Manfred Linke

Improved Produce Quality and Safety by Controlled Warming After Cold Storage of Fruits

Generally, extension of shelf life can be obtained by manipulation of reaction rates due to temperature decrease. However, cooling requires a re-warming step commonly leading to disadvantageous condensation of water at the produce surface at temperatures below the dew point. The amount of condensate is a function of the produce surface temperature and of the surrounding air flow conditions which are strongly affected by the packaging system used. The temperature equilibrium is often obtained not before several hours. If the water remains at the sample surface for a long time period while temperature increases, unwanted microorganisms are able to grow under certain conditions resulting in produce deterioration and reduced shelf life. The objective of this study was to minimize condensation effects by controlling the air flow conditions close to the produce surface. Selected fruit samples in various open packaging were warmed after the cold storage using different flow conditions. The time-dependent amount of condensate was calculated using a certain heat and mass transfer model for the produce in the packaging unit. The data clearly show that low air convection results in small amounts of condensate persisting on the product surface in the packaging during extended periods (up to 10 hours). When increasing the air velocity higher amount of water vapor condensates, but remaining on the produce surface for shorter time. The data presented in this study point out the effect of air flow condition, packaging and temperature on the postharvest behavior of stone fruits (sweet cherry, plum), resulting in strategies for improved post-cold storage handling.

Aktive Transpondertechnik in der Nacherntekette von Obst und Gemüse

Capacity features and operation criteria of active transponders for the process control of fruits and vegetables are discussed here. Such systems measure the thermal stress on the harvested products and are simultaneously a medium for transmitting the information along the post-harvest chain. Correspondingly diverse possibilities for quality safeguarding of high-value fruit and vegetables arise. Basically detailed consumer information, as well as data on traceability, can be provided.