Sweet potatoes are being shipped from Miyazaki to all around the world. What makes them so enticing is the sheer number of varieties of sweetness and textures!

Southern Kyushu is rich in volcanic ash soil with good drainage, which makes it perfect for growing sweet potatoes. Within this region is Miyazaki Prefecture, and at the southernmost tip is Kushima City, which has long been known for its sweet potato production. Kushima City is home to Kushima Aoi Farm, one of the top agricultural companies in Japan in terms of annual shipments and exports. The company has focused on exports since its establishment, and President Mr. Yosuke Narasako wants the whole world to experience the deliciousness of Japanese sweet potatoes. Here, he tells us about the many initiatives he has been working on in this regard.

The Japanese word for sweet potato is satsumaimo. Satsuma is the old name for Kagoshima (Miyazaki's neighboring prefecture), and imo means potato. They say it was originally introduced to Kagoshima from China via Okinawa in the early 16th century. Southern Kyushu, including the Kagoshima and Miyazaki regions, is one of the leading producers of sweet potato in Japan because sweet potatoes prefer well-drained soil, which the region has in abundance due to the ash and pebbles from ancient volcanic eruptions. Kushima Aoi Farm further improves its soil by turning the surface black soil with the underground red soil. The resulting soil is called akahoya, and it is great for growing because it has fewer natural pests.

Mr. Yosuke Narasako is the President of Kushima Aoi Farm, an agricultural venture born in Kushima City, Miyazaki Prefecture. The president at the time was originally a sweet potato farmer who founded the agricultural company in 2013 as a means to take on new challenges. Kushima Aoi Farm has attracted many young and highly motivated people with its grand idea of delivering the deliciousness of Japanese sweet potatoes to the world. Mr. Narasako is just one of those people.

"Field research revealed that people in Southeast Asia like to steam sweet potatoes in rice cookers and so they prefer a smaller size," Mr. Narasako explains. "We also found that many local customers said that they are unable to eat an entire large sweet potato. Smaller-sized produce is often discarded as producers believe they won't sell, so I thought this would be a great opportunity for us."

In order to grow smaller-sized sweet potatoes for export, the company developed a unique method of "dense-hilled planting." By reducing the amount of space between seedlings and their hilled rows, they are able to harvest a large number of smaller-sized potatoes.

The company has furthered its stable production system by increasing the number of endorsed contract farmers. It currently has contracts with about 230 farmers, and of the 8,200 tons of produce handled annually, 20% is exported internationally. It is one of the largest agricultural companies in Japan, and its strength lies in the fact that it not only handles production, but also the entire processing and sales process.

Kushima Aoi Farm is also rather particular about how it stores its sweet potatoes. Sweet potatoes are generally planted during April and May, and they are then harvested throughout September to November. The sweet potatoes are then cured in a storage facility to convert the starch into sugar for a sweeter potato. Kushima Aoi Farm installed one of the largest curing storage facilities in the country in 2016. "When you cure the sweet potatoes, you activate their ability to self-heal," says Mr. Narasako. "Leaving the potatoes in a hot and humid environment for a while causes a sort of cork layer to form over the damage caused by the harvest. This allows for long-term preservation."

The potatoes are then transferred to a temperature-controlled storage facility with a temperature of 13-15°C and 100% humidity where they are cured for at least two months before being shipped out sequentially. The shipping facility is a one-stop shop for washing, drying, and packaging, and it can ship 20 tons per day.

Kushima Aoi Farm gradually increased the number of varieties of sweet potato it can handle in response to requests from supermarkets and other retailers. Now, its ability to handle such a wide variety, including the Miyazaki Beni variety, makes it unique. It can also differentiate the potatoes through unique naming and branding.

