Purity and yield of collagen extracted from southern catfish (Silurus meridionalis Chen) skin through improved pretreatment methods

Figures & data

Table 1. Design of decolouring experimental program.

pH of solution(A)	Concentration of H2O2 (B)	Number of technics
8	0.5%	A1B1
	1%	A1B2
	2%	A1B3
	4%	A1B4
9	0.5%	A2B1
	1%	A2B2
	2%	A2B3
	4%	A2B4
10	0.5%	A3B1
	1%	A3B2
	2%	A3B3
	4%	A3B4
11	0.5%	A4B1
	1%	A4B2
	2%	A4B3
	4%	A4B4

Table 2. The fat content and skim rate of NFS, NFS1, NFS2, and NFS3.

	Fat content* (%)	Degreasing rate (%)
NFS	3.68 ± 0.17	—
NFS1	1.13 ± 0.03	69.37
NFS2	0.70 ± 0.07	80.95
NFS3	0.36 ± 0.04	90.24

*Values are average ± standard derivation (N = 3).

Table 3. The yield and Hyp content of collagen extracted from the different pretreatment technics.

	Extraction rate of wet weight* (%)	Extraction rate of dry weight* (%)	Content of Hyp (μg mL^−Citation1)
A1B1	22.86	77.63	329.30
A1B2	21.48	72.95	335.56
A1B3	21.26	72.19	343.22
A1B4	21.79	73.98	311.89
A2B1	22.00	74.69	320.25
A2B2	22.12	75.10	327.90
A2B3	21.70	73.69	328.60
A2B4	20.90	70.95	301.45
A3B1	23.14	78.57	391.26
A3B2	22.54	76.53	380.12
A3B3	22.21	75.45	372.46
A3B4	22.49	76.35	375.94
A4B1	21.73	73.79	380.12
A4B2	23.06	78.30	398.91
A4B3	22.58	76.68	417.01
A4B4	22.48	76.32	409.36

*Dates are shown as the mean (all are within ±0.30) from three independent repeats.

Table 4. Proximate analyses of NFS and PFS.

	NFS*	PFS*
Moisture (%)	65.63 ± 0.25	76.10 ± 0.15
Protein** (%)	89.67 ± 0.43	93.05 ± 0.50
Ash** (%)	0.56 ± 0.02	0.41 ± 0.01
Fat** (%)	3.68 ± 0.17	0.36 ± 0.04

*Values are average ± standard derivation (N = 3).

**Represent the content on the dry weight basis.

Figure 1. SDS-PAGE pattern of collagen by different pretreatments (A1–A4: pH 8, 9, 10, 11; B1–B4: concentration of H₂O₂ 0.5%, 1%, 2%, 4%).

Figure 2. Tissue images of NFS and PFS dyed by heamatoxylin-eosin method at a magnification of 100 (a1, a2 and c1, c2: transverse cutting figure of NFS and PFS, respectively; b1, b2 and d1, d2: longitudinal cutting figure of NFS and PFS, respectively).

Table 5. Amino acid composition of collagens (residues/1000 residues).

Amino acids	Southern catfish skin	Calf skin
Asp	43	45
Thr	24	18
Ser	39	33
Glu	65	75
Gly	347	330
Ala	115	119
Cys	1	0
Val	18	21
Met	8	6
Ile	13	11
Leu	24	23
Tyr	1	3
Phe	11	3
Lys	28	26
His	6	5
Arg	54	50
Pro	120	121
Hyl	6	7
Hyp	77	94
Total	1000	1000
Imino acid	197	215

Figure 3. Ultraviolet spectra of collagen extracted from Southern catfish skin (a) and calf skin (b).

Figure 4. FTIR spectra of collagen extracted from Southern catfish skin (a) and calf skin (b).

Figure 5. DSC thermograms of FC (a) and CC (b) solutions.

Li, Z.R.; Wang, B.; Chi, C.F.; Zhang, Q.H.; Gong, Y.D.; Tang, J.J.; Luo, H.Y.; Ding, G. Isolation and Characterization of Acid Soluble Collagens and Pepsin Soluble Collagens from the Skin and Bone of Spanish Mackerel (Scomberomorous niphonius). Food Hydrocolloids 2013, 31, 103–113.

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