Why do animals experience rigor mortis after death, but supermarket meat does not?

People who like to watch detective movies and read detective novels may come across this piece of physiological knowledge: after an animal dies, the body will gradually harden and rigor mortis will occur.

When rigor mortis sets in, the elasticity of the muscles begins to decrease, and when rigor mortis reaches its peak, the muscles reach maximum stiffness.

So does anyone have the same question as Tadpole - why is the meat not hard after being slaughtered and transported to the supermarket?

In fact, we can eat tender meat that is not prone to rigor mortis thanks to a great man, a famous scientist and historical figure - Benjamin Franklin, a founding father of the United States.

Image source: Wikipedia

An ordinary boy who loves to play with lightning

The story begins with his love for thunder and lightning.

In 1752, the intrepid Franklin allegedly conducted a famous experiment during a thunderstorm: he flew a kite in such extreme weather to prove that the appearance of "lightning" was caused by electricity.

You know, some other scientists who conducted similar experiments at the same time were killed by electric shock, so there is a lot of controversy about whether Franklin conducted this experiment, but there is no doubt that Benjamin Franklin invented something very great, that is, the lightning rod.

But what everyone doesn’t know is that this brave young man is not only a boy who loves to play with lightning... he also likes to use electricity to make turkeys... What is going on?

In 1749, Franklin had a sudden idea that after electrocuting a turkey, the meat tasted tender. In his book Experiments and Observations on Electricity, Franklin clearly recorded: "We successfully killed a turkey with electricity for dinner, and roasted it on an electric roasting fork after it died. Miraculously, the meat of the turkey killed by electrocution tasted surprisingly tender."

Image source: Wikipedia

An accidental discovery made Franklin a pioneer in using electric shock to make "fresh meat".

What determines the tenderness of “fresh meat”?

When consumers buy meat, one of the most important quality indicators is the freshness of the meat. In order to ensure the freshness of the meat, some countries have formulated corresponding standards. For example, Australia has a set of specially formulated MAS (Australian Meat Standards).

In modern food research, it is found that the tenderness of meat is mainly determined by three key points:

The first point is the length of the animal's sarcomere (the basic unit of muscle fiber). The second is the decomposition of myofibrillar protein (proteolysis) in the muscle. The third is the hardness of the muscle connective tissue.

Muscle cross-section diagram, source: Wikipedia

However, the hardness of muscle connective tissue is related to the muscle type and age of the animal, and it is difficult to change artificially. Therefore, in the meat processing industry, it is also called background toughness, that is, basic hardness.

Therefore, changing the sarcomere length and the breakdown of myofibrillar protein in the muscle is the main way to tenderize meat.

Development of electric shock technology in meat processing

In the 20th century, a large number of studies have found that an electrical stimulation technique can make meat tender, that is, electric shocks are given to the carcasses of animals that have died not long ago after being slaughtered. In the mid-20th century, after the popularization of refrigerators, some meat processing companies have begun to apply electrical stimulation technology to change the taste of meat on a large scale, so that beef and mutton will not become hard after being put into the refrigerator.

Image source: Wikipedia

According to Bekhit, a food technologist at the University of Otago in New Zealand, New Zealand was the first country to use electric shock technology to prevent muscle stiffness.

Seventy years ago, meat processing workers in New Zealand discovered that if cattle and sheep were placed directly into the freezer without being processed after slaughter, the meat would become very hard due to muscle contraction. These teeth-hard beef and mutton were exported to Europe, causing dissatisfaction among many European consumers. Later, New Zealand began to widely adopt and apply the use of electric shock to tenderize the meat.

Bekhit introduced that in New Zealand, cattle and sheep are subjected to a short voltage stimulation of around 25,000 volts after being slaughtered. Later, Australia and other countries followed New Zealand's example and followed suit.

Why does electric shock tenderize meat?

In fact, the principle of electric shock tenderization has not been fully understood so far. However, scientists believe that electric shock stimulates the meat, which consumes the energy reserves of the muscles, that is, it promotes muscle glycolosis.

When an animal is electrocuted shortly after death, the energy is used up early, so the muscle fibers cannot contract during the slow rigor mortis process, and the muscles will not become stiff.

In addition, electrical stimulation can also quickly release calcium ions in the muscles, thereby increasing the rate of protease decomposition and making the protein in the muscles decompose more quickly.

In addition to electric shock technology, hanging the meat upside down and using mechanical stretching can also achieve a certain meat tenderizing effect.

Although electric shock can tenderize meat, it may also affect the color of the meat, cause water loss, and make the meat tough, so it is not a perfect way to tenderize meat.

Many meat processing experts will apply salt and sugar to the meat, increase the concentration of protease, and stretch the muscles before the animal rigor mortis sets in. These are common practices in the industry to tenderize the meat.

In addition to the above methods, some stores also use chopping, mincing, pounding and other methods to tenderize the meat.

Tender and delicious steak

If Franklin knew that the electric shock technology he accidentally discovered would be so developed by modern people, he would definitely sigh in admiration.

Do you know any other ways to tenderize meat?

END

Review expert: Wang Guoyi, postdoctoral fellow in food safety.

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