Hydrosols and hydrolates Obtaining, composition, preservation and applications

Essential oils, natural extracts obtained mainly by hydrodistillation or steam distillation, are now well-known consumer products. The same cannot be said of the aqueous fraction recovered. It's called floral water if a flower is distilled, or hydrolat if another part of the plant is used.

However, these extracts are not without interest, and their use has been growing steadily in recent years.

These aqueous solutions, containing low quantities of volatile organic compounds, are the ideal alternative to other natural extracts used in pharmaceuticals, nutraceuticals, cosmetics, perfumery and dietary supplements. In fact, their concentrations of active ingredients of interest are low enough not to have to worry about increasingly stringent regulatory constraints.

Nonetheless, there are still a number of drawbacks to their valorization, chiefly their conservation and the lack of reliable information on their biological properties.

Indeed, these aqueous solutions, which may contain traces of organic residues, are highly susceptible to bacterial and fungal contamination, which greatly limits their shelf life.

Still little studied by the scientific community, very little research has been published on their biological properties, apart from organoleptic ones. The information found in consumer publications is generally extracted from the properties of essential oils from the same plant, or from data based on empirical knowledge.

It therefore seems important to present an overview of what we know about these natural ingredients, in particular their extraction methods, focusing on the most modern ones, their chemical compositions, especially their differences from essential oils, the difficulties involved in preserving them, and their main applications.