Scary! The beef I just bought is "jumping"! Is it a parasite?

On short video platforms, you can often see videos like this: the beef that netizens bought home keeps jumping or shaking after being cut.

So some people are worried, is there a parasite? Is it okay to eat beef that is jumping?

The "jumping" beef, captured from the video

If you encounter such a situation, you don't need to worry too much. The throbbing of beef usually means that it is fresh and edible. However, to buy really delicious meat, freshness alone is not necessarily enough. The subsequent processing of the meat and the quality of the meat are also reference factors.

01

Beef is jumping?

The phenomenon of "beef moving" is not uncommon, and it has attracted attention on social media since at least 2015. At that time, Ms. Cheng from Jining, Shandong, bought beef that kept shaking, and she took a photo of it with her mobile phone in time.

People are afraid to eat twitching beef. Image taken from the news

Shandong Satellite TV reported the incident at the time and consulted inspector Lu Suwen from the Animal Health Inspection Institute of Lixia District, Jinan City about Ms. Cheng's video.

At that time, Shandong TV reported this incident. Picture taken from the news

Inspector Lu Suwen gave a clear explanation for this phenomenon: the meat was slaughtered relatively recently, the animal's central nervous system has died, but the nerve endings around or inside the muscle have not died and are still beating. This situation will be fine if left for a while.

During the interview, the reporter also asked whether there were any unscrupulous vendors who used some means to create the illusion of muscle tremors. Inspector Lu said: "Based on my many years of experience, I have not found such a situation, and there are no drugs or other methods to cause muscle tremors."

In short, it is a transient state of muscles "shortly after the animal dies."

In theory, all kinds of animals will have such a transition period after death. However, the "cut meat tremor" seen in reality mainly occurs in beef, and is not seen in other animal meat. This may be because cattle are larger in size, and the peripheral nerves can remain active for a longer time after the central nervous system dies.

02

The freshest meat

Not necessarily the most delicious

Generally speaking, we like meat that is as fresh as possible. But in terms of taste, the freshest meat that has just been slaughtered is not always the best.

Before an animal is slaughtered, its cells are constantly metabolizing. After slaughter, different life activities stop at different rhythms, and some biochemical reactions continue, which can affect the "quality" of the meat in several ways.

First, there are some collagen and elastin in the muscle that hold the muscle cells together. The older the animal grows, the more of these strong proteins there are and the tighter the connection is, and the "older" the meat is. After the animal dies, these proteins will slowly degrade, making the meat "tender".

Second, some enzymes break down certain proteins into single amino acids or polypeptides composed of several amino acids. Some amino acids produce the "flavor" of meat.

Third, some fats will oxidize. Originally, fat oxidation is something that food should avoid, but proper oxidation of meat will bring a different flavor from fresh meat, and this flavor will be liked by many people.

This process of making meat undergo appropriate changes is called "post-ripening", which is an important area in the meat products industry. For example, high-grade steaks must undergo "dry aging" - after slaughter, large pieces of meat are quickly cooled to refrigeration temperature and hung up for a week or even half a month. In the end, the surface meat has become dry and difficult to eat, and only the inside of the steak is taken. Beef treated in this way is not only tender but also has a unique flavor. It is of high quality and naturally has a high price.

03

Acidity of meat

Will change over time

Normally, animal muscles contain a large amount of glycogen. After the animal is slaughtered, the glycogen slowly turns into lactic acid, and the pH value of the meat slowly drops, falling below pH 6.2 after 24 hours. These lactic acids make the meat tender, increase the flavor, and have a certain antibacterial effect.

Normal meat looks like this:

Normal meat, Image source: Reference [1]

However, if the pigs are frightened before slaughter or are under great stress due to other factors, they will secrete a large amount of adrenaline, causing the glycogen to decompose rapidly. After slaughter, lactic acid will form rapidly, and excessive lactic acid will make the meat pale (pale), extremely soft (soft), and have exudative (exudative). The pH value of such meat can drop to between 5.4 and 5.6 after 24 hours, and it is called "PSE meat".

This kind of meat is neither good-looking nor tasty. Typical PSE meat looks like this:

PSE meat, Image source: Reference [1]

If the decomposition of glycogen does not occur immediately before slaughter, but lasts for a long time, the lactic acid produced may be metabolized in advance. At this time, there is little glycogen after slaughter, and not much lactic acid can be converted, so the pH value cannot be fully reduced. After 24 hours, the pH value may still be between 6.4 and 6.8. Such meat is dark in color, firm and dry, and is called "DFD meat".

DFD meat is also neither good looking nor tasty. The typical color is as follows:

DFD meat, image source: Reference [1]

In reality, pork is more likely to produce PSE meat, while beef and mutton are more likely to produce DFD meat.

To avoid PSE meat, pigs should be kept in a comfortable state before slaughter, without injury or shock. The United Nations Food and Agriculture Organization recommends that pigs rest quietly for 24 hours before slaughter to retain as much glycogen as possible in the muscles.

04

Color of meat

Changes also occur in storage

The color of meat mentioned above refers to the color within 24 hours of slaughter. During longer storage, the color of normal muscle will also change.

The color of beef is mainly determined by myoglobin, which combines with oxygen to form oxymyoglobin when it comes into contact with air, and the meat then appears bright red.

The color of oxymyoglobin, copyrighted image from the gallery, any reproduction or use may result in copyright disputes

This reaction is reversible. In a low-oxygen environment, such as a vacuum-packed bag, oxymyoglobin will turn dark purple due to the loss of oxygen; however, after opening, they will combine with oxygen and quickly return to bright red.

Consumers like the bright red color. However, when exposed to air for a long time and under the irradiation of indoor light, oxymyoglobin will oxidize to form metmyoglobin. Metmyoglobin is brown, and beef loses its pleasing red color.

The color of the beef becomes darker after being left for a period of time. This is a copyrighted image from the gallery. Reprinting and using this image may lead to copyright disputes.

Many fresh meats sold in supermarkets now have a special mixture of oxygen and carbon dioxide in their packaging, which not only inhibits bacterial growth but also prevents oxymyoglobin from converting into metmyoglobin, thus keeping the meat bright in color. This technology is called "controlled atmosphere preservation".

In short, choosing meat is a science. I hope everyone can eat delicious and safe meat.

References:

[1] D. Dave, AE Ghaly. Meat Spoilage Mechanisms and Preservation Techniques: A Critical Review. American Journal of Agricultural and Biological Science.6(4):486-510,2011

Source: Guokr

The cover image and some images in this article are from the copyright library

Reprinting may lead to copyright disputes