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Influence of drying parameters and browning inhibitor on infrared drying of apple

The results of infrared drying of Jonagold apple are presented in this paper.A Mettler Toledo HR 73 thermogravimetric analyser was used to obtain the drying. The investigation involved drying temperature of 70 – 90 ºC, three drying programmes and two different dimensions of samples (10x10x5 mm, 20x20x3 mm). Temperatures of dried samples were measured during the whole drying process. Colour changes of dried samples, with regard to the colour of fresh apple sample, were determinated by Minolta CR-300 Chroma Meters. The influence of pretreatment solution (1.5% K2S2O5) on the colour change of dried samples was investigated too.The integral and differential drying curves for all the dried samples, were plotted by experimental model of drying. The estimated values corresponded well with experimental data. With an increase of a drying temperature the maximum drying rate is increased too. The maximum drying rates of the 20x20x3 mm samples were higher than the drying rates of 10x10x5 mm samples. Pretreating of fresh apple samples with 1.5% solution of K2S2O5 had an influence on achieving compared to drying rates of untreated samples. In addition to that 1.5% pretreating solution K2S2O5, used as a browning inhibitor, had significant impact on decreasing the entire colour change.

infrared drying; drying kinetics; thermogravimetry; apple; colour

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