How did this salad dressing ferment?

March 20, 2023 9:39 AM

Previously unopened, not expired, shelf-stable salad dressing was fermented when I opened it. How?

Recently opened a bottle of Trader Joe’s roasted sesame salad dressing. It doesn’t need to be refrigerated until it’s been opened and it expires sometime in 2024. It has not been exposed to severe heat or cold since I bought it a couple months ago. I gave it a good shake and opened it, whereupon it fizzed briefly like pressure was being released. I set it on the counter and after a moment it began to foam up and overflow. I set it in a bowl and watched it and over the next 10-15 minutes it probably foamed out about a quarter of the bottle, and had little bubbles in it.

To be clear, this is not a “Can I eat this” question, as I definitely did not. (I took the very tiniest taste and it tasted like the dressing should but with a fizzy feeling on my tongue.) I’m just curious about what conditions would have lead to this unopened non-expired dressing fermenting like this?

posted by skycrashesdown to Food & Drink (4 answers total)

Search terms might include anaerobic fermentation and lactic acid fermentation.
posted by aniola at 9:48 AM on March 20, 2023

I would suspect mishandling during production most likely, or maybe warehousing, or shipping. I am very familiar with that dressing myself and often stock it up in my pantry and have never had this problem even with fairly aged bottles, but looking at the ingredients this stuff would WANT to ferment given half a chance:

ORGANIC HIGH-OLEIC SUNFLOWER OIL, WATER, ORGANIC TOASTED SESAME OIL, ORGANIC BROWN SUGAR (ORGANIC CANE SUGAR, ORGANIC MOLASSES), ORGANIC SOY SAUCE (WATER, ORGANIC SOYBEANS, ORGANIC WHEAT, SALT, ORGANIC ALCOHOL), ORGANIC DISTILLED WHITE VINEGAR, ORGANIC SESAME SEEDS, ORGANIC YEAST EXTRACT, ORGANIC BLACK SESAME SEEDS, ORGANIC DRIED EGG, SEA SALT, XANTHAN GUM.

I would wonder if there was a quality control fail during production that left the bulk dressing at an inappropriate temperature while exposed to air so that fermentation began before bottling. Or the components/procedures that are supposed to suppress fermentation in the bottle weren't correctly applied or suffered some other checklist fail.
posted by Lyn Never at 9:53 AM on March 20, 2023 [2 favorites]

[I suggest reporting it to TJs with whatever batch info can be found on the bottle.]
posted by beagle at 10:39 AM on March 20, 2023 [11 favorites]

I recently returned a Trader Joe's dressing (a different one) that had the plastic seal intact but was secreting a small amount of dressing. The cap had some sort of slight deformation that prevented full 360 degree closure.
posted by dusty potato at 11:50 AM on March 20, 2023 [1 favorite]