Method of tenderising meat before slaughtering

Abstract: A method of pre-tenderising meat is provided which involves stunning an animal (1) with a mechanical stunning pistol (6) to cause brain death, infusing a proteolytic enzyme (such as papain bromelain or ficin for example) into the animal under gravity with a syringe (7) whilst the animal's heart is still beating and then bleeding the animal in order to stop the heart beating after a suitable time has elapsed for the enzyme to be distributed within the vascular system of the animal. The enzyme can be infused more easily when the animal is in a prone position, and the process is faster and more humane than prior art processes in which the enzyme was injected into the conscious animal.

Description: The present invention relates to a method of pre-tenderising meat. It has been known for many years that if an animal is injected with a proteolytic enzyme before the animal is slaughtered, the tenderness of the meat obtained from the animal is enhanced. It should be noted that in processes of this type much if not most of the enzyme action which is responsible for the tenderisation occurs during cooking. Acordingly such processes are referred to herein as "pre-tenderising" processes. A number of suitable enzymes are known, including bromelain, ficin and papain. In the past, as disclosed in GB1161722 internal haemorrhaging and other undesirable physiological side effects sometimes occurred before the animal was slaughtered. It was originally thought that these side effects were due to impurities to the enzymes used, and accordingly GB 1161722 discloses a method for preparing a purified bromelain solution comprising adjusting the pH of the solution to at least 7.5 and maintaining the solution at this pH for at least six hours. Subsequently, the enzyme present in the solution is reversably de-activated. It is explained GB1448498 and its equivalent IR38718 that proteolytic enzymes, which commonly comprise an active enzyme component and a reversibly inactive enzyme component (which is gradually-activated when injected into the animal's body) can cause an adverse reaction in an animal which is due solely to the active enzyme per se . Accordingly GB1448498 (and IR38718) disclose certain disulphide compounds which are capable of reversibly deactivating proteolytic enzymes. A proteolytic enzyme deactivated in this manner contains little or no activated enzyme and when injected into an animal's body, is slowly reactivated over a period of time by reducing compounds such as thiols present in the animal's body. IR44891 discloses a method of reversibly deactivating a proteolytic enzyme, namely papain or ficin which does not require the use of a disulphide or other compound which would require Government regulatory approval. In the process described in IR44891, the papain or ficin is reversibly deactivated by subjecting it to a pH of 11 to 12.5. The resulting reversibly deactivated proteolytic enzyme can be safely injected into a living animal and is gradually re-activated in the animal's vascular system by the action of heat and reducing compounds such as thiols which occur naturally in the animal's body. Thus it will be apparent that many of the problems associated with ante-mortem meat pre-tenderisation have been substantially overcome, and antemortem meat tenderisation has received regulatory approval in the United Kingdom. In practice, a beast is led into a weighing crate and weighed in order to determine the required dose of proteolytic enzyme. The weighing crate doubles as a restraining pen. A halter is put round the animal to turn its head to one side to expose the jugular vein, into which the calculated dose of proteolytic enzyme is injected. The animal is subsequently slaughtered. However the above process requires a skilled operator, is somewhat cumbersome and time consuming and does not lend itself to automation. Furthermore there is continuing concern among animal rights pressure groups and others that such a process might cause unnecessary suffering to the animal. A further inefficiency arises from the delay between injection and slaughtering. An object of the present invention is to alleviate at least some of the above disadvantages. Accordingly, the present invention provides a method of pre-tenderising meat wherein a proteolytic enzyme is introduced into the vascular system of an animal and the animal is stuck and bled after sufficient time has elapsed for the proteolytic enzyme to be distributed through the animal's vascular system by the action of the heart, characterised in that the animal is stunned, and the proteolytic enzyme