Physicochemical characteristics and molecular structures of gelatin extracted from bovine skin: effects of actinidin and papain enzymes pretreatment

Figures & data

Table 1. Yield and pH of the bovine skin gelatin extracted using enzymes actinidin and papain at different levels. Values are given as mean±SE from triplicate determination

Treatment levels	Yield (%) of gelatin extracted using enzyme		pH of gelatin extracted using enzyme
	Actinidin	Papain	Actinidin	Papain
Control	17.90 ± 0.19^d	17.90 ± 0.19^f	2.16 ± 0.05^b	2.16 ± 0.05^c
0	15.44 ± 0.25^eB	24.56 ± 0.23^bA	2.71 ± 0.04^aA	2.25 ± 0.07^bcB
5	17.52 ± 0.23^dB	22.30 ± 0.26^cA	2.66 ± 0.06^aA	2.34 ± 0.02^bB
10	20.14 ± 0.22^cA	20.28 ± 0.27^eA	2.71 ± 0.01^aA	2.50 ± 0.01^aB
15	21.58 ± 0.21^bA	21.17 ± 0.20^dA	2.72 ± 0.02^aA	2.36 ± 0.02^abB
20	22.67 ± 0.29^aB	23.59 ± 0.34^aA	2.74 ± 0.01^aA	2.36 ± 0.05^abB
25	19.79 ± 0.30^cB	20.06 ± 0.18^eB	2.70 ± 0.02^aA	2.35 ± 0.04^bB

Values with different superscripts in the same column or row show a significant difference at P < 0.05. Treatment levels 0, 5, 10, 15, 20, and 25 indicate the units of enzymes used per gram of skin.

Table 2. Amino acid composition (%) of control gelatin, gelatin extracted using actinidin, and papain enzymes from the bovine skin

Amino acids	Control	Levels of enzyme actinidin/g of skin						Levels of enzyme papain/g of skin
		0	5	10	15	20	25	0	5	10	15	20	25
Hydroxyproline (Hyp)	14.14	15.17	13.51	12.69	12.21	12.06	10.93	14.82	13.37	14.75	15.39	12.40	14.96
Aspartic acid (Asp)	4.06	3.76	3.83	3.73	3.17	3.26	2.95	3.91	3.38	3.81	3.95	3.37	3.80
Serine (Ser)	2.82	2.96	2.67	2.52	2.39	2.35	2.11	3.18	2.60	2.92	3.11	2.50	3.11
Glutamic acid (Glu)	7.81	7.52	7.41	7.20	6.32	6.41	5.70	7.81	6.67	7.45	7.87	6.71	7.63
Glycine (Gly)	19.87	21.00	19.56	18.97	17.83	17.71	15.97	21.47	19.16	20.63	21.74	18.27	21.38
Histidine (His)	0.82	0.90	0.79	0.72	0.69	0.68	0.57	0.96	0.80	0.90	0.96	0.77	0.93
Arginine (Arg)	6.87	7.42	6.56	6.20	5.85	5.72	5.26	7.22	6.48	7.08	7.44	5.93	7.14
Threonine (Thr)	1.63	1.76	1.58	1.47	1.40	1.37	1.30	1.67	1.54	1.71	1.79	1.41	1.72
Alanine (Ala)	6.50	6.59	6.15	5.94	5.45	5.50	5.01	7.47	5.87	6.56	7.30	5.94	6.79
Proline (Pro)	10.29	11.08	9.93	9.65	9.06	9.08	8.31	10.52	9.79	10.80	10.96	8.87	10.14
Tyrosine (Tyr)	0.62	0.65	0.58	0.53	0.50	0.49	0.47	0.66	0.64	0.71	0.75	0.56	0.72
Valine (Val)	2.11	2.26	2.03	1.94	1.82	1.80	1.68	2.13	2.00	2.21	2.25	1.77	2.13
Lysine (Lys)	3.13	3.08	2.89	2.81	2.56	2.55	2.32	3.06	2.73	3.07	3.22	2.64	3.15
Isoleucine (Ile)	1.30	1.41	1.23	1.19	1.12	1.10	1.02	1.35	1.27	1.41	1.43	1.12	1.36
Leucine (Leu)	2.66	2.87	2.55	2.44	2.29	2.26	2.12	2.67	2.53	2.83	2.87	2.23	2.71
Phenylalanine (Phe)	1.78	1.95	1.73	1.63	1.55	1.53	1.41	1.85	1.72	1.90	1.94	1.51	1.85
Total	86.41	90.38	83.00	79.63	74.21	73.87	67.14	90.74	80.53	88.74	92.97	76.01	89.50
Imino acids (Pro+Hyp)	24.43	26.25	23.44	22.34	21.28	21.14	19.25	25.34	23.15	25.54	26.34	21.27	25.10

