DE1000223B - Freeze-drying process of meat - Google Patents

Description

GERMAN

Drying is the preferred method for preserving food. Bacteriological or enzymatic decomposition processes can be switched off under suitable conditions will. In addition, the weight loss of the product is another benefit.

Almost all foods have been able to be dried successfully so far. However, this is an exception Meat. The main reason for the poor results is the protein nature of the cellular like the fibrous components of the muscles. It causes the tendency, above all, of the myosin molecules, to lose their colloidal dispersion and coagulate with the usual drying processes. As is the case with most other foods, the diffusion of the water does not succeed to influence the drying process in such a way that it evaporates on the surface without creating a hard, shrunk product that is difficult to re-moisten with water to lead. Rather, the protein molecules are denatured, with the drying product as well the destruction of enzymes suffers further chemical changes. It is therefore extremely important to find an economical process that converts meat into a storable dry form while maintaining its most important properties as a food.

In itself, the process of freeze-drying appears suitable, which in terms of taste quality, Aroma content and, above all, the ability to rewet the dried meat To meet requirements. The main disadvantage of this method in its previous form is the long duration of the drying process, which makes the process so expensive that it is general in spite of it recognized advantages are difficult to achieve in practice. This is stated at various points in the specialist literature Set out in detail. So z. B. R. Gane: Freeze-drying of foodstuffs. Tn: Freezing and drying, report of a Symposion Held, June 1951.

As a generally accepted teaching is therefore that in the freeze-drying of food a storable Product only arises when drying to a residual moisture content of 1% or a maximum of 2% is continued. This rule has been confirmed by numerous studies. In USA is stipulated by law that dried food, including meat, has no minor residual moisture than ι ° / o may show.

Our own studies have shown that such a rule makes sense for most foods is, while meat has a special position. Experiments with thrombokinase extracts delivery freeze-drying process of meat

Applicant: Leybold high vacuum systems limited liability company,
Cologne-Bayenthal, Bonner Str. 504

Dr. med. Karlheinz Neumann, Cologne-Bayenthal
has been named as the inventor

the result, for example, that with a moisture content between 2 and 3 ° / o the enzyme

ao preparations became unusable after just a few months and with a residual moisture content of 8%> were unusable after a few weeks.

The new method according to the invention avoids the disadvantages indicated and provides by freezing

s5 drying a long-lasting dried meat suitable for nutrition with a residual moisture content between 6 and 15%. To this end, the raw or cooked fresh meat is first frozen rapidly, the critical temperature range zwisehen + 2, and - (. Less than 15 minutes) 4 ⁰ C in a short time must be passed through. This is followed by a sublimation of the ice from the frozen meat under the action of a vacuum until the dry goods have a residual moisture content of 6 to 15%. It is also possible to expose the meat to the effect of vacuum without first freezing it. In this case, the evaporative cooling that occurs when the pressure is reduced leads to the desired rapid undercooling of the meat.

It was very surprising that, contrary to previous views, a residual moisture of 6 up to 15% does not affect the shelf life and taste of the freeze-dried meat, so that the process can be terminated after these residual moisture levels have been reached.

However, this results in a significant technical advance, since it is precisely to achieve the small residual moisture of around 1 to 2%, long additional drying times are required. this shows the graph in FIG. 1, with the residual moisture for a certain types of meat (chicken) are served.

The inventive method therefore allows a

significantly better utilization of the freezing jib

Claims (5)

system, as the meat needs to remain in the system for relatively short periods of time. This is what makes it possible to use the freeze-drying process economically for preserving meat in the first place. According to the invention, the freezing drying process is to be controlled in such a way that temperatures between -5 and -8 ° C result on the surface of the meat. These values are much higher than those normally permitted for other substances. In-depth tests have shown that here, too, there is no deterioration in the storage and use properties of the freeze-dried meat. A further reduction in manufacturing costs is thus achieved, since a lower surface temperature would mean a further additional energy supply. The new process makes it possible to complete the drying process in about a third of the time required according to the previous state of the art. With a given facility, this means a tripling of production. After the freeze-drying process has been completed, the meat is immediately packed in appropriate aroma-tight casings. Suitable plastics are particularly suitable as packaging material. The packaging is expediently made in such a way that the set residual moisture no longer changes during the storage period. Under certain circumstances, however, it can be difficult and expensive to carry out such an absolutely tight packaging in which the residual moisture content no longer changes noticeably. For many purposes it is therefore easier to freeze-dry down to slightly lower residual moisture levels, namely to values that correspond to the permissible residual moisture level of 15%, less the moisture percentages that occur during the intended storage time. If, for example, it is known that the meat in a certain packaging absorbs 3%> moisture for 6 months, then one first dries to 12% residual moisture and thus has the certainty that after the permissible storage time has expired a perfect product with a maximum 15% residual moisture is present. The freeze-drying process can of course also be carried out in the open packaging if the packaging is designed accordingly. The packaging must then be closed after the freeze-drying process has been completed. Since the comparison of the shelf life of meat cannot be carried out completely without personal evaluation moments, the result obtained should be confirmed by graphical representation of the times after which a recognizable mold formation occurred (cf. FIG. 2). Of the many options for quality testing (taste, smell, etc.), this appears to be the most objective method, since the presence of a mold is equally evident for different observers, while in the other assessments (smell, taste, etc.) the opinions are often very different from one another differ. Observation of the curves shows that with residual moisture levels below 15%, no mold formation occurred during the test period, so that the product can be described as storable, since the additional taste and odor tests also did not show any noticeable deterioration. Demands for action 1. Freeze-drying process of meat, preferably for meats of higher quality, characterized in that the raw or cooked fresh meat is subjected to a rapid freezing process in order to maintain the cell structure, the critical temperature range between + 2 and -4 ⁰ C being passed through as quickly as possible, preferably in less than 15 minutes, and that freeze-drying is terminated as soon as a residual moisture level between 6 and 15% is reached. 2. The method according to claim 1, characterized in that the temperature of the meat between - 5 and - 8 ⁰ C is during the freeze-drying process. 3. The method according to claim 1 or 1 and 2, characterized in that the finished product immediately after completion of the drying process in a manner known per se using aroma-tight plastic casings in this way is packed so that the set value of the residual moisture is retained during the subsequent Storage time practically no longer increased. 4. The method according to claim 1, in particular together with claim 2, characterized in that that the residual moisture is initially chosen to be as many percent smaller than 15% as this increases as expected during the storage time, so that the meat after the intended Storage time has a residual moisture of 15%. 5. The method according to claim 1, characterized in that the rapid temperature decrease between -f- 2 and - 4 ⁰ C is achieved by rapid evaporation of a corresponding proportion of the water contained in the meat. Considered publications:
MW Tuchschneid, "The Cold Treatment of Perishable Foods", 189 to 191, 1951. For this purpose ι sheet of drawings