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Doctoral thesis2023Open access

Improving and predicting storability of Swedish apples with IAD and improved storage conditions

Sjöstrand, Joakim


Only around 30% of the apples consumed in Sweden are produced within the country, even though many customers prefer locally produced fruit. One way to increase the availability of Swedish fruit is to reduce post-harvest losses to pathogens and disorders, which increase if fruit is not harvested at optimal maturity. This thesis examined ways of improving the storability of Swedish apples by reducing losses due to fungal decay and to the physiological disorder soft scald, and by using different measures for establishing optimal harvesting time for mid- and late-season cultivars.  

Weather conditions were found to have an effect on the incidence of soft scald, with humidity and rain increasing the incidence in some cases. Rainy weather also increased fungal decay. Absorbance difference index (IAD) was shown to be correlated with harvest time, apple firmness and Streif index before harvest. The strength of correlations showed high between-cultivar and between-year variations. IAD was found to be a possible complement to existing maturity indices, but causes of variation in the accuracy of IAD as a predictor of maturity need to be identified. 

Controlled storage atmosphere was found to be the most effective measure to control soft scald, while delayed cooling had little effect. Fruit maturity had a significant effect on soft scald incidence in some cases, but not every year. A strong effect of year was seen in most measurements, e.g. for strength of correlations, soft scald incidence and fungal decay.


Apple; storability; IAD; soft scald; ULO; maturity index

Published in

Acta Universitatis Agriculturae Sueciae
2023, number: 2023:84ISBN: 978-91-8046-220-4, eISBN: 978-91-8046-221-1
Publisher: Swedish University of Agricultural Sciences

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