Pyrolysis is a thermo-chemical process that converts the solid biomass into a liquid (biooil/liquid smoke), gas, and solid.
Liquid smokes are usually obtained from the condensation of wood smoke produced by smoldering wood chips or sawdust under limited oxygen. Those raw materials consist of enough cellulose and lignin contents.
The diversity of raw materials and liquid smoke production method result in complex chemical component with various structure, reactivity and sensory activity.
The various phenolic compounds present in liquid smoke lowers the pH and destroys the walls of bacterial cells.
Study found the major proportion of commercial full-strength liquid smoke to be composed of water (11–92%), tar (1–17%), acids (2.8–9.5%), carbonyl containing compounds (2.6–4.6%) and phenol derivatives (0.2–2.9%). However, in the manufacturing of liquid smokes, a variety of ingredients may be used, such as salts, fatty acids, fatty esters and carriers like saccharides.
Partial pyrolysis of lignin produces various types of phenolic compounds. Phenols are obtained from lignin pyrolysis. The quantity and quality of phenol compound that can be found on liquid smoke is related with lignin-content and pyrolysis temperature.
Phenolic compounds have antibacterial properties and can also act as antioxidants by stabilizing free radicals. Liquid smoke provides a specific aroma and better color quality to smoked products.
Carbonyl-containing compounds impart sweet or burnt-sweet aroma and tend to soften the heavy smoky aroma associated with phenolic compounds with some “typical smoke-cured” aroma and flavors. The compound inhibits the growth of bacteria by interfere the use of nutrient of the bacteria in smoked product.
Furthermore, carbonyl-containing compounds are involved in textural changes in smoked food caused by interaction with proteins, and contribute the golden-brown color of smoked products due to reaction with amino acids, and the formation of Maillard reaction products.
Organic acids which have important role in liquid smoke is acetic acid. It can inhibit bacterial growth by penetrating into the cell wall of bacteria and disrupt the normal physiological function of the cells.
Chemical composition in liquid smoke
