紫 yam or spud?

What is the botanical difference and the usage difference and the nutrition difference between a purple yam and a purple sweet potato

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Illustration of a purple yam and a purple sweet potato side by side, including their skin, flesh, and leaves for comparison.

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From the viewer’s perspective, the purple yam (Dioscorea alata) is on the left side, and the purple sweet potato (Ipomoea batatas) is on the right side. You can distinguish them by their texture— the yam has rough, bark-like skin, while the sweet potato has smoother, reddish-purple skin.

Purple yams (Dioscorea alata) and purple sweet potatoes (Ipomoea batatas) are often confused due to their similar appearance, but they belong to different botanical families and have distinct differences in texture, taste, nutrition, and culinary use.

1. Botanical Difference

• Purple Yam (Dioscorea alata): Belongs to the Dioscoreaceae family and is a true yam. It is also known as ube in the Philippines. The skin is rough, bark-like, and can range from light brown to purple, while the flesh is deep purple.

• Purple Sweet Potato (Ipomoea batatas): Belongs to the Convolvulaceae family, which includes morning glories. The skin can be smooth and varies in color from reddish-purple to white, while the flesh is typically purple.

2. Usage Difference

• Purple Yam: Commonly used in desserts, especially in Southeast Asian cuisine. It has a soft, starchy, and slightly sticky texture when cooked, making it ideal for cakes, ice cream, and jams (e.g., ube halaya).

• Purple Sweet Potato: Used in both sweet and savory dishes. It has a denser, drier texture and is often roasted, mashed, or used in pies and fries. It is also popular in Japanese and Hawaiian cuisines.

3. Nutritional Difference

Nutrient	Purple Yam (per 100g)	Purple Sweet Potato (per 100g)
Calories	~140 kcal	~110 kcal
Carbohydrates	32g	26g
Fiber	~4g	~4g
Protein	1–2g	2g
Vitamin C	Moderate	High
Vitamin A	Low	High (beta-carotene in some varieties)
Antioxidants	High (anthocyanins)	Very High (anthocyanins)

• Both are rich in anthocyanins, which give them their purple color and have antioxidant benefits.

• Purple sweet potatoes tend to be lower in calories and carbohydrates.

• Some purple sweet potato varieties have more vitamin A due to their beta-carotene content, whereas purple yams do not.

Conclusion

• If you want a smoother, stickier texture for desserts, go with purple yam (ube).

• If you need a denser, drier texture for roasting or frying, use purple sweet potatoes.

• Nutritionally, both are excellent sources of fiber and antioxidants, with sweet potatoes offering slightly more vitamin A.

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In Japan, both purple yams and purple sweet potatoes have specific varieties with unique names:

1. Purple Yam (Dioscorea alata) – Japanese Variety

• Daijo (ダイジョ / 大薯) – A variety of Dioscorea alata sometimes found in Okinawa, though not as commonly used as sweet potatoes.

2. Purple Sweet Potato (Ipomoea batatas) – Japanese Varieties

• Murasaki Imo (紫芋) – General term for purple sweet potatoes in Japan, meaning “purple potato.”

• Beni Imo (紅芋) – A famous Okinawan variety with deep purple flesh, commonly used in desserts like beni imo tart and ice cream.

• Ayamurasaki (アヤムラサキ) – A variety with intensely purple flesh and high anthocyanin content, often used for food coloring and sweets.

The Okinawan sweet potato (Beni Imo) is often mistaken for ube (purple yam), but it is actually a type of purple sweet potato.

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Aerial (Regular yam) growing method

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