DE2039126C3 - Method of spray cooling beef - Google Patents

Description

30th

The invention relates to a method for spray cooling fresh beef during transport in a storage chamber by introducing a low-boiling point taken from a liquid container Coolant via openings, which are longitudinally spaced from one another, one above the item arranged spray line depending on the determination of the chamber gas temperature.

It is known in such a method (US-PS 32 87 925), liquid in the material storage chamber Inject nitrogen. However, particular problems arise when the beef shipped for relatively long periods of time, e.g. B. 24 to 30 hours or more, in a refrigerated but not frozen state should be held. Lasts of this size are often encountered in practice when the beef shipped from a slaughterhouse by rail or road to a remote retail market.

If the storage chamber is not opened frequently during transport and therefore with the outside air connected, the periodic introduction of cold nitrogen gas (by a to maintain a predetermined low temperature range) in the storage chamber to a Nitrogen atmosphere of comparatively great purity. A slight excess nitrogen gas pressure is often used maintained to prevent warm air from entering.

It has been found that fresh beef which has been exposed to a nitrogen atmosphere for periods of at least 24 hours can acquire a gray or purple color on the outside and sometimes a slippery texture. Surprisingly, this surface ^quality occurs even at low temperatures of - 1 to 5 ° C, and only with fresh beef.

That is, fresh pork does not take on an adequate surface texture when it is exposed to the same environment and temperature for the same length of time. The surface discoloration also does not occur when fresh beef is essential to the aforementioned cold nitrogen environment is exposed to shorter periods of time, e.g. B. for less than about 24 hours.

The color of fresh beef is determined by the chemical state of the muscle pigment myoglobir This complex protein contains an iron porphyrin group and can be oxygen in a loose and bind easily reversible combination, in which the iron remains in the reduced (ferrous) state, Although the iron atom combines with oxygen in myoglobin and maintains its reduced state, the oxygen, for which myoglobin is a carrier, also looks for the pigment in the oxidized ones To convert (ferric) state. In the presence of oxygen, myoglobin turns into two different ones Pigments converted, namely into metmyoglobin (brown) and oxymyoglobin (red), which oxidized or oxygenated form. The relative proportions of these two forms depend on the partial pressure of the oxygen; the formation of metmyoglobin is favored at low oxygen partial pressure.

At all oxygen pressures there is a constant conversion of myoglobin or oxymyoglobin held in metmyoglobin. As a result of the enzymatic oxidation of substrates, especially glucose, However, there is a constant supply of reducing substances that are able because; Reduce metmyoglobin. If fresh beef is kept in the air, on the surface, wc both oxygen and reducing substances are available in abundance, the light red ones Color of oxymyoglobin observed. However, there is essentially no oxygen inside the myoglobin is in the reduced state and has a typical dark purple color. As long as ir If there is a supply of reducing compounds in the tissue, the pigment remains in the reduced state as either myoglobin or oxymyoglobin. Once these connections are up are needed, the iron of the myoglobin is oxidized, resulting in brown metmyoglobin. There is also an egg apparently when beef is kept in a nitrogen atmosphere for an extended period of time.

The described discoloration of the outside of fresh beef often occurs depending on the extent and the duration of the metmyoglobin conversion only briefly. Will such beef again die exposed to normal partial pressure of oxygen in air, it will gradually bloom; d. H. it takes again a red color. The beef shipped, however, is often almost immediately upon arrival sold to retailer at destination exercise drastically limit marketability.

Fresh, chilled: beef should be kept in warm, moisture-laden air during transport not exposed frequently. Excessive moisture tends to condense on the meat condense and contribute to a slippery appearance. For long-distance transport of chilled beef meat, d. H. for transports over more than 640 km this is usually not a problem because the Doors of the good chamber are not opened frequently

observed slippery texture is therefore due to pt3 warm air. While the meat may lose its original moisture under the influence of the cooling process, that is to say, it may or may not, the refrigeration of beef cannot be improved by exposing the product to hot, humid air. Furthermore, Ji * does not solve the problem of long-distance transport cooling of fresh beef by preventing enrichment to over 21 ⁰ ZoO ₂ , so that increased flammability is excluded avoided. On the other hand, since the gas temperature is at most 5 ° C, bacterial growth and pigment conversion into metmyoglobin are delayed. The simple, compact devices that were previously used for the spray cooling of fresh beef

The gas that is exercising oxygen is enriched in oxygen, and pure nitrogen has been used for meat rapid burn come ka kih d

■ there can be rapid burns. ^r * It is also known (US-PS 31 02 777), in a storage chamber equipped with lelverdampferschlangen, ie a storage chamber with a closed cooling circuit, in which the refrigerant is consumed, compressed, cooled, condensed, expanded and then fed back to the cooling hoses a gas atmosphere consisting of 1 to

