In this paper an alternative physical method for enhancing the drying rate
of seedless grapes is proposed. It consists of the superficial abrasion of
the grape peel using an inert abrasive material. The effectiveness of this
novel process was compared to that of the traditional ethyl oleate dipping
process by analysing not only their respective drying times, but also the p
eel surfaces by scanning electron microscopy. Moreover, the drying kinetics
of the above two treatments was reconstructed by using a mathematical mode
l in which the grape pretreatment used was assumed to affect the water diff
usivity in the grape peel, but not in the grape pulp. Even though the abras
ion method was found to be as effective as the traditional method and gave
rise to a darker final product, which is less attractive to consumers, it w
ould allow grape pretreatment thus avoiding the use of chemical additives,
and permit safer raisins to be produced. (C) 2000 Elsevier Science Ltd. All
rights reserved.