Quality index method (QIM) sensory scheme for gutted greenback grey mullet Chelon subviridis and its shelf life determination

Figures & data

Figure 1. Each quality attributes evaluated with QIM scheme for greenback grey mullet (Chelon subviridis) stored on refrigerator over each day analyzed against storage days (1^st and 16^th day, respectively); A1-A2: overall appearance in 1^st and 16^th day, respectively; B1-B2: eye in 1^st and 16^th day, respectively; C1-C2: gill in 1^st and 16^th day, respectively; D1-D2: fins in 1^st and 16^th day, respectively; E1-E2: fins in 1^st and 16^th day, respectively; F1-F2: caudal fin in 1^st and 16^th day, respectively; G1-G2: dorsal in 1^st and 16^th day, respectively; H1-H2: flesh in 1^st and 16^th day, respectively

Table 1. QIM scheme for assessing gutted refrigerated storage greenback grey mullet (Chelon subviridis)

Quality attributes	Parameter	Characteristics	Score
Overall appearance	Skin	Bright/Vivid and defined/Glossy/Brightness intense	0
		Slightly bright/discoloration on the side/Brightness loss/Partially glossy	1
		Loss of glossiness/Dull/pale/wrinkled or failed skin/opaque	2
	Texture	Firm/Elastic/Finger mark disappears rapidly	0
		Soft/Flabby/finger mark delays disappear	1
Eye	Cornea	Clear and crystalline	0
		Clear or slightly cloudy	1
		Opaque	2
	Pupil	Slightly opaque/Absence of a white spot	0
		Opaque/small white spot	1
		Gray opaque/large white spot	2
	Shape	Convex/Protuberant	0
		Flat/Plane	1
		Sunk/Concave	2
	Eyeball	Intact	0
		Detached	1
Gill	Color	Bright red/Slightly viscous	0
		Red/Some viscous	1
		Reddish pink keen brown/Some viscous	2
	Odor	Fresh/Specific species	0
		Destruction of fish specific smell/neutral	1
		Low and medium rancidity	2
		High rancidity/Stinking	3
Fins	Dorsal/Ventral/Caudal	Full/Wet/With elasticity	0
		Full/resected tips/with low elasticity	1
		Failed/resected tips/no elasticity	2
Caudal fin	Moisture	Totally moist	0
		Dry on the edge	1
		Totally dry	2
	Color	Light	0
		Dark	1
Dorsal	Elasticity	Elastic	0
		Inelastic	1
	Color	Dark green	0
		Light green	1
		Light blue and dark	2
Abdomen (Internal)	Color	Fresh color/bright red blood	0
		Yellowish pink flesh/dark red blood	1
		Brownish pink or darkened/Brown blood	2
	Odor	Fresh or neutral	0
		Rancid/Slightly ammonium	1
		Putrid	2
Abdomen (outside)	Overall aspect	Flexible/shiny/Moist	0
		Loss of elasticity/Slightly discolored	1
		Inelastic/Dry/Discolored	2
Flesh	Color	Dark and bright red	0
		Bright red	1
		Pale red or brownish/discolored	2
	Odor	Fresh or neutral	0
		Rancid/Slightly ammonium	1
		Putrid	2
	Firmness	Firm/Compact	0
		Soft/Crumbling	1
Total QIM Score			0–34

Figure 2. a.Linear correlation between QIM and storage time of greenback grey mullet (Chelon subviridis) during the refrigerated storage (A); Figure 2b. Partial Least Squares (PLS) regression for Quality Index Method (QIM) of greenback grey mullet (Chelon subviridis) during the refrigerated storage and the predicted values (B)

Table 2. Average scores for each quality parameters assessed with the QIM scheme for greenback grey mullet (Chelon subviridis) stored in the refrigerator and the correlation to days in the refrigerator

Parameter/days in refrigerator	0	4	8	12	16	r
Overall appearance of skin	0.00 ± 0.00^b	0.33 ± 0.33^b	1.00 ± 0.57^ab	1.66 ± 0.33^a	2.00 ± 0.00^a	0.843*
Overall appearance of texture	0.00 ± 0.00^b	0.33 ± 0.33^ab	0.33 ± 0.33^ab	1.00 ± 0.00^a	1.00 ± 0.00^a	0.756*
Eye cornea	0.00 ± 0.00^b	0.66 ± 0.33^ab	1.00 ± 0.57^ab	1.33 ± 0.66^ab	2.00 ± 0.00^a	0.738*
Eye pupil	0.00 ± 0.00^b	0.66 ± 0.33^ab	0.66 ± 0.33^ab	1.33 ± 0.33^a	1.66 ± 0.33^a	0.788*
Eye shape	0.00 ± 0.00^c	0.66 ± 0.33^b	1.00 ± 0.00^b	1.33 ± 0.33^b	2.00 ± 0.00^a	0.904*
Eyeball	0.00 ± 0.00^b	0.33 ± 0.33^ab	0.33 ± 0.33^ab	0.66 ± 0.33^ab	1.00 ± 0.00^a	0.661*
Gill color	0.00 ± 0.00^c	0.66 ± 0.33^bc	1.00 ± 0.57^abc	1.66 ± 0.33^ab	2.00 ± 0.00^a	0.828*
Gill odor	0.00 ± 0.00^b	0.33 ± 0.33^b	2.00 ± 0.57^a	2.33 ± 0.33^a	2.66 ± 0.33^a	0.862*
Dorsal/Ventral/Caudal fins	0.00 ± 0.00^c	0.33 ± 0.33^c	1.00 ± 0.00^b	1.66 ± 0.33^a	2.00 ± 0.00^a	0.924*
Moisture caudal fin	0.00 ± 0.00^b	0.33 ± 0.33^ab	0.66 ± 0.33^ab	0.66 ± 0.33^ab	1.00 ± 0.00^a	0.661*
Color fin	0.00 ± 0.00^b	0.66 ± 0.33^ab	0.66 ± 0.33^ab	1.00 ± 0.33^a	1.00 ± 0.00^a	0.700*
Dorsal elasticity	0.00 ± 0.00^b	0.33 ± 0.33^ab	0.66 ± 0.33^ab	0.66 ± 0.33^ab	1.00 ± 0.00^a	0.661*
Color dorsal	0.00 ± 0.00^b	0.33 ± 0.33^b	0.66 ± 0.33^b	1.66 ± 0.33^a	2.00 ± 0.00^a	0.883*
Color abdomen (Internal)	0.00 ± 0.00^b	0.66 ± 0.33^b	0.66 ± 0.33^b	2.00 ± 0.00^a	2.00 ± 0.00^a	0.883*
Odor abdomen (Internal)	0.00 ± 0.00^b	0.66 ± 0.33^b	0.66 ± 0.33^b	1.66 ± 0.33^a	2.00 ± 0.00^a	0.866*
Overall aspect abdomen (outside)	0.00 ± 0.00^b	0.33 ± 0.33^b	0.33 ± 0.33^b	1.33 ± 0.33^a	2.00 ± 0.00^a	0.849*
Color flesh	0.00 ± 0.00^c	0.66 ± 0.33^b	1.66 ± 0.33^a	2.00 ± 0.00^a	2.00 ± 0.00^a	0.883*
Odor flesh	0.00 ± 0.00^b	0.66 ± 0.33^b	0.66 ± 0.33^b	1.66 ± 0.33^a	2.00 ± 0.00^a	0.866*
Firmness flesh	0.00 ± 0.00^b	0.33 ± 0.33^ab	0.66 ± 0.33^ab	0.66 ± 0.33^ab	1.00 ± 0.00^a	0.661*

