Post-harvest ripening increase cultivar specific sensory and analytical aroma profile in apple juice: A study of four commercial cultivars in Denmark

Abstract

Apples are normally produced with focus on the fresh fruit marked, which imply high priority on storability and shelf life. The fruits used for juice are normally those discarded along the post-harvest chain. If the main goal is changed to production of high-quality juice with emphasis on single cultivar characteristic flavours, focus can be on optimal fruit ripening for flavour development. To investigate the juice quality potentials during post-harvest ripening, four apple cultivars: ‘Aroma’, ‘Holsteiner Cox’, ‘Ingrid Marie’ and ‘Rajka’ were sampled and juiced after 5 and 10 days of post-harvest storage at room temperature (20°C). The soluble solids content (SSC) of ‘Ingrid Marie’ fruits increased most, and after 10 days, it had the lowest starch content of the four cultivars studied. The mid-to-late season cultivars ‘Ingrid Marie’, ‘Holsteiner Cox’ and ‘Rajka’ had higher SSC/acidity ratio than the middle early season ‘Aroma’ ‘and all of them showed an increase of the ratio SSC/acidity during storage’. The volatile compound measurements (GC-MS) of the juices indicated that particularly ‘Holsteiner Cox’ and ‘Ingrid Marie’ have the ability to produce fruity volatile compounds like ethyl acetate, propyl acetate, 2-methylpropyl acetate, butyl acetate, hexyl acetate, hexanal, ethyl propanoate, pentyl acetate and ethyl 2-metylbutanoate exhibiting remarkable changes during ripening. These volatile compounds may explain the post-harvest development of interesting fruity nuances perceived by the sensory panel. The terms ‘apricot’, ‘peach’ and ‘pineapple’ were used to describe the odour and flavour properties of these cultivar juices in the sensory analysis. ‘Aroma’ apples ranked high on ‘citrus’, ‘red berries’ and ‘pear’ flavour descriptors after 5 days of storage, whereas ‘Rajka’ showed the weakest aroma profile of the group of cultivars. To exploit the aroma and sensory potential fully, apple cultivars should be further investigated in regards to effects of delayed harvest and different post-harvest treatments.

Keywords:

• flavour
• high-quality juices
• Malus domestica
• post-harvest
• sensory analysis
• volatile compounds

Acknowledgements

We acknowledge the Danish Ministry of Food, Agriculture and Fisheries for funding this study under the project ‘Ydun: Potential for specialty juices from Danish local apple cultivars’. We also express our gratitude to our project partner NordGen. The help from the Pometum, University of Copenhagen personnel is highly appreciated.