In an era characterized by the search for functional and sustainable foods, yam (Ipomoea batatas) emerges as a rediscovery of an ancient ally of human nutrition. Often mistakenly confused with the potato (Solanum tuberosum) due to the similarity of the name and the mere appearance of a tuber, yam is a tuberized root that belongs to a completely different botanical family and boasts a distinctive nutritional profile.
Its pulp – which can display bright colors, from creamy white to intense orange to deep purple – is a visual indicator of the presence of precious bioactive compounds: carotenoids in the orange variant, anthocyanins in the purple one.
Globally, sweet potato production reached 93.5 million tonnes in 2023. It is the seventh most produced food crop after maize, rice, wheat, sugar crops, potatoes and barley and has the potential to help meet the nutritional needs of low- and middle-income countries. Its adaptability to different climates, combined with natural resistance to many adversities and the properties of a superfoods, makes it an ideal crop for low-input agriculture increasingly appreciated and cultivated in southern Europe.
The vast majority of yam produced in Italy comes from certified organic farming. The conventional (non-organic) companies that produce it are often those that include it in rotation marginally and without specific valorisation.
Botany and taxonomy of Ipomoea batatas
Classification and relatives
The sweet potato belongs to the kingdom Plantae, division Magnoliophyta, class Magnoliopsida, order Solanales, family Convolvulaceae.
The genus Ipomoea is the largest in the family, including over 500 species. Ipomoea batatas is the most economically important species. It is a perennial herbaceous plant, but is cultivated as an annual in temperate regions.
It has no relation to the Solanaceae, which include the common potato, along with tomato, eggplant and pepper.
Plant morphology: roots, stems, leaves and flowers
The sweet potato does not produce true tubers (which are modified stems, as in the potato), but tuberized roots. These originate from secondary thickening of adventitious roots, becoming storage organs where the plant accumulates starch, sugars and other compounds. The shape and size are extremely variable depending on the cultivar.
I stems they are prostrate or creeping (shoots), can reach several meters in length and root at the nodes when they come in contact with the ground.
The leaves are alternate, cordate or palmately-lobed in shape, with a long petiole. The color varies from light green to dark green, sometimes with purplish hues.
I flowers, finally, similar to those of the perennial herbaceous plant Convolvulus, are funnel-shaped, white, pink or light purple in color. Flowering in temperate regions is rare and not necessary for production, which occurs asexually, i.e., through vegetative parts (such as cuttings, roots, stems) rather than by flowers or seeds.
The tuber formation mechanism
The tuberization is a complex process regulated by hormonal factors, particularly the balance between gibberellins (which promote growth) and abscisic acid, ABA (which induces dormancy) and environmental factors (photoperiod and temperature).
The sweet potato is a short-day plant. The formation and enlargement of tuberous roots are favored by shorter days and longer nights, typical of late summer and autumn periods. Mild temperatures are also crucial for proper development.
The main varieties cultivated in Italy
Varietal choice is fundamental for adaptation to the Italian climate. The main ones are:
– Beauregard. The most widespread. Intense orange flesh, elongated and regular shape, high productivity and very rich in beta-carotene;
– Georgia Jet. Early, suitable for cooler climates. Orange flesh, reddish copper skin;
– Murasaki (or Japanese). Whitish skin and white-cream flesh. Dryer and less sweet, similar in taste to the common potato;
– Viola di Napoli or Tonda di Napoli. Variety with purple flesh, very rich in anthocyanins. Of ancient tradition in Campania, it has been recently recovered;
– Evangeline. Variety with orange flesh, very productive and with good disease resistance.
Historical origins and global diffusion
The cradle in Central-South America and the mysterious journey to Polynesia
Genetic evidence points to the origin of the sweet potato in the regions between the Yucatán Peninsula (Mexico) and the mouth of the Orinoco River (Venezuela), from where it spread throughout Central and South America.
Archaeological finds in Peru (Tres Ventanas caves and Chilca Canyon) date its use to over 8000 years ago. It was a staple food for pre-Columbian civilizations.
The presence of the sweet potato in Polynesia (where it is called ‘kumara’, a name very similar to the Quechua ‘kumal’) long before the arrival of Europeans is one of the great mysteries of archaeobotany. Linguistic evidence and the discovery of carbonized remains dated 1000-1100 AD in Polynesia support the hypothesis of a pre-Columbian transoceanic voyage, possibly by Polynesian navigators who reached South America and returned with the precious tuber.
