Why Are Apples Red Inside (cause for concern?)

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Apple trees and the apples they produce are incredibly popular, easily being one of the most common fruits consumed worldwide. Imagine being shocked when I discovered one of my apples was red inside. This got me asking the question of do other apples have red flesh. Why are apples red inside? 

The most common reason why apples are red inside is the MYB10 gene. This is a localized genetic protein with an R2R3 transcription factor for anthocyanin pigmentation pathways. This causes a mutation in some apple species to develop a red fleshy interior. 

Other causes for red insides are:

• The oxidation process.
• External environmental actors.
• Other fruits and vegetables.
• Just general deterioration of your apple. 

So are red interiors in your apple bad? And what other colors can the fleshy part of an apple be? Keep reading to find out more!

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Why are apples red inside?

To understand why apples are red inside, I did a deep dive into the scientific literature and journals, got in touch with my local botanical gardens, and even surveyed five plant paladin readers. 

All to ensure you have the most detailed post on why some apples are red inside. 

To summarize: 

• The main reason some apples are red is genetic factors. 
• Certain species, such as Firecrackers, pink pearls, and winter red flesh, have a genetic predisposition that causes them to develop a red interior. 
• Scientifically, the reason for this is the MYB10 gene which causes a genetic mutation in the apple’s genes. 
• This gene, then classified as a localized genetic protein, contains a transcription factor, which dictates the pigment of the skin, insides, and overall color of the apple. 
• As the transcription factor contains an R2R3 transcription factor, this causes certain pieces to develop a red flesh interior. 
• Other significant causes for an apple to develop red insides include environmental factors, stress, disease, rotting and death, and oxidization. 

This is quite a lot of information, so let’s break these down in more detail. 

Staring, of course, with the most common reason – species and genetics! 

Species and genetics 

So, the first significant cause of an apple with red flesh/red insides is just the species of apple. 

Believe it or not, several (quite popular) apple species have genetics predisposing them to develop a red interior. 

This is highly common in species that already have red skin. 

Now at first glance, you might think that these species might be dangerous to eat but rest assured, they taste the same as other apple species. 

Even better yet, the red may contain more antioxidants than the regular white interior apple counterparts. 

What species of apple have red flesh? 

So as mentioned, apples with red flesh/interiors are widespread. 

Still, the following are amongst the most popular sub-species: 

Almata, Firecracker, Geneva, Giant Russian, Hidden rose, Mountain rose, Pink Pearl, Pink Sparkle, Red Flesh, Scarlet Surprise, Thornberry, and Winter Redflesh Appples are all widespread apple sub-species with red flesh/interiors.

Now there are well over 100 apple species with red flesh interiors, so I’ve pulled as comprehensive a list s list as possible here:

Complete list of red-fleshed apples: 

• Airlie Red Flesh/Hidden Rose Apple
• Almata Apple
• Apricot Apple
• Bakran Apple
• Baldwin Red Flesh
• Baya Marisa Apple
• Belle Fleur Krasny Apple
• Blush Rosette Apple
• Breunsdorfer Apple
• Brown’s Apple
• Budavgosky Apple
• Bundy’s Ringwood Red Apple
• Burford’s Red Flesh Apple
• Burgundy Apple
• Christmas Pink Apple
• Clifford Apple
• Devonshire Quarrenden Apple
• Dirleton Red Apple
• Discovery Apple
• Dubbelman Apple
• Eagle Point Star Apple
• Firecracker Apple
• Geneva Apple
• George’s Red Apple
• Giant Russian Apple
• Glowing Heart Apple
• Grenadine Apple
• Hall’s Pink Apple
• Hansen’s Red Flesh Apple
• Harry Baker Apple
• hidden rose
• Kingsbury Priory Apple
• Laura Apple
• Laxton’s Fortune Apple
• Maypole Apple
• Merton Knave Apple
• Merylinn Apple
• Mott’s Pink Apple
• Mountain rose
• Niedzweckyana Apple
• Norfolk Rattlebox Apple
• Peach Melba Apple
• Pendragon Apple
• Pink Beauty Apple
• Pink Bouquet Apple
• Pink Parfait Apple
• Pink Pearl Apple
• Pink Princess Apple
• Pink Sparkle Apple
• Pixirosso Apple
• Pomfital Apple
• Purple Passion Apple
• Purple Wave Apple
• Raven Apple
• Devil Apple
• Red Flesh Apple
• Red Hook Apple
• Red Miller’s Seedling Apple
• Red Moon (Roter Mond) Apple
• Red wonder
• Redfield Apple
• Redford Apple
• Redlove Apple
• Rosette Apple
• Roter Herbstkalvill Apple
• Rubaiyat Apple
• Scarlet Surprise Apple
• Scugog Apple
• Soulardii Apple
• Surprise Apple
• Thornberry Apple
• Totem Apple
• Vampire Apple
• Watermelon Apple
• Webster’s Pinkmeat Apple
• Weirouge Apple
• Winter Redflesh Apple

