Quality of frozen mackerel during storage as processed by different freezing methods

Figures & data

Figure 1. Change of central temperature (A), thawing loss (B), centrifugation loss (C) and cooking loss (D) of spiral tunnel freezing (SF), quick freezer freezing (QF), refrigerator freezing (RF) and plate freezing (PF) groups during frozen storage. The different letters in the figure mean significant difference (p < .05).

Figure 2. Change of L* (A), b* (B) of sample color, hardness (C) and elasticity (D) of SF, QF, RF and PF groups during frozen storage. The different letters in the figure mean significant difference (p < .05).

Figure 3. Change of electrical conductivity (A), TVB-N (B), MDA (C) and K-value (D) of SF, QF, RF and PF groups during frozen storage. The different letters in the figure mean significant difference (p < .05).

Figure 4. Change of sulfhydryl content (A) and magnetic resonance imaging (MRI) (B) of SF, QF, RF and PF groups during frozen storage. The different letters in the figure mean significant difference (p < .05).

Table 1. Effects of different freezing methods on secondary structure contents from amide I band region of different components in mackerel during frozen storage

secondary structure	groups	Storage time (day)
		0	5	30	60	90
α-Helix (%)	SF	23.78 ± 0.26	22.15 ± 0.52^a	20.31 ± 0.39^a	19.24 ± 0.16^a	17.02 ± 0.18^a
	QF		22.63 ± 0.17^a	19.83 ± 0.78^b	18.40 ± 0.5^b	16.92 ± 0.44^b
	RF		19.59 ± 0.84^b	19.13 ± 0.39^c	17.11 ± 0.8^c	16.47 ± 0.12^b
	PF		19.65 ± 0.33^b	18.26 ± 0.89 ^d	16.56 ± 0.68^d	15.63 ± 0.54^c
β-Sheet (%)	SF	31.14 ± 0.26	31.83 ± 0.87^d	34.87 ± 0.56^c	36.66 ± 0.9^c	41.25 ± 0.35^c
	QF		32.05 ± 0.3^c	35.88 ± 0.12^b	38.57 ± 0.91^b	41.34 ± 0.78^c
	RF		33.17 ± 0.16^b	36.13 ± 0.9^a	38.98 ± 0.66^b	42.54 ± 0.36^b
	PF		33.97 ± 0.36 ^a	36.40 ± 0.1^a	40.46 ± 0.96^a	43.17 ± 0.09^a
Random (%)	SF	28.63 ± 0.48	32.21 ± 0.1^c	33.20 ± 0.24^d	37.15 ± 0.96^c	38.94 ± 0.55^d
	QF		32.76 ± 0.86^b	34.06 ± 0.14^c	38.01 ± 0.19^b	40.58 ± 0.37^c
	RF		32.98 ± 0.01^b	36.06 ± 0.15^a	38.48 ± 0.94^b	42.38 ± 0.52^b
	PF		33.26 ± 0.09^a	36.99 ± 0.97^a	39.81 ± 0.86^a	44.74 ± 0.64^a
β-Turn (%)	SF	22.64 ± 0.48	23.06 ± 0.65^b	22.86 ± 0.83^b	23.01 ± 0.66^a	18.51 ± 0.46^c
	QF		19.55 ± 0.27^c	23.04 ± 0.34^a	18.21 ± 0.43^b	25.84 ± 0.58^a
	RF		19.68 ± 0.43^c	22.02 ± 0.89^b	18.23 ± 0.51^b	19.96 ± 0.68^b
	PF		25.77 ± 0.89^a	20.75 ± 0.71^c	17.59 ± 0.91^c	18.45 ± 0.05^c

a-d Means with different lowercase letters within the same storage month are significantly different (p< 0.05). The 0d samples were not involved in the comparison. The results are presented as mean ± standard deviation of three individual replications.

Table 2. Effects of different freezing methods on water ratio of different components in mackerel during frozen storage

components	groups	Storage time (day)
		0	5	30	60	90
P1 (%)	SF	2.43 ± 0.19	2.35 ± 1.21^a	2.31 ± 0.81^a	2.63 ± 0.09^b	2.29 ± 0.71^c
	QF		2.01 ± 0.76^b	2.38 ± 0.37^a	2.42 ± 0.14^c	2.22 ± 1.49^c
	RF		2.35 ± 0.65^a	2.26 ± 0.83^b	2.36 ± 0.14^c	2.77 ± 0.47^a
	PF		2.34 ± 0.80^a	2.35 ± 0.50^a	2.77 ± 0.91^a	2.67 ± 0.18^b
P2 (%)	SF	96.01 ± 0.34	95.85 ± 1.20^a	95.45 ± 1.13^a	95.07 ± 0.12^a	94.83 ± 0.92^a
	QF		95.59 ± 0.94^b	95.03 ± 0.52^b	94.70 ± 0.02^b	94.26 ± 1.80^b
	RF		95.00 ± 0.89^c	94.76 ± 1.23^c	94.14 ± 0.27^c	93.59 ± 0.58^c
	PF		94.52 ± 0.96^d	94.50 ± 0.35^c	93.87 ± 0.68^d	93.51 ± 0.47^c
P3 (%)	SF	1.54 ± 0.17	1.79 ± 0.09^d	2.26 ± 0.32^d	2.40 ± 0.20^c	2.86 ± 0.25^c
	QF		2.38 ± 0.17^c	2.64 ± 0.32^c	2.87 ± 0.12^b	3.51 ± 0.30^b
	RF		2.64 ± 0.24^b	2.97 ± 0.67^b	3.48 ± 0.29^a	3.63 ± 0.15^b
	PF		3.13 ± 0.43^a	3.15 ± 0.27^a	3.34 ± 0.34^a	3.90 ± 0.36^a
T22 (ms)	SF	51.11 ± 1.97	47.68 ± 1.14^a	45.55 ± 1.84^a	45.55 ± 1.06^a	44.54 ± 1.84^a
	QF		46.88 ± 0.99^b	45.28 ± 1.84^a	45.17 ± 1.06^a	44.02 ± 1.84^b
	RF		46.62 ± 0.99^b	45.02 ± 1.72^a	44.48 ± 0.99^b	43.89 ± 1.72^b
	PF		46.08 ± 1.06^c	44.48 ± 1.84^b	43.89 ± 1.06^c	43.49 ± 1.84^c

a-d Means with different lowercase letters within the same storage month are significantly different (p < 0.05). The 0d samples were not involved in the comparison. The results are presented as mean ± standard deviation of three individual replications.