Penaeus orientolis prawn freshness rapid determination method based on electronic nose and non-linear stochastic resonance technique

Figures & data

Figure 1. Physical/chemical index examination results: (a) firmness; (b) pH; (c) TVB-N; (d) TVC; (e) sensory evaluation.

Table 1. Sensory scheme for evaluating the jumbo squid during the refrigerated storage

	Attribute degree
Attributes	5	4	3	2	1
Appearance of the skin	Very bright	Bright	Slight dull	Dull	Very dull
Touch	Very hard	Hard	Slight soft	Soft	Very soft
Color	Pink	Slight red	Red	Dull red	Black red
Odor	Neutral	Slight fishy	Fishy	Slight odorous	Pungent odorous
Viscidity	Smooth	General smooth	Slight viscous	Viscous	Very viscous

Figure 2. E-nose detecting results: (a) prawn sample measurement; (b) PCA result: PC1 VS. PC2; (c) PCA result: PC1, PC2 VS. PC3; (d) SR SNR spectrum; (e) DCSSR SNR spectrum; (f) freshness predicting model.

Table 2. Multiple variable regression between SR eigen values and physical/chemical indexes (F= 77.1599)

Index	Value	Error	t-Value	P
Y-Intercept	−79.5226	7.10593	−11.191	0.04674
Firmness	0.00102	0.00732	0.13966	0.91166
pH	−0.03659	0.82895	−0.04414	0.97192
TVB-N	0.08123	0.04032	2.01448	0.29333
TVC	−2.96E-08	1.81E-08	−1.63267	0.34986
Sensory	−0.34408	0.17609	−1.95395	0.30114

Table 3. Multiple variable regression between DCSSR eigen values and physical/chemical indexes (F= 109.66052)

Index	Value	Error	t-Value	P
Y-Intercept	−48.29699	39.80333	−1.21339	0.00081
Firmness	−0.03516	0.041	−0.85753	0.54873
pH	−0.00878	4.64332	−0.00189	0.9988
TVB-N	0.02929	0.22586	0.12969	0.91789
TVC	−2.22E-07	1.01E-07	−2.18471	0.27328
Sensory	1.58907	0.98637	1.61102	0.35365

Table 4. Freshness forecasting results (√ = right; x = wrong; / = not calculated)

Sample No.	Forecasting value	Forecasting time(d)	Practical time(d)	Predicting error (%)	Freshness	Result
20	−46.3619	3.78	4	5.82	non-fresh	√
3	−44.2949	1.07	1	7.0	fresh	√
6	−44.5758	1.87	2	6.95	fresh	√
48	−50.6028	5.68	6	5.63	non-fresh	√
80	−46.9865	4.17	4	4.08	non-fresh	√
11	−44.2087	0.04	0	/	fresh	√
17	−45.5388	3.13	3	3.33	non-fresh	√
26	−45.2773	2.87	3	3.33	non-fresh	√
44	−44.2708	0.91	1	9.0	/	x
39	−52.0826	6.11	6	1.80	non-fresh	√
8	−51.4335	5.93	6	1.18	non-fresh	√
15	−51.2268	5.87	6	2.21	non-fresh	√
21	−46.8834	4.11	4	2.68	non-fresh	√
69	−45.5496	3.14	3	4.46	non-fresh	√
2	−44.704	2.11	2	5.21	fresh	√
14	−45.6834	3.26	3	7.98	non-fresh	√
27	−45.5823	3.17	3	5.36	non-fresh	√
36	−44.2759	0.94	1	6.0	fresh	√
54	−45.4752	3.07	3	2.28	non-fresh	√
56	−49.1356	5.17	5	3.29	non-fresh	√
51	−51.1928	5.86	6	2.39	non-fresh	√
62	−44.7337	2.16	2	7.41	fresh	√
9	−45.5068	3.1	3	3.33	non-fresh	√
66	−44.2097	0.17	0	/	/	x
73	−44.2949	1.04	1	4.0	fresh	√
76	−44.6867	2.08	2	4.0	fresh	√
63	−44.616	1.95	2	2.50	fresh	√
79	−46.5896	3.93	4	1.78	non-fresh	√
83	−49.3741	5.26	5	4.94	non-fresh	√
28	−48.3296	4.84	5	3.31	non-fresh	√
19	−52.6192	6.25	6	4.17	non-fresh	√
39	−49.2406	5.21	5	4.03	non-fresh	√
37	−46.4967	3.87	4	3.36	non-fresh	√
24	−46.9175	4.13	4	3.15	non-fresh	√
77	−47.1643	4.27	4	6.32	non-fresh	√

Figure 3. E-nose system: (a) systematic diagram; (b) SR; (c) DCSSR.