And before people ask about sniffing it, the second paragraph:

People often recognize spoiled meat through a characteristic rotting odor caused by chemical compounds called biogenic amines or BAs. Food quality inspectors quantify these compounds using procedures that involve direct meat sampling and time-consuming laboratory analysis. However, once meat is sealed and distributed for commercial retail, such testing becomes impractical, making spoilage difficult to detect.

You can’t sniff it through the packaging. Even when opened, your nose isn’t accurate enough to know if something has just started to spoil, or if only a little bit of it has. And not everyone has good (or any) sense of smell.