Refrigiration systems and post-harvest performance of vegetables - conclusions for a research system to study the effect of fluctuating climatic conditions on stored plant organs

摘要

Post-harvest loss of Chinese cabbage, carrots and celery, stored in three different refrigeration systems were investigated in orderto improve storage conditions. Two directly cooled systems, one equipped with a thermal expansion valve and the other one with an electronically controlled stepper motor driven valve, were compared to a jacketed cooling system. Decay of stored vegetables proved to be higher at quick temperature and vapour pressure deficit fluctuations with small hysteresis values compared to storage conditions fluctuating slowly with relatively high deviations. Such a result was unexpected. Thus there was a need to construct a research system to study the effect of variable fluctuating storage conditions on post-harvest reactions of plant organs. Sinus shaped temperature variations with differing values of hysteresis and frequency fixed in a function simulate the temperature fluctuations in a cold-storage room. The system includes 12 acrylic cuvettes, a volume of 26 litres each. The temperatures in these cuvettes can be increased periodically by power-controlled heating elements and cooled down through the outer surface. Investigating physiological reactions of vegetables stored at differently fluctuating conditions transpiration and respiration rates of crops are determined by infra-red absorption in an "open system". Temperature and humidity conditions in each cuvette are measured using high accuracy systems. Data acquisition and controlling the system are performed by a data logger in communication with a process computer running specialised software.