Table 2.

Electronic sensors.

System	Measured Parameters	Species	Place of Application	Statistical Analysis	R2/ Classification Rate (%)	Reference
Gas sensor array (FishNose)	TVC, Off Odor Rancid, LAB	Atlantic salmon	Both confined and open air	PLSR	94%	[38]
Integrated metal oxide micro-sensors	TVC	Sardine	Confined air (sampling vessel)	SVM/PLSR	0.91, 100%	[39]
Optical electronic nose	Bacterial growth	Tilapia	Confined air	-----	-----	[40]
MOS sensors (Mastersense)	TVC	Plaice, salmon	Confined air	KNN	92%	[41]
Metal oxide sensors	TVBN, bacterial counts	Hairtail fish	Confined air	PCA	0.91 0.97	[42]
Metal oxide sensors (UTS NOS.E)	Freshness state	Salmon	Confined air	Hidden Markov model	96%	[43]
Potentiometric electrodes	pH, TVBN, Microbial analysis	Sea bream	Contact with filet samples	MPL, PLSR	0.96	[44]
Au/Ag wires	K-value	Sea bream	Contact with sample solution	Least Square Method	0.96	[45]
Voltammetric sensors	K-value, TVB-N	Cod	Contact with filet samples	PLSR	0.79 0.73	[46]
Commercial e-tongue (ASTREE)	K-value	Canned tuna	Contact with sample filtrate	PCA	----	[47]
Commercial e-tongue (SA402B)	8 basic sense of taste	Grass carp	Contact with sample solution	----	----	[48]
Alluminium and silica-based materials	Microbial counts	Sea bream	Near to the sample (open air)	PLSR	0.92	[50]
Chemo-sensitive compounds	TVB-N, TBA, pH	Atlantic salmon	Near to the sample (confined air)	Linear fit	0.73 0.89 0.91	[51]
Copolymer substances	TVB-N, Microbial growth	Tilapia	Near to the sample (confined air)	----	----	[52]
Anthocyanin extracts	TVB-N	Mud Carp	Near to the sample (confined air)	----	----	[53]
Filter paper coated with a sol-gel matrix	TVB-N	Red drum	Fish package	Linear fit	0.97	[54]
Polydiacetylene nanofibers (ForceSpun)	Biogenic ammines	Not specified	Near to the sample	Linear fit	0.97	[55]
Agar with natural dyes	Volatile compounds	Wuchang sea bream	Near to the sample	PCA	87.5%	[56]
Computer vision system	Lightness, Yellowness, Redness	Salmon		----	----	[57]
Canon EOS digital camera	Gill and eye color changes	Gilthead sea bream		ANN	>96%	[58]
Nikon D300 digital camera	Eye lightness	Snapper		Excel correlation function	----	[59]
Nikon D90 digital camera	Gill color changes	Indian rohu		Statistical mean and STD calculation	----	[60]
Computer vision system	Gill and pupil color changes	Tilapia		Linear fit	>0.98	[61]
Nikon D7000 digital camera	Eye chromatic	European hake		PCA	r > 0.82	[62]
Computer vision system	Texture features	Common carp		SVM K-NN ANN	91.5% 90.5% 93.0%	[63]