DE2039126B2 - METHOD OF SPRAY COOLING BEEF - Google Patents

Description

The invention relates to a method for spray cooling of fresh beef in transit in a storage chamber by introducing a a liquid container removed, low-boiling coolant over at a longitudinal distance from each other lying openings a spray line arranged above the product 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 relatively great purity. A slight excess nitrogen gas pressure is often used maintained to prevent warm air from entering.

It was found that fresh beef, which is subjected to a StickstoiTatmosphäre during periods of at least 24 hours can have on the outside a gray or purple color and sometimes a slippery texture, surprisingly it comes to this surface ^6s beschaiTenheit even at low Temperaluren from - 1 to 5 C. and only for fresh beef This means that fresh pork does not acquire a corresponding surface quality if it is exposed to the same environment and temperature for the same period of time. The surface discoloration also did not appear when fresh beef was exposed to the abovementioned cold stickiness environment for significantly 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 myoglobin certainly. This complex protein contains an iron porphyrin group and can contain oxygen in a loose and bind easily reversible combination in which the iron remains in the reduced (ferrous) state. Although the iron atom in myoglobin combines with oxygen 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 into fatty myoglobin (brown) and Öxymyoglobin (red), the oxidized or oxigenic form. The relative proportions of these two Forms depend on the partial pressure of oxygen, with the formation of metmyoglobin at low Oxygen partial pressure is favored.

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 to Reduce metmyoglobin. If fresh beef is kept in the air, on the surface will where both oxygen and reducing substances are available in abundance, the bright red Color of oxymyoglobin observed. However, there is essentially no oxygen inside; the myoglobin is in a reduced state and has a typical dark purple color. As long as in If the tissue has a supply of reducing compounds, the pigment remains in the reduced state as either myoglobin or oxymyoglobin. Once these connections are used up the iron of the myoglobin is oxidized; brown metmyoglobin is formed. It comes to that 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 for a short time. Will such beef again that exposed to normal partial pressure of oxygen in air, it gradually blooms; i.e. H. it takes again a red color. However, the beef shipped is often practically immediately upon arrival Sold to the retailer at destination, otherwise even a temporary discoloration drastically limit marketability.

Fresh and chilled food should be used during transport; Beef warm air laden with moisture 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 kn this is usually not a problem, because di Doors, the good chamber are not opened often

The slippery texture observed is therefore due to moist warm air. While that Beef does not lose its original moisture content under the influence of the refrigeration process, i.e. H. dry out, the cooling of the beef cannot be improved by the fact that the goods are often warmer, exposed to moist air. Furthermore, the problem of remote transpurt cooling of fresh Do not dissolve beef by oxygenating the surrounding gas which can cause rapid burns.

It is also known (US-PS 31 02 777), in a storage chamber equipped with refrigerant evaporator coils, ie a storage chamber with a closed cooling circuit, in which refrigerant is evaporated, compressed, cooled, condensed, expanded and then fed back to the cooling coils, consisting of a gas atmosphere from 1 to 10 vol. ⁰ o O ₂ , an amount of CO., corresponding to 0.5 to 6 times the oxygen volume, remainder N. “to be maintained by adding a corresponding gas mixture, which is apparently at room temperature, to one of the chamber gas temperature independent amount is introduced into the storage chamber. Thus, animal and vegetable foods are protected during relatively long periods of time before spoilage, the gas mixture in the storage chamber in this method, in general, from 4 ^Ü ο O ₂ is intended. 86 ° ο N ₂ and 10% CCX exist, whereby the COv component is given particular importance in order to avoid unwanted decomposition processes.

The known method, which works with a closed cooling circuit, requires an external power source. This is particularly problematic in transport refrigeration processes. The overall cooling system is complicated: it takes a long time to cool down the cooling chamber and load it off the outlet temperature to the desired lower storage tank temperature. The special problems the cooling of fresh beef, especially the risk of surface discoloration, is not there Taken into account.

