By Kim Robson:
The process of preserving fresh foodstuffs without the use of salting or drying began during the first years of the Napoleonic Wars, when the French government offered 12,000 francs in prize money to anyone who could invent a cheap and effective way to preserve large amounts of food. In fact, it was Napoleon himself who famously noted, “An army marches on its stomach.” At that time, due to food availability, military campaigns of the day were limited to the summer and autumn months.
Then Nicolas Appert, a French confectioner and brewer, found that food cooked inside a jar didn’t spoil unless the seal was broken, and developed a method of sealing food in glass jars. Glass jars, however, were hard to transport because of breakage.
Commercial canneries opened for business, and glass jars were gradually replaced with metal canisters (“cans” for short). Cans are cheaper and much more durable than glass jars, which are still popular for some high-end confections and home canning. Interestingly, can openers didn’t appear until thirty years later. Until then, soldiers had to slice open cans with bayonets or smash them open with rocks.
The main forces driving the market for preserved foods were historic and, to some degree still, war and exploration. In 1824, Sir William Edward Parry took canned beef and pea soup with him on his voyage to search for a northwestern passage to India. In 1829, Admiral Sir James Ross took canned food to explore the Arctic, as did Sir John Franklin in his 1845 effort to chart and navigate the Northwest Passage. Early canning methods used lead solder to seal the cans, which may have poisoned the 1845 Franklin expedition.
Because the process of canning initially was slow and labor intensive (each can was handmade, and contents took up to six hours to cook), canned food was too expensive for ordinary people. In fact, during the mid-19th century, canned food, seen as a frivolous novelty, was a status symbol for European middle class households. Urban Victorians demanded inexpensive varieties of quality food that could be kept at home, eliminating the need to go shopping daily.
The Industrial Revolution led to better mechanization of the canning process plus a spike in urban populations across Europe resulted in higher demand for canned food. Inventions and improvements followed, leading to smaller machine made steel cans, and cooking times reduced from six hours to around thirty minutes. Today, most cans are commonly made from tin coated steel.
In a 1997 study, canned fruits and vegetables were found to be as rich in dietary fiber and vitamins as the same fresh or frozen foods, and in some cases the canned products were richer than their fresh or frozen counterparts. The heating process of canning makes dietary fiber more soluble, therefore more easily fermented into gases and physiologically active byproducts during digestion. Canned tomatoes have higher levels of available lycopene.
Canned goods often are high on the list of items stocked during emergencies. Canning supplies sell particularly well in times of recession, when financially stressed individuals are seeking ways to save money and become more independent.
Those with health concerns, though, may want to avoid eating canned vegetables for the following reasons:
Bisphenol A is an ingredient in the epoxy commonly used to coat the inner surface of cans. Though food manufacturers use BPA to protect food from metal corrosion and bacteria, it’s a concern because it is a potential endocrine disruptor and may affect neural development in fetuses.
Canned foods can have high levels of BPA that some find unacceptable. One study found BPA levels in canned foods to be 200 times higher than those the U.S. government regards as safe. BPA also can leach from the liner into food. One random sampling of 50 cans from the U.S. and Canada found detectable BPA levels in 46 of the 50 cans. The highest was found in a can of green beans.
Never, ever purchase a can that is dented or otherwise less than perfect. A dent can damage the liner and contaminate the contents with chemicals.
Salt has been used to preserve food for thousands of years. Some people are on a low salt diet for health reasons; however, the long-held belief that sodium causes high blood pressure, heart attacks or strokes has been officially debunked. Some canned vegetables may have high levels of sodium. Check the labels if you’re concerned about your salt intake.
Sulfites are sulfur based compounds commonly used as food preservatives. Very few people (one percent of the population) are sensitive to sulfites, but those who are can have deadly reactions. A bad reaction manifests as shortness of breath or wheezing in just 15-30 minutes after eating foods with sulfites. Those with sulfite sensitivity should watch for these ingredients on food labels: sulfur dioxide, potassium bisulfite, potassium metabisulfite, or sodium sulfite.
Vegetables in general are always a good choice for healthy eating. It’s generally best to choose fresh or frozen vegetables first, and canned vegetables second.