How Electrical Stimulation Improves Meat Tenderness

Meat quality is an essential factor for both producers and consumers. Tenderness, in particular, is one of the most valued attributes, as it directly influences the meat eating experience. Several factors influence tenderness, such as species, age of the animal and post-mortem handling. In this context, electrical stimulation (ES) has emerged as an effective technique to improve tenderness by accelerating the meat tenderisation process and improving overall meat quality.

What is electrical stimulation?

Electrical stimulation involves the application of electrical currents to the freshly slaughtered animal to induce muscle contractions before rigor mortis sets in. This technique was originally developed to accelerate the maturation of meat and improve its texture. During slaughter, oxygen supply ceases and ATP, which is essential for muscle relaxation, is depleted. Electrostimulation helps to reduce the time in which rigor mortis occurs and, in doing so, helps the maturation process to be faster and more effective.

How does Electrical Stimulation work?

Electrical stimulation acts on muscles at the biochemical level. After slaughter, muscles undergo significant post-mortem changes, such as acidification, loss of flexibility and the development of rigor mortis. The application of electrical stimulation through electrified rails before rigor mortis is complete generates forced contractions in the muscles, accelerating glycogen degradation and ATP depletion. This process decreases the rigidity of rigor and contributes to a rapid onset of the maturation phase, where natural enzymes tenderise the flesh.

The effect on the muscle fibre is remarkable. The repeated contractions induced by the electric current break part of the myofibrillar structures, especially those formed by contractile proteins such as actin and myosin. This micro-damage, together with the enzymatic activity that follows, leads to increased tissue fragility, resulting in more tender meat.

Key benefits of Electrical Stimulation

1. Accelerated maturation: Electrostimulation allows muscles to enter a state of maturation more quickly. Normally, rigor mortis can cause stiffening of the muscle if it occurs at low temperatures, resulting in less tender meat. By applying electrostimulation, collagen and proteins are broken down more efficiently, which softens the muscle fibres and improves the final texture of the meat.
2. Reduction of cold shortening: One of the main challenges in meat preservation is to avoid ‘chilling shortening’. This phenomenon occurs when meat is rapidly chilled before the rigor mortis process is complete, causing excessive muscle contraction. Electrical stimulation, by accelerating this process, minimises the risk of shortening, resulting in more tender meat.
3. Optimisation of water retention capacity: By improving cell structure, Electrical Stimulation helps meat retain more water, which not only improves juiciness, but also reduces weight losses during storage and cooking. This feature is especially important for producers looking to maximise quality without increasing operating costs.
4. Improved tenderness: One of the main benefits of Electrical Stimulation is its ability to improve tenderness. Studies have shown that, by applying appropriate electrical stimulation, it is possible to significantly reduce the time required to reach ideal meat maturity. This process accelerates the proteolysis of muscle fibres, softening the connective tissue and allowing for greater palatability.
5. Improvement of sensory properties: In addition to tenderness, electrostimulation can influence other sensory attributes, such as colour and flavour. By improving blood circulation and accelerating post-mortem blood drainage, ES contributes to cleaner and more attractively coloured meat. Improved tenderness has also been observed to be accompanied by a more uniform chewing experience, which may positively influence flavour perception.

Biochemical factors influencing meat tenderisation

The process of muscle contraction and subsequent meat tenderisation is linked to several key proteins. Myosin and actin, two proteins present in myofibrils, are central to the contraction and relaxation mechanism. During electrical stimulation, post-mortem changes in these proteins, together with the release of calcium ions, trigger a series of biochemical reactions that accelerate the degradation of muscle fibres.

In addition, enzyme activity plays a crucial role in meat tenderisation. In particular, proteases such as calpain and cathepsins are responsible for the degradation of connective tissues, which contributes to a more tender and chewy meat. The electrical stimulation process favours the activation of these enzymes, improving tenderness from the early stages of maturation.

Technical considerations for the application of electrostimulation

The effectiveness of electrostimulation depends on several technical factors, among them:

• Voltage and frequency: The appropriate voltage varies according to species and carcass size. In cattle, some voltages are used, while in pigs and sheep other voltages are usually used. The frequency of stimulation is also a decisive factor and can help both in blood drainage and in accelerating muscle contraction and tenderisation.
• Duration of the stimulus: The duration of the stimulation is also important as depending on the time it may cause damage to the muscle structure and negatively affect the texture of the meat or may not even be effective in achieving the desired tenderisation.
• Time of application: The ideal timing for the application of stimulation is crucial. Applying electrostimulation before critical pH levels are reached in the muscle prevents shortening of muscle fibres and improves tenderness. Stimulation results in an accelerated lowering of pH, which prevents abnormalities such as chilling shortening, a common problem in untreated refrigerated meats.

Electrical stimulation has established itself as a key tool in the modern meat industry. Not only does it significantly improve meat tenderness, but it also accelerates the maturation process, reduces the time required to obtain a quality product and improves water retention. By optimising these characteristics, the resulting meat is juicier and offers a better consumer experience, which in turn increases its commercial value. This process can also be adapted to different species and slaughter methods, making its application versatile and suitable for various productions. In short, ES not only benefits producers, but also end consumers.