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Brown Lines in Mango – What is It? Safe to Eat?

Discovering brown lines on the flesh of your mangoes can understandably make you question whether it is safe to eat or not.

Especially if you got a big batch of mangoes, it would be such a waste to toss them all out because of these unidentified brown lines. But of course, safety matters first. So, what’s the deal with these strange brown lines on your mangoes?

Brown lines in mango – what is it and is it safe to eat?

What Are the Brown Lines in Mangoes?

Brown lines in mangoes can be caused by three things: first, it can be due to heat damage when mangoes are subjected to a hot water bath to kill fruit flies, causing internal browning. Second, it could be due to extreme cold storage. Third, it could be due to a disease called Resin Canal Discoloration, a darkening of the normally flesh-colored vascular canals of the mango due to bacteria. While it may look unappetizing, in both these cases, the mangoes remain safe to eat.  

Brown Lines in Mango - What is it? Safe to Eat?
Brown Lines in Mango – What is it? Safe to Eat?

What Causes Brown Lines in Mangoes?

In an ideal world, mangoes would always be juicy, succulent, and have a perfect golden yellow hue. However, sometimes, that’s not the case. Mangoes, like other fruits, are also sensitive to storage and handling and can be infected by pests and bacteria.  

If you notice that your mangoes have started to look sinister and have developed brown vein-like lines, three reasons below are the likely culprits.

1. Hot Water Treatment

All mangoes that are imported into the U.S. must undergo a hot water treatment in order to ensure that no foreign pests like fruit flies will unwittingly be let into the country with the mangoes. This step is necessary to protect plant life and animal life in the country. The Animal and Plant Health Inspection Services, or APHIS is responsible for overseeing this process.

All mangoes imported into the U.S. are subjected to hot water treatment to kill pests and fruit flies.
All mangoes imported into the U.S. are subjected to hot water treatment to kill pests and fruit flies.

The Process

The mangoes are brought to a designated facility in the exporting country and are dipped in hot water with temperatures of at least 115°F.  This hot water is also treated with chlorine.

The length of time the mangoes are dipped in the hot water depends on the origin, size and weight, and cultivar of the mangoes. A detailed process can be found here.

After dipping, the mangoes are then allowed to cool in a controlled environment before being transferred to a carefully controlled insect-free facility where they will stay until they are ready to be packed for export and distribution.

The hot water treatment heats up the interior of the mango, the pulp to a certain temperature, and kills any pests that may be lurking in it, allowing it to last longer. It also kills off any larvae or eggs possibly hiding on the surface of the mango which may cause problems later on. 

Why It Can Cause Problems

Though it happens rarely, if the mango is soaked for too long or if the mango is especially delicate, hot water treatments may cause internal damage to the mango which may manifest as the browning of certain parts, including the vascular canals known as resin canals.

The browning may be the result of the disruption of the normal flow of nutrients within the mango due to extreme temperatures and the result of these affected compounds interacting with each other, causing a change in the mango’s color. 

Mangoes that have internal damage may then go bad faster, but for a short period, they are viable and safe to eat. If the browning is not extreme, you may safely eat them, or you may just cut away the discolored parts and proceed to eat your mango as is.

2. Extremely Cold Temperatures

Mangoes are a tropical fruit that dislikes cold temperatures. Storing in extremely cold temperatures can cause damage to the cell walls and the internal nourishment system of the mangoes, causing chemicals to leak out and interact with each other which may lead to browning and other discoloration on the flesh and skin. 

While some cold is necessary for preservation and while it very rarely happens, it is possible, especially when the mangoes are kept in cold conditions for a long period of time.

As with the damage caused by heat, damage caused by extreme cold will also not be a health hazard, so you may just cut away the discolored parts and safely eat your mango as you would.

Subjecting mangoes to too cold or too hot temperatures may cause internal damage to the mangoes and lead to discoloration.
Subjecting mangoes to too cold or too hot temperatures may cause internal damage to the mangoes and lead to discoloration.

3. Resin Canal Discoloration

Lastly, brown lines in mangoes can be caused by a disease called Resin Canal Discoloration.

Resin Canal Discoloration is a condition where red-brown or black vein-like lines appear on the flesh (and sometimes the skin) of affected mangoes, and if it is extreme, it can look like your mangoes are being infested by thin worms, or else look like they’re turning evil. 

It is often readily seen on the flesh of the mangoes, but sometimes you can see them on the skin as well.

What Are Resin Canals?

Resin canals are a network of little tubes in the mango fruit that are thought to be part of its defense system against pests, storing and transporting necessary compounds it might need.

Normally these are the same color as the flesh of the mango so you do not really see them. But if the mango is infected with RCD, it may manifest as brown-black lines that look like little worms. 

Resin canals are usually flesh-colored as the flesh that's why we do not usually see them, until they get infected with RCD.
Resin canals are usually flesh-colored as the flesh that’s why we do not usually see them, until they get infected with RCD.