10 VoL- ⁰ OO _ä , one 0.5 to 5 times that of the acid, can be used practically unchanged.

The method of the invention has been used with success to process fresh beef for periods of time to refrigerate and preserve for at least 8 to 10 days. That means the beef is on At the end of this period of time no irreversible color change has been suffered, it regains its red color if it is exposed to the air is not slippery and by conventional standards can be considered totally

_{CO 2} amount corresponding to the volume of substance, remainder N ₂ , ao can be properly addressed by using a corresponding, open

bar at room temperature gas mixture in siges oxygen-nitrogen mixture with 10 to a 13 mol% oxygen and 87 to 90 mol% stick amount, which is independent of the Carnmer gas temperature is inserted into the storage chamber. The substance to be used and the chamber gas temperature with animal and vegetable foods to keep at - 1 to 1 ° C during 25.

The invention is illustrated below with reference to Aus

are protected, the gas mixture in the storage chamber in this process should generally consist of 4 _{% O 2} , 86% N ₂ and 10% CO ₂ , with the

Particular importance is attached to the CO proportion, the flow of oxygen concentration and to delay undesired decomposition processes.
The known method, which works with a closed cooling circuit, requires an external power source.
This is particularly important when it comes to transport refrigeration processes
problematic. Overall, the cooling system is compli- 35
adorns; it takes a long time to cool down the cooling chamber and load it off
the initial temperature to the desired lower storage tank temperature. The special problems

R. "..,, JV ----! T- »* 1Π- · -I- - 11 ·

g g

Management examples explained in more detail in conjunction with the drawings. It shows

F i g. 1 is a graph showing the item i d T

on the color value of beef ribs reveals if the meat is used for periods of up to five days is stored in cold nitrogen serving as a cooling medium,

F i g. 2 is a graph showing the influence of oxygen concentration and temperature illustrated on the color value of beef fillet,

F i g. 3 a graphical representation of the influence of temperature on the growth of aerobic bacteria

the cooling of fresh beef, especially the 40 series of beef ribs, in a gas mixture

Risk of surface discoloration is not taken into account there.

The invention is based on the object of providing a method for cooling fresh beef 13% O ₂ and 87% N ₂ for periods of up to five days,

F i g. 4 a graphical representation of the cooling speed of warm beef, if this is to be created during transport, which is simply and ^{reliably placed in an oxygen-nitrogen gas mixture at I 0} C with insensitive, only little usable space,

Figure 5 is a graph of the cooling rate of warm beef when exposed to an oxygen-nitrogen gas mixture at 3 ° C will and

F i g. 6 is a graph of the cooling rate of warm and moderately warm beef; if this is exposed to an oxygen-nitrogen gas mixture at - 1 ° C.

A number of experiments were carried out placing different cuts of beef in under

demanding equipment is feasible and that ensures that the beef reaches its destination with red color and without loss of moisture, however not slippery, achieved.

According to the invention, this object is achieved in that a mixture of liquid oxygen and nitrogen with 7 to 15 mol% oxygen and 85 to 93 mol% nitrogen are provided and the refrigerant mixture is periodically sprayed into the storage chamber in such a way that the material fSkffG b

surrounded with oxygen-nitrogen gas and the different oxygen-nitrogen environments be mergas temperature is kept at - 1 to 5 ° C. different temperature values were saved

The oxygen content of the liquid coolant. For these experiments, selected dei Mixture of at least 7 mol% prevents a Rin that meets the usual quality requirements irreversible conversion of the surface pigment obtained 4 to 72 hours after sacrifice

The meat internal or core temperatures were between 13 and 32 ° C on arrival at the test site. II In some cases the meat was from body temperature in a conventional manner by agitation

of fresh beef in metmyoglobin when the beef during the cold, nitrogen-rich gas exposed to a prolonged period of time. On the other hand, the upper limit of the Oxygen content of 15 mol%, above which there is no further improvement in the red color of the fresh Beef has been chilled down, a sourest! T cold air. Strip-shaped len The parts were removed from the gutted animals and cut into several equal-sized pieces. Ever

des of the pieces had a long back muscle and a large lumbar muscle. At the storage chamber For the first series of tests, it was a double-walled, heat-insulated storage chamber of conventional design in which a device for storing and dispensing a under Pressurized, low-boiling, liquefied oxygen-nitrogen mixture was housed. The inside of the storage chamber was 2.13 m wide, 4.1 m long and 1.82 m high. The oxygen concentrations were determined using a conventional analyzer. The temperatures of the surrounding beef Gas and the core temperature of the beef were continuously recorded. The relative Humidity was measured but not controlled. The beef was on a cantilever Suspended rail. After the beef was placed in the chamber, the chamber became with purged with the desired test gas in order to bring the oxygen content to the target value. The Test gas was sprayed into the chamber as a function of the temperature measurement in such a way that a predetermined temperature range has been maintained. To determine the quality of the beef, a number of subjective and objective experiments were made. Among other things were Reflection spectra recorded, the color, the pH, the rancidity, the taste and that The aroma is determined and bacterial analyzes are carried out. The samples were at the beginning of the test series and checked at regular intervals after storage. Probably the most informative Attempts were color tests.

