The Postharvest and Quality research area focuses on the influence of different storage conditions on the preservation of quality and the occurrence of post-harvest diseases. For this purpose, long-term storage trials (6 - 8 months) with fruits and vegetables – often new and old cultivars - are performed with different combinations of temperature, humidity and atmosphere composition (normal or controlled atmosphere). In addition, various plants (carrots, tomatoes, radish and up to African leafy vegetables) needed for several research projects are cultivated under controlled conditions in a climate chamber and a greenhouse.
Furthermore, a research focus is on hot water (46 - 52 °C, 2 - 10 minutes) treatment of fruit and vegetables before storage, a method used to reduce postharvest diseases or rots due to filamentous fungi.
Effects of different treatments (hot water treatment, different storage temperatures and atmospheres) on the quality and storability of fruit and vegetables are characterized by using conventional and modern analytical procedures. For example, apples are first visually evaluated by determination of occurrence of external and internal diseases like superficial scald and internal flesh browning. In addition, valuable nutrients like vitamins, sugars, total phenolic content, total titratable acid are determined as conventional quality parameters at the beginning and the end of the storage period. Enzyme activities and fruit firmness are also measured on a regular basis.
For a comprehensive characterization of the products the metabolome analysis approach (metabolomics) is applied. This method allows the determination of several hundred metabolites with only one analysis at the same time. The comprehensive view on different compound classes – e.g., sugars, amino acids, organic acids, phytosteroles, fruit waxes or phenoles – enables a deeper understanding of the coherences which form the basis of fruit quality. For instance, metabolome analyses allow
- to determine cultivar and origin-specific differences in the food composition profile
- to evaluate the influence of storage conditions on the composition of fruits
- to investigate the molecular processes connected with storage diseases
- to understand fruit reactions on fungal infestations
- to identify markers related to higher or lower fungal resistance of certain fruit cultivars
Metabolome analyses are conducted with modern analytical techniques. In the Institute of Safety and Quality of Fruit and Vegetables, mainly comprehensive two-dimensional gas chromatography-mass spectrometry is used.