Chemical contents and blue mould susceptibility in Swedish-grown cider apple cultivars

Craft apple cider is obtained by fermentation of juice from tannin-rich cider apple cultivars. Polyphenols in cider apples are very important; while procyanidins are the only true tannins, other phenolic compounds can act as precursors for cider aroma. Several recent studies have also reported that a high content of polyphenols in apple decreases susceptibility to the common storage rot blue mould caused by Penicillium expansum. Chemical content was determined in fruit of 19 Swedish-grown cider apple cultivars and 5 dessert apple cultivars in 2016. Inoculation with blue mould spores was undertaken in 2016 on 5 cider apple cultivars and 5 dessert apple cultivars, and repeated again in 2017 on 8 of these cultivars. Contrary to expectations, the cider apple cultivars were significantly more susceptible to blue mould in spite of their higher phenolics content. Although apparently unrelated to amount of phenols in the fruit of our study cultivars, heritability of blue mould susceptibility should be further investigated since all of the cider apples had one parent in common; 'James Grieve'.