Canning is a common method that has been used for centuries to preserve food. The canning process alters the chemical make-up of food by changing the pH, salinity, or moisture levels to protect against microbes, such as bacteria, mold, and yeast. It limits the activity of food enzymes, which also contribute to decomposition.
These chemical modifications, combined with physical barriers such as cans, seals and lids, are an effective defense against decay. However, the canning process has its limitations. Canning reduces the nutrient value of food. It also requires a significant investment of time and equipment, and inadequate processing or poor sanitation can result in a deadly contamination.
The canning process often requires cooking the food you want to preserve. Cooking stops the natural enzymatic action in fruits and vegetables that helps them to ripen in the first place. If the enzymes are not stopped, or denatured, the food will over-ripen and become spoiled. Cooking raw fruits and vegetables to prepare them for the canning process is often done by blanching-a quick 3- to 5-minute dunk in boiling water. Fruits and vegetables are rich in minerals and water soluble vitamins that leech from the foods during blanching; essentially, leaving much of the benefit of these foods behind in the boiling water bath.
Further losses of nutrients, including fat-soluble vitamins, occur during the heating step of the canning process and throughout their long shelf lives. Canned fruits and vegetables have about 35 percent of the vitamins and minerals their fresh counterparts contain.
Many canned foods contained high levels of sodium. The salt helps preserve the food, but can elevate blood pressure, cause you to retain water and increase calcium loss. Sodium is not always obvious. Even if the label does not indicate "salt" as an ingredient, it is still possible for the product to be high in sodium. Other forms of sodium added to canned foods include monosodium glutamate, sodium citrate, and onion salt.
Canned goods are considered a good option if you are buying fruits or vegetables that are not in season but canned fruits often contain heavy syrups. The added sugar makes the fruits more palatable and more dessert-like. Unfortunately, it also increases the calorie and carbohydrate count of the final product. One way to avoid this is to choose fruits canned in water or in their own juice.
Some fruits and vegetables are less nutritious when canned. According to www.ehow.com, removing the peel of a fruit or vegetable reduces its fibre content. Since this is a common practice in canned foods, you will miss some important nutrients if you choose canned foods over fresh fruits. Vitamin C also is destroyed during the cooking and canning process. Other nutrients, including vitamin A, potassium, and Lycopene survive the canning process well.
Many fruits and vegetables simply do not take well to being canned. Some fruits can be put into cans, but are not very popular because they simply do not taste as good as they do when they are fresh. Finding canned broccoli, bananas, apples, or potatoes is difficult, if not impossible. If you want a variety of fruits and vegetables, fresh or frozen offer more varieties.
Canning requires a good deal of equipment, from glass jars to hold food to the sturdy kettles to heat-seal the goods. Some other special equipment may be required if you are planning to do pressure canning or to preserve meats and fish. The good news is that most of the equipment can be reused, though the upfront costs can be intimidating to a novice. If you are not canning your own produce, you will also have to factor in the cost of fresh food. Do not forget the cost of pickling spices, herbs, sugar, and salt.
Perhaps the biggest disadvantage to canning food is the potential for contamination. Beginners fear creating a shelf full of tainted canned goods. Proper techniques based on the acidity of the fruits and vegetables to be canned must be strictly adhered to in order to prevent contamination from yeast, mold or bacterial spores such as Clostridium botulinum, a soil-dwelling bacterium that creates a neurotoxin-causing botulism that can lead to death. Thorough cleansing of fruits and vegetables to rid them of soil, as well as careful selection of fresh produce, is imperative. Luckily, Clostridium botulinum is susceptible to high salt and acidity levels and can be destroyed when thoroughly heated. This is why conscientious attention to all steps is essential during the canning process.
