What is hygroscopy?
Hygroscopy means 'tending to retain moisture'. The word is derived from Greek and means that products that are hygroscopic attract water (from the surrounding air). This can be seen in crisp cookies that become soft and moist, salt and other herbal powders that start to clump, or sweets that become sticky. This is because the water vapour molecules that are in the air surrounding the product are attracted by the hygroscopic material and start to settle in the pores.
What happens with hygroscopy?
Hygroscopy causes salt to clump, biscuits to become soft and moist and confectionery to become sticky. This is because the moisture starts to settle in your product, as described above.
Now you might wonder what this means for your product? The consequences of a hygroscopic reaction on the quality of a product are nil. Apart from the fact that it lumps, becomes soft or feels sticky, the quality of the ingredients remains the same. Your candy will become slightly less tasty in structure but the taste remains the same, the same goes for cookies and other products. Allthough eating a softened cooky is usually no longer very tasty.
The solution against hygroscopy
When you notice that your hygroscopic powder becomes lumpy, this can easily be remedied by simply grinding it again. The lumps go out and the powder reverts to it's original state, without loss of quality.
Finally, a handy tip to prevent lumps from forming. Add something to your hygroscopic powder that attracts even more moisture than your powder does. Rice grains, for example. Rice attracts a lot of moisture. Add a few grains to your pot of salt and the salt will remain dry and loose. It will no longer clump. Replace the grains when they are saturated. If you do not, clumping will occur eventually. Always store a hygroscopic powder in a dry place.