Smoking.
Hot-smoked salmon is cooked; cold-smoked salmon is raw fish that has been salted, dried and flavoured. The difference decides how each must be handled.
Wood heated with too little air to burn cleanly gives off smoke: a mixture of water vapour, gases, tiny droplets and particles. Its phenols (guaiacol, syringol) bring the smoky flavour and some antimicrobial and antioxidant effect; carbonyls react with proteins on the food's surface to give the brown-gold smoke colour, a Maillard-like browning (VIII.1). Smoke also carries unwanted compounds, including polycyclic aromatic hydrocarbons (PAHs), which form most at high combustion temperatures and in soot; clean, smouldering smoke at moderate temperature and avoiding flare-ups keeps them low.
There are two kinds. Hot smoking, roughly 60–120 °C, smokes and cooks at once: hot-smoked fish, barbecue, Chinese tea-smoked duck (樟茶鸭). Cold smoking, below about 30 °C, flavours and dries without cooking: smoked salmon, many hams and bacons, some cheeses. Smoke alone is a weak preservative; cold-smoked food is safe only because it was cured (XIII.5), dried and kept cold, and Listeria remains its particular hazard. The workshop smokes a salmon fillet.
Below: the centre and surface temperatures of a 25 mm salmon fillet in a smoker at the temperature you choose (thermal bench), with the FDA's hot-smoking target of 62.8 °C held for 30 minutes, and the minutes the centre spends at or above it.
- Explain what smoke deposits on food.
- Distinguish hot and cold smoking.
- Keep unwanted smoke compounds low.
- Handle cold-smoked foods safely.
Hot cooks; cold only flavours
In a 90 °C smoker for two and a half hours, a 25 mm salmon fillet reaches 74 °C at its centre and spends about 46 minutes at or above 62.8 °C in this model, meeting the FDA's target for hot-smoked fish; it is cooked through and flakes. In a 25 °C cold smoke for six hours its centre is 25 °C: raw, salted and flavoured, and safe only because of the cure and the cold chain that follows.
Practical smoking. Use dry hardwood or fruitwood chips, or for Chinese tea smoking a mix of tea leaves, rice and sugar in a foil-lined wok; aim for thin, bluish smoke, not thick white or black smoke, which is bitter and sooty. Dry the surface before smoking (a pellicle forms in a few hours in the fridge) so smoke sticks evenly. Keep cold-smoked foods refrigerated, and the at-risk groups should eat cold-smoked fish only when cooked (XII.4). Leave home cold-smoking of meat and fish to tested recipes with a measured cure.
Tea-smoke something small: line a wok with foil, add two tablespoons each of rice, tea leaves and brown sugar, set a rack above with marinated chicken thighs or tofu, cover tightly, and smoke over medium heat for 10–15 minutes, then rest covered.
Terms
- Hot smoking
- Smoking at about 60–120 °C, which also cooks the food.
- Cold smoking
- Smoking below about 30 °C, flavouring without cooking.
- Pellicle
- A tacky, dried surface layer that takes smoke evenly.
- PAHs
- Polycyclic aromatic hydrocarbons, unwanted compounds formed in hot, sooty combustion.
Sources
- U.S. FDA, Fish and Fishery Products Hazards and Controls Guidance, 4th ed. (2020), ch. 13 and 16: hot-smoked fish held at an internal temperature of 62.8 °C (145 °F) for at least 30 minutes; cold-smoked fish relies on salt, refrigeration and control of Listeria and C. botulinum.
- H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.
- A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.