Sweet potatoes come in a range of colors, from orange and yellow to white and purple. The most commonly found sweet potato is orange-fleshed, but white-fleshed sweet potatoes are gaining popularity as well. So what makes a sweet potato white? The answer lies in the genetics and biochemistry of the sweet potato plant.
The Genetics Behind White Sweet Potatoes
Sweet potatoes (Ipomoea batatas) produce storage roots that vary widely in flesh color, from cream and yellow to orange and even purple. The predominant pigments that give sweet potato flesh its color are carotenoids – plant pigments that range from yellow and orange to red. The most abundant carotenoid in orange sweet potatoes is beta-carotene, the same pigment that gives carrots their vibrant color.
White-fleshed sweet potatoes, on the other hand, lack or have very low levels of carotenoids. So what accounts for this difference? It comes down to genetics. The genes responsible for carotenoid production and accumulation are essentially “turned off” or expressed at very low levels in white varieties. There are a few key genes involved:
- Phytoene synthase (PSY) – a key enzyme in the carotenoid biosynthesis pathway
- Lycope ne cyclase (LCY) – converts lycopene into beta-carotene
- Beta-carotene hydroxylase (BCH) – converts beta-carotene into zeaxanthin
Varieties with mutations in these genes disrupt carotenoid production at different points in the pathway. Disrupting PSY reduces total carotenoid levels, while disrupting LCY and BCH impacts specific carotenoids like beta-carotene and zeaxanthin.
Breeders have selected for sweet potato varieties with reduced carotenoid levels to create cream, white, and yellow-fleshed varieties. So white sweet potatoes lack carotenoids simply because of genetic differences that minimize pigment production.
Other Factors Influencing Flesh Color
Genetics aren’t the whole story when it comes to sweet potato flesh color. Environmental factors and post-harvest handling can also impact pigmentation:
- Growing conditions – Longer daylight exposure, higher temperatures, and drier conditions encourage carotenoid development.
- Storage conditions – Cool, dark storage helps preserve carotenoids.
- Cooking methods – Boiling and canning destroy more carotenoids compared to roasting, baking, or microwaving.
While these factors can deepen or reduce intensity of orange color, they won’t make an inherently white-fleshed variety suddenly become orange. The genetic basis for color is the overriding factor.
Nutritional Differences
Besides color, are there any nutritional differences between white and orange sweet potatoes? In a nutshell – yes. Here’s a comparison:
| Nutrient | White Flesh | Orange Flesh |
|---|---|---|
| Beta-carotene | Very low | Very high |
| Vitamin A | Low | High |
| Vitamin C | Moderate | High |
| Potassium | High | High |
| Fiber | Moderate | High |
Orange sweet potatoes are richer in vitamins A and C, thanks to their carotenoid content. They also contain more fiber. White sweet potatoes are not devoid of nutritional value, but they don’t offer the same micronutrient boost as their orange counterparts.
Taste and Texture
Color aside, white and orange sweet potatoes differ slightly in taste and texture too. Here’s an overview:
Taste
- White: Mildly sweet with a subtle chestnut flavor
- Orange: Robust sweetness with hints of spice
Texture
- White: Fluffy, drier, and starchier
- Orange: Dense, creamier, and moist
These descriptions are subjective, but the consensus is that white sweet potatoes tend to be less sweet and have a drier texture when cooked. You’ll also often see white varieties labelled as “dry” or “firm” sweet potatoes.
Popular White Varieties
Some commonly available white-fleshed sweet potato varieties include:
- Japanese – Shorter, squat shape with thin white skin and drier flesh
- O’Henry – Moderately sweet flavor and creamy texture
- Muraski – Sweet, dense flesh perfect for baking
- Bonita – Cream-colored skin and flesh with a creamy mild taste
New white-fleshed varieties are constantly being developed. Some aim to enhance nutrients like antioxidants while retaining the classic white sweet potato texture.
Uses for White Sweet Potatoes
White sweet potatoes can be used anywhere regular orange sweet potatoes are used. Their milder flavor lends itself well to:
- Baking into casseroles, breads, and pastries
- Mashing or creaming into soups and purees
- Frying into chips, fritters, or hash browns
- Roasting whole or in wedges
Their lower moisture content means they hold their shape better during cooking compared to orange sweet potatoes. Try substituting white sweet potatoes into your favorite recipes to appreciate their unique qualities.
Availability
White sweet potatoes were once relatively rare, but are now easy to find due to increased commercial production. In the U.S., you can find them at:
- Grocery stores – sold individually or in bags
- Farmers markets – available seasonally
- Food delivery services – home delivery options from local farms
Their rising popularity means white sweet potatoes are now a regular sight right alongside traditional orange ones.
Conclusion
White sweet potatoes offer a tasty alternative to the classic orange ones we’re used to. The lack of carotenoid pigments accounts for their pale color, driven by genetic differences that limit production of these compounds. White varieties are milder in flavor and have a characteristic dry, fluffy texture when cooked. Though not as nutrient-dense as orange sweet potatoes, they contain plenty of starch, fiber, potassium and other beneficial nutrients. Best of all, the “new to the scene” white sweet potato is now easy to find at stores and markets, joining its orange cousin as a versatile, nutritious root vegetable.
