HYGROMETRIC EVALUATION OF PERMEABILITY OF PLUM CUTICLE AFTER PRETREATMENTS TO DRYING

A non destructive hygrometric measuring procedure capable of quantifyi ng in advance the effectiveness of different pretreatments to whole fr uit drying was developed. The results obtained with hygrometric measur ements were verified by monitoring the drying time of plum samples sub mitted to the same pretreatments. The permeability evaluation required only a short time for the analysis (20 min) and, under our experiment al conditions, had a good repeatability and discriminated between samp les with slight differences in permeability. From hygrometric data a ' 'permeability index'' (b') was calculated. The sample submitted to dip ping in NaOH solution showed b' values 5 times higher than raw sample. The products which had a higher skin permeability also showed the sho rtest drying times. In particular, raw plums ranged between 940 and 96 0 min plums dipped in ethyl oleate emulsion between 760 and 820 min an d plums dipped in hot NaOH solution between 630 and 670 min. In this w ay, the hygrometric tests could be used to predict the drying behaviou r of whole fruit.