Research needs and opportunities in the dry conservation of fruits and vegetables

The consumer demand for healthy convenience meals with 'near fresh' properties challenges researchers and industry to develop new or improved conservation procedures for food products. However, this recent food trend towards fresh image on one side and convenience on the other side often conflict. In most cases the fresh quality is negatively affected by the processing procedure. Therefore nowadays efforts are focussed on extending the shelf life of fresh products. However, sophisticated energy demanding facilities are required for storage and transporation, whereas the use of ecologically unsound cooling agents is a major drawback. The development of a dehydration process on the basis of electromagnetic energy (EME) may bring about a major breakthrough with respect to the retention of product quality and improved rehydration characteristics. Due to the tenfold weight reduction established in the dehydration process transport and storage costs are minimised thus reducing energy consumption. In comparison with fresh and frozen products minimal storage facilities are required. The strategy of a consortium of five EC-research centres and two dutch drying companies is to combine and fine tune hot air drying (low processing costs) and EME-drying (quality retention) into a hybrid process, to compare the performance with conventional methods and to include packaging and storage effects. Optimisation of the rewettability is one of the major concerns since food materials with near fresh properties can only be obtained from dry material if rehydration characteristics are excellent. To establish such dried fruits and vegetables will be considered as blends of polymeric materials. Many quality deterioration mechanisms can be attributed to the mobility of the polymeric matrix and the diffusion of water. Properties thus depend on the composition, the physical properties of the polymers (mobility) and the overall structure of the dried material. This approach in which process conditions in the dehydration of food materials are linked to a broad range of relevant macroscopic as well as microscopic data is highly innovative and will provide important scientific information. The process-quality relationships are a solid basis to optimize both existing and novel dehydration methods.