The meat color scale used in these experiments is given in Table I, while the Data for the first series of experiments are summarized in Table II. In appreciating this data Note that beef with a color rating of at least 8 (purple) is fresh Color regains when exposed to air,

ίο without permanent discoloration. Color ratings below 8 can result in permanent loss of fresh color, even though beef with color ratings of at least 5 is acceptable from an economic point of view.

Table I.
Color values for meat

evaluation

description

10
9
9
8th

as 7
6th
5
4th
3

2
1

bright red

bright red

dark red

purple

purple

red-brown

purple gray

purple green

Gray

black

gray-green

Table II

attempt

Initially

Beef-

core temp.

( ⁰ C)

Chamber gas temp.

( ⁰ C)

Oi in the chamber gas

(Mol .- '/ o)

Relat. Initially Color of color of

Humid of beef beef

Chamber gas after 3 days

1 32 -1 0.1-0.2 <90 Red purple 2 32 5 0.2-0.8 <90 Purple purple 3 24 -1 0.1-0.2 <90 purple purple 4th 32 5 0.4-1.4 <90 purple purple 5 31 1 1.5-3.0 90 Purple Purple 6th 21 1 8.0-10.0 <90 Purple Purple 7th 36 1 8.0-10.0 <90 Purple Purple 8th 30th 1 10 > 90 Purple Red 9 27 3 7th > 90 purple Red 10 30th 3 10 > 90 Purple Red 11th 13th 5 0.8-7.0 <90 Purple purple 12th 35 5 0.8-7.0 <90 Purple purple

It can be seen from the tables that in experiments Nos. 1 to 4 the oxygen concentrations in the nitrogen-rich gas were extremely low (0.1 to 1.4 Mol-VoO _x ) and that the purple color means a permanent loss of fresh color after three days. In particular, it should be pointed out that this occurred at relatively low temperatures of −1 to S ^° C., at which the rate of propagation of aerobic bacteria is desirably low and it could be expected that a relatively minor pigment oxidation to the undesirable brown metmyoglobin occurs. In experiments No. U and 12, the oxygen concentrations are lower trations higher than in experiments 1 to 4 (0.8 to 7.0 mol.- · / · O ₂ ), but on average still below the lower limit of the method according to the invention, ie 7 mol.- ⁰ / « . The purple color

again leaves an irreversible discoloration and a recognize considerable surface oxidation to metmyoglobin.

In contrast, Runs Nos. 6-10 illustrate the superior results obtained with the

Processes according to the invention are obtainable. After three days of storage, the color of the beef was either the highly desired red (experiments No. 8 to 10 or the reversible purple red (experiments

No. 6 and 7). Run no. 9 is of particular importance since it shows that the red color in an atmosphere of 7% oxygen and 93 ⁰ Zo nitrogen can be obtained at 3 ° C if the beef at the beginning has a purple-colored surface. Run no. 5 seems in some respects with test Nos. 1 to 4 are not in compliance because the beef color did not deteriorate from the original Purple, although the oxygen concentration only 1.5 to 3.0 mol ⁰ Zo fraud. The explanation for this is probably due to the fact that the relative humidity in the chamber was higher in experiment no. 5 than in experiments nos. 1 to 4.

In another group of experiments, a plastic chamber of 120 cm was 60 cm X 60 cm used to simulate X to various environmental conditions during the cooling of fresh beef during transport. The chamber was flushed with the oxygen-nitrogen mixture at a flow rate of 1 l / h. The control meat samples were exposed to circulating air. The relative humidity was thereby regulated. that Glycerine solutions of different ratios were provided in shallow dishes within the test and control rooms. In order to regulate the relative humidity in the test room, the oxygen-nitrogen gas mixture was passed through a glycerine solution * before it was introduced into the chamber. In these particular experiments the relative humidity was kept at 70%.

In the graphs of FIGS. 1 and 2, the data from these experiments are compiled, the influence of ambient temperature and oxygen concentration on the color of show two different pieces of beef (rib and fillet) for periods of up to five days.

If one compares the experiments with 13 ⁰ ZoO ₂ and 21 ⁰ ZoO ₂ at 3 ° C., it can be seen that the color of the beef was very similar at the end of the storage period. The ambient gas consisting of 13 ^fl Zo O ₂ and 87 ⁰ _{ZoN 2} is advantageous insofar as it avoids the possibility of oxygen enrichment and thus increased flammability.