Data within the same row with different letters are significantly different (p < 0.05).

* indicates a significant correlation.

Table 3. Microbiological evaluation of greenback grey mullet (Chelon subviridis) during refrigerated storage (log CFU/g)

Days of storage	0	4	8	12	16	r
Mesophilic bacteria	3.94 ± 0.00^d	4.89 ± 0.00^c	5.83 ± 0.00^b	7.06 ± 0.02^a	7.24 ± 0.32^a	0.971*
Psychrotrophilic bacteria	3.97 ± 0.00^e	4.83 ± 0.03^d	5.83 ± 0.00^c	6.87 ± 0.00^b	7.55 ± 0.33^a	0.985*

Data within the same row with different letters are significantly different (p < 0.05).

* indicates a significant correlation (p < 0.05).

Table 4. Greenback grey mullet (Chelon subviridis) physicochemical parameter changes during refrigerated storage

Days of storage	0	4	8	12	16	r
TVBN (mg N/100g muscle)	2.60 ± 0.11^e	9.10 ± 1.21^d	16.26 ± 1.21^c	30.40 ± 3.21^b	39.66 ± 0.33^a	0.976*
pH	6.87 ± 0.01^b	6.96 ± 0.02^b	7.12 ± 0.06^b	7.12 ± 0.00^b	7.54 ± 0.18^a	0.814*
TBARS (mg MDA/kg muscle)	0.66 ± 0.11^c	1.30 ± 0.05^b	1.53 ± 0.33^b	1.28 ± 0.01^b	2.19 ± 0.04^a	0.792*
FFA (% oleic acid)	1.05 ± 0.01^b	3.60 ± 0.93^ab	6.82 ± 0.29^b	10.36 ± 0.22^ab	10.79 ± 0.33^a	0.966*
TMA (mg N/100g muscle)	2.53 ± 0.52^d	3.61 ± 0.64^cd	6.60 ± 1.55^bc	8.80 ± 1.28^b	15.81 ± 1.03^a	0.905*

Data within the same row with different letters are significantly different (p < 0.05).

* indicates a significant correlation (p < 0.05).

Table 5. Greenback grey mullet (Chelon subviridis) color parameters (a*, b*, L*, C*_ab, H^º_ab, W) changes during refrigerated storage

Days of storage	0	4	8	12	16	r
a*	13.03 ± 0.48^a	12.53 ± 0.60^a	12.44 ± 1.54^a	12.91 ± 0.69^a	12.55 ± 0.42^a	−0.066
b*	12.48 ± 0.52^a	16.99 ± 0.20^b	15.66 ± 0.73^b	16.27 ± 0.08^b	13.78 ± 0.36^a	0.149
L*	45.69 ± 1.62^b	42.74 ± 0.01^b	50.89 ± 1.56^a	49.99 ± 0.56^a	42.58 ± 0.97^b	0.038
C*ab	18.04 ± 0.71^b	21.11 ± 0.52^a	20.03 ± 1.55^ab	20.78 ± 0.36^ab	18.82 ± 0.15^ab	0.103
H^ºab	0.75 ± 0.00^bc	0.93 ± 0.01^a	0.89 ± 0.04^ab	0.89 ± 0.02^ab	0.82 ± 00.03^bc	0.205
W	45.75 ± 4.18^ab	38.76 ± 0.25^b	46.95 ± 2.04^a	45.84 ± 0.38^ab	39.63 ± 0.93^b	−0.159

Data within the same row with different letters are significantly different (p < 0.05).

* indicates a significant correlation (p < 0.05).

Figure 3. Principal Component Analysis (PCA) of the study quality parameters of Greenback grey mullet (Chelon subviridis) stored at refrigerator: (A) the parameters of the quality index as follows: sensory, TMC, PTC, TVBN, TMA, pH, TBA, FFA (B) 1 = day 1, 4 = day 4, 8 = day 8, 12 = day 12 and 16 = day 16