Changes in wheat and potato starches induced by gamma irradiation: A comparative macro and microscopic study

Figures & data

Table 1. Linear, exponential, and binomial regressions for AAC, WSI, and SP, respectively. X = ID (irradiation dose, kGy).

Variables	Coefficients			Significance
Y	a	b	c	R^Citation2
AAC (%)	Linear law: Y = a + b X
Wheat starch	34.24	–0.42	—	0.98
Potato starch	30.55	–0.44	—	0.97
WSI (%)	Exponential law: Y = a. e^b.X
Wheat starch	3.31	0.031	—	0.99
Potato starch	2.68	0.017	—	0.98
SP (g/g)	Binomial law: Y = a + b X + c X^Citation2
Wheat starch	12.92	0.58	–0.014	0.92
Potato starch	39.88	1.17	–0.035	0.93

Figure 1. Ratio of apparent amylose content (AAC) of irradiated starch (IS) to AAC of native starch (NS) vs. irradiation dose (▲: wheat starch, ■: potato starch). AAC of native starches were: 34.5% ± 0.2 for wheat starch and 30.1% ± 0.1 for potato starch.

Figure 2. Ratio of water solubility index (WSI) of irradiated starch (IS) to WSI of native starch (NS) vs. irradiation dose (▲: wheat starch, ■: potato starch). WSI of native starches were: 3.3% for wheat starch and 2.6% for potato starch.

Figure 3. Ratio of swelling power (SP) of irradiated starch (IS) to SP of native starch (NS) versus irradiation dose (▲: wheat starch, ■: potato starch). SP of native starches were: 11.5 ± 0.1 (g/g) for wheat starch and 33.7% ± 1.1 (g/g) for potato starch.

Table 2. Gelatinization maximum consistency (C_max, UB) of native and irradiated wheat and potato starches prepared at different concentrations: 16% (w/v) for wheat starch and 8% (w/v) for potato starch.

Starch	Irradiation dose (kGy)
	0	3	5	10	20	35	50
Wheat	999.7 ± 0.6 (a)	997.7 ± 0.6 (a)	721.7 ± 18.9 (b)	226.7 ± 11.5 (c)	35.0 ± 5.0 (d)	0.0 ± 0.0 (e)	0.0 ± 0.0 (e)
Potato	702.0 ± 19.7 (a)	413.3 ± 11.5 (b)	373.3 ± 11.5 (c)	334.0 ± 12.7 (d)	217.7 ± 2.5 (e)	78.3 ± 2.9 (f)	0.0 ± 0.0 (g)

Values are means of three replicates ± standard deviation.

Values with different letters in the same line are significantly different (p < 0.05).

Figure 4. Shear stress versus shear rate curves of native and irradiated A: wheat; and B: potato starch pastes obtained at different irradiation doses: (●) 0 kGy; (■) 3 kGy; (▲) 5 kGy; (□) 10 kGy; () 20 kGy; (x) 35 kGy; and (+) 50 kGy.

Figure 5. Shear stress versus shear rate curves of native wheat (▲) and potato (■) starch pastes prepared at different concentrations: 16% (w/v) for wheat starch and 8% (w/v) for potato starch.

Table 3. Hysteresis buckles surface S (cm²) and parameters of the power law model shear stress-shear rate curves of native and irradiated wheat and potato starches.

Starch	Parameter	Irradiation dose (kGy)
		0	3	5	10	20	35	50
Wheat	S (cm^Citation2)	2.26 ± 0.01a	1.68 ± 0.03b	1.48 ± 0.02 c	1.00 ± 0.01d	0.00 ± 0.00e	0.00 ± 0.00e	0.00 ± 0.00e
	n	0.32 ± 0.01c	0.33 ± 0.01c	0.32 ± 0.02c	0.41 ± 0.01c	0.82 ± 0.23b	0.88 ± 0.07b	1.18 ± 0.08a
	K (Pa.sⁿ)	22.81 ± 0.65a	17.04 ± 0.27b	18.58 ± 1.49b	11.48 ± 1.79c	3.97 ± 0.58d	4.57 ± 1.69d	0.03 ± 0.01e
Potato	S (cm^Citation2)	2.32 ± 0.01a	1.93 ± 0.03b	1.88 ± 0.02c	1.84 ± 0.01d	0.00 ± 0.00e	0.00 ± 0.00e	0.00 ± 0.00e
	n	0.53 ± 0.01c	0.45 ± 0.02e	0.45 ± 0.01e	0.42 ± 0.02e	0.49 ± 0.02d	0.62 ± 0.02b	1.16 ± 0.07a
	K (Pa.sⁿ)	21.24 ± 0.58a	18.21 ± 1.81b	14.82 ± 0.65c	16.08 ± 1.19c	4.47 ± 0.53d	1.27 ± 0.09e	0.01 ± 0.00e

Values are means of three replicates ± standard deviation.

Values with different letters in the same line are significantly different (p < 0.05).

Table 4. Maximum extrusion force (F_max) and extrusion surface (S_E) of native and irradiated starches.

Starch	Parameter	Irradiation dose (kGy)
		0	3	5	10	20
Wheat	Fmax (N)	1.67 ± 0,14a	1.58 ± 0.05a	1.51 ± 0.04a	1.31 ± 0.01b	0.89 ± 0.00c
	SE (N.s)	2.93 ± 0.25a	2.79 ± 0.10a	2.66 ± 0.08a	2.35 ± 0.02b	2.12 ± 0.01c
Potato	Fmax (N)	4.37 ± 0.38a	2.98 ± 0.28b	2.55 ± 0.24b	1.98 ± 0.16c	1.75 ± 0.11c
	SE (N.s)	7.44 ± 0.60a	5.34 ± 0.49b	4.86 ± 0.32b	3.65 ± 0.31c	3.25 ± 0.23c

Values are means of three replicates ± standard deviation.

Values with different letters in the same line are significantly different (p < 0.05).

Figure 6. Scanning electron micrographs of: potato starch in the dry state (A–D); potato starch pastes heated to 61.3°C (E–H); wheat starch pastes heated to 58.5°C (I–L; 500×; 5.0 kV). Irradiation doses: (A, E, I) 0 kGy, (B, F, J) 5 kGy, (C, G, K) 20 kGy, and (D, H, L) 50 kGy.

Buléon, A.; Colonna, P.; Planchot, V.; Ball, S. Starch Granules: Structure and Biosynthesis. International Journal of Biological Macromolecules 1998, 23, 85–112.

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