Hydrosol

Herbal distillates, also known as floral waters, hydrosols, hydrolates, herbal waters, and essential waters, are aqueous products of distillation. They are colloidal suspensions of essential oils as well as water-soluble components obtained by steam distillation or hydrodistillation (a variant of steam distillation) from plants/herbs. These herbal distillates have uses as flavorings and cosmetics (skin care).

Herbal distillates are produced in the same or similar manner as essential oils. However, the essential oil will float to the top of the distillate where it is removed, leaving behind the watery distillate. For this reason perhaps the term essential water is more descript. In the past, these essential waters were often considered a byproduct of distillation, but now are considered an important co-product. The produced herbal waters are essentially diluted essential oils at less than 1% concentration (typically 0.01% to 0.04%).cite

Cosmetics and toiletries makers are finding many uses for herbal distillates. Distillates are also used as flavorings and curables.

The science of distillation is based on the fact that different substances vaporize at different temperatures. Unlike other extraction techniques based on solubility of a compound in either water or oil, distillation will separate components regardless of their solubility. The distillate will contain compounds that vaporize at or below the temperature of distillation. The actual chemical components of distillates have not yet been fully identified, but distillates will contain essential oil compounds as well as organic acids and other water-soluble plant components. Compounds with a higher vaporization point will remain behind and will include many of the water-soluble plant pigments and flavonoids.

Because hydrosols are produced at high temperatures and are somewhat acidic, they tend to inhibit bacterial growth but not fungal growth. They are not sterile. They are a fresh product, like milk, and should be kept refrigerated. Small-scale producers of hydrosols must be particularly aware of, and take steps to prevent bacterial contamination.

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Wikipedia