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Food preservation: the story on HearLore | HearLore
Food preservation
In 1806, the French Navy began feeding its sailors meat and fruit preserved in sealed containers, unaware that they were participating in a chemical experiment that would eventually save millions of lives. This process, known as canning, was invented by Nicolas Appert, a French confectioner who discovered that heating food and sealing it in glass jars could prevent spoilage. However, the science behind why this worked remained a mystery for nearly sixty years. It was not until 1864 that Louis Pasteur, a French chemist, finally connected the dots between microorganisms, food spoilage, and illness. Before Pasteur's revelation, Appert's method was a trial-and-error process that relied on heat and sealing to create an environment hostile to invisible invaders. The French Navy's adoption of this technique marked a turning point in history, allowing ships to travel longer distances without the threat of scurvy or food poisoning. Yet, the lack of understanding meant that some batches were dangerously underprocessed, leading to cases of botulism, a severe illness caused by the toxin of Clostridium botulinum. This bacterium, an obligate anaerobe, thrives in the oxygen-free environment of a sealed can, producing a toxin that is undetectable by taste or smell. The tragedy of botulism highlighted the dual nature of preservation: it could save lives, but without proper knowledge, it could also take them.
Ancient Earth And Fire
Long before the invention of the can, ancient civilizations relied on the earth itself to preserve their harvests. In rural Afghanistan, grapes are still stored in kangina, disc-shaped vessels made of mud and straw, which can keep fresh grapes alive for up to six months by passively controlling gas exchange and water loss. In Odisha, India, rice is buried underground to store it for three to six months during the dry season, utilizing the cool, dry conditions of the soil to prevent spoilage. The practice of burial is not limited to grains; in Ireland, butter has been preserved as bog butter in peat bogs for centuries, where the lack of oxygen and cool temperatures create a natural refrigerator. Similarly, century eggs are created by placing eggs in alkaline mud, a process that raises the pH and results in an inorganic fermentation that breaks down complex proteins into simpler, more flavorful ones. These methods, which predate the dawn of agriculture, demonstrate a deep understanding of environmental factors such as light, oxygen, temperature, and pH. In northern US farms, cabbage was traditionally buried during autumn to preserve it, a process that could either keep it crispy or transform it into sauerkraut. The earth, with its ability to act as a desiccant or a freezer, has been a silent partner in human survival for millennia.
The Science Of Salt And Smoke
Common questions
When did the French Navy begin feeding sailors meat and fruit preserved in sealed containers?
The French Navy began feeding its sailors meat and fruit preserved in sealed containers in 1806. This initiative was part of a chemical experiment that eventually saved millions of lives through the development of canning.
Who invented the process of canning and when did Louis Pasteur explain the science behind it?
Nicolas Appert invented the process of canning by discovering that heating food and sealing it in glass jars could prevent spoilage. Louis Pasteur connected the dots between microorganisms and food spoilage in 1864, explaining why Appert's method worked.
How do ancient civilizations like those in rural Afghanistan and Odisha preserve food without modern technology?
Rural Afghanistan uses kangina vessels to store grapes for up to six months by passively controlling gas exchange and water loss. In Odisha, India, rice is buried underground to store it for three to six months during the dry season using the cool, dry conditions of the soil.
What health risks are associated with the process of curing and smoking meat?
The International Agency for Research on Cancer classified processed meat as carcinogenic to humans in 2015. The use of nitrites in curing raises health concerns, and smoking deposits pyrolysis products that act as antimicrobial agents.
How does food irradiation work and does it make food radioactive?
Food irradiation exposes food to ionizing radiation such as beta particles or gamma rays to kill bacteria, molds, and insect pests. Irradiated food does not and cannot become radioactive despite consumer fears.
What role do lactic acid bacteria play in the fermentation of food?
Lactic acid bacteria produce active antimicrobials such as lactic acid, acetic acid, hydrogen peroxide, and peptide bacteriocins. These substances create an environment toxic for other microorganisms and extend the shelf life of food.