is then introduced into the vascular system of the substantially brain-dead animal whilst the animal's heart is still beating. Accordingly the enzyme can be introduced whilst the animal is in a prone position and no weighing crate or other restraining means is required. Furthermore the jugular vein can be found and the enzyme injected much more easily when the animal is prone and lifeless, and accordingly, much less operator skill is required. Preferably the animal exhibits substantially no involuntary limb movement immediately prior to introducing the proteolytic enzyme. If such involuntary movement is detected, it can be stopped by pithing the animal. In the case of cattle for example the animal is normally shot in the head with a captive bolt and is then pithed by mechanically disrupting the remains of the animal's brain with a suitable implement. However it is considered that the animal is substantially brain dead immediately after stunning and is incapable of feeling pain at this stage. Although it is considered that the main application of the invention is to bovine animals it is envisaged that the invention is also applicable to other edible animals which are commonly slaughtered for human consumption such as pigs for example. Normally, stunning does not stop the animal's heart from beating (although it may be advisable to check this in individual instances) and the heart is capable of beating for a considerable time after brain death. Preferably the animal is bled within five minutes of introducing the proteolytic enzyme. Preferably the animal is weighed at a first station (for example by being guided over a weighing platform) and is subsequently stunned at a second station (in a stunning box for example) which is different from the first station, the amount of the proteolytic enzyme being determined in accordance with the weight of the animal. Although it is not essential that the proteolytic enzyme is reversibly deactivated, this is preferable since there is a danger that active enzyme might cause the animal's heart to stop beating and impair the distribution of the proteolytic enzyme in the animal's blood stream. The proteolytic enzyme may be papain, bromelain or ficin for example. A method of pre-tenderising meat in accordance with the invention will now be described by way of example only with reference to the accompanying drawing, Figure 1, which is a diagrammatic elevation showing the main stages in slaughtering and injecting cattle. As shown in Figure 1(a) the animal is first led onto a weighing platform 2 and the required dosage of 4% acqueous papain solution is calculated from the weight indicated by the scale 3 of the weighing platform and also on the basis of the sex and age of the animal. A guillotine door 4 is opened and the animal is moved forward into a stunning box 5. The door 4 is then closed and the animal is shot in the head using a captive bolt pistol 6. At this stage the animal is optionally pithed and is released from the stunning box by opening a hinged door 10 which is rotated about its axis as shown by the curved arrow in Figure 1(a). The lifeless animal then falls onto a horizontal floor surface as shown in Figure 1(b) and the enzyme solution is infused into the jugular vein under gravity with a burette 7 containing the required dosage of 4% acquous papain solution. After infusion the body is shackled by the rear legs and hoisted upright. After two minutes the beast is stuck and bled and dressed in a conventional manner and is conveyed over a bleeding trough 9 on an overhead conveyor 8 as shown in Figure 1(c). EXAMPLE 1 The above process was applied to a number of cattle in order to test its efficacy. The test results were as follows: All the carcases were dressed in the standard way, weighed and classified after bleeding,then placed in a chiller set at +1°C until ready for evaluation, after forty eight hours. To evaluate the presence of enzyme in the muscle tissues, several muscles were taken and subjected to three types of test. The muscles taken were: leg, striploin, shin, silverside and the two fillets either side of the shoulder blade. The test were (a) heating in a water bath set at 60°C for three hours, (b) dry roasting in an oven at 175°C until an internal temperature of 70° C was achieved, and finally (c) steaks were grilled on medium heat, for seven minutes per side. The water bath results were as follows: Cut a) b) c) d) e) f) g) h) Silverside 5 5 1 2 4 2 N/A 4 Striploin 5 5 1½ 4 5 2 N/A 4 Blade Fillet (1) 4½ 5 1 3 4 1 N/A 5 Blade Fillet (2) 4½ 5 1 3 5 1 N/A 4 Leg 5 5 1½ 3 4 1 N/A 4½ Shin 5 5 1 3 4 1 N/A 4 The above tabulated values range