Lettuce is a highly perishable food, so it can be tricky to keep it fresh. It is one of those commodities that require extra care during handling and storage. On a large-scale set up, lettuce is often packed in modified atmosphere packaging (MAP) and stored at low temperatures. MAP is a packaging technology wherein the gas composition is modified. Generally, the oxygen level is reduced, while the level of other gases, usually nitrogen and/or carbon dioxide is increased. This is done because oxygen is a factor that affects the shelf life of plant-derived foods. For this reason, MAP is mostly used on fresh or minimally processed foods that are still respiring.
Respiration in fruits and vegetables involves the production of ethylene gas. It is a naturally occurring hydrocarbon in fruits and vegetables that plays an important role in ripening. However, its presence also leads to accelerated senescence in lettuce and other leafy vegetables. Senescence basically refers to deterioration in plant cells. With lettuce, it is apparent when it starts to discolor and wither. But MAP can delay senescence and prevent these undesirable changes from occurring because oxygen is necessary to produce ethylene.
At home, there are 3 simple tips that you can follow keep lettuce fresh for longer. Here they are.
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STORE LETTUCE IN A BREATHABLE CONTAINER
Like most leafy vegetables, lettuce still respire after harvest. So what you need to manage here is oxygen. To do this, simply store lettuce in a breathable container. There are two options for this: a plastic container with holes or a perforated paper bag. The holes will allow air to circulate around the produce. This will prevent moisture from building up that might wilt and spoil the lettuce quickly.
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Storing lettuce in an airtight container or packaging without holes will trap the moisture and make the lettuce damp. There are instances that this is the only way to store lettuce. If you are in this situation with your green, put paper towels between layers of lettuce before closing the lid. This way, the paper towels will absorb the excess moisture and prevent the lettuce from wilting. Just make sure to replace the paper towel every few days to keep it fresh.
KEEP LETTUCE DRY
Minimizing moisture contact is one of the steps in keeping lettuce fresh. So you would want to keep it as dry as possible. While lettuce bought from the market is usually washed and sorted, it is a good practice to wash it and at the same time remove bad leaves. This helps remove dirt and harmful bacteria.
After washing, make sure to remove the excess water. This can be done using a salad spinner or patting it dry using a paper towel. The paper towel can also be placed inside the container along with the lettuce to absorb the remaining moisture. Again, ensure that you replace the paper towel regularly to prevent the growth of bacteria. If you see moisture build up inside the container, wipe it out with a paper towel.
PLACE LETTUCE IN THE CRISPER DRAWER OF THE FRIDGE
The crisper drawer or crisper is the most ideal place in a refrigerator for storing fruits and vegetables. It is because its humidity level and temperature (32ºF to 40ºF) are optimized to keep produce fresh for longer.
To store lettuce in the crisper drawer, place it in a perforated plastic bag or one with a paper tower inside. Be also mindful of the other produce inside the crisper. Some fruits and vegetables such as bananas, apples, and tomatoes produce significant amounts of ethylene gas. While ethylene is beneficial in ripening produce, you would not want it if you wish to keep lettuce fresh. Storing lettuce in close proximity with these ethylene-producing produce will wilt and spoil the lettuce much faster.
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Most crisper drawers have adjustable settings that allow you to easily regulate airflow to and from the bin by sliding a meter between lower and higher humidity levels. The crisper drawer must be set to high humidity. A high humidity setting is ideal for vegetables, especially those that wilts, such as lettuce, asparagus, and other greens.
THE SHELF LIFE OF LETTUCE
Lettuce is a perishable item—it has a short shelf life. The length of time lettuce stays fresh depends on a number of factors, including the type of lettuce, how it was stored, and the temperature and humidity of the surrounding environment.
The 3 tips discussed above should help you maximize its shelf life. When stored properly, lettuce can last anywhere from a few days (7 to 10 days) to a couple of weeks. It is important to note that even with proper storage, lettuce will eventually spoil much quicker. It is critical to look for signs of spoilage, such as wilting, discoloration, unpleasant odor, and a slimy texture. If you observe any of this, it is best to discard the lettuce. This will ensure that you do not fall ill from consuming bad lettuce. According to Centers for Disease Control and Prevention (CDC), leafy greens are a major source of E. coli O157 infections.
If you have kept the lettuce in its original packaging, you can check the expiration date or “enjoy-by” date on the label. In most cases, the lettuce is still fit for consumption (as long as it smells and looks good) after it has passed the expiration date. But it is ideal to consume it before the date to ensure its freshness.
