Pallavi Lodhe, Priyanka Kar, Aamir Bhat, Rajat Bagdas, Santhosh V R and S. Talukder
Division of LPT, Indian Veterinary Research Institute, Izatnagar, UP-243122
Tenderization process of meat begins immediately after animal’s death and followed with disruption of the muscle structure by endogenous proteolytic enzyme systems. It is influenced both by pre and post slaughter interventions. These Interventions are electrical stimulation, suspension methods, blood tenderization, tumbling, use of exogenous enzymes and traditional ageing etc., currently employed by meat industry to improve the meat tenderness. Technology advancement resulted in development of several novel methods for maximizing the tenderness which are quick, economical,non invasive, green and energy efficient. By comparing traditional and advancedtechnological methods it is easy to understand feasibility and benefits of novel technologies. Here discussion has been made about the benefits and advantages of different emerging tenderization techniques such as hydrodynamic pressure processing, chemical methods, enzymatic methods.Application of moderntechnologies provides potential to reduce energy consumption, production cost, improve sustainability of meat sector without infrastructural changes of meat production chains.
Key words: meat tenderization, electrical stimulation, tender meat, consumer satisfaction, meat quality
Meat tendernessis defined as some total of mechanical strength of skeletal muscle tissue. Tenderness is one of the most important quality attribute perceived by the consumer and factor affecting consumer satisfaction and perception of taste. There is huge variation between tenderness of meat obtained from different meat species. These variations are influenced by breed,age, genetic makeup and pre and post slaughterchanges, condition of nutrition, amount of exercise of animaletc. Tenderness also depends on amount of connective tissue present between the muscle fiber and to a less extent on the thickness of muscle fibre themselves. Several methods through which tough meat obtained from different animal especially aged animal, domestic animals can be converted into reasonably tender meat.
Mechanism of tenderization
Tenderization process is nothing but the proteolysis that is the degradation of skeletal, cytoskeletal and myofibrillar proteins by enzyme systems leads to the meat tenderization. There are three proteolytic enzyme systems viz., Calpain system, Lysosomal Cathepsin, Multicatalyticproteinase complex. The Calpain andmulticatalytic proteinase complex both are present in sarcoplasm.These enzymes cause changes in myofibrilar and surrounding connective tissue like collagen and ground substances like proteoglycans.
Methods of meattenderization
1. Conditioning of meat
It is also called as ageing, ripening, setting up. It is a natural process of tenderization when meat stored or aged post rigor at 0-3°Ctemperature in absence of microbial spoilage,the proteolytic enzymes of muscle fibre brings desirable changes that is called conditioning or ripening and there is marked increase in flavor, juiciness, tenderness etc. But these changes inhibited completely below the freezing temperature.
Cooking of meat which is having more contractile proteins makesmeat tough but cooking of meat which is having more connective tissue like collagen makes it tenderer. Cuts having less connective tissue are cooked with dry heat,broiling, roasting,barbecuing etc.Meat cuts with more connective tissue need long and slow cooking techniques viz., braising, stewing that is moist heat process. Cooking process convert the tough collagen into tender gelatin.
3. Pressure treatment
The pressure treatment decreases the toughness of meat. Hydrodyne process is used for beef muscles. This process uses a small amount of explosive to generate a shock wave in water. The meat piece is submerged in water and due to pressure treatment there is acceleration of glycolysis and causes improvement in tenderness.
4. Mechanical methods
Tender stretch method
Stretching ofmuscle givestenderizing effect and shortening of muscle gives toughening effect. It can be achieved by hanging beef sides or whole carcass by hook inserted behind the Achilles tendon during conditioning. Some group of muscle stretch while others freelycontract. In this method many muscles are into stretch tension. During this process the sarcomere length increases.Hanging from aitch bone by using hook inserted into obturator foramen or Pope’s eye stretching also can be done. In this case the muscles of hind limbremains in relaxedposition. Pelvic suspension or hip free suspension is more effective in enhancing tenderness, but if kept for longer time the shape of carcass get changed. The duration of 24 hours of hanging by aitch bone and then to Achilles tendon is the most effective process. It gives improvement in the tenderness of rump, thick flank, and strip loin. This method is equivalent to three weeks of aging at 2°C.
