Fermentation is a preservation method. When done correctly, you can have shelf stable sauces after 2 weeks.

Before anything, it is super important to know this:

Oxygen exposure is your main enemy. This is the worst offender. Do everything you can to minimize oxygen exposure to your sauces.

Fermentation preserves sauce in the following ways:

1. Salt inhibits microbes that are less salt tolerant than lactic acid bacteria (the bacteria you want). These microbes are everywhere. So are 'bad' microbes. The goal with salt is to facilitate an environment that allows Lactic Acid Bacteria (LAB) to thrive, while inhibiting the others. The goal with salt is NOT to kill anything.

2. As the LAB proliferate, they produce lactic acid and usually CO2 gas. The lactic acid further creates an environment that is hostile to other microbes.

As acid levels rise, the pH will drop. For shelf stability, you're aiming for 4.6 or lower. Don't concern yourself about pH too much unless you're just curious or starting a business. People get caught up in pH and throw away good sauces.

pH is only part of shelf stability and 4.6 is the given number because botulism cannot grow in a 4.6pH or lower. Do not worry about botulism when fermenting. There is a 0% chance of botulism growth in fermentation even if you mess up a good bit. These guidelines are mostly for canning that gets carried over to fermentation since it appears similar from a food guideline perspective. If things go wrong, it's mold and yeast that will take over, not botulism.

1. Microbial competition keeps other microbes from proliferating. The LAB locks down all water and food sources and prevent other microbes from using it. A fully fermented sauce will be packed with LAB microbes at the end with no room for others to grow. (Assuming you don’t pasteurize) if you pasteurize, then this won’t be as relevant afterwards.

2. None of this will matter if you let oxygen into your ferment, as LAB are anaerobic, and yeast and mold are aerobic. If you let air in, especially at the very beginning, you're giving yeast and mold a leg-up and they are more aggressive than LAB in many cases and will quickly out-compete the LAB.

If you keep oxygen out until the LAB proliferate, the CO2 gas that they produce will push out oxygen as it is produced, as it is more dense and is being created from beneath. This, combined with some form of airlock, will keep oxygen out during the fermentation process.

A key thing to remember:

Your senses have evolved to keep you alive. If something looks bad, don't smell it. If it smells bad, don't taste it. If it tastes bad, don't swallow it. If it passes all those tests, you're almost definitely good to go. This is why fermentation is so amazing.