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Department of Safety and Quality of Fruit and Vegetables

Depending on the cultivar and on the conditions, apples can be stored up to 10 months. However, a fungal infection before harvest may affect storability strongly by causing an early spoilage. This problem is especially relevant for organic cultivation where the application of synthetic fungicides is not allowed. However, it was shown by the MRI in a former project that a hot water treatment of apples before storage can, for instance, reduce substantially the postharvest losses due to fruit rot caused by the fungus Gloeosporium. Usually, this is already achieved by immersion the apples for 2-3 minutes in 48-52 °C warm water. While the fruits of some cultivars tolerate such a treatment, others develop peel browning within the following weeks. The reasons for this different behaviour are not known so far.

The Department of Safety and Quality of Fruit and Vegetables of the Max Rubner-Institut investigates in cooperation with the Karlsruhe Institute of Technology (Workgroup of Prof. Burkhard Luy, Institute of Organic Chemistry, Chair for Bioanalytics) the metabolic changes in apple peel caused by hot water treatment. For this purpose, the metabolite profile of apple peel is analyzed before and after hot water treatment as well as after subsequent storage. In order to cover a broad spectrum of compounds, untargeted metabolome analyses are performed with comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-MS) and nuclear magnetic resonance spectroscopy (H-NMR). The aim of this project is to describe the acute and the long-term metabolic effect of hot water treatment on apple peel at the molecular level. In addition, it is to clarify whether the hot water treatment at the level of individual ingredients has also long-term effects.

Does a hot water treatment affect apple quality?