Lately I have stuck to reading more than replying. I must interject here because there are plenty of misconceptions surrounding liquid smoke like the above mentioned.
I have represented companies that manufacture liquid smoke and I know how it is made, how it works, where it applies and why they exist in the first place. I will be brief .....but probably not....
Liquid smoke is made through wood pyrolysis which consist of burning saw dust in a very hot chamber without air. Instead of igniting the wood in flames it releases its essence by smoking. The hard residue left behind is essentially charcoal dust. The smoke is channeled upwards in a stack where fine water mist cloud condenses the smoke. A collection chamber accumulates the liquid. Overtime 3 separation phases appear: heavy tar at the bottom, liquid smoke in the middle and wood wax on top.
Through separation the middle part is isolated and sold as liquid smoke (flavour). The tar and charcoal dust is used as combustible fuel to heat and dry the saw dust before the pyrolysis chamber. The saw dust used is waste created by hardwood furniture manufacturers or the like.
Liquid smoke is composed of essentially 3 functional components: acids, carbonyls and polyphenols.
Acids reacts with the surface (proteins) of meats which creates a skin. Acidified proteins become tough and lose its ability to hold water (like tannin leather).
Carbonyls are highly reactive (sugar-like) compounds. They also react with surface proteins to impart surface colour through the Maillard reaction (surface browning).
Polyphenols impart the distinctive taste of smoked products (acrid).
Liquid smoked is preferred by large smokehouse operations for ease of use and fire insurance purposes (because large scale smoking is a fire hazard). Liquid smoke is applied by direct spraying or dipping the meat as well as using compressed air to create a mist in the smokehouse like traditional smoke would be used.
Health wise: actually liquid smoke is much safer than natural (traditional) smoking because the tar and wood wax is removed. In particular, the wood wax contain a known carcinogenic compound called benzopyrene (see: Benzopyrene - Wikipedia, the free encyclopedia
). Traditional smoking cannot control or take out any of these toxic compounds.
Interested in knowing who makes most of the liquid smoke in the world?:
search for Zest_i_(space) S_mok_e and Red_ar_row_us_a.
They are (probably) the source supplier for any commercial products out there.
If you are interested in knowing how smoke is manufactured in large scales in smokehouses? one way is by rapidly rotating various length round logs and applying a dull scraper on the surface. By pure friction, smoke is generated. The sound is horrendous!!!.