The invention is based on the object of a method for cooling fresh beef to create that easily and reliably during transport with insensitive, little usable space demanding equipment is feasible and that ensures that the beef reaches its destination with a red color and without loss of moisture, but not slippery.

This object is inventively achieved in that a mixture of liquid oxygen and nitrogen having 7 to 15 MoI.- ⁰ ο oxygen and 85 to 93 Mol.- ⁰ Zo nitrogen provided in the liquid container, and the refrigerant mixture is periodically so sprayed into the storage chamber, that the material is surrounded by oxygen-nitrogen gas and the chamber gas temperature is kept ^{at - 1 to 5 C C.}

The oxygen content of the liquid refrigerant mixture of at least 7 MoL- ⁰ Zo prevents an irreversible conversion of the surface pigment of fresh beef into metmyoglobin. when the beef is exposed to the cold, nitrogen-rich gas for an extended period of time. On the other hand, the upper limit of the oxygen content of 15 moles- ⁰ %, above which no further improvement in the red color of the fresh beef fish can be achieved. oxygen enrichment to over 2I ⁰ AO _{2 is} prevented, so that increased flammability is excluded. With a chamber gas temperature of at least - IC, freezing of the moisture in the beef is avoided. On the other hand, since the gas temperature is 5 C or less, bacterial growth and pigment conversion into metmyoglobin are delayed. The simple, compact devices, as they were previously used for the spray cooling of fresh beef with pure nitrogen, can be used practically unchanged.

The method of the invention has been used with success to process fresh beef for periods of time to be chilled and preserved 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

ίο be addressed properly.

Particularly expedient it proved a fiüssices oxygen-nitrogen mixture containing 10 to 13MoL- ⁰ O oxygen and 87 to ⁰ O 9OMoL- nitrogen to use as well as the chamber gas temperature of - 3 to 1 to keep C.

The invention is illustrated below with the aid of exemplary embodiments explained in more detail in connection with the drawings. It shows

Fig. 1 is a graph showing the influence reveals the color value of beef ribs from oxygen concentration and temperature, when the meat is stored in cold nitrogen as a refrigerant for periods of up to five days will.

Fig. 2 is a graph showing the influence of oxygen concentration and temperature on the color value of beef fillet illustrated.

F i g. 3 a graphical representation of the temperature influence on the growth of aerobic bacteria in cattle ribs in a gas mixture of 13 ⁰ OO., And 87 ⁰ ZoN ₂ during periods of up to five days,

F i g. Figure 4 is a graph of the cooling rate of warm beef when this is exposed to an oxygen-nitrogen gas mixture at 1- C,

F i g. Figure 5 is a graph of the cooling rate of warm beef when it is exposed to an oxygen-nitrogen gas mixture at 3 C and

6 shows a graphic representation of the cooling speed of warm and moderately warm beef, if this is an oxygen-nitrogen gas mixture exposed at - 1 ° C.

A number of experiments were carried out in which different cuts of beef were stored in different oxygen-nitrogen environments at different temperatures. For these tests, selected sides of the bovine animals corresponding to the usual quality requirements were procured 4 to 72 hours after sacrifice. The meat inside or core temperatures were between 13 and 32 ^° C on arrival at the test site. In some cases the meat had been cooled down from body temperature in a conventional manner by circulating cold air. Strip-shaped loin parts were removed from eviscerated animals and cut into several equally cross pieces. Each-

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 training in which one s facility to store and dispense an 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. That 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 Recovers color when exposed to air 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

valuation

description

10
9
9
8th
7th
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)

Οι in the chamber gas

(Mol.-Vo)

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 No. 1 to 4 the oxygen concentrations in the nitrogen-rich gas were extremely low (0.1 to 1.4 mol- ⁰ ZoO ₂ ) 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 5 ° 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 nos. 11 and 12, the oxygen concentrations trations higher than in experiments 1 to 4 (0.8 to 7.0 mol.-Vo O ₂ ), but on average still below the lower limit of the method according to the invention, ie 7 mol- ¹ vol. The purple color in turn leaves irreversible discoloration and considerable surface oxidation to metmyoglobin recognize.

