Most salsa recipes for canning contain a mixture of low acid foods, such as onions and chilies paired with a traditional tomato base for balance. Acids like lemon juice or vinegar must be added to prevent Clostridium botulinum bacteria from growing. Botulism is a deadly toxin which can cause serious damage to the central nervous system or even death, even when consumed in small amounts. It is very important to use only recipes that have been tested, to ensure the proper balance of acids in order to process your salsa safely when canning.
It is highly important to follow the directions listed in salsa recipes for canning recipe exactly. Use the same amounts of each vegetable listed in the recipe and use the exact amount of vinegar or lemon juice required. You can safely decrease the amount of spices, but do not use canned salsa recipes that do not follow guidelines set by the Food and Drug Administration. Do not thicken salsa using corn starch or flour prior to canning, it is unsafe and could cause bacteria to grow.
Pressure Canner
Just as important as it is to follow the directions of the recipe, it is also necessary to follow the manufacturer's guidelines when it comes to pre-treating lids and jars. Make sure the jars are hot and clean and do not leave any salsa on the lid, wipe it clean with a damp paper towel and place the lids on the jar and screw on metal bands. When processing salsa using a boiling water canner, make sure to use a rack to keep the jars from touching the bottom of the pot and make sure the water is simmering. Do not pour water over the jars directly, and put a tight-fitting lid on the pot.
If you use a pressure canner for water bath canning salsa, leave the lid uncovered to prevent a pressure buildup and explosion. After the jars of salsa are in place, bring the water back to a rolling boil and follow the recommended processing time. Once time is up, you need to remove the jars without tipping, the salsa could spoil if left in hot water too long, so pay attention to the time, it's very important. Do not touch the lids or rings, put the jars on a cloth or rack and do not use a fan to cool off the jars or re-tighten the bands after processing.
Once you have processed your salsa, you will want to check the lids the next day. Make sure your lid is pressed down in the center and that it does not move when you press on it. Tap the lid with a spoon and make sure you hear a clear, ringing sound, if the jar of salsa is not sealed right, stick it in the fridge and use it up soon. You can also reprocess canned salsa the next day, but when you do it, be sure to heat it up back to boiling before packing, wipe the rims clean and use a new lid.
Wipe your jars clean and label with the contents and date and remove the screw bands in order to avoid rusting. You can then store your jars of salsa in a cool, dark place and for the best taste, eat it up within a year. Heat, frost, freezing temperatures, light and dampness will all affect the quality of your salsa, so put it in a cabinet where it will be safe and stable when stored. Before you open a jar, make sure your lid is not bulging or leaking and that the salsa still has a good color. If it stinks, has molded or foam on it when you open it, throw it out or you risk getting very sick. Salsa is very easy to can at home and once you've done it, you'll never go back to eating store- bought salsa again.