Let’s break down the ten most common species in a little bit more detail: 

Airlie Red Flesh

The Airlie Red Flesh, or the Hidden Rose Apple, is a unique apple variety with a bright green exterior that hides gorgeous pink or rose-colored flesh.

It was first discovered in Oregon, USA, in the 1960s and is a hybrid of two different apple varieties.

It has become popular recently for its striking appearance and distinctive taste and is used in baking, juicing, and eating fresh. 

The apple has also been praised for its high antioxidant content and potential health benefits.

Almata Apple

So unlike some of the other apples in this list, it’s often argued that the red-fleshed Alamata apple is a crab apple. 

These apples are beautifully round, have sharp red/pink skin, and, most importantly, have a deep red fleshed interior. 

These apples can be commonly found/grown in Oregon. 

Firecracker apples.  

These resemble something of a pink lady; these Firecracker apples have a beautiful bright red fleshy interior. 

Firecracker apples have several uses, including turning them into juice, cider, or for desserts. 

Geneva apples.  

Geneva apples are relatively small, well-kept apples with red and white interior flesh. 

While the red insides will not be as deep as some others on this list, this apple can be used as ornamental food and a vital ingredient in ciders and other drinks. 

Giant Russian

Developed by the soviet union in 1978, this apple is a mix of Antonovka and Jonathan varieties. 

Both the skin and inside of this apple will turn red when ripe. 

Hidden rose

The Hidden Rose apple, also known as the Airlie Red Flesh or the Oregon Red apple, is a unique and rare variety of apples known for its striking pink-red flesh. 

The apple was discovered in the 1960s, growing on a farm in Airlie, Oregon.

It remained relatively unknown for several decades until it started to gain popularity among apple enthusiasts and specialty growers.

The Hidden Rose apple is characterized by its green-yellow skin, often dotted with pink, and its juicy, crisp flesh, a deep pink-red color throughout. 

Mountain rose

The Mountain rose apple is a deciduous tree that can grow up to 30 feet tall. 

It produces small to medium-sized apples that are usually round or slightly oblong. 

The fruit’s skin is typically yellow-green or golden-yellow, and it may have a pink blush on the side exposed to the sun.

Pink pearl apple 

The Pink Pearl apple is a unique variety of apple that is known for its distinctive pink flesh. 

It is believed to have originated in Northern California in the mid-20th century and is a hybrid of the Surprise and Golden Delicious apple varieties.

The Pink Pearl apple is medium-sized and round, slightly flattened. 

The skin is typically yellow-green or light green with a pink blush, but the flesh sets this apple apart. When sliced open, the flesh of the Pink Pearl apple is a deep pink or rose color, which fades to white near the core. 

The flesh is firm, juicy, and sweet, slightly tart flavor.

Pink sparkle apple 

Developed by the University of Saskatchewan and released to the public in 1978, this apple is a scientific wonder. 

A mix of pink pearl and sparkle apples, its pink skin and pink flesh are highly sought out. 

Red flesh. 

Red flesh apples have a distinctive red or pink interior flesh instead of most apple varieties’ typical white or yellow flesh. 

The flesh of these apples can range from light pink to deep crimson and have various flavors, from tart to sweet.

