Triple washed salad is washed in chlorinated water

The Sunday Teardown · Produce

Nearly every bag of spring mix in an American grocery store has spent part of its short life floating down a channel of water treated with sanitizer, usually chlorine, and the chlorine is there to protect the water more than to clean the leaves. Thousands of pounds of cut greens pass through the same flume every hour, and without a sanitizer held at a measured level, a single contaminated head could seed every clean leaf that followed it downstream.

That makes the chlorine the part of this bag least worth worrying about. The phrase on the front deserves more skepticism, because triple washed has no federal definition, and what actually decides whether the salad is safe and how long it lasts is a sequence of steps the bag never mentions. Cutting a leaf starts a clock, and nearly everything that happens on a fresh-cut line exists to slow it down.

Triple washed means whatever the packer says it means. No federal standard stands behind the phrase. FDA does not require leafy greens to be washed at all, and it does not define triple washed or pre-washed as terms with fixed meanings. In practice the 3 steps are a pre-rinse to remove soil and grit, a sanitizer wash in the flume and a final rinse in potable water. That sequence is industry convention rather than a requirement, and a bag that says triple washed has not been shown to be any safer than one that simply says washed.

The sanitizer is a water specification. As cut leaves move through a shared tank they release sap, sugars and soil, and that organic load begins consuming the chlorine within minutes. If the level runs down unnoticed, the water itself becomes the vehicle that carries contamination from one leaf to the next. The chlorine is doing for the flume roughly what it does for a swimming pool, which is keeping the water from becoming the problem.

Washing removes most of what is on a leaf, and none of what is in it. Commercial washing removes up to about 99% of the organisms on the surface of the leaves, by Consumer Reports' account. The fraction that survives can still make someone sick, and some contamination is not on the surface at all, since bacteria drawn up through the roots from irrigation water can end up inside the leaf tissue, where no wash can reach them.

Washing it again at home can make it worse. FDA's guidance is that pre-washed, ready-to-eat bagged greens can be used without further washing. California's public health department goes further, advising that organisms which survive commercial washing are likely to resist a second wash, and that the cross-contamination risk from a sink, a colander and a pair of hands may outweigh any benefit. The bag came out of a validated process with monitored sanitizer levels, and a kitchen sink did not.

USDA researchers who worked on this question with FDA and the fresh-cut industry identified cross-contamination during washing as the central risk, which is why their number is a floor for the water rather than a dose for the lettuce. The pH column matters as much as the chlorine column, for a reason that has more to do with chemistry than cleanliness, and it is one of several things on the line that the bag never mentions.

That leaves the question the label cannot answer. A product washed this carefully still lasts only about 2 weeks, and the leaves in it were cooled within hours of being cut. The reasons for both are on the line.

Below the line for paid subscribers. I walk the line from the field to the sealed bag, from the vacuum cooler that pulls the heat out of a load of greens in about half an hour to the nitrogen flush that slows the leaves' breathing inside the bag, and I explain why the pH of the wash water decides whether the chlorine works at all. I cover where spring mix grows in each season and why the industry moves south every November, what the organic bag is washed in, and the federal rule that will decide how quickly a contaminated lot can be traced. I also put the bags and the whole heads on the same basis, which shows what you actually pay per ounce to have someone else hold the knife, and I close with what I buy.