Uncooked peppers and garlic in olive oil fizzled when opened

As a health inspector for over 20 years, I am astounded by the lack of awareness that food safety controls are based on science and not on individual inspectors' personal fears and bad moods. Botulism control is based on some of the following facts: botulinum spores are commonly found in soil and on vegetable surfaces, botulinum grows in low or no oxygen envt., botulism has high virulence. (Virulence is a technical term for the fact that a high number of botulism victims end up dead (like Listeriosus of raw milk fame), in contrast to other food borne illnesses like Staph or Campyllobacter.) When considering the fact that botulinum grows slowly, and food borne illnesses whack people more often with weak immune systems, such as the elderly, the ill, and the very young, the food producer may have just been lucky that the product never created a problem, or the very real option that a problem was never narrowed down to the product.

As to the argument that old time recipes have been made for centuries, as in this case, (I am a bit of a foodie and Italian), the big difference is that many products were never made for mass production and or to stick around on shelves for long periods of time, and if so, any data, let alone food safety data, is unavailable for historic food products. In fact, the link between bacteria and illness was scientifically proven by Koch as late as the late 1800's. Another fact is that the CDC's data shows that outbreaks over the last 50 years are fewer, involve much higher number of victims and are more often associated with mass production and distribution of food. My health dept. receives notices of food recalls at least once a week.

In the case of botulism and fresh garlic in oil, it's considered so risky that acidification is required nationwide. In California, there is a state lab that specializes in evaluating botulism safety for commercial operations. (It's funded by taxes to keep cost to businesses low and is considered a public service.) I would recommend that producers contact their State health depts. and work with them to identify any and all options available for the canning and sale of any low acid food - including acidification, using dried ingredients, temperature control, flash heating (called a "kill step"). The majority of us inspectors truly focus on how to sell food safely and do not approach their jobs as stopping people from making a living. And surprise surprise we don't always think alike, just don't get me started. However, I'll finish with the following consideration of the implication that "life has it's many risks" argument that we inspectors hear often. When it comes to death, the public, the politicians and the members of responsible industry itself does not tolerate "a little death."

I agree that fermentation from bacteria is the most likely explanation. So, to tackle your questions point by point:

1. It is unsafe, as the other posts already mentioned, due to botulism danger. Plant matter without access to oxygen is not shelf stable, unless it has been pickled with sufficient acid.

2. There will be some chemistry going on between garlic and oil, but not much of it. Most of it will be solubility stuff; some reactions will probably happen too, but nothing you will notice. Most important, there will be no oil-garlic explosions.

   The results you are seeing are most likely caused by some microorganism (bacteria or yeast) gorging itself on the sugars in your garlic and burping out some gas, probably CO2. There is nothing strange about the gas building enough pressure to get a bit of oil out. Brewers can tell you that you never stopper a bottle or carboy in which something is undergoing primary fermentation, else your cork blows out or the whole vessel shatters. If you ever popped a champagne bottle, you know how much force you can get in there.

3. The gas from the fermentation could not dissolve in the oil (the way it would had happened with CO2 in a watery medium). It built up pressure against the cork. I suspect that the cork was not perfectly tight, else it'd have shot out. Instead, the foam probably pushed it up a bit until it could flow around it, and got out. The pressure fell, and the remaining oil stayed in the bottle.

As to making yummy oil with garlic safely, TonyArra already told you: you can keep it in the fridge and eat it up within a few days. Don't top it up with new oil! It is perishable just like mayonnaise or milk, but the ugly part about it is that you won't notice anything if there is a lively botulinum colony in there. No off smells, color changes or similar. Most bacteria which live in food don't survive without oxygen (c. botulinum is an exception) and the ones which make food smell bad will not be present even if you have botulinum in your oil.

If you want something which keeps, look into recipes which require pickling or freezing. You won't be able to get a garlic oil with them, but maybe a garlic spread will work for your bread too.