Welcome to the third part of the series! This time, it’s all about ensuring the high quality of canned foods. You’ll learn how to select and prepare products to best maintain color and flavor in canned goods, become acquainted with acidity levels and basic packing processes. Let’s get started!
Food acidity. To decide on the suitable preserving process for your goods, you have to get familiar with the acidity of foods. Low-acid canned foods are not acidic enough to prevent the growth of bacteria, while acid foods contain enough acid to block their growth or destroy them when heated. Acidity may be natural, as in most fruits, or added, as in pickled food. Acidity levels can be increased by adding lemon juice, citric acid, or vinegar. The measure of acidity is pH; the lower its value, the more acidic the food. Foods that have a pH level of 4,6 or higher are considered low-acid. I find this chart useful:
Selecting products for canning. Either you buy from a grocery store, at the farmer’s market, or pick from your own garden, always examine food carefully for freshness and wholesomeness. Food products are mostly at their peak of quality within 6 to 12 hours after harvest, but apricots, nectarines, peaches, pears and plums can be ripened 1 or more days before canning. Keep fresh produce in a cool place, not exposed to direct sunlight. When preparing, discard moldy food, trim small diseased or bruised spots.
Retaining optimum color and flavor. Oxygen and enzymes are the enemy when it comes to looking good. Most fresh foods contain 10 to more than 30% air, and high quality depends on how much of that air is removed before the jar is sealed. Don’t expose prepared foods to air unnecessarily: while preparing a batch, keep peeled, halved, sliced or diced produce in a solution of 3 grams (1 tsp) ascorbic acid to 4 litres of cold water to prevent discoloration.
And now packing processes, or in other words, the methods used for preparing and placing food in a jar prior to sealing.
Raw-packing is the practice of filling jars tightly with freshly prepared, but unheated food. Such produce, especially fruit, will float in the jars, and the entrapped air may cause discoloration. The juice, syrup, or water to be added to the foods should be heated to boiling before adding it to the jars.
Hot-packing is the practice of heating freshly prepared food to boiling, simmering 2 to 5 minutes, and promptly filling jars. This method helps to remove air from food tissues, shrinks food, helps keep the food from floating, increases vacuum in sealed jars, thus improving shelf life. Use this process whenever possible! Within the storage period, both color and flavor of hot-packed foods will be superior to that of raw-packed.
That’s that for the day. In the next part of the series we are filling the jar!