from 1 (no breakdown) to 5 (mushy) on a subjective scale. The following day, two of the cuts, i.e. the Blade Fillet and the Silversides were cut into small roasting joints and placed in a Rapidaire convection oven set at 175°C, until an internal temperature of 70°C was achieved. The results were as follows:- The evaluation of the cooked meat was made on the subjective scale of 1 - Tough to 10 = V. Tender by four experienced tasters. Blade Fillet Joints A.K. B.S. S.W. I.R. Average a) 7 6 6 4 5.75 b) 9 9 9 9 9 c) 3 2 2 2 2.25 d) 7 5 6 7 6.25 e) 7 6 6 6 6.25 f) 2 1 2 N/A 1.7 h) 7 8 6 8 7.25 Silversides A.K. B.S. S.W. I.R. Average a) 6 8 6 7 6.75 b) 8 9 9 9 8.75 c) 5 3 3 8 4.75 d) 6 5 4 5 5 e) 6 4 (variable) 6 5 5.25 f) 3 2 2 5 3 g) 8 8 8 8 8 h) 7 8 7 7 7.25 The final evaluation was to griddle Blade Fillet Steaks on medium heat for seven minutes per side, turning once. Again the grading was 1 = Tough, 10 = V. Tender, on a subjective scale. A.K. B.S. S.W. I.R. Average a) 4 3 4 4 4 b) 8 8 8 8 8 c) 4 2 2 3 2.75 d) 6 6 3 6 5.25 e) 6 3 6 2 4.25 f) 3 3 1 1 2 h) 6 5 6 6 5.75 It will be seen from Tables 2, 4 and 5 that with the exception of Example f) (in which the vein could not be found) the tenderness of the meat was better than the tenderness obtained in control example c) (in which no enzyme was injected). Furthermore it will be apparent that the tenderness was comparable to the tenderness obtained in comparative example h) (in which the enzyme was injected before stunning). Furthermore the average time between stunning and sticking the animal in the examples of the invention was of the order of 2½ to 3 minutes, which is appreciably shorter than the period of approximately six minutes between infusing and sticking which is required in the prior art process. It is envisaged that the problem in finding the vein as experienced in example f) should not occur once experience has been gained in using the new technique. The problem experienced in example d) in which the animal's heart stopped beating could be detected by checking on the heart action, for example by using a stethoscope or by inserting a hollow needle into a vein and observing whether blood is periodically expelled from the needle. It is envisaged that similar results will be obtained if other proteolytic enzymes such as bromelain or ficin for example were used. Accordingly it will be seen that the invention provides a humane and practical method of pre-tenderising meat which is well suited for an automated slaughtering process.

Claims: A method of pre-tenderising meat wherein a proteolytic enzyme is introduced into the vascular system of animal (1) and the animal is stuck and bled after sufficient time has elapsed for the proteolytic enzyme to be distributed through the animal's vascular system by the action of the heart, characterised in that the animal is stunned, and the proteolytic enzyme is then introduced into the vascular system of the substantially brain-dead animal (1) whilst the animal's heart is still beating. A method as claimed in Claim 1, wherein the animal (1) exhibits substantially no involuntary limb movement immediately prior to introducing the proteolytic enzyme. A method as claimed in Claim 1 or Claim 2 wherein the animal (1) is bled within 5 minutes of introducing the proteolytic enzyme. A method as claimed in any preceding Claim wherein the animal (1) is stunned with a captive bolt. A method as claimed in any preceding Claim wherein the animal (1) is pithed after being stunned but before the proteolytic enzyme is introduced. A method as claimed in any preceding Claim wherein the animal (1) is weighed at a first station (2), and subsequently stunned at a second station, the amount of proteolytic enzyme being determined in accordance with the weight of the animal. A method as claimed in Claim 6 wherein the animal (1) is weighed by being guided over a weighing platform (2) at said first station. A method as claimed in any preceding Claim wherein the animal (1) is stunned in a stunning box (5), then a proteolytic enzyme is introduced, and then the animal is stuck and conveyed along a bleeding trough (9) by overhead conveyor means (8). A method as claimed in any preceding claim wherein the proteolytic enzyme is a reversably deactivated enzyme. A method as claimed in any preceding claim wherein the proteolytic enzyme is papain, bromelain or ficin. A method as claimed in any preceding claim wherein the animal (1) is a bovine animal.

Inventors: WARREN SIMON JAMES, WARREN, SIMON JAMES
Applicants: BRITISH BEEF CO LTD, BRITISH BEEF COMPANY LIMITED
Application year: 1991
Main classification: A23L1
IPC codes: A23L1, A23B4