Rheological Properties and Emulsifying Activity of Gum Karaya (Sterculia Urens) in Aqueous System and Oil in Water Emulsion: Heat Treatment and Microwave Modification

Figures & data

FIGURE 1 Flow chart representing microwave treatment of gum karaya.

A′, B′, and C′: Unheated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D′, E′, and F′: Unheated microwave powder samples at 1000 W for 8, 10, and 12 min, respectively.G′, H′, and I′: Unheated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J′, K′, and L′: Unheated microwave treated solution samples at 1000 W for 8, 10, and 12 min, respectively.A″, B″, and C″: Heated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D″, E″, and F″: Heated microwave treated powder samples at 1000 W for 8, 10, and 12 min, respectively.G″, H″, and I″: Heated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J″, K″, and L″: Heated microwave solution samples at 1000 W for 8, 10, and 12 min, respectively.

TABLE 1 p-Value and F-ratio of microwave condition variables in the final reduced model (emulsion system)

Independent variable		Volume weighted mean [D4,3]		Surface weighted mean [D3,2]		Viscous modulus G″ (Pa)		Elastic modulus G′ (Pa)		Viscosity (mPa.s)
		p-value	F-ratio	p-value	F-ratio	p-value	F-ratio	p-value	F-ratio	p-value	F-ratio
Main effects	X1	<0.0001	924.83	<0.0001	6875.18	<0.0001	140.93	<0.0001	279.15	<0.0001	527.30
	X2	<0.0001	130.45	<0.0001	750.70	<0.0001	25.42	<0.0001	83.79	<0.0001	148.82
	X3	<0.0001	318.27	<0.0001	1405.06	<0.0001	180.03	<0.0001	120.50	<0.0001	178.47
	X4	<0.0001	2463.86	<0.0001	22071.14	<0.0001	192.08	<0.0001	225.38	<0.0001	831.93
Interaction effects	X1X2	0.0223	4.12	<0.0001	50.57	—	—	<0.0001	11.79	0.0042	6.15
	X1X3	0.0262	5.26	<0.0001	1226.96	0.0039	9.22	<0.0001	24.24	<0.0001	69.80
	X1X4	<0.0001	196.72	<0.0001	5508.72	0.0094	7.32	0.0158	6.26	0.0001	17.87
	X2X3	0.0007	8.53	<0.0001	262.40	<0.0001	17.89	<0.0001	40.54	<0.0001	14.03
	X2X4	<0.0001	47.08	<0.0001	709.78	—	—	—	—	—	—
	X3X4	<0.0001	32.84	<0.0001	416.05	0.0001	17.15	0.0411	4.40	0.0102	7.15
	X1X2X3	0.0070	5.51	<0.0001	207.58	—	—	<0.0001	22.09	—	—
	X1X2X4	0.0154	4.56	<0.0001	36.16	<0.0001	13.59	—	—	0.0065	5.60
	X1X3X4	0.0099	7.22	<0.0001	1494.51	<0.0001	28.69	—	—	<0.0001	25.73
	X2X3X4	<0.0001	16.02	<0.0001	239.76	—	—	—	—	—	—
	X1X2X3X4	—	—	<0.0001	219.32	<0.0001	22.17	—	—	—	—

x₁, x₂, x₃, and x₄ represents the single effect of powder (W), time (min), temperature, and gum phase, respectively;

x₁x₂, x₁x₃, x₁x₄, x₂x₃, x₂x₄, x₃x₄, x₁x₂x₃, x₁x₂x₄, x₁x₃x₄, x₂x₃x₄, and x₁x₂x₃x₄ represents the interaction between of powder (W) and time (min), powder (W) and temperature, powder (W) and gum phase, time (min) and temperature, time (min) and gum phase, temperature and gum phase, powder (W) and time (min) and temperature, powder (W) and temperature and gum phase, time (min) and temperature and gum phase as well as powder (W) and time (min) and temperature and gum phase, respectively.

TABLE 2 p-Value and f-ratio of microwave variables in the final reduced model (aqueous system)

