title: Impact of several pre-treatments on the extraction of phenolic compounds in winegrape varieties with different anthocyanin profiles and skin mechanical properties.
abstract: This study was performed to evaluate and compare the effects of different pre-treatments of whole grape berries (freezing with dry ice or in a cold room, steam blanching with different exposure times, and microwave heating with different exposure times and microwave power density) on total content of some phenolic compounds and the composition of individual anthocyanins released into the pulp during the treatment and those extracted during the maceration step. Two red winegrape varieties with different proportions of di- and trisubstituted anthocyanins were used (Nebbiolo and Barbera, respectively). Pulp-extracted anthocyanins were more significantly influenced by the pre-treatment. The results highlighted that freezing with dry ice, followed by freezing in a cold room and steam blanching for 5 min, have a great potential from an industrial point of view. They facilitated the extraction of anthocyanins in the must prior to maceration, when compared with the control samples, increasing their total content (+37.8-83.6%), and modifying the anthocyanin profile through the enrichment in the most stable compounds (+2.8-6.6% malvidin derivatives) to the detriment of others more prone to oxidation (-0.8-11.0% cyanidin derivatives). In Nebbiolo winegrapes, an improved extraction of low- and high-molecular weight flavanols into the pulp was also observed (+60.4-73.4%). Significant relationships between the phenolic composition of treated berries and the corresponding skin mechanical properties were also studied, but they were variety dependent. Discriminant analysis permitted a correct classification of the samples according to the variety and pre-treatment.
authors.affiliation: Dipartimento di Scienze Agrarie, Forestali e Alimentari, Università degli Studi di Torino , Via Leonardo da Vinci 44, 10095 Grugliasco, Torino, Italy.
authors.forename: Susana
authors.initials: S
authors.lastname: Río Segade
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Torchio
authors.forename: Simone
authors.initials: S
authors.lastname: Giacosa
authors.forename: Davide
authors.initials: D
authors.lastname: Ricauda Aimonino
authors.forename: Paolo
authors.initials: P
authors.lastname: Gay
authors.forename: Milena
authors.initials: M
authors.lastname: Lambri
authors.forename: Roberta
authors.initials: R
authors.lastname: Dordoni
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Gerbi
authors.forename: Luca
authors.initials: L
authors.lastname: Rolle
mesh_terms: D000872:Anthocyanins / Q000737:chemistry / Q000302:isolation & purification*; D001696:Biomechanical Phenomena; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry / Q000302:isolation & purification*; D027843:Vitis / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D010636:Phenols
keywords: anthocyanins; dry ice; extraction; flavanols; grape pre-treatments; microwave; skin mechanical properties