The arrival in Europe: Columbus and the Iberian welcome
Christopher Columbus was the first European to encounter the sweet potato during his first voyage to Hispaniola (1492). Brought to Spain, it initially spread in botanical gardens as a curiosity and later as horticultural crop in the southern Iberian regions, where the climate allowed its cultivation. In England it was known as ‘potato of Spain'.
The diffusion in Italy: between niche horticultural cultivation and recent rediscovery
In Italy, the sweet potato was for centuries a marginal crop, confined to family gardens, especially in the South. The purple-fleshed variety (Viola di Napoli) was historically cultivated in Campania.
The true production boom is a recent phenomenon, of the last 10-15 years, driven by three factors:
– the growing consumer demand for healthy and exotic foods;
– climate change, with hotter and longer summers that favor its cultivation;
– the pioneering work of innovative farmers who have tested and adapted the cultivars.
The nutritional and nutraceutical profile: a concentrate of well-being
Macrocomponents: complex carbohydrates, fiber and proteins
Sweet potato is mainly a source of complex carbohydrates (starch), which provide slow-release energy. It contains a fair amount of simple sugars (sucrose, glucose, fructose), which determine its sweet taste, especially after cooking which hydrolyzes the starch. The content in fiber is high, especially if consumed with the skin (rich in insoluble fiber) and contributes to intestinal health and to satiety. The protein content is modest.
The myth of vitamin A: beta-carotene and bioaccessibility
The varieties with orange flesh are among the richest plant sources of beta-carotene, a precursor of vitamin A (retinol). An average sweet potato can cover over 400% of the daily vitamin A requirement. Bioaccessibility of beta-carotene (i.e., the amount our body can absorb) is greatly increased by cooking and the presence of fats (e.g., seasoning with extra virgin olive oil).
The purple-fleshed sweet potato: a reservoir of antioxidant anthocyanins
Purple-fleshed varieties owe their color to anthocyanins, powerful antioxidants of the flavonoid family. These compounds are associated with a wide range of benefits for health: anti-inflammatory activity, improvement of cognitive function, vision protection, and potential anti-cancer effect. They have also been shown to possess anti-glycemic properties, improving sugar metabolism.
Vitamins, minerals and minor compounds: a complete profile
Besides provitamin A, the sweet potato is a considerable source of:
– vitamin C, important antioxidant and cofactor for collagen synthesis;
– vitamin B6, crucial for energy metabolism and brain function;
– potassium, essential for blood pressure regulation;
– manganese, involved in bone metabolism and antioxidant function.
Glycemic index, a matter of variety and cooking method
Theglycemic index (GI) of sweet potato is often misunderstood (Dongo, 2025). It is not universally low, but varies according to variety and cooking method. In fact,
– sweet potatoes with purple flesh and those white tend to have a lower GI (around 50-60) compared to very sweet orange ones (up to 75-80 if baked);
– the steaming or the boiling generally maintain a lower GI compared to prolonged baking. The cooling after cooking allows starch to retrograde, forming resistant starch, which further lowers the GI.
Italian sweet potato production: from Campania to Veneto
Cultivation areas: an expanding mosaic
The Italian production, although still modest compared to the world giants (China, Nigeria, Tanzania), is strongly growing and extends from North to South.
The South and the islands represent the traditional and most suitable area. Campania (particularly the Caserta and Naples areas), Apulia, Calabria, Sicily, and Sardinia benefit from long and warm summers.
In central Italy, significant cultivations are present in Tuscany, Lazio, and Marche.
In the North, the Po Valley (Emilia-Romagna, Veneto) sees increasingly numerous cultivations, favored by hot summers and the use of plastic mulch to warm the soil.
Agronomic techniques: cuttings, mulching and sustainable management
Sweet potato is not propagated by seed but by rooted cuttings (called 'barbatelle' or 'slips'). The mulching (especially with black plastic film) is an almost mandatory practice in Italy: it warms the soil, controls weeds, and retains moisture. Drip irrigation is the most efficient. It is a rustic crop with few fertilization needs and naturally resistant to many pests, ideal for organic farming.
Short supply chain and territorial enhancement
Italian production focuses entirely on quality, on freshness and on traceability.
