A street cart runs for hours without a refrigerator while dispensing chutneys from open containers. The composition of those chutneys is what makes the arrangement workable.
Acidity is the main defense
Tamarind, lime and unripe mango push a chutney to a low pH, and most spoilage organisms grow poorly in strongly acidic conditions.
This is why the sour chutney on a cart is genuinely sour rather than mildly tangy. The acidity is doing a job beyond taste, and diluting it weakens both.
Vinegar-based and yogurt-based preparations sit at opposite ends here. One arrives acidic and stays that way, while the other is a dairy product with all the handling that implies.
Sugar and salt reduce available water
A tamarind chutney carries a substantial quantity of jaggery or sugar, which binds water in the same way it does in a preserve.
Salt in the green chutney does similar work at lower concentration, which is part of why an under-salted batch turns before a properly seasoned one.
Together these give a preparation that is thick, concentrated and slow to spoil, which is a different product from a fresh herb sauce blended with water for volume.
Spices contribute more than flavor
Several culinary spices contain compounds with antimicrobial activity, which is one reason heavily spiced cooking developed in hot climates and persisted there.
The effect is real but modest and should not be treated as a substitute for temperature control. A spiced sauce spoils more slowly, not never.
Mustard oil and roasted spice pastes are used the same way in pickles, where the fat layer also seals the surface from air and from contamination by hands.
Turnover does much of the rest
A busy cart empties and refills its containers repeatedly, so nothing sits for long. Volume is a safety mechanism as much as a commercial one.
Vendors also work from small refill containers rather than one large open pot, which limits how much is exposed and how long any portion has been out.
Dispensing with a dedicated ladle rather than a shared spoon matters for the same reason, since cross-contamination between containers is a faster route to trouble than time alone.
Reproducing this at home needs caution
A home cook usually makes a milder, less acidic, less salty version and then stores it exactly as a cart would, which removes the protection while keeping the risk.
Public health guidance on holding foods outside refrigeration is specific and worth following, and a home batch should be treated as a perishable sauce unless it is genuinely a preserve.
Freezing green chutney in small portions is the usual solution, since the herbs darken but the flavor holds and each portion is thawed only when it is needed.