Investigation of physical changes occur in quince structure during drying

In this study; dehydration kinetics, rehydration characteritics and total color changes in dehydration of ekmek species of quince, growth in Adapazarı province, were investigated. For this aim, pre-treated and fresh quinces dried with different thicknesses at different temperatures in drying oven; at a constant vacuum pressure but different temperatures and at a constant temperature but different vacuum pressures in vacuum drying oven and at different microwave power degrees in microwave dryer. At the beginning and at the end of drying, color measurements were taken. Samples dried in drying analyses, were rehydrated in pure water at laboratory temperature. As pre-treatment being; honey, sucrose and glycose sugary solutions which are 65 brix, %5 Na2S2O5 and %5 Na2S2O5 + %2 EO chemical solutions and ascorbic acid were used. As rehydration liquid being; only pure water at laboratory temperature was used. It was seen that dehydration velocity was increased with increasing temperatures of drying oven and vacuum drying oven, vacuum pressure, microwave power degree and with decreasing thickness. At these conditions, decreasing moisture content with time was reached lower values. It was observed that diffusion coefficient was increased with conditions (except thickness) which increased the dehydration velocity and with increasing thickness. It was determined that drying activation energy was lower in thick samples. When pre-treatments are sorted by drying activation energy values a result like; sugary solutions > ascorbic acid > chemical solutions was found. It was observed that microwave dryer > vacuum drying oven >drying oven when the methods are sorted by their dehydration velocities. It was observed that total color change in dryed samples was seen most in microwave drying, least in vacuum drying. In all methods, most color change with regard to pre-treatments was like in samples with ascorbic acid > samples with sugary solutions > fresh samples > samples with chemical solutions. It was determined that the samples which dried faster were rehdrated faster ,too. In that respect, for 10 mm thickness, velocity of rehydration and rehydration ratio of samples are highest to lowest listed as quinces dried in microwave, vacuum drying oven and drying oven. Rehydration ability of thinner samples was found higher than thicker samples.