For some reason, people of a certain age love to collect bottles of expired salad dressing. In fact, a recently expired bottle of Trader Joe’s Green Goddess dressing in my own fridge is just one more damning piece of evidence I am slowly morphing into my grandmother, one food item at a time (the package of cheap bologna only confirms it).
But what of those expiration dates? Do they really mean anything, or are they just part of scheme to get us to buy more salad dressing? To answer these burning questions, I contacted Dr. Donald Schaffner, extension specialist in food science and distinguished professor at Rutgers University.
The first thing I wanted to know is how serious those dates on printed on the label are. “I think you are correct in that the numbers are probably conservative in most cases,” Dr. Schaffner said via email. “Remember that the food company wants you to have a positive experience when you consume their product, so they may err on the side of good quality.”
Luckily, quality is something you can taste. If you encounter a bottle of expired dressing in your parents fridge (or even in your own), you can use your senses to make sure the dressing doesn’t smell rancid, and toss anything that doesn’t taste like the salad topping you know and love. “Since salad dressings often have a high fat content, they are prone to oxidation,” explained Schaffner. “Keep in mind that it might not just be a rancid smell, it may have another off-flavor. I still remember tasting an out-of-date salad dressing one time and I could’ve sworn I was tasting cardboard. It turns out that ‘cardboard’ is an actual official descriptor for some off-flavors.”
But that’s flavor. Luckily, when it comes to bacterial growth, formulation is on our side. “Most salad dressings are formulated in a way to resist growth of pathogenic microorganisms,” Schaffner explained, “and in fact would steadily kill any organisms that were present. It’s also rather unlikely that someone could contaminate their own dressing.”
It is, however, still best to throw away any dressing that looks a little…fuzzy. Schaffner confirmed that, “mold formation is a definite possibility. Molds tend to be more hearty than bacteria. Some molds may make toxins, so it’s always a good idea to toss out the food that has mold. With salad dressing, there’s not really a safe way to remove the moldy part and leave the rest, like you might do if you found a small spot of mold on a piece of bread.”
Unopened, expired bottles may still be okay to consume, but it’s impossible to provide a time frame that would apply to every single brand of dressing. “Because all products are different, it’s not possible to specify a specific time,” Schaffner said. “Again, the manufacturer is going to be the most reliable source of information, as they have likely done extensive shelf-life studies on their product to ensure their customers are getting the best quality. It’s also going to depend how that product was held. For example: Was it on a shelf in the sunlight where it could get warm, or was it stored in a cool dark basement? Colder temperatures and less light mean higher retention of quality.”
The best way to know for sure? Give it a sniff and a taste. “If it’s unopened and it’s past its best-by date, I would try tasting a little bit,” Schaffner said. “If it tastes OK, then it’s good to go! Because of the way these products are processed and formulated, I think it’s highly unlikely that you would find any mold upon opening. But depending upon how far past the date and how it’s been handled, it might taste oxidized or otherwise ‘off.’”
So the next time you’re at your parents house, round up their many bottles of sketchy dressing do a little taste-testing. You might find some perfectly good raspberry vinaigrettes in there; you might find some ranches that taste of cardboard. The process won’t be pleasant, but at least you’ll be able to properly identify which ones are suffering from “off-flavor.”
This interview was lightly edited for clarity.