What Science say about cold-smoking food safety?

 

What is cold-smoking?

Cold smoking is a traditional flavouring technique in which food is exposed to smoke at low temperatures (typically 15–30°C / 60–85°F) without applying direct heat. Unlike hot smoking (which uses higher temperatures above 50–80°C and actually cooks the food), cold smoking gently infuses smoky aroma while leaving the product uncooked.

A third method, warm smoking (30–60°C), falls in between. At RauchBohne, we exclusively use cold smoking on our freshly roasted coffee beans. This gentle approach allows us to develop rich BBQ-style notes without over-roasting the beans or generating the higher levels of compounds typically associated with hot smoking.

What the science says about smoking food in general, including cold-smoking methods?

While cold smoking (typically at 15–30°C) can introduce trace amounts of polycyclic aromatic hydrocarbons (PAHs) from wood or charcoal smoke, scientific evidence shows that levels remain very low when using controlled conditions: natural hardwoods (e.g., apple, oak), high-quality charcoal, low temperatures, and short smoking durations. These practices significantly reduce PAH formation compared to hot smoking.

Although no direct peer-reviewed studies exist on smoked coffee beans specifically, the principles of PAH mitigation in cold smoking apply well to roasted coffee — a dry, low-moisture product. Our process is designed to stay well within generally accepted safety margins for occasional and daily consumption.

We can summarize the results of our research based on the references listed below as follows:

 

1. Effects of Smoking Temperature, Smoking Time, and Type of Wood Sawdust on Polycyclic Aromatic Hydrocarbon Accumulation Levels in Directly Smoked Pork Sausages (2020)

Key Finding: At low temperatures (55°C, akin to upper cold smoking range), PAH4 levels were <12 μg/kg after 3 hours, well below EU limits; levels rose >3-fold at 95°C. Cold/warm smoking (15–50°C) is recommended to avoid contamination. Among natural hardwoods, apple and walnut sawdust yielded the lowest PAHs (~20–30% less than beech), while oak was comparable to standard beech.

Context: Controlled lab smoking of sausages using seven hardwood types; supports natural wood selection for safe flavor infusion without risk.

Authors: Pöhlmann M, et al.

DOI/Link: [10.1021/acs.jafc.0c04116]

 

2. Effects of Smoke Flavoring Using Different Wood Chips and Barbecuing on the Formation of Polycyclic Aromatic Hydrocarbons and Heterocyclic Aromatic Amines in Salmon Fillets (2020)

Key Finding: Cold smoke flavoring (24°C for 5 min) with natural woods like bourbon-soaked oak, cherry, and hickory increased total PAH8 by only 0.03–0.29 ng/g (to 0.47–0.73 ng/g total), reducing post-barbecue PAHs vs. non-flavored controls (P<0.05). All levels < EU limits; phenolic antioxidants in these woods inhibit PAH formation.

Context: Mimics cold smoking pre-treatment; barbecued samples remained safe, emphasizing low-risk PAH/HAA profiles with select natural woods.

Authors: Oz F, et al.

DOI/Link: [PMC6959562].

 

3.Impact of Smoking Technology on the Quality of Food Products: Absorption of Polycyclic Aromatic Hydrocarbons (PAHs) by Food Products during Smoking (2023)

Key Finding: Cold smoking (15–25°C, 1–14 days) results in lower PAH accumulation than hot methods, with benzo[a]pyrene often <5 μg/kg in compliant setups using hardwood chips (e.g., oak, beech <20% moisture). Hardwoods reduce emissions vs. softwoods; fragmented chips further lower PAHs by 20–50%.

Context: Review of 20+ studies on fish/meats/cheeses; highlights sustainable natural wood use (alder, apple) for minimal health risks in long-duration cold processes.

Authors: Wójciak KM, et al.

DOI/Link: [10.3390/su152416890].

 

4. Effect of Charcoal Type on the Formation of Polycyclic Aromatic Hydrocarbons in Grilled Meats (2021)

Key Finding: White (high-carbonized) charcoal produced the lowest PAHs (e.g., 4 key congeners <50% of extruded types) in grilled meats, especially low-fat cuts; black charcoal was intermediate. Natural charcoal at controlled burns minimizes heavy PAHs.

Context: Standardized grilling (71–75°C internal, proxy for post-cold smoke); supports charcoal-wood combos for reduced contamination in flavor-focused processes.

Authors: Kim S, et al.

DOI/Link: [10.1016/j.foodchem.2020.128748].

 

5. Analysis of Factors that Influence the PAH Profile and Amount in Meat Products Subjected to Thermal Processing (2021)

Key Finding: Low-temperature smoking (<30°C) and short durations with appropriate natural fuels (hardwoods) keep PAHs below regulatory thresholds; barriers/distancing from smoke source or acidic marinades (phenolic-rich) cut levels by 30–70%. High-fat products absorb more, but roasted beans' low moisture aids low uptake.

Context: Meta-analysis of smoking/grilling factors; advocates wood type (e.g., low-resin hardwoods) and process tweaks for negligible risk.

Authors: Wołoszyn J, et al.

DOI/Link: [10.1016/j.tifs.2021.09.011].

Conclusion:

These studies confirm that proper cold smoking—using clean, dry natural hardwoods/charcoal, low temps, and ventilation—poses no significant health risks, as PAH exposure stays far below daily tolerable intakes (e.g., 0.1–4 ng/kg body weight per EFSA).