Canning at High Altitudes

January 19, 2025 Grow Organic

Introduction

Canning is not rocket science, but it is NOT the time to give your culinary creativity full rein. Keep it clean, follow the most current directions, and be sure to adjust canning times for your altitude. This article is your guide to high-altitude canning and safe home food preservation.

B is for Botulism, C is for Canning Safely

There. We said it. Botulism. The word that scares so many people away from home canning. According to the USDA, botulism is "an illness caused by eating toxin produced by growth of Clostridium botulinum bacteria in moist, low-acid food." The purpose of careful canning is to destroy such microorganisms in the food and allow you to store and eat it safely.

Some foods are naturally high in acid and can be safely canned using the hot water bath method (e.g., pickles, berries, peaches, salsa, and chutney). High sugar levels in jams and jellies also retard the growth of microorganisms. However, always check the pH of foods like tomatoes and figs as they may require acidification with lemon juice or citric acid to ensure safety. Use litmus paper to measure acidity, and adjust as needed.

High-Altitude Adjustments

Altitude affects boiling temperatures and, consequently, the effectiveness of canning methods. At higher altitudes, water boils at lower temperatures, requiring adjustments to processing times and pressure settings.

Hot Water Bath Canning

For hot water bath canning, increase processing time based on your altitude. Follow these guidelines from Colorado State University:

If the sea level time is less than 20 minutes, add 1 minute per 1,000 feet above sea level.
If the sea level time is more than 20 minutes, add 2 minutes per 1,000 feet.

Pressure Canning

Pressure canning requires increasing the pounds of pressure to achieve 240°F. Refer to the chart below for adjustments based on altitude:

Safe Canning Practices

Follow these safety tips to reduce the risk of botulism and ensure successful canning:

Sterilize: Clean jars, lids, and tools thoroughly before use.
Follow Tested Recipes: Use recipes from trusted sources like the USDA or the National Center for Home Food Preservation.
Monitor Seals: Check jar seals after processing to ensure a proper vacuum.
Discard Suspect Jars: If you suspect spoilage, discard the contents carefully, wearing gloves.

Tools for High-Altitude Canning

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In our video series, Tricia demonstrates how to can grape juice using a steam juicer and shows how to make and can applesauce. Follow her step-by-step tutorials to confidently preserve your harvest.

FAQ About Canning At High Altitudes

Which foods can be safely processed using the water bath canning method?

Botulism is a rare but serious illness caused by toxins produced by the bacterium Clostridium botulinum. These bacteria can grow in moist, low-acid, oxygen-free environments such as improperly canned foods, which is why proper canning methods are essential for safety.

Which foods can be safely processed using the water bath canning method?

High-acid foods such as berries, peaches, pickles, jams, and jellies can usually be safely preserved using water bath canning. Their higher acidity prevents the growth of harmful bacteria during storage.

Why does altitude affect home canning?

At higher elevations, water boils at lower temperatures, which can reduce the heat needed to destroy harmful microorganisms during canning. Because of this, canning guidelines recommend increasing processing time or pressure to ensure food is safely preserved.

When is pressure canning required?

Pressure canning is required for low-acid foods, such as vegetables, meats, and some soups, because it can reach temperatures around 240°F (116°C) that are necessary to destroy dangerous bacteria and spores.

What are some important safety practices for home canning?

Safe canning practices include sterilizing jars and tools, following tested recipes from trusted sources, checking jar seals after processing, and discarding any jars that show signs of spoilage. These steps help prevent contamination and ensure safe food preservation.

More Resources

For additional guidance, explore the National Center for Home Food Preservation or check out Preserving Food at Home, a trusted book for all your canning questions.