Scarlet Surprise. 

Scarlet Surprise is a type of apple developed in the late 20th century by Cornell University’s apple breeding program.

 It is a cross between two apple varieties called Macoun and Honeygold.

Scarlet Surprise apples are medium-sized and have a conical shape with a slightly flattened base. 

The skin is bright red with greenish-yellow undertones and a waxy texture.

The science behind red-fleshed apples 

So now you know that some apples have red interiors; what science causes this to occur in most species? 

Well, as mentioned, I looked at as many scientific studies and research as possible to get a clear understanding of this, and in a nutshell, it comes down to one crucial word. 

Genetics. 

Like us, apples have billions of genes that impact every aspect of their being. 

Genes to determine how sweet an apple is, genes to determine when it will ripen, and, in the interest of this post, genes that determine the pigment of the skin and interior of the apple.

The pigment itself is better known as something called Anthocyanin. 

The more Anthocyanin found in apples, the higher the chance of an apple developing a red flesh interior. 

When scientists sequenced the DNA of red-fleshed apples, they identified a gene called MYB10. 

This gene controls the amount of Anthocyanin found in apples – directly impacting the color of an apple’s flesh and skin. 

Apples with a higher transcription factor of R2R3 were more likely to have higher anthocyanin levels, leading to apples with red flesh. 

What do the studies say

As mentioned, I didn’t want you to take my findings but reference the studies that found this research.

The breakthrough study has to be from Epsley and Allen, which found a derelict correlation between myb10 and the red flesh color. 

In their experiments: 

• First, they introduced the gene encoding MYB10 into a tobacco leaf and showed that the patch on the leaf where the gene was introduced went red. This meant the MYB10 protein could force tobacco plants to make a lot of anthocyanins. This experiment gave them a quick, clear result, confirming they were on the right track.
• Next, they made a transgenic apple plant that contained an extra copy of the gene encoding MYB10 in every cell. They made sure that every cell produced a lot of MYB10 protein by including a strong promoter in front of the gene. All the tissues of the transgenic plant were red.
• As a final check, they looked at the levels of expression of MYB10 protein in apple flesh. This showed much more MYB10 in red flesh than in white flesh.

Together, these experiments confirmed that MYB10 controlled red coloration in apples, including red flesh color.

Other studies that also found the same results include: 

• Wang et al. – MYB10 genome determined apple skin and flesh color 
• Change et al. – Found the r3r3 MYB transcription factor causes red flesh

Why are my apples red inside – other factors 

So now we have covered the main reason why apples have red interior flesh. What are some of the other reasons that can cause this? 

I’ve broken these down in more detail below: 

Oxidization

When an apple is exposed to air, the enzymes in the apple’s flesh react with oxygen in the air, causing a chemical reaction called oxidation. 

This process results in a brownish/reddish discoloration of the apple’s flesh. 

Limiting the apple’s exposure to air can slow down or prevent this reaction. For example, you can keep cut apples from turning brown by dipping them in an acidic solution, such as lemon juice or vinegar.

How to prevent apple oxidization?

There are several ways to prevent apple oxidation and keep your apples looking fresh:

Cut the apple just before you are ready to eat it. Cutting an apple exposes more of its flesh to air, accelerating oxidation. 

Cutting the apple just before you eat it minimizes the time it is exposed to air.

Dip the cut apple into an acidic solution. Acids such as lemon, lime, or vinegar can help slow oxidation by slowing down the enzymatic reaction that causes the apple to brown. Dip the cut apple slices in the acidic solution for a few seconds, then pat them dry with a paper towel.

Store the apple in airtight containers. Store cut apples in an airtight container or resealable plastic bag. Limiting the apple’s exposure to air can also help slow down oxidation. 

Also, place a damp paper towel over the apple slices before sealing the container to keep them moist.

Keep the apple in a cool place. Store apples in the refrigerator if possible. Oxidation happens faster at higher temperatures, so keeping your apples cool can help slow down the process.

Is it safe to eat oxidized apples?

