Abstract
We describe production of Fleur de sel in the solar saltponds of Castro Marim （Portugal） where the local producers reoriented and substantially increased output of this variety of salt. Indeed this culinary specialty is commercialized for a price order of magnitude higher than coarse marine salt which traditionally dominated the production. Because of a complete lack of published information on that subject the present study aims to elucidate factors, which influence the quality and characteristics of the end product. Crystals size, and density of Fleur de sel samples, collected during the period of 70 days in an artisanal salt unit, were studied. The study resulted in a classification of 3 types of crystals according to their size. Category A was attributed to the biggest crystals, with surface ranging from 18 to 24 mm2, considered as the best quality crystals taking into account market requirements. Their formation took place in the following atmospheric conditions: air temperature of 29.6 ℃; relative humidity of air of 40.3 ％; southern wind direction and speed of 6.0 knots; solar radiation of 31,227 KJ/m2; and, an evaporation rate of 1.38 mm/day. Main physicochemical parameters of the brine measured during the formation hours of the biggest crystals were significantly different from those prevailing during the formation of other two categories of crystals. Typical values of the measured parameters corresponding to the best quality crystals were: surface electric conductivity （EC） of 215.32 mS/cm and bottom EC of 216.76 mS/cm; surface temperature of 37.16 ℃ and bottom temperature of 37.28 ℃. The worst quality （C） formed at lowest values of EC and temperature with a mean surface and bottom EC of 200.15mS/cm and 196.86mS/cm, respectively; and 32.45 ℃ and 32.75 ℃ surface and bottom temperatures, respectively. Moreover, during the formation of category A crystals the difference between surface and bottom temperature was the lowest and bottom EC was higher than surface EC. 1 gram of category C crystals contained 156.51（13.59 St Dev） particles, while category A samples contained 96.73（7.11 St Dev） particles. The former results should be considered when focusing on the production of Fleur de sel, by adjusting some of the described parameters, such as the brine characteristics according to the weather forecast or on a real time basis.