What Causes Resin Canal Discoloration?

For a while, researchers and growers were baffled because the cause of this ugly disease in mangoes was unknown, but it seemed to happen more often post-harvest and seemed to affect certain cultivars more than others, and happened more as the mangoes ripened. 

A few years ago in Australia, they discovered that the disease was caused by bacteria. This was good news to growers because specific measures can then be undertaken to prevent the spread, and this knowledge provided better opportunities to protect their crops and their sales. Because while affected mangoes are safe to eat, they won’t win points in appetite appeal.

Are Brown Lines in Mangoes Safe to Eat?

Brown lines in mangoes, if caused by any of the things we mentioned above, are safe to eat. It may not be the most appetizing thing in the world, seeing little vein-like things in your mangoes, but it won’t kill you. 

You can opt to cut away the affected parts if it’s just one small part of the mango, or not eat it altogether if it has infested most of the surface of your mango. I certainly would not blame you!

How Do I Know If Mangoes Have Gone Bad

Brown lines in mangoes won’t be harmful to your health but it won’t hurt to check for other signs that the mango is still good to eat before you proceed. 

Below are some signs to watch out for to know if your mangoes are still good to consume.

1. Texture

Fresh, ripe mangoes should be soft but still firm to the touch. If they are too soft and mushy, it means they are overripe. Overripe mangoes may be safe to eat for a while but they may be sweeter than usual and the texture may not be as desirable as they may become too mushy at some point.

2. Smell

Over time, because the sugars in the mango will keep fermenting, they may develop off odors and smells and may even smell alcoholic. If you notice any strange smell on your mango, toss it in the bin.

3. Appearance

Some discoloration is expected from mangoes as they age and depending also on how they are handled and treated, and they may not necessarily make you sick, but if you notice an abundance of dark spots with liquid oozing out or if you see mold or see damaged skin, it’s best to just toss it.

If you are in any way unsure, I say to just err on the side of caution and toss it. Mangoes should juicy, delightful and delectable anyway. If your mango isn’t any of these things, what’s the point of eating one?

You can tell if a mango is rotten by its appearance, smell and texture..
You can tell if a mango is rotten by its appearance, smell and texture..

How to Store Mangoes

Unripe or less than ripe mangoes can be stored at room temperature, in a brown paper bag to allow them to ripen for a few days.

Once ripe, mangoes can be stored in the fridge where they can last for a week or two if kept whole. Once sliced, they will last just a few days as the inside has already been exposed to oxidation. 

Do not refrigerate unripe or less than ripe mangoes. They will not ripen properly in the fridge and you might end up with a less than satisfying, sweet but not quite there batch of mangoes.

If you want to store them for longer, you may peel, cut them into cubes, store them in a freezer bag and freeze them. Storing them in this way makes it easier for you to add them to your smoothies and other recipes.

Frozen mangoes can last indefinitely in the fridge, but for best quality they are best used up within 6 months. Also, do not expect that they will be the same consistency as fresh mangoes when you thaw them, as of course freezing will change their texture.

Are Mangoes Healthy?

Mangoes are rich in vitamin C which promotes immunity and aids other processes in our bodies like cell growth and repair. It contains vitamins and minerals that promote heart health and may help prevent diabetes and certain cancers. 

It contains lots of fiber, which helps with digestive health. It helps reduce inflammation, contains antioxidants, and may help prevent anemia and help strengthen bones.

Mangoes are not just good to eat, but good-for-you, too.

Conclusion to Brown Lines in Mango – What is It? Safe to Eat?

Seeing brown lines in your mangoes can be alarming at first, but as long as there are no other signs of food spoilage, they are usually safe to eat.

Brown lines may be caused by extreme hot and cold temperature changes which can cause internal damage to the mangoes, resulting in browning or darkening of the resin canals. It may also be caused by a condition called Resin Canal Discoloration, a fruit disease caused by bacteria.

No matter the cause, it is important to always inspect and check the food for any off appearances, smells, textures, and odors. This way, you won’t be unnecessarily subjecting yourself to the risk of food poisoning, or the unpleasant experience of eating a bad mango.

Frequently Asked Questions to Brown Lines in Mango

Are Mangoes Infected with Resin Canal Discoloration Safe to Eat?

They are safe to eat provided that there are no other signs of food spoilage. You may cut away the affected parts and consume your mango as is.

Are the Black Veins In Mangoes Safe to Eat?

Black veins in mangoes are likely caused by Resin Canal Discoloration, a condition caused by bacteria in mangoes. If it is this condition, it is safe to eat, though not necessarily appealing.

Author Bio

Daniel Iseli (Head Chef)

Hi, my name is Daniel and I am passionate about cooking. I have been cooking for the past 20 years and am happy to share my best recipes and cooking-related knowledge with you.