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Purple sweet potato

Beotanics blog - 13th April 2019

Purple sweet potato

Due to their high levels of nutrients and minerals along with their resistant nature, sweet potatoes have become a crop of great importance globally. With 95% of sweet potato cultivation occurring in developing countries. It is evident from known research that this crop is considered to be a true ‘superfood’, and is often associated with famine relief. Sweet potatoes are known to contain high levels of phenolic acids and flavonoids, which are known to have an inverse correlation with the occurrence of many chronic diseases. While orange and white fleshed sweet potatoes are considered to be potent nutraceutical foods, purple sweet potatoes have been shown to have higher concentrations of bioactives and greater industrial and pharmaceutical applications. Purple sweet potatoes can contain anywhere from 4-7 times the amount of anthocyanins found in other types of sweet potatoes. These purple sweet potato anthocyanins have also been shown to maintain a high cell viability, and positively impact the growth of retinal pigmented epithelial cells, as well as protecting against chronic diseases through antioxidant activity. Anthocyanins from purple sweet potatoes can also be used as natural pigments to great effect. They are not only more stable than most other anthocyanin-based pigments, but also possess more bioactive properties than others currently in use. These purple pigments are utilised in a multitude of commercial products in Asian markets, from McDonalds milkshakes, to coated peanuts. By availing of such potent nutraceutical foods and their products, Western diets could be vastly improved with quite little real change.

Ipomoea batatas (also known as sweet potato) is a dicotyledonous crop which originated from Latin America, and is now cultivated worldwide. Sweet potatoes are believed to have been domesticated over 5,000 years ago and were introduced to China in the 16th century. The crops adaptability, due to its phenotypic and morphological variability, allowed it to spread effectively through Asia, Africa and Latin America during the 17th and 18th centuries and could allow it to effectively be manipulated to serve a variety of nutritional purposes. Around 95% of sweet potato crop worldwide is grown in developing countries, and it is the most cultivated root crop in the developing world. It has a long history of being used as a lifesaving, famine-relieving crop due to its adaptability and high nutrient content and is referred to as the “protector of children” in some parts of east Africa for these reasons.

The crop has gained increased attention from the developed world due to its potential as a high nutrient commercial crop and there have been many developments in the production of cultivars for utilisation in specific sweet potato products and in niche markets. Sweet potato extracts have been shown to exhibit antibacterial and antifungal activities, glycaemic control functions, and carotenoids have been shown to exhibit antioxidant and anticancer activity. Anthocyanins, which are abundant in many varieties, have also been shown to possess many health benefits and contribute to the pigmentation of the crop. These bioactive molecules are present in many fruits and vegetables. Sweet potato flesh can vary from white, to orange, to purple. These different varieties of sweet potato all share similar health benefits, but often to different degrees due to differences in concentrations between bioactive molecules. The skin and flesh colouring of sweet potatoes are thought to be controlled by separate sets of genes in many cases.

Purple-fleshed sweet potato contains the highest concentration of anthocyanin pigments of all known sweet potatoes (4-7x more than orange fleshed sweet potato). They are rich in carbohydrates and dietary fibre and exhibit stronger antioxidant activity than many other fruits and vegetables due to its high content of anthocyanins and polysaccharides. Purple sweet potato polysaccharides have been shown to function as antioxidants, by carrying out free radical scavenging and ferrous iron chelating, and exhibit specific anticancer activity. The main anthocyanins present in purple sweet potatoes are cyanidins and peonidins which are abundant in the root flesh.

Sweet potato cultivation has come a long way since its beginning over 5000 years ago. While orange and white sweet potatoes can provide a bountiful supply of nutrients and bio-actives, purple sweet potatoes have been shown to have the potential to deliver higher levels of the same benefits. Their elevated levels of anthocyanins and other polysaccharides, vitamins and minerals give them the title of the ‘super’ sweet potato. Purple sweet potato anthocyanins are superior to other red and purple natural food colourings in terms of antioxidative capacity, stability, bioactivity and longevity. The added bioactive benefits of these pigments include a potent iron chelating activity and a wide range of specific reported anti-cancer activities. Purple sweet potato extracts could be much more valuable than those of other sweet potato varieties and many other vegetables. Purple sweet potato pigments attractive colours and biological activities could prove quite useful in addressing the growing consumer demand for natural food and beverage colourings in lieu of artificial additives. Resistant starch side stream could also be produced from purple sweet potatoes which are being harvested for their bioactive rich extracts. This resistant starch can act as a prebiotic and only increases the industrial value of this crop, while also reducing waste.

Beotanics has been involved in development of sweet potato as a European crop since 2006. Through Nativaland its JV company in Portugal huge capabilities in purple sweet potato has been established. With a selection program involving over 30 selections of high yielding purple sweet potato accessions our capabilities in the purple sweet potato food and nutraceutical ingredient development are unsurpassed in Europe.

For more information on Purple Sweet Potato click here