Volatility of apples during air and freeze drying

The volatility of some representative aroma compounds during the freeze and convective drying of apples was analysed by gas chromatography/mass spectrometry (GC/MS). Among the 36 aroma compounds identified by GC–MS, three representative components of the apple flavor, ethyl acetate, ethyl butyrate and methyl anthranilate, were examined in detail. The retention of the above compounds and moisture content retention during freeze and conventional drying at three different temperatures was investigated. Drying kinetics of volatile compounds and moisture content were studied by introducing a first order kinetic model, involving a characteristic parameter (drying constant), as a function of the drying temperature. Most of the losses of the flavor compounds occurred during the early stages of drying. Retention of aroma was affected by the temperature of drying and the drying method used. Lower drying temperatures and freeze drying method are suggested for maximum retention of flavor in the dried product.