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Lettuce Turning Red or Pink: We Explain Why & Are They Bad

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The leaves of lettuce are turning red or pink. You must be worried about the causes of this color change. Besides this, you may think about whether you can eat red or pink lettuce? Let’s find out. 

Lettuce turns its color to red or pink due to mainly two reasons. The first is the exposure to ethylene gas, and the second is the exposure to high temperatures. The other reason it turns red or pink is when it is not getting enough water. It can stay this way until it dies and falls off the plant.

There’s a lot to learn about the topic. Keep reading this article to know more about why lettuce turns pink and can pink lettuce is safe to eat?

Why Does Lettuce Turn Pink

Lettuce turning pink

Oxidation and exposure to ethylene gas is the first reason for lettuce turning pink. Lettuce comes into contact with ethylene gas. This exposure causes the color of lettuce to turn pink. 

The other reason is because of the surface discoloration.

Surface discoloration in leafy vegetables is widely attributed to the oxidation of phenolic compounds to produce quinones, which are then further oxidized to produce colored compounds.

Polyphenols are compounds naturally found in plant foods, such as fruits, vegetables, herbs, spices, tea, dark chocolate, and wine.

The amount and type of polyphenols in foods depend on the food, including its origin, ripeness, and how it was farmed, transported, stored, and prepared.

Lettuce is kept in stores in sealed bags with higher nitrogen and carbon dioxide levels than in the surrounding environment’s air. When the packaging with lettuce is opened, it gets exposed to the environment’s high oxygen levels. 

The greater the flow of oxygen, the greater the oxidation process. Hence, air plays an essential part in turning the color of lettuce to pink. 

Therefore, carelessness in packaging and storage causes the oxidation process to fasten itself and contributes to turning the lettuce to pink color. 

The second reason behind turning lettuce pink is exposure to high-temperature levels. 

High temperature causes lettuce to overmature faster. This contributes to spoiling its green color. Lettuce must always be kept in cooler places. 

If they are kept in warm places, they lose their quality and freshness. Hence, turning it Pink. 

These are the two main reasons that contribute to turning the color of lettuce from green to pink. 

Is Lettuce that Turns Red Bad?

Lettuce is a common food that humans often consume. It is usually green and has a crisp texture. 

This food can grow quickly, so it is eaten either fresh or in salads. Lettuce can be eaten raw or cooked, but some people prefer to cook it because they believe the nutrients will be more available to the body this way.

Turning the lettuce from green to Pink is because of a chemical reaction. It isn’t because of microorganisms, bacteria, fungi, etc.   

Polyphenols are a category of plant compounds that offer various health benefits. Pink rib lettuce is safe to eat because regularly consuming polyphenols are thought to boost digestion and brain health and protect against heart disease, type 2 diabetes, and even certain cancers.

However, as the lettuce matures, even in storage, it will eventually go bad, producing a slimy film with a bad odor.

Lettuce that is past its expiration date, wilted, slimy, or bad-smelling should be tossed, as eating expired foods can make you unwell. 

To make sure that lettuce is safe to eat when it turns pink, check:

– Is the lettuce wilted? If yes,
then it should not be eaten because it has been sitting out for too long and could be contaminated with bacteria.

– Is there any mold on the lettuce?
If yes, then do not consume it, as this shows that fungi are growing.

Similar questions can be asked and you are good to figure out whether it’s fine to eat lettuce or not. 

What Affects the Pink Color In Lettuce

Following are some reasons that contribute to affecting the pink color in lettuce: 


The light affects the pink color of lettuce by making it more intense. The light causes a chemical reaction in the plant that makes it more intense. 

The chlorophyll and carotenoid molecules react to produce the pink color.


Water is one of the main factors that can affect the color of lettuce. If you wash your lettuce with water, it will absorb some of the water and make it a lighter shade. 

On the other hand, if you use vinegar or lemon juice to wash your lettuce, it will make it a darker shade.


Trauma, bruising and harsh handling can trigger the production of phenols. Even at low temperatures within cold storage, lettuce can still produce these color-changing compounds if they are subjected to rough handling.

The handling of lettuce can make a difference in the pink color of the lettuce. The more bruising and tearing, the more likely it will turn brown.

Lettuce is often a part of many dishes and salads because of its fresh flavor, crunchy texture, and a wide variety of colors found in different types. 

