Nature of Crystallinity in Native and Acid Modified Starches

Figures & data

Figure 1 X-ray diffractograms of selected starches before and after modification With acids. 1 = Native, 2 to 5, modified with HCl, HNO₃, H₂SO₄ and H₃PO₄, respectively (0.5 N acid, 50°C, 1.5h).

Figure 2 Schematic Intensity plots at specific 2θ values of A, B and C type starches as per Zobel, 1964. Intensity scale: Weak (W), Medium (M), and Strong (S). The observed 2θ values for starches are indicated alongside for comparison.

Table 1 Diffraction spacing ‘d' and crystal size ‘D' of native and acid modified starches

						Modified using
	2θ	2 θ	Reflection (hkl)	Native		HCl		HNO3		H2SO4		H3PO4
	(°)	(°)		d	D	d	D	d	D	d	D	d	D
Starch	Exptl	Cal∗		Å	Å	Å	Å	Å	Å	Å	Å	Å	Å
Potato	5.6	5.3	(001)	15.80	133 ± 13	15.80	159 ± 15	15.39	133 ± 13	15.57	133 ± 13	15.51	145 ± 14
	11.5	11.4	(111)	7.70	44 ± 4	7.80	47 ± 4	7.70	47 ± 4	7.57	38 ± 3	7.76	40 ± 4
	15.5	15.2	(140)	5.89	62 ± 6	5.91	62 ± 6	5.83	62 ± 6	5.77	57 ± 5	6.03	80 ± 8
	17.1	17.6	(131)	5.17	134 ± 13	5.16	134 ± 13	5.16	146 ± 14	5.13	146 ± 14	5.19	157 ± 15
	19.7	19.3	(103)	4.51	231 ± 20	4.48	162 ± 16	4.48	162 ± 16	4.47	231 ± 23	4.49	179 ± 17
	22.2	22.6	(113)	4.00	135 ± 13	4.03	115 ± 11	3.97	81 ± 8	3.97	147 ± 14	3.99	180 ± 18
	23.9	23.3	(132)	3.72	116 ± 10	3.70	84 ± 8	3.67	162 ± 16	3.69	116 ± 11	3.69	163 ± 16
	26.4	26.5	(142)	3.48	54 ± 5	3.43	90 ± 9	3.38	136 ± 13	3.40	117 ± 11	3.39	136 ± 13
Tapioca	11.2	11.4	(111)	7.69	42 ± 4	7.86	44 ± 4	7.63	36 ± 3	7.79	38 ± 3	7.63	36 ± 3
	15.3	15.2	(140)	5.79	114 ± 10	5.83	134 ± 13	5.82	134 ± 13	5.83	115 ± 11	5.79	134 ± 13
	17.3	17.5	(131)	5.13	134 ± 13	5.17	134 ± 13	5.13	134 ± 13	4.93	134 ± 13	5.10	134 ± 13
	18.0	18.3	(150)	4.93	115 ± 10	4.93	134 ± 13	4.93	134 ± 13	–	134 ± 13	4.93	101 ± 10
	20.4	20.0	(032)	4.36	202 ± 20	4.40	203 ± 20	4.40	289 ± 28	4.36	202 ± 20	4.40	162 ± 16
	23.2	23.2	(132)	3.84	90 ± 9	3.84	86 ± 8	3.84	90 ± 9	3.84	96 ± 9	3.84	85 ± 8
	26.4	26.5	(142)	3.38	136 ± 13	3.38	102 ± 10	3.38	117 ± 11	3.37	102 ± 10	3.35	136 ± 13
Wheat	11.8	11.4	(111)	7.51	38 ± 3	7.50	40 ± 4	7.49	38 ± 3	–	–	–	–
	15.2	15.2	(140)	5.83	134 ± 13	5.87	119 ± 11	5.83	118 ± 11	5.79	122 ± 12	5.82	116 ± 11
	17.3	17.6	(131)	5.13	161 ± 16	5.13	134 ± 13	5.13	149 ± 14	5.13	161 ± 16	5.18	161 ± 16
	18.2	18.3	(150)	4.88	183 ± 18	4.90	161 ± 16	4.91	161 ± 16	4.90	201 ± 20	4.96	134 ± 13
	20.0	20.0	(032)	4.44	126 ± 12	4.44	135 ± 13	4.44	135 ± 13	4.46	115 ± 11	4.44	202 ± 20
	23.3	23.3	(132)	3.82	92 ± 9	3.85	87 ± 8	3.84	94 ± 9	3.84	85 ± 8	3.84	75 ± 7
	26.4	26.6	(142)	3.38	183 ± 18	3.43	68 ± 6	3.35	164 ± 16	3.45	102 ± 10	3.38	136 ± 13
Maize	11.5	11.4	(111)	–	–	–	–	7.57	42 ± 4	7.76	44 ± 4	7.44	38 ± 3
	15.2	15.2	(140)	5.84	132 ± 13	5.83	134 ± 13	5.83	134 ± 13	5.83	132 ± 13	5.79	67 ± 6
	17.0	17.6	(131)	5.16	161 ± 16	5.13	134 ± 13	5.16	161 ± 16	5.16	161 ± 16	5.13	134 ± 13
	18.0	18.3	(150)	4.93	134 ± 13	4.93	126 ± 12	4.93	161 ± 16	4.93	134 ± 13	4.88	161 ± 16
	19.8	19.3	(103)	4.48	126 ± 12	4.44	135 ± 13	4.44	202 ± 20	4.42	162 ± 16	4.44	202 ± 20
	23.2	23.3	(132)	3.84	92 ± 9	3.84	87 ± 8	3.85	95 ± 9	3.80	86 ± 8	3.84	90 ± 9
	26.2	26.6	(142)	3.40	68 ± 6	3.37	136 ± 13	3.36	164 ± 16	3.39	102 ± 10	3.35	136 ± 13
Finger millet	11.5	11.4	(111)	7.70	38 ± 3	7.44	34 ± 3	7.63	40 ± 4	7.54	33 ± 3	–	–
	15.3	15.2	(140)	5.80	145 ± 15	5.76	129 ± 12	5.82	136 ± 13	5.76	124 ± 12	5.83	114 ± 11
	17.3	17.6	(131)	5.12	134 ± 13	5.10	161 ± 16	5.16	161 ± 16	5.10	161 ± 16	5.16	175 ± 17
	18.2	18.3	(150)	5.10	201 ± 20	4.88	161 ± 16	4.88	161 ± 16	4.88	134 ± 13	4.90	161 ± 16
	20.2	20.0	(032)	4.40	289 ± 28	4.40	162 ± 16	3.85	161 ± 16	4.38	269 ± 26	4.48	134 ± 13
	23.2	23.3	(132)	3.84	85 ± 8	3.82	98 ± 9	3.85	93 ± 9	3.83	108 ± 10	3.84	102 ± 10
	26.4	26.6	(142)	3.38	136 ± 13	3.34	204 ± 20	3.38	117 ± 11	3.33	136 ± 13	3.36	136 ± 13
Chick pea	11.5	11.4	(111)	7.70	56 ± 5	7.79	61 ± 6	7.69	38 ± 3	7.63	42 ± 4	7.76	42 ± 4
	15.2	15.2	(140)	5.83	110 ± 10	5.79	115 ± 11	5.83	54 ± 5	5.79	134 ± 13	5.79	115 ± 11
	17.3	17.5	(131)	5.13	80 ± 8	5.13	98 ± 9	5.16	89 ± 8	5.16	89 ± 8	5.13	92 ± 9
						–	–	–	–	–	–	–	–
	23.2	23.2	(132)	3.84	75 ± 7	3.83	77 ± 7	3.87	72 ± 7	3.84	70 ± 7	3.82	73 ± 7
	26.5	26.5	(142)	3.36	163 ± 16	3.40	82 ± 8	3.40	91 ± 9	3.39	117 ± 11	3.40	102 ± 10
Green gram	11.5	11.4	(111)	7.76	42 ± 4	7.76	42 ± 4	7.79	44 ± 4	7.87	44 ± 4	7.63	33 ± 3
	15.4	15.2	(140)	5.77	115 ± 10	5.83	134 ± 13	5.76	115 ± 11	5.83	134 ± 13	5.84	127 ± 12
	17.4	17.5	(131)	5.10	134 ± 13	5.16	161 ± 16	5.09	115 ± 11	5.18	115 ± 11	5.09	134 ± 13
	18.1	18.3	(150)	4.90	134 ± 13	4.95	115 ± 11	4.90	115 ± 11	4.93	158 ± 15	4.93	134 ± 13
	20.0	20.0	(032)	4.44	202 ± 20	4.40	269 ± 26	4.48	115 ± 11	3.41	135 ± 13	–	–
	23.2	23.2	(132)	3.84	81 ± 8	3.84	90 ± 9	3.84	90 ± 9	3.85	81 ± 8	3.40	81 ± 8
	26.2	26.4	(142)	3.41	81 ± 8	3.38	91 ± 9	3.35	163 ± 16	3.41	108 ± 10	3.35	102 ± 10
Waxy rice	11.6	11.4	(111)	7.63	35 ± 3	7.63	33 ± 3	NE	NE	NE	NE	NE	NE
	15.3	15.2	(140)	5.79	107 ± 10	6.92	115 ± 11
	17.3	17.6	(131)	5.13	161 ± 16	5.10	134 ± 13
	18.1	18.3	(150)	4.87	134 ± 13	4.87	134 ± 13
	20.1	20.0	(032)	4.42	269 ± 26	4.38	269 ± 26
	23.2	23.3	(132)	3.84	90 ± 9	4.98	90 ± 9
	26.5	26.6	(142)	3.36	136 ± 13	3.39	102 ± 10
∗This is the nearest 2 θ value to the experimental one for which the reflection (Miller indices, hkl) could be assigned, based on unit cell parameters for the starch type. NE: Not examined; a dash indicates absence or ambiguous presence of the peak.

