AIM: To study the copigmentation between different wine flavonols (myricetin, quercetin, kaempferol, isorhamnetin and syringetin 3-O-glucosides) and malvidin 3-O-glucoside to detect differences in the interactions due to the flavonol type. Considering the existing interactions of anthocyanins and flavonols in wines with mannoproteins1, copigmentation was also studied in the presence of 5 different mannoproteins. METHODS: 36 model systems were built in wine-like solution in triplicate. One of them contained only the anthocyanin. 10 were anthocyanin-flavonol (AF) or anthocyanin-mannoprotein (AM) binary systems. 25 contained the anthocyanin, one type of flavonol and one type of mannoprotein (AFM). Concentrations used were 0.41mM for the anthocyanin and flavonol and 400 mg/L for the mannoprotein. UV-vis spectra were measured at days 1, 2, 5, 8 and 22, calculating then, CIELAB parameters and copigmentation indexes, such as CCI (% of colour due to copigmentation)2. HPLC-DAD-MSn analyses1 were performed at day 22 to study anthocyanin degradation and the possible and distinct formation of anthocyanin-derived pigments. RESULTS: In AF binary systems, the occurrence of copigmentation was demonstrated from the CCI values (>23 in all model systems from day 1 to day 22). Copigmentation increased during the first 8 days and then tended to decrease until day 22. Isorhamnetin 3-O-glucoside appeared to be the best copigment (CCI 70) whereas kaempferol 3-O-glucoside caused the lowest CCI values. In AM binary systems, copigmentation was not observed and, for some mannoproteins, even an anticopigmentation effect was detected. In AFM ternary systems, the effect depended both on the flavonol and on the mannoprotein, pointing to different interactions probably related to structural differences. CONCLUSIONS: The magnitude of the copigmentation phenomenon between malvidin 3-O-glucoside and different flavonols depend on the structure of the flavonol and can be differently affected by the presence of different types of mannoproteins in the medium.
Authors: Cristina Alcalde Eon – Grupo de Investigación en Polifenoles, University of Salamanca, Salamanca, Spain,María de las Nieves FELIPE-JIMÉNEZ. Grupo de Investigación en Polifenoles, University of Salamanca, Salamanca, Spain Ignacio GARCÍA-ESTÉVEZ. Grupo de Investigación en Polifenoles, University of Salamanca, Salamanca, Spain María Teresa ESCRIBANO-BAILÓN. Grupo de Investigación en Polifenoles, University of Salamanca, Salamanca, Spain
Keywords: anthocyanins, flavonols, copigmentation, mannoproteins, colour stability