Independent variable		Span		Viscous modulus G” (Pa)		Elastic modulus G’ (Pa)		Viscosity (mPa.s)		Emulsion stability (%)
		p-value	F-ratio	p-value	F-ratio	p-value	F-ratio	p-value	F-ratio	p-value	F-ratio
Main effects	X1	<0.0001	227.33	<0.0001	1442.51	<0.0001	266.91	<0.0001	2682.60	<0.0001	96.91
	X2	<0.0001	13.81	<0.0001	66.88	<0.0001	14.89	<0.0001	248.19	<0.0001	28.67
	X3	<0.0001	158.52	0.0014	11.50	<0.0001	32.40	<0.0001	2314.76	<0.0001	36.20
	X4	<0.0001	650.74	<0.0001	981.13	<0.0001	304.57	<0.0001	1870.21	<0.0001	306.25
Interaction effects	X1X2	0.0021	7.05	<0.0001	13.28	—	—	<0.0001	12.74	—	—
	X1X3	—	—	<0.0001	66.24	<0.0001	26.59	<0.0001	150.70	—	—
	X1X4	0.0001	17.57	<0.0001	77.12	—	—	0.0201	5.78	—	—
	X2X3	—	—	—	—	—	—	—	—	—	—
	X2X4	—	—	0.0037	6.29	—	—	—	—	0.0105	5.01
	X3X4	—	—	0.0073	7.86	0.0058	8.33	<0.0001	210.32	<0.0001	26.83
	X1X2X3	—	—	—	—	—	—	<0.0001	47.70	—	—
	X1X2X4	0.0059	5.73	0.0041	6.18	0.0134	4.73	0.0022	6.99	—	—
	X1X3X4	—	—	<0.0001	28.48	<0.0001	41.36	<0.0001	306.13	—	—
	X2X3X4	—	—	—	—		—	0.0056	5.80	—	—
	X1X2X3X4	—	—	<0.0001	21.58	—	—	0.0003	9.75	—	—

x₁, x₂, x₃, and x₄ represents the single effect of powder (W), time (min), temperature, and gum phase respectively;

x₁x₂, x₁x₃, x₁x₄, x₂x₃, x₂x₄, x₃x₄, x₁x₂x₃, x₁x₂x₄, x₁x₃x₄, x₂x₃x₄, and x₁x₂x₃x₄ represents the interaction between of powder (W) and time (min), powder (W) and temperature, powder (W) and gum phase, time (min) and temperature, time (min) and gum phase, temperature and gum phase, powder (W) and time (min) and temperature, powder (W) and temperature and gum phase, time (min) and temperature and gum phase as well as powder (W) and time (min) and temperature and gum phase, respectively.

FIGURE 2 Scanning electron micrographs (SEM) of A: gum karaya; B: microwave treated gum, magnification; 250 ×; scale bar = 20 µm.

TABLE 3 Effect of different heat- and microwave treatments on average particle size and distribution of gum karaya in oil in water (O/W) emulsion

Sample	Code	Treatment			Volume weighted mean [D4,3] (μm)	Surface weighted mean [D3,2] (μm)
		Phase	Power (W)	Time (min)
Unheated microwave samples	A′	Powder	700	8	5.29 ± 0.07^b	1.82 ± 0.06^b
	B′			10	3.68 ± 0.02^c	1.39 ± 0.03^d
	C′			12	2.84 ± 0.04^e	1.23 ± 0.08^f
	D′		1000	8	2.56 ± 0.08^f	1.38 ± 0.06^e
	E′			10	2.24 ± 0.07^g	1.31 ± 0.01^e
	F′			12	1.43 ± 0.01^i	0.39 ± 0.08^gh
	G′	Solution	700	8	1.31 ± 0.05^ij	0.41 ± 0.04^g
	H′			10	1.23 ± 0.02^ijk	0.32 ± 0.05^gk
	I′			12	1.12 ± 0.03^jkl	0.36 ± 0.09^gi
	J′		1000	8	1.01 ± 0.07^kl	0.30 ± 0.01^jk
	K′			10	0.92 ± 0.05^lm	0.28 ± 0.02^kl
	L′			12	0.89 ± 0.04^lm	0.30 ± 0.05^jk
Heated microwave samples	A″	Powder	700	8	3.36 ± 0.11^d	1.69 ± 0.08^c
	B″			10	2.57 ± 0.07^f	1.69 ± 0.02^c
	C″			12	2.57 ± 0.08^f	1.33 ± 0.03^d
	D″		1000	8	1.70 ± 0.50^h	0.31 ± 0.01^igk
	E″			10	1.26 ± 0.01^ij	0.33 ± 0.01^ig
	F″			12	1.08 ± 0.01^jkl	0.28 ± 0.06^kl
	G″	Solution	700	8	1.12 ± 0.01^jkl	0.25 ± 0.01^lm
	H″			10	1.00 ± 0.02^kl	0.25 ± 0.04^lm
	I″			12	1.00 ± 0.05^kl	0.25 ± 0.02^lm
	J″		1000	8	0.71 ± 0.03^mn	0.23 ± 0.08^m
	K″			10	0.62 ± 0.07^no	0.22 ± 0.05^m
	L″			12	0.44 ± 0.06°	0.21 ± 0.03^m
Control					22.40 ± 0.20^a	8.66 + 0.05^a

a–o: significant different at p < 0.05.

