Freshness assessment of shrimp Metapenaeus affinis by quality index method and estimation of its shelf life

Figures & data

Table 1. QIM scheme for sensory evaluation of shrimp metapenaeus affinis.

Quality attributes	Parameter	Characteristics	Score
Color	Head	Bright pink, no spots	0
		Blue-green, or slight dark, with moderately spots	1
		Dark	2
	Body	Blue-green, bright and iridescent	0
		Brownish red, opaque, with moderately spots	1
		Dark	2
	Tail	Bright pink, no spots	0
		Blue-green or slight dark, with moderately spots	1
		Dark	2
	Meat	Translucent and shiny	0
		Lime color	1
		Slightly pinkish	2
		Pinkish or light yellow	3
Texture	Appearance	Shape intact, head firmly attached with body	0
		Shape intact, head slightly attached with body	1
		Flesh loosely attached with shell, head loosely attached with body	2
		Flesh loosely attached with shell, head very loosely attached with body	3
	Meat	Hard, elastic texture	0
		Slightly soft, loss of elastic	1
		Moderately soft	2
		Soft and watery texture	3
Odor	Meat	Fresh to sea	0
		Neutral	1
		Weak ammonia	2
		Putrid	3
Total QIM Score			0–18

Table 2. Average scores for each quality parameters assessed with the QIM scheme for shrimp Metapenaeus affinis stored on ice and the correlation with days on ice

Parameter/storage time (days)	0	3	6	9	12	r
Color head	0.00	0.00	0.66	1.00	1.33	0.728*
Color body	0.00	0.33	0.66	1.33	1.66	0.819*
Color tail	0.00	0.33	1.00	1.33	2.00	0.828*
Color meat	0.00	0.00	1.33	2.00	2.33	0.921*
Texture appearance	0.000	0.33	1.33	1.66	3.00	0.923*
Texture meat	0.00	0.66	1.66	2.00	2.66	0.925*
Odor meat	0.00	0.66	1.66	2.00	3.00	0.954*

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

* indicates a significant correlation.

Figure 1. Linear correlation between QIM and storage time of shrimp Metapenaeus affinis during the ice storage (a); Partial Least Squares (PLS) regression for Quality Index Method (QIM) of shrimp Metapenaeus affinis during the ice storage and the predicted values (b)

Table 3. Microbiological evaluation of Metapenaeus affinis during ice storage (log CFU/g)

Days of storage	0	3	6	9	12	r
Mesophilic bacteria	2.42 ± 0.05^d	3.89 ± 0.32^c	6.29 ± 0.21^b	7.13 ± 0.06^a	7.58 ± 0.32^a	0.954*
Psychrotrophilic bacteria	1.67 ± 0.42^d	3.11 ± 0.29^c	4.79 ± 0.23^b	6.42 ± 0.10^a	6.73 ± 0.50^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. Changes of physicochemical parameters of Metapenaeus affinis during storage on ice

Days of storage	0	3	6	9	12	r
TVBN (mg N/100g muscle)	11.89 ± 0.34^e	16.92 ± 0.88^d	28.68 ± 0.43^c	34.57 ± 0.34^b	39.59 ± 0.33^a	0.986*
TMA (mg N/100g muscle)	0.40 ± 0.09^e	1.25 ± 0.01^d	2.92 ± 0.20^c	5.18 ± 0.02^b	6.72 ± 0.19^a	0.987*
pH	7.26 ± 0.08^c	7.31 ± 0.04^c	7.53 ± 0.01^b	7.58 ± 0.04^b	8.08 ± 0.09^a	0.888*
TBARS (mg MDA/kg muscle)	0.26 ± 0.01^e	1.02 ± 0.01^c	1.70 ± 0.08^b	2.04 ± 0.01^a	0.56 ± 0.05^d	0.343
FFA (% oleic acid)	1.32 ± 0.10^e	3.53 ± 0.01^d	6.23 ± 0.33^c	10.46 ± 0.12^b	12.07 ± 0.00^a	0.990*

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

* indicates a significant correlation (p < 0.05).

Figure 2. Principal Component Analysis (PCA) of the study quality parameters of ice-stored Metapenaeus affinis: (a) the parameters of the quality index as follows: sensory, TMC, PTC, TVBN, TMA, pH, TBARS, FFA (b) storage time (day): 0, 3, 6, 9, and 12