Читать книгу Canning Essentials - Jackie Callahan Parente - Страница 23

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.