Rheological and structural properties of fish scales gelatin: Effects of conventional and ultrasound-assisted extraction

Figures & data

Figure 1. Storage modulus and loss modulus of the extracted gelatin from bighead carp scales by conventional water bath (CWB) and ultrasound-assisted water bath (UWB) upon temperature sweep from 40°C to 10°C (A) and from 10°C to 40°C. CWB60, CWB70, CWB80, UWB60, UWB70, and UWB80 mean fish gelatin was extracted at temperatures of 60°C, 70°C, and 80°C by CWB and UWB for 1 h, respectively.

Table 1. Gel point, melting point, and max modulus of the extracted gelatin by CWB and UWB at a temperature of 60–80°C for 1 h.

	Conventional Water Bath			Ultrasound-assisted Water Bath
Parameters	CWB60	CWB70	CW80	UWB60	UWB70	UWB80
Gelation point	21.94	21.54	20.93	22.94	21.93	21.13
Melting point	28.94	28.54	28.04	29.54	28.74	28.24
Max Storage Modulus (Pa)	4740	4490	4340	5000	4660	4480

CWB: conventional water bath; UWB: ultrasound-assisted water bath; CWB60, CWB70, CWB80, UWB60, UWB70, and UWB80 mean fish gelatin was extracted at temperature of 60°C, 70°C, and 80°C by CWB and UWB for 1 h.

Figure 2. Gel strength (A) and tan δ (G”/G’) (B) of gelatin gels upon frequency sweep at 10°C; the viscosity of different gelatin solutions upon shear rate was set at 25°C (C). CWB60, CWB70, CWB80, UWB60, UWB70, and UWB80 mean fish gelatin was extracted at temperatures of 60°C, 70°C, and 80°C by CWB and UWB for 1 h, respectively.

Table 2. Emulsifying and peak intensity at 7° of X-ray (counts) of gelatins extracted by CWB and UWB.

	Conventional Water Bath			Ultrasound-assisted Water Bath
Parameters	CWB60	CWB70	CW80	UWB60	UWB70	UWB80
EAI (m2/g	98.50 ± 1.31^a	105.88 ± 3.55^b	97.69 ± 1.04^a	101.23 ± 1.48^ab	121.45 ± 1.06^c	97.38 ± 2.07^a
ESI (%)	12.03 ± 0.42^a	12.74 ± 0.22^a	13.03 ± 0.31^a	12.94 ± 0.74^a	12.27 ± 0.08^a	12.82 ± 0.77^a
Peak intensity at 7° of X-ray (counts)	193.16	188.65	170.72	244.91	169.85	145

Different letters (a–c) within a column indicate significant difference (p < 0.05).

EAI—Emulsion activity index; ESI—Emulsion stability index.

Figure 3. X-ray spectra of gelatin extracted by CWB and UWB; CWB60, CWB70, CWB80, UWB60, UWB70, and UWB80 mean fish gelatin was extracted at temperatures of 60°C, 70°C, and 80°C by CWB and UWB for 1 h, respectively.

Figure 4. Nanostructure of fish gelatin extracted by CWB and UWB; CWB60, CWB80, UWB60, and UWB80 mean fish gelatin was extracted at temperatures of 60°C and 80°C by CWB and UWB for 1 h, respectively.