If the thought of drying your body with a towel steeped in the fragrance of “mikan” mandarin oranges has ever appealed, you’re in luck. Ehime Prefecture, the nation’s primary producer of mikan, is also renowned for its Imabari brand of cotton towels.
Marrying these two aspects of the local culture was a no-brainer. Researchers developed a towel which features the essence of the citrus fruit based on cellulose nanofiber (CNF) derived from the fruit’s peel. CNF is created by mashing the outer coating into nanometer levels (one nanometer is one-millionth of a millimeter).
As materials with CNF become stickier and stronger, the ingredient is thought to have applications for the production of reinforced resin and rubber. Among the nation’s 47 prefectures, Ehime is renowned for its “Unshu-mikan” species, and is the leading producer of citrus fruits for 42 years in a row. The challenge was what to do with the peel and seeds after the juice from mikan was extracted. Ehime University and a papermaker developed CNF from cellulose in mikan leftovers as part of a trial run.
When the prefectural fiber and dyeing industrial association here learned about the process, it hit upon the idea of using mikan-derived CNF as glue to strengthen the cotton yarn for towels. When cotton yarn is woven into towel cloth by machinery, glue is applied to strengthen the threads so they don’t break during the manufacturing process. The glue is removed afterward, giving the finished product high water-absorbing quality and softness.
While starch-based glue is traditionally used for Imabari towels, it is costly to remove from the towel as well as treat the leftover waste water. Ryuji Hiratsuka, 50, head of the association’s sales promotion department, learned of the citrus-derived CNF when he attended a lecture session themed on the fiber last August.
“I assumed that glue using CNF made from citrus fruits could be removed without chemical agents because it is a natural ingredient,” Hiratsuka said. The association contacted the paper manufacturer in the prefectural city of Shikoku-Chuo to test-create glue from mikan CNF.
The company processed the peel of mikan provided by a major beverage maker into CNF and managed to apply the fiber as glue to towels late last year.
The special glue can be washed away in hot water, making it unnecessary to use chemicals or treat waste water. Towels treated with the mikan-derived adhesive give off a subtle, orange-like smell.
Mikan-flavored towels have two advantages in environmental terms: They don’t need to be washed with chemical agents and mikan peel does not go to waste. The remaining challenge is the high production cost.
As it currently costs between 5,000 yen and 10,000 yen ($46.75 to $93.45) to make 1 kilogram of CNF from mikan, the prefectural government, the university and other parties are pursuing a public-private project to bring that down to around 500 yen.
“Citrus-based CNF is a dreamy ingredient,” Hiratsuka said. “It is our hope to produce towels that are unique to Ehime Prefecture and friendly to the environment.”