Effect of the Extraction Technique and Operational Conditions on the Recovery of Bioactive Compounds from Chestnut (Castanea sativa) Bur and Shell

Abstract

The aim of this work was to study the extraction of phenolic compounds from chestnut bur and shell, both waste products of chestnut processing in the food industry. Two extraction techniques were compared—maceration with solvents and microwave-assisted extraction. The influence of the solvent used (water, 50% MeOH or 50% EtOH) and temperature (25-50-75°C) on extraction yield and extract total phenols content and FRAP, DPPH, and ABTS antioxidant activities was studied. In the conventional extraction, the yield was significantly higher for the bur (8.54–19.58%) than for the shell (2.91–13.27%); however, the shell extracts showed substantially greater properties. The best extract properties were achieved at 75°C using 50% MeOH for the bur and water for the shell and phenolic compounds with demonstrated antioxidant properties, as gallic acid esters of glucose and ellagic acid, were identified in these extracts by RP-HPLC-ESI-TOF. In addition, the aqueous extracts showed ability to inhibit the growth of gram positive and negative bacteria but not fungi. The kinetic of the extraction process was well fitted by the Peleg's model. The non-conventional microwave-assisted extraction slightly improved the chestnut bur extraction by reducing the extraction time.