The acid ingredients used in salsa help preserve it and prevent botulism poisoning. You must add acid to canned salsas because the ingredients’ natural acidity may not be high enough. Commonly used acids in home canning are vinegar and lemon juice. Lemon juice is more acidic than vinegar, but has less effect on flavor. Use only vinegar that is at least 5% acid and use only bottled lemon juice.
In theory, yes – BUT – there’s no way to test the finished product and confirm that it will heat evenly to ensure safe processing. You’re adding chunky,starchy bits that are likely to make the salsa thicker. Thick product slows down heat transfer. This may mean that the processing time needs to be increased to make sure that it heats all the way through, or it could push it to the point where it would not be recommended for home pressure canning, like pumpkin butter. (It’s safe to can pumpkin chunks, but it is not safe to can pumpkin butter.)
CAUTION: Most salsa recipes contain a mixture of low-acid foods, such as onions and chiles. Acid, such as vinegar or lemon juice, must be added to prevent the bacteria Clostridium botulinum from growing. This bacteria produces a deadly toxin (botulin) that can cause serious damage to the central nervous system or death (botulism) when eaten even in small amounts. These salsa recipes have been tested to ensure that they contain enough acid to be processed safely in a boiling-water canner.
As you will notice when we dive a little further into these recipes, Mexican food has a stunning range of somewhat special ingredients. From Masa Harina, the essential ingredient of corn over a wide array of chilies either fresh, dried or ground to Mexican oregano and tomatillos. Some of these may at first glance seem foreign and difficult to come by, but fear not we’ll discuss the individual ingredients as we go and they’ll be easier to come by than you think.