(a) Field of the Invention
The present invention relates to instant-cooking dry macaroni and like macaroni type food products, and a method of manufacturing such dry foods. 
(b) Description of the Prior Art
In the past, macaroni products including spaghetti and vermicelli, have been produced by adding water to starch components consisting mainly of strong wheat flour such as Semolina of the Durum Wheat family, uniformly distributing the added water throughout the starch components by kneading the mixture, and thereafter by subjecting the kneaded mixture to extrusion under pressure to shape the material into individual pieces of macaroni products of a desired shape, and then drying them for a substantially long period of time such as 24 hours.  Such macaroni products have been widely sold in the market. 
However, these well known foods are not given an .alpha.-conversion treatment during their manufacturing process.  Accordingly, in case these foods are to be eaten, they must be boiled for a substantial length of time for the purpose of cooking before being served.  Thus, these known products are not of the type that they can be instantly cooked or transformed into an edible state before being served. 
As for those macaroni products which are placed on the market as being instantly cookable foods, there are known those macaroni products which are produced by first subjecting raw macaroni pieces to a boiling treatment for .alpha.-conversion of the starch components, and by packing the boiled macaroni pieces with a heat-resistant film or like wrapping sheet, and thereafter subjecting the packed macaroni to a heating-and-pasteurizing step.  Also there are known those macaroni products which are produced by a manufacturing process similar to that stated above excepting that the packed macaroni is subjected to a freezing step at a temperature of about -30.degree.  C.
These known instant-cooking macaroni products which have been subjected to a heating-and-pasteurizing step during their manufacturing process can be instantaneously cooked and served only by heating them in hot water or through like heating means.  However, because these macaroni products have a fairly high content of water, there is the disadvantage that the .alpha.-converted starch components are subjected to .beta.-conversion during storage, and that, thus, when the instantly cooked macaroni are served, they give to the person who eats them a sense, feel and taste as if the cooked macaroni are not sufficiently boiled and feel like raw wheat flour, which is caused by .beta.-conversion which arises during the storage.  Thus, these known instant-cooking products macaroni are poor in sense, feel and taste when eaten, and in addition thereto, when these known macaroni products are stored for more than a week at room temperature, there tends to develop mold on the product, and accordingly they cannot be termed as being stable during storage for an extended period of time. 
On the other hand, those products having been given a freezing treatment are superior to those having been subjected to heating-and-pasteurizing treatment with respect to stability of quality during storage for an extended period of time.  However, these frozen products require the additional troublesome step of passing boiled macaroni through a low-temperature zone, and what is more, these frozen macaroni products have the further disadvantage that, as with the heated-and-pasteurized macaroni, the once .alpha.-converted starch components are .beta.-converted during the period in which the macaroni products are de-frozen before being served, and that thus they give similar raw wheat flour-like sense, feel and taste when the instantly cooked macaroni are eaten. 
Also, as stated in U.S. Pat.  No.  3,537,862, there is known a method of obtaining .alpha.-converted pasta by mixing wheat flour and/or other grain powder with water, followed by extruding the mixture directly through a die to form a pasta, and then steaming this pasta at an appropriate temperature while applying hot water thereto, and thereafter drying same.  This known method is able to reduce the time required for drying, as viewed from the aspect of manufacture alone, since the pasta is subjected to steaming.  Also, this method is able to eliminate the development of muddiness of the surfaces of the product which, otherwise, would be caused by the exudation of those starch components which takes place when the pasta is boiled for being served to a consumer.  However, the product obtained according to this known method requires that the product be boiled to elevate .alpha.-conversion in order to serve to the consumer for being eaten, and thus this product cannot be rendered to an edible state during a very short period of time by immersion in hot water.  If, however, it is intended to elevate the .alpha.-conversion degree of the pasta to solve such inconvenience as stated above, there will arise portions of adjacent products sticking to each other and also there will arise deformation of the products during steaming of the pasta, resulting in noneven .alpha.-conversion.  As a result, such a product will not transform uniformly to an edible state when immersed in hot water, and accordingly will fail to give the consumer a good sense, feel and taste.  As such, this known method is unable to attain the object of the present invention. 
Furthermore, there is known a manufacturing method of obtaining .alpha.-converted pasta by mixing, without heating, wheat flour and water, and extruding the resulting mixture dough under a high temperature and high pressure, and thereafter drying same, as stated in U.S. Pat.  No.  4,044,165. 
