fruit and fruit juices together with a high sugar content. The high concentration of sugar helps prevent the growth of microorganisms. Pickles must also be water-bath canned. Using salt, vinegar, and other naturally occurring substances, the pickling process raises the acid level of the pickled food, creating an environment that is unfriendly to harmful microorganisms. Pickling is suitable for a range of vegetables, including cucumbers, peppers, cabbage, and cauliflower, as well as green tomatoes.
Think of all the pies you can make with home-preserved cherries or other tasty fruits. Turning your harvest into pantry staples is simple with water-bath canning.
PRESSURE CANNING
In this method, you also preserve food in glass jars with two-piece lids. Pressure canning must be used for low-acid foods and involves using an appliance called a—what else?—“pressure canner” to achieve a temperature of 240 degrees Fahrenheit, which is substantially higher than the 212 degrees that the water-bath method can achieve and is sufficient to kill both microorganisms and their spores, including botulism, to which low-acid foods are vulnerable. As with water-bath canning, subsequent cooling creates a vacuum seal, which prevents air and microorganisms from entering and causing spoilage. This is the only safe way to can low-acid foods such as vegetables, meats, and seafood because of their susceptibility to botulism.
Corn is one of many vegetables that should be pressure-canned. To can corn, you’ll need to cut it off the cob (individual recipes will explain how to do this).
FOLLOW THE RULES
Be sure to follow the recipes exactly, without adjusting the ingredients, proportions, type of processing, or processing time. For extra guidance, check with your local Cooperative Extension Service or USDA Guides to Home Canning and Preserving.
SPOILAGE: SIMPLE BIOLOGY AND CHEMISTRY
Safe home food preservation is simply a matter of obeying the rules of biology and chemistry. If left to nature, food will spoil, become inedible, and possibly transmit bacteria. This is caused by naturally occurring processes and organisms. Home food preservation involves identifying them and creating environments that stop or retard the processes and destroy the organisms so that the food remains safe to eat. If you’ve looked into home food preservation, you’ve surely heard about food that has spoiled and had to be discarded—or worse, horror stories about food poisoning and botulism. The truth is that some preserved food does spoil; on very rare occasions, this causes serious consequences. That’s why it’s very important to understand the mechanics of food spoilage and to always follow safe food-preservation practices. There is no one more vested in the safety of your food than you are!
Thoroughly washing your produce is one of the most important steps to creating a delcious and healthy product.
HOW ACID AND HEAT WORK TOGETHER IN FOOD PRESERVATION
If you’re around food preservation circles it won’t take long before you hear folks talk about high-acid and low-acid foods. This is a fundamental concept in food preservation because it serves as an index for measuring whether a particular food will provide a friendly or unfriendly environment for the invasion of microorganisms that cause food spoilage. The portion of this discussion that deals with high-acid and low-acid foods applies to canned foods only, not to frozen foods.
Like all creatures, the microorganisms that cause food spoilage are looking for a happy place to live and multiply. Many of them like it warm but not too warm. That’s why we refrigerate our food—to delay spoilage. Some are sensitive to the amount of acid in a food. Most need some oxygen to thrive, which is why we seal the jars that we process. But some, such as the dreaded bacterium that causes botulism, prefer no oxygen. This can make things a bit tricky. Understanding how microorganisms respond to heat, moisture, acid, and air helps us understand which food preservation method will be best for us.
Some recipes will call for blanching vegetables (boiling or steaming and then rapidly cooling them). One of the reasons for blanching is to kill off some harmful microorganisms.
HOT STUFF
First, let’s look at how different microorganisms are affected by heat. See the table “Processing and Storage Temperatures for Food Preservation” for an illustration. There are three things that can cause your food to spoil: enzymes, fungi (molds and yeasts), and bacteria.
