“I always wash lettuce to remove germs. That works, right?”–don’t bet your life on it! – Part 3: in the kitchen

In Parts 1 and 2, we discussed what can be done on the farm and at the food store to minimize the risk of illness from contaminated lettuce. This now leads us to the final part, about what we can do in our kitchen.

Up to this point, if everything was done correctly on the farm, throughout distribution, and in the food store, then we should have brought safe lettuce into our kitchen.


When you bring the groceries home, practice the same principles that you used in the food store. Keep the lettuce in a bag or a container so that the lettuce leaves do not become contaminated with another surface. Also, don’t place the lettuce under other foods that could drip onto the lettuce.

Preparing the lettuce

From a food safety perspective, there’s an important difference between romaine and iceberg lettuce. Leaves of iceberg lettuce are tightly bundled, making it difficult for pathogens to contaminate leaves under the surface. On the other hand, romaine leaves are more exposed to the environment, making it easier for particles (like bacteria) to contaminate the food. This fact is one reason that makes romaine lettuce more susceptible to contamination and causing foodborne illness. However, risk can be reduced for both types of lettuce, simply by removing and discarding the outermost layers.

The original question posed in Part 1 was, “I always wash lettuce to remove germs. That works, right?” Unfortunately, it doesn’t.

Bacteria produce a glue-like substance that tightly adheres them to surfaces. From their standpoint, it keeps them close to nutrient sources. However, for us, it means they are extremely difficult to remove. Therefore, simply rinsing lettuce (or any food item) under running water is not going to make the food safe. “But”, you may say, “what about the sanitizing solutions that I’ve heard about?” It’s true. Products are marketed, claiming to reduce bacteria on produce by 99%. However, let’s translate that into practical terms. Suppose there are 1000 cells of E. coli on a head of romaine lettuce. A 99% reduction means 1% of the E. coli are still remaining, meaning you’d be eating 10 cells of infectious E. coli, which is not a safely margin that I’d recommend.

Safely preparing a Caesar salad

Based on epidemiological reports, if anything can go seriously wrong with lettuce, the kitchen is usually where it does.

A term for what goes wrong is ‘cross-contamination‘–that is, contaminating a surface with another surface. For example, rinsing chicken in the sink and then washing lettuce in the same sink, without cleaning and sanitizing the sink between the chicken and lettuce. And by the way, rinsing chicken in the sink does not make it safe; it only increases the chance of spreading pathogens throughout your kitchen!

As we did when shopping, it makes good sense to handle lettuce first and then the raw chicken. In this way, we reduce the chance of contaminating lettuce with raw chicken juices. However, sometimes it is necessary to prepare both at the same time, or the chicken first.

In all situations, be sure to thoroughly wash your hands between preparation of different food items, and after touching a potentially contaminated surface.

When using cutting boards, the safest practice is to use 2 boards–one for cutting the chicken and another board for cutting the lettuce, thus preventing cross-contamination.

If you must to use a single cutting board for preparing both lettuce and chicken, ideally cut the lettuce first. However, if chicken must be cut first, thoroughly wash the cutting board in hot soapy water after cutting up the chicken. Then, soak the cutting board in a chlorine solution (2 teaspoons of bleach per gallon of water) for 2 minutes, rinse with tap water, and air-dry.

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