In contrast, Runs Nos. 6 through 10 illustrate the superior results obtainable with the method of the invention. The color of the beef was (after three days of storage, either the highly desired red Experiment Nos. 8 to 10 or the reversible magenta (Experiments

No. 6 and 7). Experiment No. 9 is of particular importance because it shows that the red color can be obtained in an atmosphere of 7% oxygen and 93% nitrogen at 3 ° C if the beef initially has a purple surface. Experiment No. 5 seems to be somewhat inconsistent with Experiment Nos. 1 to 4 because the beef color did not deteriorate from the original purple-red, although the oxygen concentration was only 1.5 to 3.0 MoL- ¹ Vo 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 measuring 120 cm X 60 cm X 60 cm was used to simulate various environmental conditions for cooling 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. Relative humidity was controlled by placing different ratio glycerine solutions 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. The relative humidity was kept at 70 ⁰ O in these special experiments.

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.

Comparing the trials with 13 ⁰ ZnO ₂ and 21 «/ oÖ., At 3 ° C, can be seen. that the color of the beef was very similar at the end of the storage period. However, the Urngebungsgas from 13 ⁰ OO "and 87 ⁰ Zon is advantageous in that as it avoids the possibility of oxygenation and increased flammability.

The tests at 3 ° C and 6 ° C with 13 ⁰ 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 the rib piece after five days of storage at 3 ⁰ C 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 one for the trade corresponds to 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.

3 shows the data from bacterial counts in rib samples in a preferred environment (13VoO ₂ and 87 Vo N ₂ ) , namely at 6 ° C. This isolates the influence of temperature on the rate of spoilage of beef, because the number of bacteria is a measure of the accumulation of mucus on the outside. Conventional smear methods (American Public Health Association, 1958) are used to estimate bacterial counts. Aerobic and anaerobic organisms were cultivated; Triptone 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 according to Table II, and in gas with a temperature of 1 ° C (Fig. 4) and 3 ° C (Fig. 5) chilled. The temperature was continuously monitored by means of three probes at depths of 25 mm (S), 76 mm (M) and 152 mm (D). The curves show a remarkable difference in cooling speeds, even though the gas temperatures differ by only two degrees. For example, was by means of l ° CwarmenGases a temperature of 3 ⁰ 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 in 152 mm Bring depth to 3 ° C; that is, the cooling time was 50% 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 chilled to a core temperature below about 16 ° C using conventional means prior to exposure to the cold oxygen-nitrogen gas mixture. The beef can then be cooled down to substantially gas temperature in a much shorter period of time; surface discoloration is minimized in the manner discussed above. This was demonstrated in a further series of incinerations in which the beef was delivered with core temperatures of 16 ° C and 34 ° C and cooled in an oxygen-nitrogen gas mixture of -1 ° C. After cooling for one day, for example, the initially 1 (j ^o C warm beef had cooled to about 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, which consists of 7 to 15 Mol.- ⁰ / · oxygen and 85 to 93 mol .-%> nitrogen and - is kept 1 to 5 ° C.

In addition 5 sheets of drawings

609529/26

Claims (3)

20 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 in the container a mixture of liquid oxygen and nitrogen with 7 to 15 mol .- / »oxygen and S5 bis; 93 MoL- ⁰ ο nitrogen is provided and the chalk carrier mixture is periodically sprayed into the chamber in such a way that the material is surrounded by oxygen-nitrogen gas and the chamber gas temperature is kept 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 ⁰ Zo oxygen and 87 to 90 mol ⁰ 0 nitrogen is used. 3. The method according to claim 1 or 2, characterized in that the chamber gas temperature is kept ^{at - 1 to 1: C.}