It is safe to eat oxidized apples. The brownish discoloration when an apple’s flesh is exposed to air is not harmful to human health. It is simply a natural chemical reaction that occurs as the enzymes in the apple’s flesh react with oxygen in the air.

While the brownish color may not look as appetizing, oxidized apples are still safe to eat and retain all their nutritional value. However, the texture and flavor of the apple may be affected by oxidation, so some people may prefer not to eat apples that have turned brown.

Temperature. 

Temperature can also affect the color of an apple’s flesh. 

Apples stored at warmer temperatures may develop a yellowish, brownish, or in severe cases, reddish tint to their flesh, while apples stored at cooler temperatures may retain their whiter color. 

This is because temperature affects the activity of enzymes in the apple’s flesh. Warmer temperatures increase the activity of enzymes that break down the apple’s pigments, causing the color to change. 

Cooler temperatures slow down enzyme activity, which helps to preserve the apple’s color.

Therefore, to prevent discoloration of an apple’s flesh, storing them in cool, dry places and limiting their exposure to air as much as possible is essential.

Stress or damage

Accidental damage or bruising can cause parts of the inside flesh of your apple to turn brown or red. 

This can also cause these apples to age resulting in a bitter taste prematurely. 

Don’t drop your apples; ensure you cut off any brown spots before tasting. 

Pests

Certain pests may indirectly affect the color of the apple’s flesh by causing damage to the skin, which can lead to increased exposure to air and oxidation.

For example, apple grubs, the larvae of a type of fruit fly, tunnel into the flesh of the apple and leave brownish tunnels as they feed.

This can lead to increased exposure of the apple’s flesh to air and oxidation, which may cause a color change.

Similarly, codling moths, another type of fruit pest, can cause brownish streaks and tunnels in the apple’s flesh as they feed.

What are the best red-fleshed apples? 

Airlie red-fleshed apples are the best, commonly known as hidden rose apples. These apples have a deep red color and dark red skin and taste delicious. These red apples also contain plenty of antioxidants, making them an ideal healthy snack. 

Can you eat apples that are red inside? 

You can eat apples with red flesh inside. This is because red flesh apples, while rare, are sub-species of apples bred to have red flesh. Some species include Airlie Red and hidden rose, which have flesh-red insides. 

Red fleshed apples contain higher levels of antioxidants leading to healthier apples overall. 

Can you make juice with apples that are red inside? 

You can make juice, other beverages, and desserts with red fleshed sd apples, as you would for white-fleshed apples. Red fleshed apples may contain more antioxidants due to the color, ensuring your beverage will be significantly healthier. 

How long do red-fleshed apples last?

The shelf life of red-fleshed apples, like any other apple variety, depends on several factors, such as the storage conditions and the ripeness of the fruit at the time of purchase.

If you have purchased red-fleshed apples that are fully ripe and ready to eat, they will generally last 5-7 days at room temperature before starting to soften and lose their flavor. However, storing them in the refrigerator can last for up to 2-3 weeks.

Are red-fleshed apples cause for concern? 

Red-fleshed apples are not a cause for concern in most cases. The red flesh is typically derived from a genetic mutation in the sub-species of the apple. These apples are safe to consume and may contain more antioxidants than their white-fleshed counterparts. 

Why are red apples with pink inside? 

Red apples with a pink inside are typically an apple species bred to contain red or pink flesh. Common species include pink pearl and hidden rose, both of which have red skin with flesh pink/red interiors. 

What other fruits have red interiors?

Several other fruit species also contain a similar gene that creates red interior flesh. 

These include: 

• Blood orange
• Watermelon
• Cherries
• Dragonfruit
• Redcurrants
• Pomegranates

Black flesh in apples

Black flesh is most commonly caused by fungal, bacterial, pest, or general accidental damage to the apple. Should your apple contain black flesh discard it to avoid any potential pathogens from entering your system. 

However, some apple varieties, such as black diamond apples, have a natural dark, deep red flesh that is safe to consume. 

Survey on why apples have red flesh. 

Finally, I asked five plant paladin readers why apples typically have red flesh inside. 

To summarize: 

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