The tangzhong method has been circulating in the Chinese baking community since Yvonne Chen's "Bread Doctor" from Taiwan (陳郁芬。《65C湯種麵包》。臺灣) was first published in 2003 or 2004. The secret to the success of this method lies in the tangzhong, or the water-roux starter (湯種). It was an ancient Chinese method used in the making of Chinese steamed buns (e.g. bao 包 and mantou 饅頭), dumplings (餃子), glutinous rice balls or tongyun (湯圓) and so forth. The Japanese recently revived the method, and it later became very popular in Taiwan, Hong Kong, China, Singapore, Malaysia and other Asia regions.
In Japanese, tangzhong means either a warm or thin starchy (flour-based) starter. Bread that's made with tangzhong is called tangzhong bread. So, how does it do the magic of producing bread that stays soft and fluffy longer without the addition of any "artificial ingredients?" As you cook the flour-water mixture for the tangzhong over gentle heat, the starch begins to react with the water via gelatinization. The mixture will subsequently thicken up as the starch traps and locks moisture from the water. The cooking will have to be stopped once the mixture has reached 65C.
I had been tempted to try out this method, but as it's time consuming to try somrthing new, therefore I keep on delaying the plan. This afternoon, while the three girls were taking their nap, I tried out this method and made some cinnamon rolls with apple + raisin today. The bread turns out to be really soft & fluffy.
How to prepare Tang Zhong? We just need 1 part of bread flour in 5 parts of water to 65°C. The tangzhong can be stored up to a few days as long as it doesn't turn grey.