Meats and Sausages
Low-Acid Acidified Foods
A considerable safety margin can be introduced into processing time by acidifying the product. If the low-acid food, for example, a cucumber, is acidified to a pH of 4.6 or less, it crosses the threshold that separates low-acid foods from the high-acid foods. In other words, it becomes a highly acidic food and, as such, it requires less severe thermal treatment to achieve sterility. It can, theoretically, be sterilized in a water bath canner (212° F, 100° C). As the thermal resistance of bacterial spores decreases in an acidic environment, they should not grow in foods with a pH below 4.6. Thermal treatment is needed to kill only spoilage bacteria, molds, yeasts, and enzymes, all of which can be killed at 212° F, 100° C.
Adding citric acid, lactic acid, lemon juice, or vinegar will lower the pH of the product and cooking media. Chicken that was marinated overnight with salt, vinegar, white wine, or lemon juice will acquire some acidity and will be more hostile to any bacterial spores than a fresh chicken. A pH meter is needed to measure acidity levels accurately; the pH color strips are suitable for checking water pH in a fish tank or for general, less critical applications. Meats, poultry, fish, vegetables, and dairy products fall into a pH range of 5.0-6.8. These are low-acid foods, so they must be processed at 240-250° F, 116-121° C, unless they become acidified to such an extent that the pH equilibrium of the finished product is pH 4.6 or lower. Acidified foods do not automatically fall into the high-acid food category; they become low-acid acidified products. As mentioned earlier, acidifying foods and establishing new processing times must be left to properly trained persons, and a homeowner should follow the rules established by USDA guidelines without regard to the extra acidity that he may have introduced.
Acidity
Acidity inhibits Cl.botulinum spores from germinating. Below pH 4.6, they will not germinate; therefore, such acidified, low-acid foods can be processed at much lower temperatures. The conclusion: adding any amount of lemon juice, vinegar, or citric acid will increase the safety factor. If you decide to do that, remember that you are not qualified to change the recipe, so maintain the original pressure, temperature, and processing time.
You will not jeopardize the safety of the recipe if you increase:
- Initial packing temperature.
- Cooking temperature.
- Cooking time. The quality and the texture of the product may be affected, but the safety will only be increased.
- Cutting meat into smaller pieces and adding more liquid will result in faster heat penetration and increased safety.
Adding starch or flour will decrease the safety as they absorb water and solidify during cooking, which slows down heat transfer. After opening, you can thicken the food with starch or flour before serving.
Increasing the amount of fat or oil decreases the safety factor, as fats act as heat insulators. They increase the thermal resistance of bacterial spores by encapsulating them in a thin layer of oil film.
If you mix vegetables and meat, you must process the mixture until both the meat and vegetables are safe to eat.
Being Safe
You may receive a home-made canned product from a friend, and the recipe and processing times may be unknown to you. To be extra safe, remove meat from the container, place it in a pan, add water if needed; be certain the meat is covered with water, and boil for 15 minutes. This will kill any vegetative bacteria and will deactivate the toxin if present.
