Table 2.

Label-free and label-based strategies for chemical contaminants detection by SERS in food.

Strategies	Recognition Elements	SERS Substrates	Distribution	Ref.
Label-free method	C≡N bond	Au NPs	Orange peels	[18]
	C–N	Poly(ethylene terephthalate)/indium tin oxide/Ag platform	Apple peels	[25]
	N–O bond	Ag NPs	Water	[19]
	O–S–O bond	Ag NPs	Wines	[29]
	O–S–O bond	Sandwiching the ZnO-paper disc	Wines	[30]
Label-based method	Probe molecules	Ag NPs	Water	[20]
	Modified substrates	Au nanorod-incorporated melamine foam	Chili sauce, dried chili, and chili powder	[21]
	aptamers	PCR sealing membrane	Cabbage	[22]