Phenols and Tannins of Apples and Ciders.

Traditionally, cider is associated with the taste sensations of bitterness and astringency which are caused by phenols and tannins in the apples. Due to the health aspects and taste sensations linked with these compounds, cider makers are interested in the polyphenols present in apples and ciders. The aim of the following research was to analyse polyphenols in apples and monitor changes in the composition due to the processing apples for cider production. The organoleptic properties of polyphenols found in cider, were also investigated. A reversed phase HPLC method was devised to detect polyphenols in apples and ciders. The classes of polyphenols identified were the dihydrochalcones, flavan-3-ols, flavonol glycosides and hydroxycinnamic acids. A method was optimised and validated for the extraction of polyphenols from apple tissues (peel, flesh, core and seeds). The extracts were quantified by reverse phase HPLC. A novel assay to indicate the varying presence of condensed tannins through the apple was devised using Porter’s reagents. The highest presence was found in the peel with the lowest in the core. The analytical methods developed were applied to pressed juices, concentrates, pomace and throughout the two fermentation processes (alcoholic and malo-lactic). A decrease in the polyphenol content was observed during the fermentations. Evidence obtained, indicated the polyphenols adhere to the metal vats in which the cider is fermented. A range of ciders were profiled for their polyphenol content. From the ciders profiled, three were analysed by a taste panel to ascertain a relationship between the taste attributes and the quantified polyphenols. After statistical analysis (ANOVA), a number of conclusions were drawn. Firstly, bitterness could be attributed to both polyphenols (catechin, epicatechin and phloridzin) and condensed tannins. Astringency was associated only with for the condensed tannins and flavonol glycosides. Significant variation between panellists was observed for the taste attributes ‘phenolic’ and ‘dessert apple’