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The cherry-red beef looks bright and tempting, and many consumers believe it is a sign of freshness. However, when purchasing vacuum-packed steaks in supermarkets, people often find that the meat color is generally darker, leading them to think that such steaks are not fresh. So, is this really the case?

 

Ruan Guangfeng, Deputy Director of the Kexin Food and Health Information Exchange Center, stated in an interview with the reporter from China Consumer News that color is often the most intuitive basis for judging the freshness of food. However, for red meats such as beef, color can sometimes "lie". The darker color of vacuum-packed steaks only indicates that the packaging is well sealed.

 

Ruan Guangfeng explained that most of the blood in slaughtered beef has drained away, and the remaining red color mainly comes from myoglobin in the muscle tissue. Myoglobin is the key factor that causes the color change of beef. The function of myoglobin is to store oxygen in muscles, and its color will undergo three transformations with changes in oxygen content: the first is a completely oxygen-deprived state, in which myoglobin will deoxygenate, presenting a deep purple or purplish red color (deoxyhemoglobin). For example, deep-layer muscles that have just been cut or muscles in vacuum packaging bags often exhibit this color. The vacuum-packed steaks that consumers buy at supermarkets have a darker color, not because they are not fresh, but because the packaging is tightly sealed and the oxygen has been pumped out. The second is a low-oxygen state, where beef is exposed to an environment with insufficient oxygen supply but not completely isolated from oxygen for a long time. At this time, the iron ions in beef myoglobin will be oxidized, and the color will gradually turn to grayish brown or brown (ferric myoglobin). The third is when beef is exposed to air, myoglobin will quickly combine with oxygen, turning into the most familiar cherry red color (oxyhemoglobin).

 

In summary, one cannot determine whether beef is fresh or spoiled solely based on changes in its color. Generally, only when the beef turns gray overall, accompanied by an unusual odor and a sticky feeling, can it be inferred that its quality has changed.

 

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