However, if you are not careful when handling your lettuce, it may turn brown or lose its fresh taste. This is because when lettuce is bruised or torn, enzymes can come in contact with oxygen, which causes the leaves to turn brown. 

Avoid any unnecessary roughness or sharp movements while handling your fresh produce to prevent this from happening.


The color of lettuce can change as it matures. The leaves will turn a darker green, and the veins may turn red. 

This is because the plant produces a pigment called chlorophyll, green, and carotenoids, which are yellow and then further pink. 

As the plant matures, more carotenoids are produced, and less chlorophyll is produced.

The maturity of lettuce also affects how crunchy it is. Younger leaves are softer and more tender than older leaves, which are more crunchy.


The storage conditions affect the color of the lettuce. 

  • If you store it in a cool and dark place, the leaves will turn a light green color.
  • If you store it at room temperature and light, the leaves will turn a darker green. 
  • If you place it in a warm place, it will start turning to pink color. 

Besides this, storage conditions can also affect the flavor of lettuce.

Does the Lettuce Turn Pink Before or After Harvesting

It is impossible to tell when lettuce turns pink before or after harvesting.

The plant hormone ethylene, which is released by the leaves and stems as they die, brings the color change in lettuce. 

It can happen at any growth stage and does not have to result after or before harvesting. However, one instance where lettuce will turn pink is probably after harvesting. 

This is because processing operations, such as cutting, washing, and trimming, can cause discoloration of lettuce leaves as it is exposed to oxygen. This lettuce is called “pink rib” for its distinct pink discoloration.

Why do Only the Outside Leaves Turn Pink or Brown

The color of leaves may change because of a variety of reasons. One of the most common reasons is the changing level of chlorophyll on the leaves.

Chlorophyll is what gives plants their green color, but as it breaks down, it can make leaves turn brown or red, and other leaves’ colors stay green.

Some outside leaves turn brown or pink, while others remain green because they contain different levels and types of chlorophylls, which break down at different rates.

The outer leaves of the lettuce head will turn brown because they are most exposed to the effects of oxygen. 

As the oxygen gas reacts with the outer leaves, it becomes depleted, and the reaction is less pronounced with the inner parts of the head of lettuce.

However, suppose the lettuce is cut in half, or the leaves are separated. In that case, the likelihood of all the leaves or the inside becoming discolored is significantly increased as the rest of the lettuce is exposed.

Lettuce that Commonly Turns Pink

The most common types of lettuce that turn pink are iceberg and romaine

We often think of iceberg lettuce when we hear “lettuce that commonly turns pink.” This type of lettuce is crisp and crunchy, and its pale green leaves are usually the most affordable in grocery stores. 

However, romaine lettuce can also turn red or pink. Romaine has a more delicate flavor than an iceberg, and it’s also more expensive.

A natural chemical reaction to the plant’s exposure to oxygen and light, called photo-oxidation, causes the color change in the leaves. 

The color change is harmless, but it can be prevented by storing the greens in an airtight container and keeping them away from light.

Why Does Lettuce Turn Brown

The pink discoloration in lettuce turns brown over time as the effects of oxidation increase.

Polyphenol oxidase (PPO), found in most fruit and vegetables, handles the enzymatic browning of fresh horticultural products following bruising, cutting, or other damage to the cell.

Sealed packaging can help prevent the discoloring effects of leafy greens like lettuce and its varieties.

Sealing the lettuce will effectively prevent the atmosphere’s intrusive oxygen from reacting with the phenols within the outer leaves.

One reason lettuce turns brown is that it was exposed to the air. This is because oxygen reacts with the chlorophyll in the leaves and causes them to oxidize. 

Another reason lettuce turns brown is because of an enzyme called polyphenol oxidase, which naturally occurs in all plants. 

The enzyme reacts with phenols and minerals in the plant, causing a chemical reaction that produces a brown pigment called melanin.

The Takeaway

Hence, it can be safely concluded that turning lettuce isn’t harmful. But you should eat pink lettuce as soon as possible; otherwise, it will get spoiled and will not be in the condition to eat. 

Turning lettuce pink is only a chemical reaction that occurs mainly due to two reasons: first, the exposure to ethylene gas, and second, the high temperature.

Other than that, there’s nothing to worry about the pink lettuce. It is safe to eat, provided no mold or sliminess is there in the lettuce.

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