1, appearance observation: seaweed is dark brown or dark brown, with hard texture, thick filamentous fibers and certain elasticity. Nostoc flagelliforme is light yellow or golden yellow, with soft texture, fine filamentous fibers and slippery touch.

2, water characteristics: seaweed will gradually soften after soaking, but still maintain a certain toughness, there will be a certain brown dissolution in water. Nostoc flagelliforme will soften rapidly after soaking, the filamentous fibers will unfold, and there will be no obvious dissolution in the water.

3, taste and taste seaweed has a tough taste, has a certain chewiness when chewing, and tastes salty. Nostoc flagelliforme is soft in taste, easy to bite when chewing and light in taste.