However, this known method carries out extrusion of material at a high temperature in order to enhance the degree of .alpha.-conversion of the product.  Accordingly, boiling of water will occur in the material during the extrusion, and thus there is the fear that an expansion of the material can take place.  If, therefore, the amount of the water added is decreased at the time of mixing to prevent the occurrence of this expansion, this will be accompanied by a shortage of water in the mixture which is necessary for effecting .alpha.-conversion, leading to the result that the degree of .alpha.-conversion of the extruded product becomes low, and this, in turn, will give to the consumer a feeling like raw wheat flour even when the product is transformed to edible state by immersion in hot water.  Thus, the product obtained according to this known method has the disadvantage represented by a loss of good sense, feel and taste.  As such, this prior art procedure is unable to attain the object of the present invention. 
These known products labeled as instant-cooking macaroni products generally further have the disadvantage that when hot water is poured onto the macaroni product, they tend to cause the hot water to become turbid and unclear due to partial exuding or dissolving of starch components in the hot water, resulting in a loss of good shape of the individual pieces of macaroni as well as a loss of sense, feel and taste, and that in some cases the macaroni pieces immersed in hot water tend to stick to each other locally. 
As stated, the known instant-cooking macaroni products have those various disadvantages and inconveniences as stated above which are required to be improved. 
The present inventors, therefore, have conducted research and many experiments to resolve the foregoing problems encountered in the prior art, and as a result they have arrived at the present invention based on the discovery that, by first forming a granular mixture of grain flour consisting mainly of wheat flour, especially of Semolina flour of the Durum Wheat family, while avoiding as much as possible causing the mixture to become kneaded during the mixing step, and at the same time adjusting the water content of the mixture so as to be 25 to 35% by weight relative to the weight of the starch components of the mixture, and continuing this mixing until the granules of the mixed material are distributed evenly throughout the body of the mixture.  Thereafter the mixture is subjected to a preliminary steaming to bring about an .alpha.-conversion degree of the starch components of the mixture from 60% to 80%, and that whereby the reticulate structure of the protein, i.e. gluten, contained in the mixture is caused to become fixed as this gluten progressively undergoes denaturalization due to the application of heat during the steaming step, resulting in those parts of the starch componets which have become like glue are enclosed in the reticulate structure and are inhibited from exuding to adhere to the surface of the mixture, which means that the surfaces of the subsequently molded macaroni products will become free from becoming sticky. 
The present inventors have found also that this reticulate structure of gluten contributes to the formation of a product texture having an appropriate degree of viscosity and resiliency of the molded macaroni pieces, so that when the material is appropriately shaped into individual molded pieces by means of, for example, an extruder, there occurs no development of phenomenon such as the surfaces of the individual molded pieces of macaroni will locally stick to each other and that the configuration of the molded pieces will become deformed, which have been encountered in conventional such foods, and which have been caused in the prior art foods due to excessive .alpha.-conversion during the boiling step in the manufacturing process. 
The present inventors have found further that, through their process, there can be obtained molded products of individual macaroni pieces which are uniform in configuration relative to each other and which do not develop muddiness on the surfaces of the individual molded pieces and which are free of stickiness between contacting portions of these molded pieces. 
The present inventors have also found that, even when the surfaces of the molded pieces which have been preliminarily steamed for an .alpha.-conversion degree of from 60 to 80% are contacted with water and when these water-carrying pieces of the material are subjected to further steaming till an .alpha.-conversion of the starch components of at least 90% is reached, in order to enhance the ability of these molded pieces to be instantaneously rendered to an edible cooked state, there arises no occurrence of exudation of the remaining starch components which are of a glue-like nature during this further steaming, and that accordingly there develops no sticking between portions of the individual molded pieces and there develops no deformation of these pieces, and that uniform .alpha.-conversion is established.  This means that the material does not stick onto the surfaces the molding apparatus, and that uniform molded pieces can be obtained. 
By drying the resulting molded pieces of material, the dried pieces will possess a fine porous structure having a pore diameter of 5.0-20.0 micrometers, which structure enables them to be transformed very quickly to an edible cooked state by immersion in hot water of 85.degree.  C. or higher for 5 minutes or less.  Thus, there are obtained instant-cooking dry macaroni and like macaroni products which exhibit good sense, feel and taste when eaten, and which are excellent in their stable duration when stored for an extended period of time of over one year.