Five Questions to Test Your Home Food Preservation Knowledge

Questions

1. The bacteria of greatest concern in canning is

1. Salmonella
2. E. Coli
3. Clostridium botulinum
4. All of the above

2. What is the pH that divides low acid from high acid foods?

1. 4.0
2. 4.6
3. 5.0
4. 5.2

3. We blanch vegetables before freezing primarily to

1. Kill bacteria
2. Destroy spores
3. Retain color
4. Inactive enzymes

4. Mold on dehydrated food can result from

1. Case hardening
2. Improper conditioning
3. Incomplete drying
4. All of the above

5. The recommended minimum temperature for home freezer storage is

1. -10°F
2. 0°F
3. 10°F
4. 32°F

Answers

1. C – Clostridium botulinum can survive under adverse conditions as a spore, which is a little survival pod. When the conditions are favorable, as in a jar of improperly canned low acid food, the spore emerges from its pod, begins to grow, and multiply and produce the deadly botulinum toxin. To prevent toxin formation, low acid foods such as vegetables, meats, poultry, seafood, and combination foods must be canned in a pressure canner for a specified amount of time at a specific pressure. Under pressure, a temperature of around 240°F is achieved, thus destroying the spore. Andy Hirneisen, Penn State Extension Educator, provides additional information about this potentially deadly bacteria in his article "Botulism: A Deadly Concern."
2. B – 4.6 is the dividing line between low and high acid foods. Foods with a pH below 4.6 are considered high in acid and can be safely processed in a water bath or atmospheric steam canner. These include most fruits, pickles, sauerkraut, jams, jellies, and other acidified foods. Plain vegetables, meat, poultry, seafood, and combinations of these foods have a pH above 4.6 and must be canned in a pressure canner. Tomatoes are on the borderline and must have acid added to ensure a pH of 4.6 or lower when processing. Check the National Center for Home Food Preservation website for further information.
3. D – Inactivate enzymes or those chemicals in food that cause food to lose color, flavor, and nutrients over time. Blanching does destroy surface bacteria, but it does not destroy spores. Proper blanching is essential for a quality frozen vegetable. For guidelines on blanching foods, see Penn State Extension's Let's Preserve: Freezing Vegetables.
4. D – All of the above.  Case hardening occurs when too high of a temperature (above 140°F) is used when drying food, thus cooking the food. This causes the outside of the food to harden, trapping moisture inside eventually resulting in mold growth. Conditioning is the process used with fruit to evenly distribute the water remaining in the fruit among all the pieces reducing the risk of mold growth. Let's Preserve: Drying Fruits and Vegetables (Dehydration) from Penn State Extension provides step-by-step guidance on dehydrating fruits and vegetables for a safe, quality product.
5. B – 0°F is the minimum temperature to maintain frozen food quality. At temperatures between -10°F and -20°F, food quality will be kept longer. At higher temperatures, food will deteriorate more quickly. Purchase a refrigerator/freezer thermometer for your freezer to monitor the temperature. Penn State Extension's “Refrigerator and Freezer Storage Guidelines" video offers additional tips for food storage.

References

• Andress, E. & Harrison, J. (2014). So Easy to Preserve (6^th ed., reviewed and reprinted 2020). Cooperative Extension, University of Georgia.
• Hirneisen, A. (2024, March 22). "Botulism: A Deadly Concern." Penn State University.
• LaBorde, L.; Zepp, M.; & Hirneisen, A. (2023, April 13). "Let's Preserve: Drying Fruits and Vegetables (Dehydration)". Penn State University.
• LaBorde, L.; Zepp, M.; & Hirneisen, A. (2023, June 8). "Let's Preserve: Freezing Vegetables". Penn State University.
• McDonald, S. (n.d.) "Refrigerator and Freezer Storage Guidelines". Penn State University.