Food Preservatives

From the moment you wake up, you are handling chemicals. The salt in your dal, the soap you bathe with, the powder that cleans your school uniform and the spray that keeps insects off the vegetables are all chemicals. Some of them come from nature, like salt from rocks and sea water and sugar from sugarcane. Others are manufactured in factories. Chemicals used for cleaning, food preservatives, pesticides, chemicals used to preserve fruits and vegetables, and chemical fertilizers are some of the chemicals we meet every day.

We can sort the chemicals in a home by the job they do. Some clean our bodies, clothes and dishes. Some kill harmful pests such as rats, cockroaches and the insects that eat our crops. Some are eaten as food, and some keep food from going bad. The five chemicals shown below are found in almost every Nepali home.

Leave a slice of bread in a warm, damp corner for a few days and fuzzy green and black patches appear on it. Leave milk outside the fridge on a hot day and it turns sour. Cooked rice kept overnight in summer becomes sticky and smells bad. In each case the food has decayed. Decay happens because tiny living things, namely bacteria, yeast and mould, settle on the food and grow on it. They feed on the food and change its smell, taste, colour and texture, and some of them make it unsafe to eat. Like all living things, these microbes need water, warmth and air to grow.

Pickle shows how this decay can be stopped. Cut radish or carrot into small pieces and dry them in the sun for a while. Put half of the pieces into a jar just as they are. Mix the other half well with salt and oil, press it down into a second jar, and leave both jars for a week. The plain pieces start to rot and grow mould. The pieces in salt and oil stay firm and fresh. Salt pulls water out of the vegetable and out of any microbe that lands on it, so the microbe cannot grow. Oil coats the pieces and keeps air away from them. Even the sun drying helps, because it removes water. Salt and oil stop food from decaying, so they are called food preservatives.

Preservatives let us store food for a long time. They are used for cereals such as rice and wheat, legumes such as lentils and beans, vegetable products, fruits and vegetables, and animal products like meat, milk and milk products. Without them, a family would have to eat everything soon after it was harvested or bought, and grain from a good season could not be kept for a hard one.

Preservatives are classified into two classes. The class depends on where the preservative comes from and on how much of it can safely go into food.

People have always found ways to keep food. Drying in the sun, keeping food in a cold place, and soaking it in salt or sugar solution are old methods that still work well. In Nepal, green leafy vegetables are fermented and dried to make gundruk, radish is treated the same way to make sinki, meat is dried into sukuti, and fruits are boiled with sugar into jam and syrup. A refrigerator is simply the modern form of a cold place.

Chemicals are also used to keep food, and other chemicals are used to make fruits ripen quickly for the market. Used carelessly or in excess, such chemicals are very harmful to human health and to the environment. So wherever a natural preservative can do the job, it is the better choice.

Food preservatives keep the nutrients of fruits, vegetables, milk, curd, meat and fish from being lost, and they prevent food spoilage. They are of three types:

• Chemical food preservatives
• Natural food preservatives
• Preservatives that induce ripening of fruits, also called artificial ripening agents

Salt and oil are chemicals too, and they control the growth of microscopic germs and organisms. Factory-made foods use other chemicals that do the same job in very small amounts. The chemicals used as food preservatives include:

• Sodium benzoate
• Sorbate
• Sulphur dioxide
• Nitrates and nitrites
• Butylated hydroxyanisole (BHA)
• Butylated hydroxytoluene (BHT)
• Calcium propionate
• Sodium metabisulfite

Next time you pick up a packet of noodles, a bottle of tomato ketchup or a box of fruit juice, read its list of ingredients. You will often find one of these names, or a code number standing for it, near the end of the list. They are permitted only in small, fixed amounts.

We use food every day and buy or harvest it again within short gaps, so a safe, natural way of keeping it matters in every home.

Mugwort, the bitter herb known in Nepal as titepati, is spread among stored grain to keep pests away. Neem oil does the same job in food stores. Lemon concentrate, a thick sour liquid made by boiling down citrus juice and sold as chuk, keeps pickles sour and safe. Traditional natural methods include drying food in the sun, keeping it in cold places or above water, covering it with wood ash, and mixing it with turmeric and oil.

Newer methods are now used in both towns and villages. Pasteurization heats milk to a set temperature for a short time and then cools it quickly, killing most harmful microbes without boiling the milk. Freezing and cold stores keep food so cold that microbes almost stop growing.

Fruits such as mango and banana are picked when they are fully grown but still hard and green. Even after reaching maturity they take a long time to ripen, so chemicals are used to make them ripen sooner.

Ethylene is a gas that ripening fruits give off on their own, and it makes the fruit soften, sweeten and change colour. Ethephon releases ethylene when it is sprayed on fruit. Calcium carbide gives off a gas called acetylene when it meets moisture, and acetylene acts on the fruit in much the same way as ethylene.

Fruit was ripened long before these chemicals existed. Farmers wrapped fruits in a jute sack, packed them with the leaves of the Malabar nut plant, which is called asuro in Nepali, kept a sack of fruit inside a pit and covered it with soil from the top, or bedded the fruit in a thick layer of husk or hay. Each of these traps the fruit's own ethylene and warmth around it, so it ripens faster with nothing added.

Nowadays calcium carbide is used excessively to ripen fruits, because it is an easier and cheaper method. Both the person using it and the person eating the fruit need to be careful.