Mr. Narasako says the company currently deals with five main varieties. The Miyazaki Beni has a purple skin and yellow flesh. It has a soft and flaky texture, which makes it suitable for baking as well as for tempura. Then there's the Beni Haruka, which has seen a boom in popularity in the last few years. It has the same purple skin and yellow flesh, but it has a stickier texture, is much sweeter, and is perfect for baking. Another driving force behind the popularity of baked sweet potatoes is the Anno variety. Its skin is light orange, the flesh is orange, and it is sticky and sweet. Next, the Silk Sweet potato has a purple skin and yellow flesh, and it is so silky smooth when baked that you can eat it with a spoon. It's not too sweet, so everyone can enjoy it. Finally, the Purple Sweet Road is purple on the inside and on the outside, and it is refreshingly sweet. It is rich in anthocyanins, which is gaining attention in the cosmetics field.

In recent times, Kushima Aoi Farm has been actively producing a variety called the Beni Masari. Sweet potato disease was epidemic a few years back and there was no specific remedy for it, but through the course of trial and error, the company discovered a variety that was resistant to this disease. The new variety is characterized by its gentle texture and refined sweetness. However, Mr. Narasako says that just because something is disease-resistant for now, it doesn't mean it will continue to be disease-resistant into the future, which is why they are working with the University of Miyazaki to develop even more disease-resistant varieties.

Kushima Aoi Farm has always been eager to expand its business overseas ever since its establishment, and it has widely promoted the delicious taste of Japanese sweet potatoes. It is currently focusing on exports to Greater China and Southeast Asia, and each country has its own particular taste that it prefers.

Mr. Narasako says that Taiwanese sweet potatoes are round and have a sticky texture on the inside, so the slender and crumbly Miyazaki Beni variety is very popular. He also says that sweet potatoes are usually steamed in Asian cultures, but baked sweet potato has been gaining traction recently. As for which variety is the most popular, Mr. Narasako tells us, "Most all varieties are popular in Hong Kong and Singapore, while the large-sized Beni Haruka is the most popular variety in Thailand and Malaysia. But no matter which country we export to, they all say that Japanese sweet potatoes are by far the sweetest and most delicious."

Mr. Narasako has eaten his fair share of sweet potatoes from all around the world, and even he agrees that foreign sweet potatoes are not very sweet, so he understands why Japanese sweet potatoes are so well received. It is surely the result of the many years Japanese people have spent on developing breeds, as well as the curing techniques that have been honed and perfected by producers like Kushima Aoi Farm.

Of course sweet potatoes can be simply steamed or baked, but they are also delicious in miso soup, a Japanese dish that is prevalent in the Asian region. Simply cut the sweet potato into half moon slices with the skin still on, soak them in water for 10 minutes to remove any impurities, then simmer in a broth until easily skewered. Finally, dissolve the miso paste into the broth and season to taste.

Sweet potato tempura is popular and it can be prepared in the traditional method of dipping in batter and deep frying, but frozen baked sweet potato has also become quite popular in Japan these days. Kushima Aoi Farm has created its own product line, and the response has been strong during the summer months. The texture of a baked sweet potato is very mellow once it's been chilled and thawed, and it makes for a satisfying dessert. You can also slice it up and serve it with ice cream for an even more luxurious experience.

Mr. Narasako says that the company will continue exporting fresh sweet potato, but they will also focus on exporting processed products in the hopes that people will be able to enjoy all the different tastes of sweet potatoes.

Kushima Aoi Farm is also actively working toward reducing food waste. The company teamed up with a materials manufacturer to develop a unique anti-condensation film to protect the produce from condensation during cargo exports, thereby reducing mold and food spoilage. The result was a significant decrease in the amount of food waste. The company also uses potatoes that are too big for sale in other products such as sweets and, in the future, it hopes to use the nutritious vines to develop supplements, and also generate biomass energy from damaged potatoes.

Mr. Narasako says, "I want more and more people to be able to enjoy delicious Japanese sweet potatoes. I don't want to just export them overseas, I want the locals to enjoy them too." One bite of that enveloping sweetness is sure to bring a smile to people all around the world.