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5 min
27/01/2026
Once you ferment in, you can’t ferment out, and that is what is happening to your jar of achar! The ingredients facilitated by the hot sun (there is a reason why achar basks in the sun after being made) create a microbiome for a certain kind of good bacteria to thrive. The fermentation magic is the work of these pesky little pests, which are actually good for you and also live inside your body.
Long before achar was under the said microscope, grandmothers knew what they were doing. Achar-making is one of the many things they are good at, and its signature sourness comes from the fermentation by the bacterial culture under the good old hot sun. That signature sourness isn’t just about taste; it’s a sign that fermentation is working. Whether it’s mangoes, limes, or chillies, the acidity in achar builds and shifts over time, depending on a couple of factors. So, what happens as time passes?
It all starts with the salt added. The salt in achar draws out water from the vegetables or fruits, creating a brine where the beneficial lactic acid bacteria (or lactobacillales) thrive. These newborn bacteria multiply and consume the natural sugars in the ingredients and produce lactic acid, which lowers the pH of the achar and creates that signature sour taste. But there’s a risk here, the bacteria might multiply out of hand. However, spices like mustard, fennel, coriander, cumin seeds, and methi (fenugreek) help control unwanted bacteria.
The rate at which achar becomes sour depends on factors like temperature, salt concentration, and microbial activity. Warmer temperatures and optimal salt levels accelerate the growth of beneficial bacteria (a reason why achar is made in late winter), leading to faster acid production. If you are a beginner, it’s vital that you stick to the exact measurements given in the recipe to avoid mishaps. The acidity might increase rapidly in the first few days, in some cases, then stabilise as the fermentation process slows down. Microbes can be moody that way.
After the initial surge in acidity, the rate of acid production slows as the fermentable sugars are consumed. This plateau phase is when the achar's flavour stabilises, and further acid production becomes minimal. The combination of salt, spices, and oil creates an environment that maintains this balance, ensuring the achar remains flavourful and safe to consume over time.
Over extended periods, achar may experience slight changes in acidity. This can be due to factors like the breakdown of acids and the slowing of microbial activity. However, these changes are typically minimal, and the achar retains its characteristic sourness. The combination of ingredients and proper storage helps maintain the achar's flavour profile over time.
Even after the main fermentation phase, residual lactic acid bacteria continue to influence the achar's acidity. These bacteria can slowly metabolise the remaining sugars, producing small amounts of acid that help maintain the achar's tangy flavour and prevent spoilage. Another reason why your achar pieces tend to get softer over time and lose their wholeness. Their ongoing activity, though minimal, plays a crucial role in preserving the achar's quality during storage.
After a particular point of fermentation, to increase the shelf life of your beloved pickle, it can be refrigerated. Once achar is subjected to refrigeration, acidity changes become more gradual. The cold temperatures slow down microbial activity, helping to maintain the achar's flavour and acidity. However, subtle changes can still occur over time, influenced by factors such as salt composition and storage conditions. Proper storage ensures the achar remains sour and safe to eat for an extended period.
As achar matures, the acidity in it helps preserve flavour by preventing spoilage, and the flavours mature, making it taste amazing, just like how a sip of a full-bodied red wine might make you feel. Though achar lasts as long as the oil in it, which could be anything between several months to a little more than a year. Too much acid or long storage can weaken the vegetable cell walls, leading to a softer, less crisp texture and mushiness that disintegrates into the achar masala. Though tasty, it's not too fulfilling.
Acidity in achar is the very thing that preserves, protects, and defines the pickle. From the quick drop in pH right after brining to later stages as the fermentation breaks down the ingredients, every phase plays a role in getting you the best pot of pickles. While traditional recipes already get a lot right, knowing what’s happening behind the scenes helps you make the most of achar-making.