The tests at 3 ° C and 6 ° C with 13 «Zo O ₂ show, after a longer storage period, a remarkable and unexpected difference with regard to the beef color. For example, it follows from FIG. 1 that after five days of storage at 3 ^° C., the piece of rib still had the maximum color rating of 10, while the ^{sample stored at 6 °} C. only had a color rating of 3, ie an irreversible gray, which is good for corresponds to the trade of an unusable product. Similarly, FIG. 2 recognize that the fillet piece after five days of storage at 3 ° C has a color rating of 5 and is therefore usable, while the sample stored at 6 ° C had a color value of only 2, which corresponds to an irreversible black and thus an unusable product.

FIG. 3 shows the data from bacterial counts in rib samples in a preferred environment (13 VoO ₂ and 87% ZoN.). In one case the temperature was 3 ° C and in the other case it was outside the range of -1 to 5 ° C according to the invention, namely 6 ° C. This isolates the temperature influence on the rate of spoilage of beef because the number of bacteria is a measure represents for the accumulation of slime on the outside. Conventional smear methods (American Public Health Association, 1958) are used to estimate bacterial counts. Aerobic and anaerobic organisms were cultivated; tryptone-glucose-yeast extract agar and thioglycollate agar were used. F i g. 3 clearly shows that the number of bacteria after four to five days of storage surprisingly at 6 ° C is several

ίο orders of magnitude greater than at 3 ° C. From it the significance of the temperature range from - 1 to 5 ° C for achieving the improved results follows of the present proceedings.

The F i g. 4 and 5 show the results of a further series of tests which reveal an additional advantage of the preferred embodiment in which the oxygen-nitrogen gas mixture surrounding the beef is kept between -1 and 1 ° C. In these experiments, the round pieces of beef hind quarters were placed in the same refrigerator compartment as used for the experiments in Table II, and in gas with a temperature of I ⁰ C (Fig. 4) and 3 ⁰ C (Fig. 5). chilled. The temperature was set by means of the

Probes at depths of 25 mm (S), 76 mm (M) and 152 mm (D) are constantly monitored. The curves show a remarkable difference in cooling speeds, even though the gas temperatures differ by only two degrees. For example, was determined by the 1 C warm gas ^c a temperature of 3 ° C in 152 mm depth within 48 hours (F i g. 4), while it required the use of 3 ° C warm gas of a 72-hour cooling to the beef bring it to 3 ° C at a depth of 152 mm; that is, the cooling time was 50 ⁰ Zo longer. This difference is of great importance because the rate of meat discoloration is temperature-dependent and the greater cooling rate significantly reduces the amount of metmyoglobin formation.

The method explained can basically be used for beef delivered at any temperature. Preferably, however, the beef is cooled to a core temperature below about 16 ° C using conventional means before it is exposed to the cold oxygen-nitrogen gas mixture. The beef can then be cooled down to essentially gas temperature within a much shorter period of time; surface discoloration is minimized in the manner discussed above. This was demonstrated in a further series of ashing in which the beef with core temperatures of 16 ⁰ C and 34 ⁰ C and delivered in an oxygen-nitrogen gas mixture by - I ⁰ C was cooled. After cooling for one day, for example, the initially 16 ° C warm beef had cooled to around 2 ° C, while the initially 34 ° C warm beef still had a temperature of 10 ^: C.

In summary, it can be stated that fresh beef can be used for relatively long periods of time (in of the order of five days) without irreversible discoloration and slippery texture who saved the can by being surrounded with a cold gas discharged from 7 to 15 mole ⁰ Z ₀ oxygen and 85 to 93 mol .- »Zo is nitrogen and - is kept 1 to 5 ^C C.

See S sheet drawings

709 610/164

Claims (3)

Patent claims: 1. A method for spray-cooling fresh beef during transport in a storage chamber by introducing a low-boiling refrigerant taken from a liquid container through longitudinally spaced openings of a spray line arranged above the goods as a function of the determination of the chamber gas temperature, characterized in that a mixture of liquid oxygen and nitrogen having 7 to 15 mol .- "*" oxygen and 85 provided ⁰ Zo nitrogen to 93 mol and the Kaitetragergemisch periodically so sprayed into the chamber in the container, that the material with oxygen-nitrogen Surround the gas and keep the chamber gas temperature at - 1 to 5 ° C. 2. The method according to claim 1, characterized in that a liquid oxygen-nitrogen mixture with 10 to 13 mol.- ^fl / o oxygen and 87 to 90 mol-o / o nitrogen is used. 3. The method according to claim 1 or 2, characterized in that the chamber gas temperature as is kept at - 1 to 1 ° C.