It is the cuttingof backbone in certain places on the carcass without cutting loin muscles. In this process the tension on the individual muscles can be reduced by severing bones and ligaments. Cutting of Achillestendon is easy to implement on commercial slaughter lines. Doing this after 45 minutes of slaughter can gives significant improvement in cattle and pork.
It is the process of disintegration of the external surfaces of the meat pieces, disruption of the muscle network, and a release of myofibrillar proteins that increases protein extractability and solubility. During this process the meat pieces are kneaded in rotating drums allowing the meatto gain energy by friction and free falling.
5. Electrical stimulation (ES)
It is a new commercial method of meat tenderization. In this process there is application sufficient current through the carcass immediately after slaughter and the current cause the muscle to contract and use the glycogen, ATP and creatinine phosphate present in muscle. It is done before the onset of rigor. In this process there is a rapid series of muscle contraction and relaxation which accelerates rigor mortis. Calcium released during contraction might stimulate Calpains and cause greater proteolytic breakdown becauseduring this process muscle the temperature and pHof muscle remains high. It can be done at any stage but better within 30 minutes of bleeding otherwise muscles lose their capacity to react with electrical stimulation.Time between bleeding and stimulation should be minimum for effective tenderization,since more time between bleeding and stimulation increases the post mortem resistance and muscles become short and tough. It is very much effective in sheep but less effective in pig because in pig the rigormortis is quicker. But with very fast chilling procedures the electrical stimulation can be beneficial in pork also.In theES the electrodes are applied between the muzzle and nose, chest and hind legs. Here a series of pulses of 1-2 sec duration and for a period of 90 Sec, it is applied.ES improves quality of meat obtained from aged or spent animals and increases tenderness and reduces ageing time.It improves appearance and color of leanmeat; advance the process of rigor mortis. It can avoid the cold shortening and thaw rigor process.There are two types of ES,
High voltage ES, in this case the current of 500-1000 voltsis used.It is a fast process. It can be applied much later after bleeding.It does not depend on nervous system, but is expensive, complex and requires safety equipments.
Low voltage ES, in this case the current of less than 75 volts is used. It is applied immediately after bleeding and it is a slower process as compared to high voltage ES.It involves nervous system.It is cheaper and does not require safety equipments.
6. Pulsed electric field (PEF)
It is a novel technology which was first applied to the commercially sterilize fruit juices. Food is passed through or placed between two electrodes and exposed to electric field pulses of short duration in the range of several nanoseconds to several milliseconds with electric field strength of 0.1-80 kV/cm. The shorter processing time and lower treatment temperature of a pulsed electric field compared to traditional process in technology and the potential for continuous flow make it very appealing technology for foodprocessors. It alters membrane properties and potentially affects the activity of calpains and thus influences rate and extent of tenderization duringageing.Itmodifies several qualities such as color, texture, water holding capacities and enhances mass transfer process due to its potential for cell membrane permeabalization. PEF is the stand alone technology where process parameters can be optimized for different muscles. It also has limited side effects such as severe structural and oxidative changes and off flavor development.
7. Shockwave or Hydrodynamic pressure processing
This process improves the tenderness of fresh meat cuts by utilizing high pressure shock waves generated by detonation of small amount of high energy explosives or by electric discharge of high voltage between two electrodes under water. These are the mechanical pressure pulses which propagate through the meat and generaterupture effect that tears the muscle structure and cause the dissipation of mechanical stress under boundaries ofacoustic impedances. It is a low cost,non invasive method with no chemical and microbial spoilage of meat.
8. High pressure processing or high hydrostatic pressure processing
It is a non-thermal food preservative techniquewhich improves quality and shelf life of food. It uses pressure under isostatic conditions by means of liquid transmitter and distributes pressure uniformly throughout the food material without changing shape and dimension of food in packaging. At low pressure less than 200 MPa it improves tenderness of pre-rigor meat by increasing proteolytic activity. High pressure damages sarcoplasmic reticular Membrane and increases calcium in the cytosol which activatescalpains protease system. Pressure of 100-200 MPa causes leakage of Cathepsin into cytosol. This leads to disruption of myofibrilar structure and thus improves tenderness.
