Gyokuroen Kombucha Kelp Tea Powder Industrial Size. It is made by carefully selecting high-quality kelp from the Shiretoko Peninsula, Hokkaido. Kombucha tea is healthy and has a relaxing effect and is ideal for drinking after a heavy and oily meal. All natural and caffeine free. The producer Gyokuroen is one of the most recognised tea makers in Japan. Its signature tea is kombucha which is loved by health-conscious tea lovers around the world. Gyokuroen has been in this business for 95 years. It can also be used as an ingredient in cooking such as hot pots, pickles, soups at home, etc.