THE WEIGHT LOSS: GENERAL THEORY AND PARTICULAR CASES

摘要

This paper illustrates the analysis of weight loss, a very important phenomenon that characterizes the storage of foodstuffs both chilled and not. It consists in the weight decrease of foodstuffs, caused by the evaporation of the contained water. The amplitude of the phenomenon is influenced by room temperature, humidity, ventilation etc., and by the intrinsic peculiarities of the product and of the refrigerating plant. In order to obtain experimental data about the time behaviour of the weight of foodstuffs, a series of experiments has been carried out on particular vegetables (swiss chard and carrot) and on cheese (fresh "caciotta"), placed inside a refrigerated box. The analysis regarded the phenomenon both in transient conditions, and in steady state. The analysis of the transient period showed that weight loss has a maximum rate at the beginning of the test and than decreases exponentially up to the minimal value. The analysis in steady state shows, instead, that the phenomenon is not influenced by the ambient humidity but it depends only on the characteristics of the food product and on the mass transfer on the cooling coils. The diagram of weight loss showed that an optimal range of the temperature difference between the food product and the cooling coil exists for the operation of the refrigerated room, within which the weight losses assume moderate values. This result must be kept into consideration in order to reduce the economic losses related to food refrigerated storage.