Structural characterisation and antioxidant activity of melanoidins from high‐temperature fermented apple

Abstract

SummaryHigh‐temperature fermented apple is a new fermented product with characteristic black appearance, which is prepared through natural fermentation of whole fresh apple at controlled high temperature (60–90 °C) and humidity (relative humidity of 50–90%). In this work, melanoidins from high‐temperature fermented apple were obtained by ultrafiltration and subsequent diafiltration. The structural characterisation of melanoidins was investigated in the present study. Results showed that the molecular weight of the obtained melanoidins was about 179 kDa and the melanoidins were comprised primarily of furans by pyrolysis–gas chromatography–mass spectrometry. Antioxidant activities of the high‐temperature fermented apple and its melanoidins were evaluated by ABTS, DPPH, hydroxyl radicals, ferric reducing antioxidant power and Fe2+‐chelating assays. Both high‐temperature fermented apple and its melanoidins showed extremely high antioxidant activities in scavenging hydroxyl radicals. High correlation between the antioxidant activity assayed methods and the physicochemical characteristics of melanoidins was obtained. The contribution of melanoidins to the total antioxidant capacity of high‐temperature fermented apple was determined.