[30-Food 视频] 食品储存有妙招 | How to preserve food

When you slice a cake, it is fresh and good to eat. But after a few days food begins to rot and decay. Left in a warm room, exposed to the air, bacteria and mould will begin to multiply and quite quickly, food can become inedible.

Keeping food good enough to eat has been one of the most important skills for human survival. For centuries, most people ate food that was grown locally, and prepared at home. Food did not have far to travel before it was eaten. But people still needed to preserve food to get through the long winter months and make sure they had enough to eat all year round and not just when the food was in season.

Today, we keep our food fresh in a fridge or freezer. In the days before electricity, people had to use many different techniques to keep food edible - like curing, drying or smoking meat, fish or vegetables.

Curing involves adding salts to draw out any moisture in the food. By removing water, the microorganisms that make our food rot are no longer able to multiply and develop. Drying food, even without using salts, is also a way of keeping it for longer - like dried fruit. Smoking helps to preserve food as the smoke prevents the growth of microbes – while giving the food a delicious smoky flavor. Sugar, too, acts as a preservative - and is boiled up with fresh fruit to make jam. Pickling uses vinegar to preserve food. The acid in the vinegar prevents bacteria from growing. The process changes the taste and the texture of the food – like gherkins, which are made from cucumbers.

But for hundreds of years, keeping food safe to eat was a serious problem for anyone far from home. Sailors on long voyages lived on a diet of salt meat and dried biscuits. As a result, many became sick with scurvy, rotten teeth, fatigue and open sores. It wasn't until the late 18th century that it was discovered that giving sailors limes or cabbages to eat, packed with vitamin C, would cure them.

Around the same time, a confectioner and chef in Paris came up with a new way to preserve food. In the early 1800s, Nicolas Appert discovered that sealing food in glass jars, then placing them in boiling water would keep the food good to eat. Legend says that French Emperor Napoleon Bonaparte was always looking for new ways to store food for his marching armies. One thing for sure the Emperor was delighted and rewarded Appert with a prize. This new method was the forerunner of the canning industry.

Preserving food with the old methods is less important today than it was a few hundred years ago: the invention of refrigeration means we can keep food fresh at home. But we still use the techniques of drying, smoking or pickling our food because we enjoy the way it tastes and because it is part of our food culture.