title: Stability of antioxidants in an apple polyphenol-milk model system.
abstract: The stability of antioxidants in an apple polyphenol-milk model system was examined. The model system consisted of skim milk fortified with pH-neutralised apple polyphenols (AP, 0-200mg per 100ml milk), with or without ascorbic acid (100mg per 100ml milk). Physical and chemical changes were evaluated after thermal treatment (120°C, 5min) and oxidative storage (20°C and 38°C, up to 12 weeks). Antioxidant capacity was determined using both oxygen radical absorbance capacity (ORAC) assay and ferric reducing antioxidant power (FRAP) assay. Significant antioxidant capacity was detected in the presence of milk. Antioxidant capacity was retained during thermal treatment but decreased slowly during storage. The concentration of ascorbic acid decreased rapidly, and was close to zero after 2-week storage at 38°C or 10-week storage at 20°C. The brownness of the polyphenol-milk system increased over storage duration of 0-12 weeks; this effect was retarded by the addition of ascorbic acid. This high polyphenol-milk has demonstrated good physical stability.
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: T F
authors.initials: TF
authors.lastname: Wegrzyn
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand. Electronic address: jfarr@hortresearch.co.nz.
authors.forename: J M
authors.initials: JM
authors.lastname: Farr
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: D C
authors.initials: DC
authors.lastname: Hunter
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: J
authors.initials: J
authors.lastname: Au
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: M W
authors.initials: MW
authors.lastname: Wohlers
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: M A
authors.initials: MA
authors.lastname: Skinner
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: R A
authors.initials: RA
authors.lastname: Stanley
authors.affiliation: Health and Food, The Horticulture and Food Institute of New Zealand Limited, Mt Albert Research Centre, Private Bag 92169, Auckland 1020, New Zealand.
authors.forename: D
authors.initials: D
authors.lastname: Sun-Waterhouse
keywords: Apple polyphenol–milk; Ascorbic acid; FRAP assay; ORAC assay; Physical stability