FIGURE 3 Effect of different heat and microwave treatments on the particle size distribution of gum karaya; A: without heat treatment and B: with heat treatment (120°C, 2 h)

a–g: significant different at p < 0.05;a–h: significant different at p < 0.05;A′, B′, and C′: Unheated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D′, E′, and F′: Unheated microwave powder samples at 1000 W for 8, 10, and 12 min, respectively.G′, H′, and I′: Unheated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J′, K′, and L′: Unheated microwave treated solution samples at 1000 W for 8, 10, and 12 min, respectively.A″, B″, and C″: Heated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D″, E″, and F″: Heated microwave treated powder samples at 1000 W for 8, 10, and 12 min, respectively.G″, H″, and I″: Heated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J″, K″, and L″: Heated microwave solution samples at 1000 W for 8, 10, and 12 min, respectively.

TABLE 4 Effect of different heat and microwave treatments on the apparent viscosity of gum karaya in the aqueous system and O/W emulsion

Sample		Code	Treatment			Apparent viscosity (mPas)
			Phase	Power (W)	Time (min)	Aqueous system	Emulsion system
Unheated microwave samples		A′	Powder	700	8	383.5 + 2.12^a	37.81 + 0.43^a
		B′			10	362.5 + 2.15^b	35.00 + 0.51^b
		C′			12	354.05 + 2.19^b	34.30 + 2.83^bc
		D′		1000	8	362.5 + 2.14^b	33.94 + 0.53^bcd
		E′			10	264 + 1.41^d	31.82 + 0.21^de
		F′			12	219.5 + 2.13^f	27.00 + 0.71^f
		G′	Solution	700	8	243.5 + 2.12^e	30.44 + 1.75^e
		H′			10	222 + 2.15^f	26.05 + 0.07^fg
		I′			12	199.5 + 3.2^g	26.05 + 0.04^fg
		J′		1000	8	144.65 + 3.08^i	24.45 + 1.20^gh
		K′			10	73.71 + 4.38^l	23.01 + 0.63^hi
		L′			12	58.25 + 1.53^m	21.78 + 1.10^i
Heated microwave samples		A″	Powder	700	8	256.5 + 2.12^de	31.65 + 0.21^de
		B″			10	199.5 + 2.12^g	30.30 + 0.42^e
		C″			12	90.60 + 0.20^k	30.40 + 0.57^e
		D″		1000	8	40.99 + 5.27^n	27.50 + 0.71^f
		E″			10	43.72 + 3.57^mn	21.88 + 0.96^i
		F″			12	167 + 1.41^h	32.14 + 0.08^cde
		G″	Solution	700	8	114.295 + 4.89^j	25.58 + 0.03^fg
		H″			10	88.2 + 5.80^kl	21.88 + 0.96^i
		I″			12	47.74 + 2.29^mn	17.75 + 1.06^j
		J″		1000	8	43.72 + 3.57^mn	13.62 + 2.52^k
		K″			10	38.88 + 2.85^n	10.51 + 1.30^l
		L″			12	256.5 + 2.12^de	31.65 + 0.21^de
Control						395.4 + 6.79^a	38.70 + 1.84^a

a–n: significant different at p < 0.05.

FIGURE 4 Steady shear rate dependence of viscosity of A: gum karaya control and microwave modified gum in emulsion system and B: gum karaya control and microwave modified gum in aqueous system.

TABLE 5 Effect of different heat and microwave treatments on the viscous modulus (G”) and elastic modulus (G’) in the aqueous system and O/W emulsion