9. Chemical method
By use of salt solution or Acid (Acetic acid/Lactic acid/Citric acid)
Salt/ acid process increases the meat collagen solubility and decreases the muscle pH.In this process the cathepsin breaks muscle structures and increases water holding capacity and causes myofibrilar swelling.
By infusion of CaCl2
It accelerates the process of ageing.One day of ageing of CaCl2tenderizes muscle similar to 7-10 days of traditional aging.
This process is advantageous because there no chance of over tenderization and no special equipment required, it is easily adaptable at retail, household and restaurant level.It also fortifies Calcium in meat.
10. Enzymatic methodsby using plant enzymes
This is a traditional, cheaper, convenient method for tenderization of meat and meatproducts. These enzymes are present in animal tissues, plants, microbes like bacteria and fungi, like papain, microbial protease, bromelin and trypsin etc. The enzyme, endopeptidase catalyzes the hydrolysis of internal peptide bonds in meat protein molecule and results in meat tenderization by disruption of muscle structure. Application of enzyme in meat can be done by various process viz., dipping insolution of enzyme, pumping the enzyme solution into meat, re-hydration of freeze dried meat by enzyme solution, and by pre-slaughterinjection (10-15 min before slaughter). Pre-slaughter injection of enzyme is the best process of meat tenderization and the optimum activity is obtained at 40-60°C. the activity of proteolytic enzymes depend on the concentration of active enzymes, pH, temperature, stability of enzyme, ability to come in contact with its substrate and its ability to digest the native protein as compared to heatdenatured proteins. The ideal meat tenderizers are the proteolytic enzymes with specificity for collagen and elastin proteins in connective tissue at relatively low pH of meat. The most important meat tenderizing enzymes are as follows,
Cucumin (Cucumis trigonus Roxb) fruit extract:
Cucumis fruit extract is made from dried,ground fruits. It increases the tenderness and juiciness of the meat.The proteolytically active principle is called as cucumin and is extracted in 10% NaCl and ammonium sulphate.Activity is highest at pH 5 and temperature 70°C.
Papain (Garcia papaya):
It is produced from latex and fruit of Carciapapaya. It has powerful hydrolyzing activity on fibrous proteins and connective tissue, at optimum temperature more than 65°C and at early stage of cooking. It can be injected just before slaughter or after slaughter or just before cooking.
Zingibain (Zingiber officinale roscae):
Clean and dried rhizome of a root stock of Ginger is used for its spicy properties and medicinal value. It’s proteolytically active principle is. Ginger protease is a thiolproteinase and its maximum activity can be achieved at 60-70°CatpH 6. The proteolytic activity of zingibain of is higher under acidic condition and at higher temperature.
Bromelin, proteolytic enzyme is obtained from pineapple. Whereas, the ficin is derived from figs.
Bacterial and fungal enzymes:
Different bacterial and fungal protease are available for meat tenderization like Protease 15,Rhozymes,Fungal amylase, Hydrolase D etc. both in liquid and powder form. The bacterial and fungal proteolytic enzyme act only on proteins of muscle fiberand causing the digestion of sarcolemmaand muscle fiber, disappearance of nuclei and cause eventualloss of crossstriations.But these enzymes do not attack the native collagen as it denatured by heat during cooking. They cause the breakdown of heat denaturedconnective tissue protein into soluble hydroprolin containing molecule.
Technological interventions like electrical stimulation, suspension method, use of exogenous enzyme and aging are effective in the meat tenderization but have some limitations and disadvantages. The modern technology of tenderization techniques like hydrodynamic pressure processing, high pressure processing has advantages over the traditional techniques.However they require initial capital investments and changes in the mid plant design. Further more research is required to optimize the process parameters for different muscles and curds before some of this novel method for find commercial application. The combination of methods such as enzymatic and mechanical or any other method within thematic method would have wider beneficial effect. Post slaughter processing such as hot bonding, electric stimulation, cooking greatly influences the tenderness of meat products.
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