What Is an Encrusting Machine? Structure, Uses, and How It Differs from a Forming Machine

One Machine Handles Both the "Crust" and the "Filling"

In Chinese, an encrusting machine is called bao xian ji (包餡機), literally a "filling-wrapping machine." The verb encrust originally means "to cover with a crust." In food production, it means having one material (the outer dough) completely enclose another (the filling). In 1961, Torahiko Hayashi, founder of Japan's RHEON, developed the world's first automatic encrusting machine. In Japanese it was called hoan-ki (包あん機), literally "a machine that wraps sweet bean paste." The English-speaking market later adopted the word encrusting, while the Taiwanese industry generally calls it bao xian ji.

Wrapping by hand means rolling out a wrapper, adding the filling, and sealing it, one piece at a time. An encrusting machine works on a completely different idea: the dough and the filling travel through separate channels and are extruded downward at the same time. At the nozzle outlet they become a continuous rope with the dough on the outside and the filling in the center. A shutter below then cuts and seals the rope section by section, and what drops out is a finished, filled piece.

Basic Structure: From Hopper to Conveyor

Details vary by brand, but most encrusting machines have these parts:

• Hoppers: one for the dough and one for the filling, loaded separately.
• Feeding mechanism: pushes material from the hopper toward the nozzle. A common setup is a screw combined with a metering pump; see Differences Between Feeding Mechanisms.
• Concentric double-layer nozzle: the inner tube delivers filling and the outer ring delivers dough. The two streams meet here; for the principle, see Co-Extrusion Principle.
• Shutter cutting mechanism: several blades arranged in a ring close like a camera iris, cutting the rope and gathering the dough closed; see Shutter Cutting and Sealing.
• Lifting conveyor: supports the bottom of the product from below during cutting and moves up and down with the shutter, so the product lands round and keeps its shape.
• Control system: sets the weight per piece, the dough-to-filling ratio, and speed. Most newer machines can store recipes; see Control Systems.

What Can an Encrusting Machine Make?

As long as both the dough and the filling have some plasticity and can be extruded, there is a good chance an encrusting machine can make the product. The RHEON USA website lists more than 50 foods the CORNUCOPIA KN551 can produce, including meat buns, char siu buns, shumai, soup dumplings, croquettes, pineapple cakes, mooncakes, mochi ice cream, sesame balls, scones, filled cookies, and fried rice balls (arancini). The universal models on RHEON's Japanese website list more than a hundred Japanese and Western confections and prepared foods, including daifuku, strawberry daifuku, chestnut manju, momoyama, mooncakes, sake manju, and sandwich cookies.

In other words, the steamed buns (包子), plain steamed buns (饅頭, mantou), mooncakes, egg yolk pastry (蛋黃酥) fillings, mochi, tangyuan (湯圓), taro balls (芋圓), croquettes, and meatballs common in Taiwan all fall within the range of encrusting machines or their close relatives.

How Is an Encrusting Machine Different from a Forming Machine?

"Forming machine" is a broader term for any machine that shapes food into a fixed form, such as pressing dough into flatbreads or pressing ground meat into burger patties. A forming machine does not necessarily handle "two materials."

The key feature of an encrusting machine is that two or more materials are extruded at the same time, with the dough completely enclosing the filling. Many production lines combine the two: the encrusting machine first makes round balls, and downstream forming devices then flatten, stamp, or pleat them; see Secondary Forming.

Another close relative is the dividing machine: it extrudes only one material and cuts it into equal-weight portions, without any filling. Dong-Yih Machinery's DY-528M Automatic Dough and Filling Dividing Machine belongs to this category, producing 3,000–12,000 pieces per hour at 10 g–30 g per piece or heavier. It is well suited to mooncake filling, mung bean paste, red bean paste, sweet potato balls, and more. For the principle, see Dividing Machines.

Dong-Yih and Encrusting Machines

When Dong-Yih Machinery was founded in Tainan in 1989, it started out in machine repair. After its reorganization in 2001, the company began specializing in manufacturing all kinds of automatic food encrusting and forming machines. If you want to know which type of machine suits your product, call us at 06-257-4644 or leave a message on our Contact page.

FAQ

Q: Is an encrusting machine the same as a forming machine?
A: No. An encrusting machine extrudes the dough and filling together and then cuts them. Most forming machines only press the material into a fixed shape, or fold and seal pre-made wrappers, which is a very different process.

Q: Can an encrusting machine make plain steamed buns without filling?
A: On most models, the dough-to-filling ratio can be adjusted down to dough only. For example, RHEON's KASEIJIN (火星人) series lists a ratio adjustable from 1:0 to 0:1, which means it can make products made purely of dough.

Q: Why is it called "encrusting" in English?
A: Encrust means "to cover with an outer crust." The word emphasizes that the dough fully encloses the filling, which is different from simple extruding.

Q: Who invented the encrusting machine?
A: Torahiko Hayashi, founder of RHEON Automatic Machinery in Japan, developed it successfully in 1961, and the first commercial machine, the N101, was released in 1963. See The World's First Automatic Encrusting Machine.