Anthocyanins are a group of pigments that impart purple, red and blue color to foods. They work as antioxidants, prevent cell damage caused by free radicals, that is — to control inflammation and protect against heart disease, cancer and type 2 diabetes.
“People expect a sweet potato to taste sweet. But the orange and purple vitamin A and anthocyanin rich varieties cannot be as sweet as the white-fleshed variety, though that doesn’t limit its culinary use,” said Dr M Nedunchezhiyan, principal scientist at Indian Council of Agricultural Research-CTCRI Bhubaneshwar regional center, which developed and introduced the purple and orange varieties in 2016. “For 100gm of fresh tuber, the Bhu Krishna variety contains 90 mg anthocyanin, while the orange variety has about 14 mg of beta-carotene, a vitamin A precursor,” he said.
Another feature is that the nutrients in these colored varieties have a high bio-availability — percentage of nutrients assimilated and used by the body, that is. The orange pigmented beta-carotene is also present in carrots, mangoes, pumpkin, papaya etc, but its bio-availability is around 30-60%. But 80% of beta-carotene in orange sweet potato is bio-available, says the CTCRI scientist. Beta-carotene is essentially two molecules of vitamin A joined by a double bond. The liver converts it to vitamin A.
Unlike in India where the white-fleshed variety is largely cultivated, the orange hued cultivar is more common in most countries. In the Japanese island of Okinawa, which has one of the longest life expectancies in the world, the staple isn’t the mainland favorite rice, but the purple sweet potato. The weather in Okinawa’s subtropical islands which experiences seasonal storms isn’t conducive for paddy cultivation, making this tuber the preferred carbohydrate. It’s a profitable crop as well, say farmers.
Pramod Bisoyi, a farmer from Nowrangpur district in Odisha has planted the colored varieties supplied by CTCRI for the third year in a row. “The soil in here is not much fertile, but despite that I get a yield of 35-40 quintal per acre. It sells at Rs 40 per kilo in the local market, and whole at Rs 25-30 per kilo. Compared to other vegetables, it’s very profitable as it’s an easy crop, doesn’t really need pesticides, can do with less fertilizer and isn’t labor-intensive.”
The sweet potato is also a climate-resilience crop, unlike rice, wheat and most vegetables, which is why a number of NGOs that work with tribal farmers have been rooting for it. Last month, over a thousand tribal farmers planted foot-long cuttings of purple sweet potato vines over hectares of not-so-fertile red loamy soil of Koraput, a drought prone district in Odisha. The region’s monsoon has been erratic this year as well but it has neither affected the vines nor the farmers. “They used to grow bringal, cabbage, cauliflower, crops which cannot tolerate heavy rain or scanty rain. In 2021, under a project aimed at doubling their income, we moved them to climate-resilient crops such as the colored sweet potato and the results have been good,” said Susanta Balabantaray of Prastutee, an NGO.
The problem though is that in the last two years the tribals have largely been selling the produce only in local markets. The shelf life of fresh tuber is a month and so the NGO this year, bought machines to convert the tubers into flour for industrial use such as making chips, pasta, gluten-free foods etc. “It’s low sugar content and high fiber makes it ideal starch for diabetics patients, but in rural markets those properties aren’t prized. We would like to be in touch with retailers in urban markets where the demand is high,” he added.
In metros such as Mumbai, Delhi and Bengaluru, the superfood status of the orange and purple sweet potato has it retailing online for around Rs 300-450 per kilogram when in season, which is from November to February. “Sweet potato invariably means the orange-fleshed ones in many countries. In India, though the orange variety is now available, it’s very difficult to source and isn’t economical, ” said Kalpana Iyer, a Bengaluru resident, whose buys it directly from farmers.
The CRCRI scientist says, majority of the produce is currently bought by food industries. “That should change. Given its nutritional profile, our aim is to have the orange and purple varieties sell along with the white-fleshed ones in local markets across the country,” said Nedunchezhiyan. The area under cultivation in India has been growing, though slowly, he said. “Today anyone can buy from us the vines, easily propagate it and cultivate. We have been getting enquiries from states such as UP, AP, Bihar, Jharkhand, Chhattisgarh and Karnataka, apart from few NGOs,” he added.