For millennia, mankind has understood that we can apply heat to raw food materials to make them safe to consume and keep their quality for longer. Cooking is even credited as being key to human evolution, as its discovery (a trick unique to humans) greatly reduced the amount of energy bodies needed to digest and extract nutrients from food, allowing saved energy to be diverted into useful pathways such as those which developed more sophisticated brains.
Later, the use of cooking and other rudimentary food preservation techniques, like fermentation, pickling, and drying, were crucial to the development of civilisation as they allowed cities to emerge whose inhabitants were free to focus on things other than hunting, gathering, and farming.
Heating has remained a key tool for treatment of food, and gradually the reasons for its usefulness have grown. Developments in France in the nineteenth century illustrate this. At the start of that century, Napoleon fostered the development of canning as a means to allow his armies to march across Europe. Later Louis Pasteur unpicked the science of what was causing food spoilage, and how heat helped to eliminate these agents.
We now know that most unprocessed food materials play host to a wide range of micro-organisms, some of which cause spoilage, while others lurk stealthily and cause illness or death. In other cases, food, being mostly of biological origins, is spoiled by the action of enzymes which break down and give foul-smelling or discoloured results.
But heating food to kill bacteria or inactivate enzymes is like hitting it with a blunt hammer – it does the job, but the process is crude and not particularly discriminating. This is because many of the characteristics we appreciate and value in our food, such as its flavour, aroma, colour, and nutritional value, are also susceptible to heat, and we end up trading off safety and stability against perceived quality and appeal. For example, consumers in many countries prefer pasteurised milk which has a two-week shelf-life and needs to be kept in the fridge to ultra high-temperature pasteurized milk which, despite having the apparently massive advantages of sterility plus a six-month shelf-life outside the fridge, simply doesn’t taste as nice.
Food scientists have long sought innovative ways to overcome the good news/bad news nature of heating food. Over a century ago an American scientist called Bert Hite at the West Virginia Agricultural Station found a possible solution, when he showed that subjecting food materials to extremely high pressures could inactivate the undesirable agents therein without use of heat. Figuring out how to apply this discovery on a large scale took most of a century, but today we can find high-pressure-processed meat, shellfish and juice products, and even raw milk (in Australia), which offer consumers the sensation of fresh, raw, or unprocessed foods, but with safety and stability built in not through the blunt force of a hammer, but the precision of a laser or scalpel, dealing with the undesirable while leaving the food’s taste relatively unaffected.
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