All the data expressed in the unit of mg/100 mg of gelatin. Measurements were performed in triplicate and data correspond to mean values. Standard deviations were in all cases lower than 2%.

Figure 1. SDS-PAGE pattern of pretreated skin (PS) sample along with gelatin samples extracted using different levels of enzyme actinidin (A) and papain (P). A0/P0, A5/P5, A10, A15/P15, A20/P20, and A25/P25 refer to corresponding actinidin/papain enzyme level of 0, 5, 10, 15, 20, and 25 unit/g of skin, respectively. M: high-molecular-weight marker. C: control gelatin

Table 3. Turbidity, gel strength, and viscosity of the bovine skin gelatin extracted using enzymes actinidin and papain at different levels. Values are given as mean±SE from triplicate determination

Treatment levels	Turbidity of gelatin extracted using enzyme		Gel strength of gelatin extracted using enzyme		Viscosity of gelatin extracted using enzyme
	Actinidin (ppm)	Papain (ppm)	Actinidin (g)	Papain (g)	Actinidin (mPa.s)	Papain (mPa.s)
Control	12.53 ± 0.20^f	12.53 ± 0.20^b	283.35 ± 1.84^f	283.35 ± 1.84^b	12.10 ± 0.23^d	12.10 ± 0.23^a
0	15.03 ± 0.20^eA	7.03 ± 0.09^eB	452.79 ± 2.50^bA	292.82 ± 1.07^aB	14.90 ± 0.15^aA	11.70 ± 0.12^aB
5	30.87 ± 0.35^dA	9.50 ± 0.35^dB	480.02 ± 1.96^aA	55.86 ± 0.72^fB	14.07 ± 0.23^bA	9.13 ± 0.26^cB
10	41.53 ± 0.38^cA	12.13 ± 0.19^bB	432.77 ± 2.42^cA	119.34 ± 1.26^cB	13.53 ± 0.09^bcA	10.10 ± 0.35^bB
15	42.03 ± 0.32^cA	9.50 ± 0.17^dB	431.26 ± 2.53^cA	68.44 ± 0.42^eB	13.20 ± 0.17^cA	9.10 ± 0.06^cB
20	70.07 ± 0.81^bA	22.00 ± 0.64^aB	366.39 ± 2.59^dA	27.02 ± 0.31^gB	13.53 ± 0.09^bcA	7.03 ± 0.03^dB
25	79.97 ± 0.78^aA	11.10 ± 0.32^cB	348.56 ± 2.18^eA	105.36 ± 1.47^dB	13.97 ± 0.15^bA	10.70 ± 0.23^bB

Values with different superscripts in the same column or row show a significant difference at P < 0.05. Treatment levels 0, 5, 10, 15, 20, and 25 indicate the units of enzymes used per gram of skin.

Figure 2. Fourier-transform infrared spectra of control (C), GEA, and GEP gelatin samples extracted at the level of 20 units of enzyme/g of wet skin

Figure 3. SEM images of control (C), GEA, and GEP gelatin samples extracted at the level of 20 unit of enzyme/g of wet skin. Magnification: 30⨰