The question of whether liquid smoke, a convenient food flavoring, presents a cancer risk stems from its origin in wood smoke. Liquid smoke is a condensed and purified essence of smoke, used to impart a smoky flavor without the lengthy process of traditional smoking. Since smoke contains harmful compounds, its safety profile is often compared to foods prepared using traditional smoking methods.
The Chemistry of Traditional Smoke and Carcinogens
Traditional smoking, such as for barbecue or cured meats, involves exposing food directly to smoke generated by the incomplete combustion of wood. This process, known as pyrolysis, creates a complex mixture of chemical compounds, some of which are known carcinogens. The primary class of concern is Polycyclic Aromatic Hydrocarbons (PAHs), which form when organic material is burned without sufficient oxygen. Benzo[a]pyrene, a well-studied PAH, is classified as a known human carcinogen by the International Agency for Research on Cancer. During traditional smoking, PAHs are deposited directly onto the food’s surface, establishing the baseline risk associated with ingesting foods treated with raw, unfiltered smoke.
How Liquid Smoke is Produced and Purified
The manufacturing of liquid smoke begins with the controlled thermal degradation of wood, typically hardwood sawdust or chips, in a limited oxygen environment. This process, pyrolysis, generates a dense, hot smoke rich in flavor compounds. Unlike traditional methods, this smoke is captured and passed through a condensation system, where it cools and turns into a liquid. The resulting raw smoke condensate contains flavorful compounds but also undesirable components like tars, resins, and high concentrations of PAHs. The purification process, involving settling, filtration, and fractionation, removes the bulk of these water-insoluble, hazardous compounds, including the majority of PAHs and other impurities. The final product is a refined aqueous solution of phenolic and carbonyl compounds responsible for the smoky flavor and antimicrobial properties.
Current Scientific Consensus on Carcinogenic Risk
The safety of commercial liquid smoke flavorings rests on the efficiency of the purification process, which drastically reduces carcinogenic PAHs compared to traditionally smoked foods. Regulatory bodies worldwide, including the U.S. Food and Drug Administration (FDA), have historically considered these flavorings safe for consumption because PAH levels, such as benzo[a]pyrene, are generally below detectable limits or far lower than those found in directly smoked foods.
However, the European Food Safety Authority (EFSA) recently conducted a comprehensive review of authorized smoke flavorings and found genotoxic compounds in several products. Genotoxicity refers to a substance’s ability to damage genetic material (DNA), which can lead to cancer. The compounds raising concern were not primarily PAHs but substances like furan-2(5H)-one and 1,2-dihydroxybenzene.
Based on a precautionary principle, the EFSA concluded that for six of the eight evaluated flavorings, the presence of these compounds meant a safety concern could not be ruled out at the proposed usage levels. This led to a decision by the European Union not to renew the safety authorization for these specific products, requiring them to be phased out. In contrast, the US and Canada maintain existing regulations permitting the use of liquid smoke flavorings below established contaminant thresholds, highlighting a difference in regulatory interpretation.
Consumption Guidelines and Safety Context
Assessing the risk of liquid smoke requires considering both dosage and overall exposure. Liquid smoke is a potent flavoring agent, meaning consumers use it in very small quantities, often measured in drops or teaspoons. Food safety agencies typically establish an Acceptable Daily Intake (ADI) or a Margin of Safety (MOS) to define the amount that can be consumed daily over a lifetime without appreciable health risk.
The minute quantities of potential carcinogens found in liquid smoke contribute only a fraction to the total dietary exposure an individual receives from other food sources. Studies have shown that a single serving of traditionally smoked food or charbroiled meat can contain significantly higher levels of PAHs than the amount present in multiple teaspoons of liquid smoke flavoring. Therefore, the use of commercial liquid smoke as an occasional flavoring presents a minor contribution to the ingestion of these compounds compared to eating traditionally prepared smoked or grilled foods.