM) was chosen to optimize the influence of solvent pH and relative proportion, and time of extraction, regarding polyphenols and radical scavenging capacity of almond (Prunus dulcis (Mill.) D.A. Webb) by-products (hulls, shells, and skins) from an almond orchard located in the North of Portugal (Lousa, Torre de Moncorvo). The RSM model was developed according to a Box-Behnken design and the optimal conditions were set for pH 6.5, 250.0 min, and 90.0% of food quality ethanol, pH 1.5, 235.0 min, and 63.0% ethanol, and pH 1.5, 250.0 min, and 56.0% ethanol for hulls, shells, and skins, respectively. The optimal conditions were obtained applying spectrophotometric techniques because of their versatility, while the chromatographic profile of extracts obtained when applied the optimal conditions indicated the presence of 3-caffeoylquinic acid, naringenin-7-O-glucoside, kaempferol-3-O-glucoside, isorhamnetin-3-O-rutinoside, isorhamnetin-3-O-glucoside, and isorhamnetin aglycone in hulls and skins. The model designed allowed the optimization of the phenolic extraction from almond by-products, demonstrating the potential of these materials as sources of antioxidant compounds with potential industrial, pharmaceutical, and food applications.
Almonds By-products Phenolic extraction Optimization process Antioxidants RSM
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The authors acknowledge João Santos and Chenyao Yang for the help with the climatic data and Alfredo Aires for the help with HPLC data.
IP received financial support from the FCT-Portuguese Foundation for Science and Technology (SFRH/BD/52539/2014), under the Doctoral Programme “Agricultural Production Chains—from fork to farm” (PD/00122/2012). RDP was supported by a Postdoctoral Contract (Juan de la Cierva de Incorporación ICJI-2015-25373) from the Ministry of Economy, Industry and Competitiveness of Spain. This work is supported by the National Funds by FCT-Portuguese Foundation for Science and Technology, under the project UID/AGR/04033/2019.
Compliance with Ethical Standards
Conflict of Interest
Iva Prgomet declares that she has no conflict of interest. Berta Gonçalves declares that she has no conflict of interest. Raúl Domínguez-Perles declares that he has no conflict of interest. Núria Pascual-Seva declares that she has no conflict of interest. Ana I. R. N. A. Barros declares that she has no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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1.Centre for the Research and Technology of Agro-Environmental and Biological Sciences, CITABUniversity of Trás-os-Montes e Alto Douro, UTADVila RealPortugal
2.Centro de Edafología y Biología Aplicada del Segura, Department of Science and Technology of Foods, Group on Quality, Safety, and Bioactivity of Plant FoodsSpanish Council for Scientific Research (CEBAS-CSIC)MurciaSpain
3.Department of Plant ProductionUniversitat Politècnica de ValènciaValenciaSpain