How much do cultivar and preparation time influence on phenolics content in walnut liqueur?

The influence of cultivar and picking date on the phenolic content of walnut liqueur was investigated using HPLC with a PDA detector. Ten phenolic compounds, namely gallic, protocatechuic, ellagic, chlorogenic (5-caffeoylquinic), syringic, p-coumaric and sinapic acids, as well as (+)-catechin, 1,4-naphthoquinone and juglone were detected. The walnut liqueur under analysis was made of the cultivars ‘Franquette’ and ‘Elit’, on two sampling dates (June 30th and July 7th). A close interaction between cultivar and sampling date was noticed for most of the phenolics analyzed. The content levels of the main phenolic compounds under investigation were highest in ‘Franquette’ at the end of June and lowest in ‘Elit’ on the second or both sampling dates, except for syringic acid. A strong influence of cultivar choice and picking date was observed. The content levels of most phenolics were higher in liqueur prepared from the cultivar ‘Franquette’, than in ‘Elit’.