a) Field of the Invention
The invention is directed to a process for stabilizing the shape of pasta, wherein the product is pressure-molded from dough with an approximate water content of 28% to 35%, heated to higher temperatures, and dried to a moisture content of less than 13% for storing at room temperature.
Classic pasta drying is based on known thermal principles whereby heat is transmissible in three forms:
radiation heat PA1 convection by transmission through air PA1 heat conduction (not important in pasta drying).
Concretely, the goal is an optimal drying process. Apart from management of the product and air temperatures, this is controlled chiefly by the relationship between the water content of the product and the relative humidity of the air. Assuming a difference in the equilibrium moisture between the product and the air, the drying process proceeds faster the higher the product temperature. This will be readily understood by the layman from experience in washing dishes in the kitchen; that is, drying should be effected at the highest possible temperature since moisture is transported fastest at higher temperatures. However, the pasta expert knows that only failure will result without controlling and adhering to proven conditions. Recent experience shows that very precise control over all drying conditions is necessary at temperatures above 70.degree. C., in particular above 80.degree. C. Extensive series of laboratory tests have even proven that there is a kind of "sound barrier" blocking a further intensifying of the drying process. When this is exceeded, e.g. a product of excellent value in terms of quality criteria which is placed on the table immediately after drying will break into many pieces without external forces. This breaking up sometimes takes minutes, sometimes hours or days.
The invention proceeds from the problem of designing the process in such a way that no "after-damage" occurs when employing high temperatures and short drying times and so that the best management of operations can nevertheless be applied vigorously and economically with respect to product quality.
The solution to this problem, according to the invention, is characterized in that the water content of the outer layer is increased in the final drying zone while the product is still warm, particularly by moistening the surface. In fact, there is no "after-damage" to the pasta products dried according to the invention, whether this is long pasta or short pasta, even under extreme climatic manipulation.
Products which were processed at the same time and with the same climatic conditions but without the addition of water according to the invention resulted in individual damage or total breakage depending on the test. This result can be traced back to great or extreme differences in tension within the product, particularly in the cooling phase at the end or near the end of the drying, since the surface is dried more intensively than the core of the pasta in traditional drying. Drying by evaporation proceeds so quickly in the final drying stage, particularly in the cooling zone, that there may be an insufficient amount of water flowing from the interior of the product to the outermost layers. The intensive action of the evaporating process when pure gasoline is applied to the hand is well known; the rapid evaporation draws warmth from the hand which gives the sensation of cooling. In the case of pasta, the evaporation heat is drawn off from the product. An excessive drying and brittleness of the boundary layer occurs. This results in a delayed shrinking process of the core of the product relative to the outer layers during cooling and accordingly in breaking tensions which can no longer be withstood by the outermost layer which has now become a crust.
This is counteracted by a deliberate increase in the water content in the outer layer which acts as a buffer allowing a more, uniform reduction in the humidity and temperature inside and outside the product. The addition of water to the surface provides a compensation of tension particularly in the cooling phase. At higher temperatures, the water penetrates very quickly into the surface and additionally imparts a plastic or elastic behavior to the outermost layer. In this way it is possible to avoid completely a brittleness and cracking during the relatively short period of reduction in temperature e.g. from 90.degree. C. to 25.degree. C. Drying can be reduced to below the desired final value beforehand so that, on the average, the product has the desired final water content again only after the addition of water. An essential idea of the invention consists in that the surface of the product is moistened after drying at a high temperature prior to a rapid reduction of the temperature of the product.
The invention allows for various particularly advantageous constructions. It is suggested that 0.1% to 2%, preferably at least 0.4% to 1.2%, water be added with respect to the entire product.
The best results are achieved, even with very intensive drying, when the addition of water is effected at a product temperature in excess of 60.degree. C., preferably even in excess of 75.degree. C. After pressing, long pasta are first heated to more than 80.degree. C. in less than an hour and are dried to approximately 13% moisture content in 2 to 4 hours at high temperature. Short pasta are heated to more than 80.degree. C. in a similar climate in less than 30 minutes and are dried at high temperature in 1 to 3 hours.
Another essential fact consists in that the addition of water is effected over a short period of time of 3 to 20 minutes, preferably 5 to 10 minutes, so that a relatively small percentage of water penetrates only into the surface and is not distributed over the entire cross section, which would increase the drying time. For example, assuming that the water only penetrates in a layer of 1/10 the thickness of the product, e.g. spaghetti, during the water addition period, a 1% water addition to only 1/10 of the product gives a moistening of 10%. This means that a product dried e.g. to 12.5% has a corresponding water content after the addition of water to the outermost layer. Immediately after the addition of water, the product temperature is reduced to less than 60.degree. C., preferably less than 30.degree. C. or even to the ambient temperature in the event that water is added at the end of drying.
In the case of products which are particularly susceptible to breakage, additional water can be added to the surface of the pasta for 5 to 10 minutes after the main drying or prior to the final drying at a product moisture content of less than 15%. Thus, in this case water is added twice. The addition of water can be effected by means of vapor or mist.
The invention is further directed to a device for stabilizing the shape of pasta which includes a dough press, a continuously operating tunnel dryer with climate control by member or zone, respectively, and is characterized in that a water addition member is arranged preferably at the end of the drying. It is particular important that control means be associated with the moistening member so that the addition of water can be limited with respect to time and the amount of water and climate can be monitored in a precise manner.
Further, it is important that the water addition member include means for maintaining a climate at high temperature. A moistening member can also be arranged at the beginning and at the end of the final drying. A sample removing device is advantageously arranged at the beginning and at the end of the final dryer for optimal control of the entire drying process.
The invention is explained in more detail in the following with reference to several embodiment examples.