While most apples have pale white or cream flesh, some varieties display a vibrant red interior. This unique coloration is a natural phenomenon, resulting from a fascinating interplay of plant biochemistry and inherited traits.
The Pigment Behind the Red
The red color observed in the flesh of certain apples comes from naturally occurring compounds called anthocyanins. These water-soluble pigments are a type of flavonoid, a broad class of plant chemicals. Anthocyanins appear red, pink, purple, blue, or black depending on their chemical structure and the pH of their environment; in the acidic conditions typical of apple flesh, they primarily display red hues.
These pigments are widely distributed throughout the plant kingdom. They are responsible for the vibrant colors in many other fruits and vegetables, including blueberries, raspberries, red cabbage, and cherries. Anthocyanins also possess antioxidant properties, contributing to the plant’s natural defenses. Their presence in various plant tissues highlights their role beyond just coloration, though their visual impact is certainly notable.
How Genetics Determine Internal Color
The appearance of anthocyanins in apple flesh is precisely controlled by specific genetic instructions within the apple’s DNA. A particular gene, often referred to as MYB10 or MdMYB1/10/110a, plays a significant role in regulating the production of these pigments throughout the apple, including its internal tissues. While most apple varieties possess this gene, its activity differs considerably between white-fleshed and red-fleshed types.
In typical apples, the MYB10 gene is primarily active in the fruit’s skin, leading to red skin coloration but not in the flesh. However, in red-fleshed varieties, a specific genetic alteration occurs within the promoter region of the MYB10 gene. This alteration involves a duplication of a DNA sequence that normally binds the MYB10 protein, causing the gene to be significantly overexpressed in the flesh. This heightened expression triggers the widespread production and accumulation of anthocyanins throughout the apple’s internal tissues, resulting in the characteristic red flesh.
Notable Red-Fleshed Apple Varieties
Several apple varieties showcase the distinctive red-fleshed characteristic. The ‘Redlove’ series, for instance, includes varieties like ‘Redlove Era’ and ‘Redlove Circe’, known for their entirely red skin and flesh, often with a sweet-tart flavor and notes of berries or cherries.
Another well-known variety is ‘Pink Pearl’, developed in 1944, which features greenish-yellow skin and bright rosy pink flesh. This variety offers a crisp texture and a sweet-tart taste, making it suitable for fresh eating or culinary uses like pink applesauce. ‘Pink Pearl’ is believed to be a descendant of ‘Surprise’, an older red-fleshed apple linked to the ancient Malus niedzwetzkyana species.
The ‘Hidden Rose’, also known as ‘Airlie Red Flesh’, is another example, recognized for its sugary aroma and mild tartness alongside its striking red interior. ‘Baya Marisa’, a more modern German introduction, presents bright red flesh and a good, firm, and juicy texture with a slightly acidic taste. These varieties demonstrate the natural diversity and appeal of apples with this unique internal pigmentation.