The chemistry that helps feed the world

The way we eat has changed profoundly over recent decades. According to the United Nations, more than half of the world’s population now lives in cities, a figure that could rise to around 70 per cent by 2050. At the same time, supply chains have become increasingly long and complex, linking producers, processing centres, transport systems, warehouses and points of sale spread across different regions and countries worldwide.

In this context, ensuring that food reaches consumers safely no longer depends solely on agriculture. It also requires a range of technologies and processes that enable products to be preserved for longer, reducing losses and ensuring their availability.

Why does food spoil?

From the moment it is harvested, processed or prepared, food naturally begins to spoil. In some cases, this spoilage results from the action of bacteria, fungi and other microorganisms. In others, it is caused by natural chemical reactions that alter the colour, flavour, texture or nutritional value of the products.

Oxidation is one of the best-known examples. When certain substances present in food come into contact with oxygen, changes can occur that accelerate the loss of quality. This is what happens, for example, when a cut apple turns brown or when fats and oils develop unpleasant odours and flavours.

Temperature, humidity and exposure to light also influence the rate of these processes. Therefore, preserving food largely involves controlling the chemical and biological reactions that lead to its spoilage. Chemistry enables us to understand these mechanisms and develop strategies to slow them down or halt them.

The tools of food preservation

One such strategy involves acting on oxidation reactions. Antioxidants are molecules capable of reacting with oxidising compounds, halting the chain reactions that degrade fats, pigments and other molecules responsible for the colour, aroma or flavour of food. Among the antioxidants used for this purpose are compounds such as ascorbic acid (vitamin C), ascorbates and tocopherols (vitamin E).

Another approach involves acidity regulators. By controlling the pH of food, they help to make the environment less favourable for the growth of bacteria and fungi and slow down certain spoilage processes.

Chemistry also allows the use of substances that create conditions less favourable to the growth of bacteria, fungi and other microorganisms. These are known as preservatives, which, when used within limits strictly defined by food safety authorities, help to extend the shelf life of certain products.

However, not all solutions involve the addition of substances. The very composition of the atmosphere surrounding food can be altered. Modern packaging, for example, plays an important role here, as it is designed to control factors such as oxygen ingress, moisture loss or exposure to light. In some cases, modified atmospheres are used, replacing some of the oxygen inside the packaging with other gases, such as nitrogen or carbon dioxide, to reduce food spoilage.

Temperature is another key factor. When food is chilled or frozen, the energy available for molecules to participate in chemical reactions decreases. As a result, both degradation reactions and the activity of microorganisms proceed more slowly, extending the shelf life of the products.

Better preservation means less waste

The importance of these processes goes far beyond consumer convenience.

According to the Food and Agriculture Organisation of the United Nations (FAO), around 13 per cent of the world’s food production is lost between harvest and distribution. Meanwhile, the United Nations Environment Programme (UNEP) indicates that, in 2022, around 19 per cent of the food available to consumers was wasted at the retail and consumption stages, including in supermarkets, the catering sector and households.

In addition to the economic and social impact, food waste has significant environmental consequences. The United Nations estimates that food loss and waste account for between 8% and 10% of global greenhouse gas emissions.

By extending the shelf life of food, reducing spoilage and increasing the efficiency of supply chains, chemistry helps to minimise these losses and make more efficient use of the resources required for food production.

Today, millions of people rely daily on food systems that operate on a global scale. Fresh produce crosses continents, processed foods remain in circulation for weeks or months, and cities are continuously supplied by complex logistics networks.

Much of this is only possible thanks to decades of scientific and technological innovation. From the design of more effective packaging to the development of preservation processes, from industrial refrigeration to the control of storage conditions, chemistry continues to play a quiet but essential role in ensuring the availability and safety of food in an increasingly urbanised and interconnected society.