Curing, a process that uses salt to draw moisture out of food through osmosis, has been a cornerstone of food preservation since ancient times. By increasing the solute concentration in the food, curing makes the environment inhospitable for microbial growth. Smoking adds another layer of protection, depositing pyrolysis products such as syringol, guaiacol, and catechol onto the food, which act as antimicrobial agents. In 2015, the International Agency for Research on Cancer classified processed meat, which has undergone salting, curing, and smoking, as carcinogenic to humans, revealing a dark side to this ancient practice. The use of nitrites, which contribute a characteristic pink color to cured meats, has also raised health concerns. Despite these risks, curing remains a vital technique, particularly for meats and fish. In the East End of London, jellied eels are a delicacy, prepared by stewing the fish in a covered earthenware jug, a method known as jugging. This process, popular until the middle of the 20th century, involves sealing the animal in a jug with brine or gravy, sometimes adding red wine or the animal's own blood. The combination of salt, smoke, and heat creates a complex flavor profile while ensuring the food remains safe for consumption.
The Cold Revolution
The introduction of commercial and domestic refrigerators in the 20th century drastically improved diets in the Western world, allowing fresh fruits, salads, and dairy products to be stored safely for longer periods. Before mechanical refrigeration, cooling was achieved through root cellars and iceboxes, where rural people often cut their own ice and city dwellers relied on the ice trade. Today, root cellaring remains popular among those who value local food, heirloom crops, and traditional home cooking techniques. Freezing, one of the most commonly used processes, preserves a wide range of foods, including prepared items like potato waffles, which are stored in freezers but would not require freezing in their unprepared state. Cold stores provide large-volume, long-term storage for strategic food stocks held in case of national emergency in many countries. The ability to freeze food has transformed the global food system, enabling the transport of perishable goods across vast distances. However, the energy required for mechanical refrigeration and freezing has a significant environmental impact, prompting a return to traditional methods like root cellaring and burial, which have lower energy inputs and carbon footprints.
The Modern Laboratory
In the 21st century, food preservation has entered the era of high-tech laboratories, where techniques like aseptic processing and irradiation are used to ensure food safety. Aseptic processing involves placing sterilized food into sterilized packaging under sterile conditions, creating a sealed product similar to canned food but with reduced damage to food quality. Irradiation, sometimes called cold pasteurization, exposes food to ionizing radiation, such as beta particles or gamma rays, to kill bacteria, molds, and insect pests. Despite the endorsement of the World Health Organization and the Food and Agriculture Organization, food irradiation remains controversial, with consumers often fearing that the food becomes radioactive. In reality, irradiated food does not and cannot become radioactive. Approximately 500,000 tons of food items are irradiated per year worldwide in over 40 countries, mainly spices and condiments, with an increasing segment of fresh fruit irradiated for fruit fly quarantine. Other modern techniques include pulsed electric field electroporation, which uses brief pulses of a strong electric field to enlarge the pores of cell membranes, killing cells and releasing their contents. These technologies, while effective, raise questions about the balance between safety, quality, and consumer perception.
The Microbial Alliance
Fermentation, a process that involves cultivating specific microorganisms to combat spoilage from other, less benign organisms, has been used for thousands of years to create foods like cheese, wine, and beer. By producing acid or alcohol, these microorganisms create an environment toxic for themselves and other microorganisms, effectively preserving the food. In fermentation pickling, bacteria in the liquid produce organic acids, typically lactic acid, through the presence of lactobacillales, creating fermented pickles such as sauerkraut, kimchi, and surströmming. Biopreservation, a benign ecological approach, uses natural or controlled microbiota or antimicrobials to extend the shelf life of food. Lactic acid bacteria, for example, produce active antimicrobials such as lactic acid, acetic acid, hydrogen peroxide, and peptide bacteriocins. Nisin, a particularly effective preservative, is produced by some lactic acid bacteria and is used in combination with other preservative techniques to control spoilage bacteria and other pathogens. This microbial alliance, once a mystery, is now a cornerstone of modern food science, offering a sustainable and effective way to preserve food without the need for harsh chemicals or high energy inputs.