Impact of air-drying on polyphenol extractability from apple pomace

• Published in: Food chemistry 2019-10, Vol.296, p.142-149
• Main Authors: Birtic, Simona, Régis, Sylvaine, Le Bourvellec, Carine, Renard, Catherine M.G.C.
• Format: Article
• Language: English
• Subjects: By-product; Chemical and Process Engineering; Chlorogenic acid; Desiccation - methods; Dihydrochalcone; Engineering Sciences; Extraction; Flavanones - chemistry; Flvonol; Food engineering; Life Sciences; Malus - chemistry; Malus - metabolism; Malus domestica Borkh; Plant Extracts - chemistry; Polyphenols - chemistry; Polyphenols - isolation & purification; Polysaccharides - chemistry; Proanthocyanidins - chemistry; Procyanidin; Quercetin glycoside
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2019.05.131

•Oxidation during drying led to relative enrichment of apple pomace in flavonols.•Hydroxycinnamic acids, dihydrochalcones, and procyanidins decreased during drying.•Procyanidins were extracted selectively by aqueous ethanol (48%).•Most polyphenols extracted after drying were either oxidised or condensed.•Antioxidant capacities (Folin-Ciocalteu) of the extracts were not influenced by drying. Little data are available on the impact of pomace pre-treatment, notably drying, on the nature and yield of polyphenols. Pomace from two apple varieties (‘Avrolles’ and ‘Kermerrien’), pressed with and without oxidation, were air-dried to different degrees. Drying led to the loss of native molecules, notably 5-O-caffeoylquinic acid and flavan-3-ols. Total polyphenol yields, after sequential pressurized liquid extraction (water 10 MPa, 70 °C, then ethanol 48%, 10 MPa, 70 °C), varied between 5 and 15 g/kg dry weight but showed no marked trend with drying. Extracts from dried pomace contained few native polyphenols. Water extracts from ‘Kermerrien’ contained flavonols, flavanols and phloridzin and those from ‘Avrolles’ contained phloridzin. Water:ethanol extracts were rich in procyanidins, especially from ‘Avrolles’, where they represented >80% of analysable polyphenols. Presence of polyphenol molecules with modified structures in the extracts of dried pomaces might lead to different biological properties than those with native molecules.