Many producers sell through short supply chains (farmers' markets, direct sales on farms, Solidarity Purchase Groups – GAS) or supply organized large-scale distribution with very high-end products, often organic farming. The recovery of local varieties (such as the Viola di Napoli) is a powerful driver of territorial marketing.
Low-cost competition
The growing domestic consumption, the added value of theItalian origin, the production organic and its resilience to climate change make sweet potato a crop with broad opportunities.
Challenges include the crop's sensitivity to low temperatures, the need for labor for harvesting (still often manual), and competition with low-cost imported products.
Industrial treatments and nutrient stability
Storage needs and convenience
Fresh sweet potato has a shelf-life relatively limited and is bulky to transport.
Industrial treatments (drying, freezing, canning) prolong its Duration, reduce the transport costs and make it convenient for use as ingredient in other products (snacks, bars, baby purees, flours).
Drying: physical principles and methodologies
Drying removes water to inhibit microbial growth and enzymatic reactions. The main methods are:
– hot air drying (hot air drying – HAD). The most common and economical method. It exposes the product to hot air flows (50-90°C). Unfortunately, high temperatures cause significant losses of heat-sensitive nutrients;
– freeze-drying (freeze-drying – FD). The product is frozen and then the water is sublimated under vacuum. It is the method that best preserves structure, flavor, and nutrients, but it is very expensive and energy-consuming;
– low temperature or air drying. Slower and more food-respecting methods, but less industrially applicable, and subject to microbial contamination when carried out in open air.
The impact of drying on physico-chemical properties
However, drying has a negative effect on the physico-chemical properties of sweet potato, particularly on the content of β-carotene and of anthocyanins. The latter can be degraded by over 50%.
This negative impact varies and is influenced by the method, conditions, slice thickness, sweet potato variety, and pre-drying treatments, as documented by a review conducted by a South African research team (Ntsowe et al, 2025).
Scientific research is studying how to mitigate these losses through pre-drying treatments and innovative technologies. The sweet potato flour (often obtained by drying and milling) is indeed an ingredient gluten-free increasingly popular for the production of pasta, bread, cookies, and snacks.
How to cook sweet potato to preserve its nutrients
At home, sweet potato lends itself to many preparation methods: roasted, steamed, boiled, mashed, fried (moderately), added to soups and stews. Young leaves are edible and nutritious, similar to spinach.
Some practical tips to preserve nutrients and maximize nutritional benefits:
– cook sweet potato without peeling it. This reduces nutrient loss by leaching into water and preserves fiber;
– prefer gentle cooking methods. Steaming or boiling in little water is better than frying or baking at high temperatures for long periods;
– add a fat. Dressing cooked orange sweet potatoes with a drizzle of extra virgin olive oil greatly increases beta-carotene absorption.
Sweet potatoes are stored in a cool, dry, and dark place.
Choosing Italian sweet potato
Buyers in the national and global market can rely on the availability of high-quality organic Italian sweet potatoes.
The expertise of GIFT (Great Italian Food Trade) can help in the search for a product that perfectly embodies the convergence of tradition, quality, innovation, and sustainability.
Marta Strinati
Cover photo by Lars Beulke from Pixabay
References
– Bovell-Benjamin A. C. (2007). Sweet potato: a review of its past, present, and future role in human nutrition. Advances in food and nutrition research, 52, 1–59. https://doi.org/10.1016/S1043-4526(06)52001-7
– FAO . 2024. FAOSTAT: Production: Crops and Livestock Products. https://www.fao.org/faostat/en/#data/QCL
– Islam, S. (2006). Sweetpotato (Ipomoea batatas L.) leaf: Its potential effect on human health and nutrition. Journal of Food Science, 71(2), R13–R121. https://doi.org/10.1111/j.1365-2621.2006.tb08912.x
– Ntsowe, K., Workneh, T. S., Laurie, S., & Emmambux, N. (2025). Different Drying Techniques and Their Impact on Physicochemical Properties of Sweet Potato: A Review. Journal of food science, 90(8), e70458. https://doi.org/10.1111/1750-3841.70458
– Woolfe, J.A. (1992) Sweet Potato: And Untapped Food Resource. Cambridge University Press and the International Potato Center (CIP), Cambridge.
Professional journalist since January 1995, she has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and magazines (NumeroUno, Il Salvagente). Author of journalistic investigations on food, she published the book 'Reading labels to know what we eat'.
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