BBC Inside Science – Wood, Smoke and Science: Cooking over fire – BBC Sounds

At the heart of this exploration is the fundamental triumvirate: wood, smoke, and the overarching science that governs their interaction with food. The choice of wood is far from arbitrary; it is a critical variable in the equation of flavour. Different species of wood, from the robust oak and hickory to the delicate fruitwoods like apple and cherry, possess unique chemical compositions. These differences manifest profoundly during combustion, dictating the aroma, flavour profile, and even the intensity of the smoke produced. Hardwoods, with their denser structure and lower resin content, tend to burn longer and hotter, yielding a cleaner, more complex smoke rich in flavour compounds. Softwoods, conversely, often contain more resins and moisture, producing acrid, bitter smoke undesirable for cooking. The science behind this lies in the pyrolysis of lignin and cellulose – the primary components of wood – which break down under heat to release hundreds of volatile organic compounds. These compounds, unique to each wood type, are the building blocks of the distinctive smoky notes we associate with fire-cooked food.

Smoke itself is a marvel of chemical engineering, a complex aerosol comprising solid particulates, liquid droplets, and various gases. It is generated through incomplete combustion, where the wood doesn’t fully burn, instead smouldering and releasing a rich cocktail of chemical compounds. Among the most significant are phenols, guaiacol, and syringol, which contribute the characteristic smoky, spicy, and clove-like notes. These compounds are highly reactive and readily adhere to the surface of food, permeating its structure and transforming its flavour. The process is a delicate balance: too much smoke, or smoke from poorly combusted wood, can overwhelm and impart unpleasant bitterness, while the right amount delivers depth and complexity. The physical interaction of smoke with food is also crucial; the particulates contribute to the formation of a desirable "bark" or crust, while the volatile compounds infuse the food with their essence.

The broader scientific principles at play extend beyond just wood and smoke. Cooking over fire involves a sophisticated interplay of heat transfer mechanisms: radiation, convection, and conduction. Radiant heat from the glowing embers sears the food, developing flavourful crusts through the Maillard reaction and caramelisation – complex chemical reactions between amino acids and reducing sugars, and the oxidation of sugars, respectively, which create hundreds of new flavour and aroma compounds. Convection, the transfer of heat through the movement of hot air and smoke, cooks the food more evenly, while conduction, where heat is transferred through direct contact with hot surfaces (like a grill grate), contributes to char marks and localized flavour development. Understanding and controlling these mechanisms is paramount to successful fire-based cooking, allowing chefs to achieve specific textures and flavour intensities.

The episode, expertly guided by presenter Marnie Chesterton, also journeyed deep into human history, exploring the profound paleoanthropological significance of cooking over fire. The ability to control fire, first harnessed by early hominids like Homo erectus approximately 1.8 million years ago, represents a monumental leap in human evolution. Cooking made food more digestible, unlocking greater nutritional value from raw ingredients. This increased caloric and nutrient absorption is theorised to have been a crucial factor in the development of larger brains, smaller teeth, and shorter digestive tracts, fundamentally reshaping human anatomy and intelligence. The act of gathering around a fire also fostered social cohesion, providing warmth, protection from predators, and a communal focus for early human groups. Dr. Ceren Kabukcu, an archaeobotanical scientist, illuminated how the study of charred plant remains – such as seeds, nuts, and wood fragments – found at ancient sites allows researchers to reconstruct the diets and culinary practices of our ancestors. These microscopic clues offer invaluable insights into what early humans ate, how they processed their food, and the types of plants they cultivated or gathered, painting a vivid picture of ancient foodways and the evolutionary journey of the human palate.

Bringing this ancient practice into the contemporary culinary landscape was chef Sam Evans of Hangfire BBQ. His expertise provided a practical, real-world demonstration of the refined techniques involved in modern fire cooking. Sam Evans’ approach to barbecue is a testament to the blend of art and science, meticulously controlling variables like wood type, smoke density, and cooking temperature to achieve optimal results. Whether slow-smoking briskets for hours to render fats and break down tough connective tissues, or flash-grilling vegetables to enhance their natural sugars, his methods exemplify how an understanding of chemistry and physics translates into delectable dishes. The challenges of fire cooking – inconsistent heat, the risk of burning, and the delicate balance of smoke infusion – are precisely what make it a craft requiring both intuition and scientific precision.

Dr. Joanna Buckley from the Royal Society of Chemistry further contextualised these discussions, highlighting the broader chemical principles at play in all forms of cooking. Her insights would have underscored the transformations food undergoes at a molecular level, from protein denaturation that tenderises meat, to the emulsification of fats, and the breakdown of complex carbohydrates. The chemistry of fire cooking also touches upon food safety, discussing the formation of both beneficial compounds that contribute flavour and potentially harmful ones (like polycyclic aromatic hydrocarbons, or PAHs) if temperatures are too high or combustion is incomplete. Understanding these chemical processes allows for informed cooking practices that maximise flavour and nutrition while minimising risks.

The live recording at the Abergavenny Food Festival 2025 undoubtedly lent an immersive quality to the broadcast, allowing the audience to engage directly with the sensory experience of cooking over fire while simultaneously absorbing the scientific explanations. The crackle of burning wood, the aroma of smouldering smoke, and the visual spectacle of food transforming over flames provided a multi-sensory backdrop to the intellectual exploration.

This enriching episode of BBC Inside Science was meticulously produced by Tim Dodd and Clare Salisbury, with programme coordination by Jana Bennett-Holesworth and editing by Martin Smith, ensuring a coherent and engaging narrative that seamlessly blended historical perspective, cutting-edge science, and practical culinary artistry. For those eager to delve deeper into the fascinating world of science, bbc.co.uk offers a wealth of content; searching for BBC Inside Science and following links to The Open University provides further opportunities for exploration and learning. This programme stands as a compelling reminder that the simple act of cooking over fire is, in fact, a sophisticated dance of molecules, a journey through human evolution, and an enduring testament to our species’ ingenuity.