INFLUENCE OF FREEZING RATE AND THE RIPENESS STATE OF FRESH COURGETTE ON THE QUALITY OF FREEZE-DRIED PRODUCTS AND FREEZE-DRYING TIME

Industrial freeze-drying of courgette sometimes leads to the alteratio n of both the appearance and the texture of the freeze-dried product a nd to varying freeze drying times. Two factors may be involved in thes e phenomena: the freezing rate and the ripeness state of the raw mater ial. In this study, we show that the freezing rate has no influence on the final quality of the product nor on the dehydration time. On the other hand, the degree of ripeness seems to be of prime importance and can be easily estimated by colorimetric measurements on the fresh veg etable skin or by calorimetric measurement of the glass transition tem perature. We also propose a colorimetric criterion for selecting courg ettes before processing and predicting the luminance of the freeze-dri ed product. Copyright (C) 1996 Elsevier Science Limited.