Flour milling method having a sorting step for raw wheat...

Solid material comminution or disintegration – Processes – Cereal and other seeds or seed parts

Reexamination Certificate

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C241S011000, C241S076000, C241S081000, C241S159000

Reexamination Certificate

active

06199777

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a flour milling method and a flour milling system having steps of such as breaking, grading, purification and reduction for the flour milling of wheat grains, and more particularly to a flour milling method having a sorting step for raw wheat grains and a flour milling system adopting the method.
(2) Description of the Related Art
As in a cross-sectional view of an inside structure of a wheat grain, there is a plurality of layers called layers of pericarp, testa and aleuron sequentially positioned from a surface portion of the wheat grains, and there is starch and gluten-parenchyma further inside thereof. It is well known that ash contents are largely contained especially in the layers of pericarp, testa and aleuron within the above constituents. In this specification, the layers of pericarp, testa and aleuron are generally called an epidermis. The wheat grain also has a peculiar longitudinal groove called a crease portion which goes deep into the inside thereof.
FIG. 1
shows a flour milling flow
100
based on a conventional flour milling system which is for producing high quality product wheat flour and in which, after the raw wheat grains are polished, the polished wheat grains are milled through a plurality of breaking steps, and the wheat grains thus milled are sifted out or classified. After foreign matters such as small stones and metal pieces or fragments are removed at a cleaning unit
108
, the raw wheat grains are introduced into a polishing unit
101
. The raw wheat grains are polished at the polishing unit
101
and are forwarded to a first break
102
via a transporting passage
109
. Wheat particles milled by the opposing rolls
102
a
and
102
b
of the first break
102
into particles of various sizes are sifted out by a sifter
103
into respective particle sizes. The wheat flour in a small particle size (e.g., smaller than 125 &mgr;m) becomes product flour, and the wheat flour in large particle size (e.g., larger than 850 &mgr;m) is forwarded to a second break
104
. Generally, the wheat flour in an intermediate particle size is supplied to steps called such as smoothing (not shown), purification (not shown) and reduction (not shown).
The wheat flour forwarded from the first break
102
and introduced into the second break
104
at a downstream of the first break is milled by breaking, and the flour thus milled is sifted out by a sifter
105
into product flour whose particle size is small, wheat flour whose particle size is large, and semolina whose particle size is intermediate. Then, these kinds of flour thus sifted out are forwarded to respectively suited steps to follow. That is, at a third break
106
at a further downstream as shown in
FIG. 1
, the flour milled is sifted out by a sifter
107
and then is forwarded to appropriate steps according to particle sizes. The later the breaking step is, the larger the epidermis contents become in the raw materials introduced.
In the above described conventional flour milling system, irrespective of whether or not a wheat polisher is used, the sifting by employing such system as a sifter is used after the milling in order to produce high quality flour with a high yield. The quality of flour depends on how the wheat flour with little epidermis can be sifted out, and how a large volume flour with ash contents lower than the related standards can be produced.
That is, in order to produce quality flour with a high yield according to a conventional technique, it was necessary to establish a highly precise and highly efficient sifting technique. However, there is a limit in the technique in enhancing the purity of the wheat flour by the operation of sifting and purification means.
Even if a technique with which the epidermis at wheat surfaces is removed in advance by a wheat polisher is introduced, practically it is difficult at the present stage to produce wheat flour of a better quality by the operation of sifting and purification means.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and a system for producing flour of a better quality with high yields whereas there was a limit therein according to the conventional technique irrespective of whether the wheat polisher was used or not.
As a means to overcome the problem, the invention provides, according to one aspect of the invention, a flour milling method for raw wheat grains in which a plurality of milling steps whose milling degrees are different from one another are performed sequentially from an upperstream to a downstream, each of the milling steps including a breaking step and a grading step, the method comprising the steps of: sorting the raw wheat grains into regular wheat grains and material other than the regular wheat grains; forwarding the sorted regular wheat grains to a milling step of the uppermost-stream; and forwarding the sorted material other than the regular wheat grains to one of a plurality of milling steps of the downstream.
It is to be noted that the terms “upperstream” and “downstream” used in this specification mean “upperstream” and “downstream” respectively as viewed in the direction of flow of wheat.
When small grains have been removed from the raw wheat grains by the sorting step, the wheat grains to be forwarded to the first break become the regular wheat grains only. The fact that only such regular wheat grains are forwarded to the first break means that only the regular wheat grains in which the ratio of epidermis with respect to endosperm of the wheat is comparatively small are forwarded. Since there are no small grains in which the ratio of the epidermis with respect to the endosperm is comparatively large, the ratio of the epidermis of the wheat thus milled is inherently small. In this way, it is possible to produce wheat flour of a better quality than that conventionally produced.
According to the invention, it is arranged that the wheat grains having been sorted out are introduced into at least one of downstream breaks at a downstream of the first break. The ratio of the ash contents in the raw material is higher as the breaking steps are later. However, if the small grains which were sorted out prior to the first break and in which the ratio of epidermis is comparatively large are introduced into, for example, the third break, the ratio of epidermis finally contained in the intermediate size and product flour is considerably reduced in the sifting after the milling by the third break since, even though the grains are small, a large amount of endosperm is contained inside thereof.
Thus, since the ratio of the epidermis contained in the intermediate size and product flour can be reduced at each breaking step, the quality and the overall yield of the product are enhanced.
According to another aspect of the invention, only the wheat grains obtained by further classifying the material other than the regular wheat grains having been sorted out at the sorting step are forwarded to at least one of downstream breaks at a downstream of the first break thereby producing the flour. In this way, in the material other than the regular wheat grains which have been sorted by the sorting step, there are contained bran particles in addition to small wheat grains and broken grains. These particles including the grains are not directly introduced into breaking steps, but at least the bran particles are first removed by classification so that only the small grains and the broken grains can be forwarded to subsequent breaking steps. The advantage obtained by forwarding the small grains and broken grains to the downstream breaking to which the material containing a large amount of epidermis is forwarded is as explained above, but the forwarding of grains even with the inclusion of the broken grains further enhances the yielding.
The broken grains developed from the regular grains are with comparatively small amount of epidermis so that, when they are introduced into downstream breaking steps, the epidermis contents in th

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