As I’ve mentioned before, my post on not using a water bath for jams and jellies sparked all kinds of discussion, even several years latter. Today, one of my readers commented:
“I know that this post deals with jams and jellies, but I make zucchini relish every year and I don’t use a water bath or pressure cooker for that either. I was on another site that says a person must use a pressure cooker on all veggies. Well, zucchini, bell peppers and onions are all veggies and I haven’t had a problem with them sealing. They have to be simmered for half an hour before the jars are filled. My family loves this relish and even people that hate store bought relish, absolutely love the zucchini relish. Every time I read about veggies having to be pressure cooked, I get a little un-nerved. What’s your take on this? thank you..” – Judi Jones
So, OK, let’s talk about this. The big issue in home canning is botulism, caused by a toxin produced when spores of the bacteria Clostridium botulinum germinate and begin to grow. First, how big a problem is it? The Centers for Disease Control and Prevention (CDC) reports that of the 145 cases in the US each year, only about 15 percent are caused by home-canned foods; that’s about 21 cases. When treated, the mortality rate is 5-10% (meaning two of the 21 die); untreated, it’s more like 40-50%. Car accidents are a much bigger risk, but that doesn’t seem to stop people driving…
Infant botulism — primarily from honey, which is why you don’t feed honey to babies under the age of one year — is the source of most C. botulinum infections. Alaska has a relatively high rate of botulism compared to other states, according to the CDC, which seems to be related to eating traditionally fermented meats or fish, and in one case, fermented seal oil. No details on preservation methods, salt contents, etc. Meats are unquestionably low acid foods, and pressure canning is strongly recommended.
The bacteria C. botulinum is found in soil, which is how it gets onto garden vegetables. The bacteria itself is relatively fragile and killed by heat, and the toxin is neutralized by heat. However, the bacteria can also produce spores, which lie dormant until conditions are right and then produce toxin as they grow. Good growing conditions are a warm, moist, low-oxygen environment, just the sort of thing found in home-canned foods. However, acid (a pH of 4.6 or less) and salt prevent growth. Most vegetables and meats are low in acid; tomatoes are considered an exception, but some of the more modern low-acid varieties may not have a high enough pH to make the grade.
What about spices, as one reader commented? Spices are known to have antibacterial effects (which is why they’ve been used for food preservation for thousands of years), but the only research I could find related to C. botulinum indicated bay leaf was the only common spice that inhibited the bacteria. Mustard seed, which is often added to zucchini relish, has no effect, nor do other common ingredients like celery seed, turmeric or nutmeg.
Canning instructions for zucchini relish vary considerably; waterbath instructions run from five to 20 minutes. I spent a good bit of time searching and didn’t find any sources that recommended pressure canning. When I make fermented zucchini relish and pickles, I refrigerate them after the first week but don’t can them. They’re still good at least a year later, and nobody’s gotten sick from eating them.
Judi notes that she’s making zucchini relish. She didn’t share the recipe, but most of the zucchini relish recipes I’ve seen use vinegar and salt. I make a fermented version (fermented foods produce acid), to which I add salt. She also cooks the relish for 30 minutes before she puts it in the hot, sterilized jars.
So, what’s the bottom line? I suspect (mind you, I’m not an expert, this is based on my research and common sense) that Judi’s relish is safe due to its salt and vinegar content plus the fact that she cooks it 30 minutes and puts it in hot sterilized jars. Her experience supports that suspicion. Obviously, my own experience with fermented zucchini relish (and similar foods like pickles) has been positive. The wide variability of processing instructions (and many zucchini relish recipes don’t have instructions about either water bath canning or pressure canning) indicates that there are plenty of people out there who just cook and seal in hot jars. If it were a major problem, I would expect the CDC investigations would have turned up zucchini relish as a botulism cause; so far, canned asparagus is the home-preserved food at the top on the list, but that’s only a few cases.
Can I say there’s absolutely no risk? Nope, and I’m not going to. This is one of those situations where every food preserver is going to have to make up his or her mind.