Grapefruit come in a range of colors, from pale yellow to deep pink and red. But are any of them truly orange? The answer depends on how you define “orange.”
The Color Spectrum of Grapefruit
Grapefruit (Citrus x paradisi) are a hybrid fruit, a cross between pomelo (C. maxima) and sweet orange (C. sinensis). They originated in Barbados in the 18th century.
There are several different varieties of grapefruit, which vary in color due to different levels of lycopene and carotenoids. The most common colors are:
- White or pale yellow
- Pink or red
- Ruby red
The paler varieties contain very little of the pigments lycopene and beta-carotene. The pink and red varieties accumulate high levels of lycopene. The deepest red ruby grapefruits also contain beta-carotene.
Lycopene produces shades of pink, red and purple. Beta-carotene produces richer orange and yellow tones. The combination of these two pigments produces the range of grapefruit colors.
Defining Orange
So how do we define “orange”? Orange is a secondary color made by combining red and yellow. It sits between red and yellow on the visible spectrum.
There are no absolute boundaries between orange, red and yellow. Colors flow gradually from one into the next. We can only really define them based on how our eyes perceive them.
In general, colors with more red in them are described as orange. Colors with more yellow are considered yellow-orange or orange-yellow.
There are also different shades of orange. Warm orange tones lean closer to red. Cool orange tones have more yellow.
Comparing Grapefruit and Orange Colors
Now let’s compare grapefruit colors to orange:
- White and pale yellow grapefruit have very little pigment. They are too light and desaturated to be considered orange.
- Pink and red grapefruit contain mostly lycopene pigments. While they may have a hint of orange, the high lycopene content pushes them into the red color spectrum.
- Ruby red grapefruit have both lycopene (red) and beta-carotene (yellow/orange). But the red lycopene tones tend to dominate, making the overall color closer to red.
So while grapefruit span a range of colors, none of them contain quite enough yellow/orange pigment to fully qualify as orange. The concentrations of lycopene make even the redder varieties register as shades of pink and red rather than orange.
Measuring Grapefruit Color Objectively
We can also measure grapefruit color more objectively using colorimetry. This involves recording the wavelengths of light reflected by a sample to produce a spectral power distribution curve.
From this curve, we can calculate chromaticity coordinates on the CIE 1931 color space. The coordinates x and y indicate hue and saturation on the visible spectrum. We can then compare these to the coordinates for red, orange and yellow:
| Fruit | Variety | x | y |
|---|---|---|---|
| Grapefruit | White | 0.351 | 0.378 |
| Grapefruit | Pink | 0.351 | 0.259 |
| Orange | Valencia | 0.488 | 0.453 |
| Red | N/A | 0.710 | 0.290 |
| Yellow | N/A | 0.417 | 0.487 |
Based on their chromaticity coordinates, even pink grapefruit are closer to red than orange on the visible spectrum. While they may appear somewhat orange to our eyes, objectively grapefruit do not reflect enough long (yellow/orange) wavelengths to be classified as orange.
Impact of Ripening on Grapefruit Color
Grapefruit color also changes as the fruit ripens. Green unripe grapefruit gradually accumulate more lycopene and beta-carotene as they ripen.
One study found white Marsh grapefruit had the following color changes during ripening:
| Weeks before harvest | x | y |
|---|---|---|
| 8 | 0.352 | 0.362 |
| 7 | 0.377 | 0.396 |
| 6 | 0.322 | 0.344 |
| 5 | 0.351 | 0.378 |
| 4 | 0.348 | 0.376 |
The grapes shifted slightly more towards the orange and red end of the spectrum. But the change was very small. Even when fully ripe, the measured color remained in the yellow spectrum.
Ruby red and pink varieties would show bigger shifts into the orange-red spectrum during ripening. But their color is still predominantly red rather than orange when ripe.
Factors Affecting Grapefruit Color
Several other factors influence the final color of grapefruit:
- Variety – Ruby reds are the reddest due to high lycopene and beta-carotene. Whites are the palest with low pigments.
- Climate – Cooler night temperatures help grapes accumulate anthocyanins and lycopene, increasing red tones.
- Cultural practices – Water and nutrient stress can impact pigment accumulation.
- Maturity – Fully tree-ripened fruit develop the deepest reds.
- Processing – Heat treatment, storage, and degreening can destroy pigments.
But while these factors may shift grapefruit color from pale yellow to deep pink, none produce a true vibrant orange color.
Examples of True Orange Citrus Fruits
If we wanted examples of true orange citrus fruits, we would have to look at other species:
- Cara cara oranges – A type of navel orange with pink/red flesh.
- Blood oranges – A mutation of sweet oranges producing dark red flesh and juice.
- Calamondin – A small sour orange-like citrus fruit.
These fruits contain a more balanced mix of orange/yellow and red pigments. Their spectral curves and chromaticity coordinates fall cleanly within the orange color space.
Conclusion
While grapefruit come in a range of colors, from pale yellow to vibrant pink and red, technically none of them fully qualify as orange.
White and yellow grapefruit are too light and lacking in pigments to be classified as orange. Meanwhile, the pink and red varieties derive their color mainly from lycopene, placing them closer to red on the color spectrum.
Objective measurement of grapefruit color confirms they reflect little long wavelength orange light compared to medium wavelength yellow and short wavelength red light.
Factors like variety, climate and maturity shift grapefruit color somewhat towards the orange end of the spectrum. But the color generally remains in the yellow to pink/red range.
So while grapefruit may have an orange appearance, scientifically their color is not defined as orange. True orange citrus fruits include varieties like cara cara oranges and blood oranges which have a more balanced orange/red pigment profile.
