Impact of pectin type on the storage stability of black currant (Ribes nigrum L.) anthocyanins in pectic model solutions.

The effects of different pectins on the stabilisation of black currant anthocyanins in viscous model solutions at pH 3.0 were investigated. For this purpose, low esterified amidated (AM), low (LM) and high (HM) methoxylated citrus and apple pectins and a sugar beet pectin were added to a purified anthocyanin extract (ACN-E) and to an extract containing anthocyanins and non-anthocyanin phenolics (PP-E). Model systems were stored at 20±0.5°C in the dark. Anthocyanin contents were monitored by HPLC analysis over a period of 18 weeks, and half-life and destruction values were calculated. In all pectic model solutions anthocyanin stability was significantly improved compared to stability of the extracts without added pectins (blank). Best stabilisation was obtained with AM pectin, followed by LM and HM pectins. In model systems containing citrus pectins, anthocyanin stabilisation was better compared to that of apple pectins having similar degrees of esterification and amidation, respectively. This was primarily due to the strong interaction of delphinidin glycosides with the citrus pectins, whereas stabilisation of cyanidin derivatives was less important. Sugar beet pectin improved anthocyanin stability only to a limited extent. In the presence of non-anthocyanin phenolics (PP-E) the impact of the pectin source was even more pronounced than the effect of the pectin type. Addition of citrate to pectic systems accelerated anthocyanin decay. Stabilising effects of pectins were hardly noticeable when evaluating total phenolic content (TPC, Folin-Ciocalteu) and antioxidant capacity during storage. Highest TPC, TEAC- and FRAP values were observed in systems containing citrus pectin, which was in contrast to sugar beet pectin, where values fell below those of the blank after storage.