In 2012, in the Wonderwerk cave in South Africa, archaeologists discovered traces of ancient cooking fires, including charred bone fragments and plant material, dating back to one million years. This find provided some much-needed evidence to an ongoing debate about when ancient hominids mastered controlled fire, and how cooked food ultimately influenced the evolution of the species. These fires are also the earliest known evidence that ancient humans knew how to improve the digestibility and safety of their food through a proven technique: heating.
As the human species evolved, we learned new and more advanced techniques for food preservation, including freezing, dehydrating, and salting—the remains of large-scale saltworks were found in China dating to 6000 BC. These techniques all kill the bacteria, such as Staphylococcus, Salmonella, Listeria monocytogenes, and Clostridium botulinum, that can lead to food poisoning. In past millennia, food production was the responsibility of individual households, so the techniques developed to preserve food safely had to be accessible and affordable. Families could preserve fish, fats, and vegetables well beyond the short growing seasons typical of seasonal climates and enjoy the security of food year-round.
As civilizations expanded so did trade, bringing with it new challenges. As supply chains developed, the tasks of fishing, baking, and preserving shifted from the home to the market. Specialty vendors, like the fishmonger and the baker, became key stakeholders in an expanding food supply chain. With that change came a loss of confidence in the quality and safety of food. If you couldn't see it being made, could you trust what the baker put in a loaf of bread? In fact, the earliest known food law was passed in England in 1202, when King John proclaimed the Assize of Bread, which prohibited adulteration of bread flour.
Over centuries, those food safety technologies and laws evolved into robust government administrations with precise requirements that dictate the quality and ingredients for thousands of foods. But a law protecting the purity and safety of a food is only as good as the technology to that detects its adulteration.
While food scientists have largely relied on chemistry to ensure food safety, photonics entered the scene in recent decades with an arsenal of new tools. Hyperspectral and multispectral imaging, used originally for Earth observation, soon saw obvious uses in remote sensing for agriculture. These methods were later adapted for food inspection lines on factory floors to quickly identify a stone on a conveyor belt full of walnuts, or bruised apples. New holographic sensors use neural networks to detect bacteria colonies in water samples. Infrared imagers detect drought stress and insect infestations in crops, and ultraviolet lights purify water.
Photonic technologies don't stop with protecting the safety of our food—they're also being used to increase yields and lengthen growing seasons. LED lights are now a mainstay in greenhouses, and are even being used to grow crops in inhospitable places, like the Arctic and the International Space Station. Solar energy is used to power irrigation pumps in remote locations, and lidar is used to map soil erosion in fields.
This issue of Photonics Focus is dedicated to the photonic technologies that keep our food safe and help ensure an agricultural production and distribution system that can feed more than nine billion people. While our techniques have become more sophisticated than those of our ancestors, and our cuisine has diversified, our basic desires have not changed: we want our food to be safe to eat, and we want to know that we'll have enough for tomorrow.
Thanks for reading,
Gwen Weerts, Managing Editor, Photonics Focus