Samples	Treatment			Aqueous system		Emulsion system
	Phase	Power (W)	Time (min)	Viscous modulus G” (Pa)	Elastic modulus G’ (Pa)	Viscous modulus G” (Pa)	Elastic modulus G’ (Pa)
Unheated microwave samples	Powder	700	8	11.75 ± 0.07^ab	13.43 ± 0.47^b	0.66 ± 0.03^a	0.94 ± 0.01^a
			10	11.35 ± 0.49^ab	12.98 ± 0.04^b	0.62 ± 0.02^a	0.89 ± 0.02^ab
			12	9.66 ± 0.47^bcd	9.10 ± 0.21^de	0.65 ± 0.01^a	0.83 ± 0.04^bc
		1000	8	6.15 ± 0.14^efg	7.16 ± 0.98^fgh	0.62 ± 0.02^a	0.79 ± 0.02^cde
			10	3.90 ± 0.13^ghi	6.90 ± 0.11^fgh	0.64 ± 0.01^a	0.75 ± 0.01^de
			12	2.74 ± 0.01^ijk	6.17 ± 0.14^h	0.64 ± 0.04^a	0.73 ± 0.04^ef
	Solution	700	8	2.74 ± 0.06^ijk	6.17 ± 0.16^h	0.62 ± 0.02^a	0.72 ± 0.03^ef
			10	2.03 ± 0.25^ijk	6.07 ± 0.04^h	0.64 ± 0.08^a	0.72 ± 0.02^ef
			12	1.30 ± 0.42^jk	5.90 ± 0.07^hi	0.60 ± 0.03^a	0.67 ± 0.08^fg
		1000	8	1.44 ± 0.18^jk	4.22 ± 0.78^j	0.40 ± 0.01^b	0.55 ± 0.0^i
			10	1.30 ± 0.42^jk	1.44 ± 0.18^kl	0.37 ± 0.02^b	0.63 ± 0.01^gh
			12	1.06 ± 0.09^jk	0.96 ± 0.09^l	0.32 ± 0.01^bc	0.58 ± 0.06^hi
Heated microwave samples	Powder	700	8	11.80 ± 0.01^ab	12.45 ± 1.05^b	0.66 ± 0.01^a	0.92 ± 0.02^a
			10	11.45 ± 0.35^ab	12.50 ± 0.71^b	0.59 ± 0.01^a	0.82 ± 0.01^bcd
			12	11.25 ± 0.35^abc	12.55 ± 0.49^b	0.65 ± 0.01^a	0.73 ± 0.01^ef
		1000	8	7.38 ± 0.31^def	7.97 ± 1.23^efg	0.62 ± 0.04^a	0.73 ± 0.04^ef
			10	5.53 ± 0.45^fgh	6.72 ± 0.88^gh	0.33 ± 0.03^bc	0.59 ± 0.04^hi
			12	3.52 ± 0.59^hij	4.68 ± 0.04^ij	0.14 ± 0.01^de	0.34 ± 0.06^j
	Solution	700	8	9.34 ± 1.75^bcd	10.60 ± 0.57^c	0.57 ± 0.02^a	0.73 ± 0.04^ef
			10	8.66 ± 0.45^cde	9.90 ± 0.57^cd	0.24 ± 0.06^cd	0.59 ± 0.01^hi
			12	5.88 ± 3.22^fgh	8.07 ± 1.09^ef	0.15 ± 0.01^de	0.61 ± 0.01^ghi
		1000	8	0.93 ± 0.05^k	2.29 ± 0.30^k	0.14 ± 0.01^de	0.61 ± 0.01^ghi
			10	0.96 ± 0.09^jk	1.15 ± 0.04^kl	0.14 ± 0.06^de	0.56 ± 0.01^hi
			12	0.64 ± 0.01^k	0.91 ± 0.01^l	0.12 ± 0.02^e	0.22 ± 0.02^k
Control				12.05 ± 0.13^a	15.39 ± 0.80^a	0.65 ± 0.01^a	0.91 ± 0.02^a

a–n: significant different at p < 0.05.

FIGURE 5 Effect of different heat and microwave treatments on the emulsion stability of gum karaya A: without heat treatment and B: with heat treatment (120°C, 2 h).

a–d: significant different at p < 0.05;a–h: significant different at p < 0.05;A′, B′, and C′: Unheated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D′, E′, and F′: Unheated microwave powder samples at 1000 W for 8, 10, and 12 min, respectively.G′, H′, and I′: Unheated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J′, K′, and L′: Unheated microwave treated solution samples at 1000 W for 8, 10, and 12 min, respectively.A″, B″, and C″: Heated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D″, E″, and F″: Heated microwave treated powder samples at 1000 W for 8, 10, and 12 min, respectively.G″, H″, and I″: Heated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J″, K″, and L″: Heated microwave solution samples at 1000 W for 8, 10, and 12 min, respectively.

FIGURE 6 Effect of different heat and microwave treatments on the moisture content of gum karaya; A: without temperature and B: with temperature (120°C, 2 h).

a–g: significant different at p < 0.05;a–h: significant different at p < 0.05;A′, B′, and C′: Unheated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D′, E′, and F′: Unheated microwave powder samples at 1000 W for 8, 10, and 12 min, respectively.G′, H′, and I′: Unheated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J′, K′, and L′: Unheated microwave treated solution samples at 1000 W for 8, 10, and 12 min, respectively.A″, B″, and C″: Heated microwave treated powder samples at 700 W for 8, 10, and 12 min, respectively.D″, E″, and F″: Heated microwave treated powder samples at 1000 W for 8, 10, and 12 min, respectively.G″, H″, and I″: Heated microwave treated solution samples at 700 W for 8, 10, and 12 min, respectively.J″, K″, and L″: Heated microwave solution samples at 1000 W for 8, 10, and 12 min, respectively.