Judge whether the longan is bad based on its appearance, smell, texture, and taste.

1. Appearance: The appearance of good longan meat should be bright red or reddish brown, and the flesh should be plump and tender. Bad longan flesh may be black or reddish in color, and the flesh may be dry, shriveled, or have rotten spots.

2. Smell: Good longan meat should have a rich and sweet taste, similar to the aroma of candied dried fruits. Bad longan meat may have a rancid or moldy smell.

3. Taste: Good longan meat should have a soft and tender texture, and the meat should be juicy and elastic in the mouth. Bad longan meat may taste dry, woody, or cloying.

4. Taste: Good longan meat tastes sweet with a hint of sourness. Bad longan meat may be bland, bitter, or have an off-flavor.