Wednesday, July 22, 2009

Pasta Technology - Die construction

Pasta Technology - Die construction
The basic operation in the manufacture of any kind of pasta is extrusion.

The dough is prepared by the mixer, kneaded by the auger from the mixer to the die chamber, and the force through a die under high pressure.

Dies perform the function of forming the dough into characteristic, familiar shapes.

They are made in both circular and rectangular form, depending on whether they are to be used in oppresses for producing short goods or in an automatic spreader for long goods.

Dies are often made of bronze but stainless steel and other alloys have also been employed.

Combinations of material can be used, as when s stainless steel frame is fitted with brass inserts which can be removed and replaced.

The simplest form of pasta is the familiar spaghetti which is a solid round strand of dough.

On the inlet side of the die the hole is about 0.19 inch in diameter, although slightly different diameters may be employed by different manufacturers.

As the channel proceeds toward the exit orifice, it tapers down to about the diameter of the spaghetti and this diameter is maintained for short distance called the gauging thickness.

Tubular forms, such as macaroni, require a pin in the center of the die. The pin is anchored by two or more wings or extensions near inlet end.

The stream of dough is, of course separated by these extensions, but quickly merges together after it passes them and continues along the channel.

Curved elbow macaroni is formed by drilling one side of the die hole deeper than the other so that the dough will flow faster on that side – there is less friction because the channel is wider for part of its course.

In large elbow macaroni with thick pins, a notch can be cut into the pin to cause the dough to flow faster. Products with wavy edges can be made by allowing the dough to flow more rapidly at the wavy edge.

The extrusion rate through a die hole in a bronze die is normally about one inch per second.

Extrusion rates can be increased and the product made smoother and yellower by putting Teflon inserts into die so that the final extrusion surface is made of this very smooth and low friction material.

Teflon does have come into wide use in marketing regions where products are packaged in transparent film and must therefore have optimum visual quality. Bronze dies are used in area where the pasta is packaged in opaque containers such as cardboard boxes.

It is generally believed that bronze dies yield pasta that cooks in a more satisfactory manner.

Water penetrates more slowly into the Teflon-extruded product and there is a tendency for the surface to become soft before the interior has been thoroughly cooked.
Pasta Technology - Die construction

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