The objective of this study was to analyze the changes in pectins and fibre during blackcurrant mash treatments using diverse methods prior to the process of pressing, as well as to determine the effect of those changes on the juice yield and the release of polyphenols including anthocyanins. Before pressing the juice, the fruit mash was treated using different methods: heat, enzymatic, or combined treatment; and the enzymatic maceration was preceded by a heat treatment. The following preparations were used to macerate mash: Pectinex BE Colour, Pectinex BE XXL, and Gammapect LC Colour; they differed in their enzymatic composition and activity. The results obtained were statistically analyzed. The significance of differences between mean values was assessed by a Duncan’s test. It was found that the changes in pectins and fibre depended on the method of mash treatment including the type of enzymatic preparation applied. Compared to the control fruit mash, the decrease in the content of total pectins ranged from 12 to 50 %. Based on the analysis of the composition of pectin fractions, it was proved that the content of water soluble pectins increased and, concurrently, the content of oxalatesoluble pectins decreased. In addition, the content of cellulose decreased. The decrease in the content of total pectins, including protopectins, and in the content of cellulose occurred along with the increase in the juice yield and with a more effective release of phenolic compounds including anthocyanins.