The takeaway beef has colored reflections. Is it bad? Can I still eat it?

Many people love to eat beef, such as beef ramen, beef vermicelli, stewed beef brisket, and fatty beef slices... they never get tired of eating them.

When eating beef, have you ever noticed this phenomenon: some beef slices have metallic colored reflections. Many people think that the beef is spoiled and dare not eat it.

Why does beef reflect color? Can such beef still be eaten? What should we pay attention to when buying beef?

Image source: ETTV News

https://www.ettoday.net/news/20170305/878034.htm

Part 1

Can I eat beef if it has colored reflections? It depends

Generally speaking, it is normal for beef to have colored reflections, and in most cases it is edible.

The phenomenon of metallic reflections on the surface of beef often occurs, and is more common in meat processing. The colors can also vary, including green, yellow, and orange.

In the 1970s, scientists conducted a special study on the phenomenon of colored reflections in meat. At present, there are two main reasons for the colored reflections in beef:

One reason is the "reflective grating diffraction effect", which is a common optical phenomenon in food physical properties, just like when playing with soap bubbles, you will often see rainbow-like colors on the surface of the bubbles under different light.

The rainbow colors on the surface of soap bubbles (Image source: veer Gallery)

The most common application of the "grating diffraction effect" is the fiber optic cables that are everywhere in our lives. Animal muscle tissue is very similar to cables, which are formed by muscle fibers tied together one by one. After the meat is cut, a regular concave-convex structure will form on the surface of the cut muscle fibers. When light shines on it, a "reflective grating diffraction effect" will be generated, and we will see a variety of colors. Not only beef will have colored reflections, but lamb and chicken sometimes also have this phenomenon.

Animal muscle tissue (Image source: Wikipedia)

Image source: Xidian University

Generally speaking, the more complete the cross section of muscle fibers, the more likely they are to have rainbow colors. The survey found that the meat of the semitendinosus muscle of beef is more likely to produce rainbow colors, with a production rate of more than 80%, which may be because the meat here has the richest muscle fibers and less fat; the second is the longissimus dorsi muscle, with a production rate of about 21%; the meat of the psoas major and biceps femoris rarely has rainbow colors.

In addition, the processing of meat will also affect the appearance of rainbow colors. When processing meat, it is easier to see rainbow colors in whole pieces or slices of meat that are cut intact. However, some hand-torn meat and meat that has been tumbled have irregular muscle fibers and messy angles, so it is not so easy to have rainbow colors. If other things are added to the meat (such as braised beef with glue injection, or starch coated on the surface), it will affect the distribution of muscle fibers and light reflection, and it is not so easy to have rainbow colors.

The rainbow effect of beef rolls in hot pot restaurants is not very obvious

(Image source: freepik.com)

Another reason for colored reflections is that the meat is contaminated by bacteria, causing it to rot. For example, protein rot will produce brown, gray or light green, fat rot will produce green, and some bacteria and mold activities can also cause meat color changes. This is also a concern.

How to distinguish which situation it is? There is a very simple way to distinguish:

Grating diffraction requires a suitable angle to be seen. Look at the beef from a different angle. If there is no colored reflection, it means the meat is not rotten and can be eaten with confidence.

However, if you find that the color does not disappear after changing the angle, or that a large area changes color, or even the smell becomes rotten, then the meat may have gone bad and it is best not to eat it.

Part 2

How to buy beef more safely?

For people who love to eat beef, the worst thing is to buy fake and unsafe beef. In addition, with the New Year approaching, many families start to buy New Year goods and stock up some beef for the New Year. So, how can we buy beef more safely? It is recommended that you pay attention to the following points when buying beef:

1. Don’t blindly pursue “good quality and low price” and beware of beef that is too cheap

Beef is delicious, but it is still more expensive than chicken, duck, and pork. Nowadays, the most common way to adulterate meat is to use cheaper meat instead of more expensive meat. This practice is difficult to distinguish with the naked eye or by tasting, but it can still be distinguished by the price. If the price is significantly lower than the market price, it means that there is a high possibility of a problem.

2. Buy fresh beef first

Fresh beef is usually not easy to fake, but meat slices, meat rolls, meat fillings, meatballs, sausages, bacon, jerky and other products have been processed and it is difficult to tell whether they are still the original beef. If possible, try to buy fresh beef.

3. Try to buy beef from regular supermarkets, markets, and e-commerce platforms

The main reason for adulteration is to save costs, which is more likely to happen in small shops, restaurants and roadside stalls. Regular supermarkets, vegetable markets and e-commerce platforms usually have stricter food safety management requirements, and the quality is more guaranteed.

Image source: freepik.com

Part 2

How to eat beef healthily?

How to eat beef healthily? You can pay attention to the following four points:

1. Eat in moderation, don't eat too much. my country's dietary guidelines recommend eating 40 to 75 grams of livestock and poultry meat every day, which is less than two taels. A plate of hot pot beef may weigh half a catty to eight taels, which is too much.

2. Pair vegetables, fruits and other ingredients to achieve food diversity. The key to health is food diversity. Eat everything, but not too much of anything. Balance vegetables and meat (the lettuce wrap barbecue party said it was delicious).

Image from freepik.com

3. Drink less soup and eat as much meat as possible. There is actually very little nutrition in the soup, and most of it is in the meat. The milky white beef soup contains a lot of fat, which tastes good, but is not healthy.

4. Use less oil and salt when cooking beef. Use less oil and pepper salt when frying steak, and use less sauce beef, braised beef, etc. These methods often contain more oil and salt. Eating them frequently will easily lead to excessive intake of oil and salt, which is not good for health. Try to eat stir-fried or stewed beef, or try to season the beef with natural seasonings such as pepper, garlic, and star anise.

There are so many things to know about choosing and eating beef! The New Year is coming, what kind of meat are you stocking up for the New Year?

References:

[1] Ji Yanfeng, Wan Hongli, Peng Zengqi, et al. Effects of common processing techniques and additives on rainbow spots in beef [J]. Food and Fermentation Industries, 2007, 33(6): 16-19. DOI: 10.3321/j.issn:0253-990X.2007.06.005.

[2] Ji Yanfeng. Research on the control technology of rainbow spots in beef products[D]. Jiangsu: Nanjing Agricultural University, 2007. DOI:10.7666/d.Y1215636.

[3] Ji Yanfeng, Wan Hongli, Peng Zengqi, et al. Investigation and analysis of the phenomenon of rainbow spots in meat and meat products [J]. Food Science and Technology, 2007, 32(10): 115-117. DOI: 10.3969/j.issn.1005-9989.2007.10.034.

[4]Dietary Guidelines for Chinese Residents. 2016

Cover image from veer gallery

Produced by: Science Popularization China

Produced by: Ruan Guangfeng

Producer: Computer Network Information Center, Chinese Academy of Sciences

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