Table 2 Unit cell dimension of A, B and C-type starches∗

Starch	Unit cell dimensions
A-type Starches:	a = 11.90 Å
Wheat, maize, finger millet, & waxy rice.	b = 17.70 Å
	c = 10.52 Å
	α = β = γ = 90°
B-type Starch:	a = 18.5 Å
Potato	b = 18.5 Å
	c = 10.4 Å
	α = β = 90° and γ = 120°
C-type Starches:	a = 18.50 Å
Chick pea, green gram, & tapioca	b = 18.50 Å
	c = 10.47 Å
	α = β = 90° and γ = 120°
∗Adapted from Zobel[2] and Sarko & Wu. [9] a, b, c are the axes of a crystal unit cell; α, β and γ are the inter axial angles.

Table 3 Relative crystallinity (%) of starches before and after 0.5N acid modification

Starch	Native	HCl	HNO3	H2SO4	H3PO4
Maize	27	27	32	28	30
Wheat	28	28	26	25	29
Finger millet	30	31	29	29	31
Green gram	32	34	34	33	31
Potato	23	27	29	29	31
Tapioca	35	34	35	34	35

Zobel , H.F. 1964 . “ X-ray Analysis of Starch Granules ” . In Methods in Carbohydrate Chemistry, , IV , Edited by: Whistler , R.L. London : Academic Press Inc. .

 Google Scholar