Effect of hydro-extraction conditions on yields and physicochemical properties of refined sea salt

Crude sea salt (CSS) is traditionally produced from evaporating the seawater in the saltpans where CSS crystalizes. In Cambodia, CSS has been dissolved and recrystallized using brine and by boiling the dissolved compound to produce refined sea salt (RSS). This method requires a long processing time and high energy consumption, and it may lose the chemical characteristics of the CSS, whereas hydro-extraction mainly focuses on mechanical washing without recrystallizing the CSS; therefore, this study employed the hydro-extraction method to investigate the effect of different CSS sizes (raw size, 2<x≤3, 1<x≤2, and x≤1 mm), salt-to-brine ratios (1:1, 1:2, 1:3, and 1:4 w/w), and washing duration (3, 5, 7, and 9 min) on the yields and physicochemical properties of RSS.

In the process, the particle size of the CSS was varied using a grinding and sieving machine. After that, the CSS was washed with different ratios of salt-to-brine and washing durations. The CSS after washing underwent a constant draining and drying process.

It was found that the CSS sizes had no significant effect on the yield, moisture, and whiteness of RSS (p≥0.05). In contrast, the salt-to-brine ratios differed significantly in yield and whiteness, while the moisture was not influenced. In addition, the washing significantly improved whiteness (p<0.05), although it had no effect on the yields of RSS. The optimum conditions (raw CSS size, 1:2 (w/w) salt-to-brine ratio, and 5 min of washing time) obtained RSS with a yield of 92.27±2.64%, a moisture of 4.49±0.7%, and a whiteness of 85.84±0.25. The selected RSS was also detected using Ion Chromatography (IC) to determine its purity and chemical composition, including NaCl (97.47±0.13%), Ca (2.78±0.19%), Mg (1.28±0.06%), K (2.62±0.06%), NH₄ (0.93±0.06%), and SO₄ (2.92±0.42%).

These results indicate that hydro-extraction could improve the whiteness and purity of CSS and reduce impurities, while providing shortened processing times and minimizing yield loss. Consequently, the findings provide invaluable insights for the cost reduction and enhancement of CSS quality for food applications.