Structural and functional modifications of kudzu starch modified by branching enzyme

Figures & data

Figure 2. HPAEC diagram of amylopectins from natural (a) and enzyme-modified kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h

Figure 1. The morphology of natural (a) and enzyme-treated kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h

Table 1. Molecular structure and hygroscopic characteristics of natural and enzyme-modified starches

Sample	Amylose content (%)	Mw (×10^8 g/mol)	Average chain length	Solubility (%)	Paste transparency (%)
Natural starch	24.3 ± 0.6^a	6.8 ± 0.5^a	19.30 ± 0.03^a	43.2 ± 0.7^g	50.6 ± 0.2^g
BE	22.6 ± 0.3^b	3.6 ± 0.3^b	17.65 ± 0.08^b	64.5 ± 0.5^f	58.6 ± 0.5^f
MA→BE (different BE time)
1 h	17.3 ± 0.5^c	2.1 ± 0.4^c	14.32 ± 0.05^c	67.5 ± 0.6^e	62.5 ± 0.3^e
3 h	15.8 ± 0.3^d	1.8 ± 0.5^c	10.85 ± 0.03^d	70.8 ± 0.4^d	64.4 ± 0.2^d
6 h	13.4 ± 0.4^e	1.3 ± 0.3^d	9.66 ± 0.03^e	73.3 ± 0.5^c	69.1 ± 0.3^c
9 h	12.7 ± 0.5^f	0.9 ± 0.4^e	7.89 ± 0.02^f	75.2 ± 0.2^b	76.2 ± 0.2^b
12 h	11.8 ± 0.1^g	0.4 ± 0.2^e	5.68 ± 0.02^g	77.9 ± 0.3^a	79.4 ± 0.2^a

Mean of three measurements ± SD values in the same column with different letters are significantly different (p ≤ 0.05).

Table 2. Gelatinization properties of natural and enzyme-modified starch granules

Sample	Onset temperature (To, °C)	Peak temperature (Tp, °C)	Conclusion temperature (Tc, °C)	Tc-To (°C)	Gelatinization enthalpy (ΔH, J/g)
Natural starch	68.5 ± 0.2^a	72.9 ± 0.1^a	82.4 ± 0.3^a	13.9 ± 0.2^a	14.8 ± 0.3^a
BE	66.2 ± 0.1^c	69.7 ± 0.5^c	78.8 ± 0.7^b	12.6 ± 0.3^a	9.4 ± 0.2^e
MA→BE (different BE time)
1 h	63.7 ± 0.5^e	68.5 ± 0.3^d	73.2 ± 0.3^d	9.5 ± 0.2^b	9.6 ± 0.2^e
3 h	64.6 ± 0.4^d	69.4 ± 0.6^c	73.8 ± 0.4^d	9.2 ± 0.4^b	10.2 ± 0.3^d
6 h	66.4 ± 0.4^c	69.7 ± 0.2^c	75.5 ± 0.2^c	9.1 ± 0.3^b	11.1 ± 0.3^c
9 h	66.7 ± 0.3^c	70.5 ± 0.4^b	75.3 ± 0.5^c	8.6 ± 0.2^c	11.7 ± 0.4^c
12 h	67.3 ± 0.6^b	70.8 ± 0.2^b	75.4 ± 0.6^c	8.1 ± 0.3^c	12.5 ± 0.3^b

Mean of three measurements ± SD values in the same column with different letters are significantly different (p ≤ 0.05).

Figure 3. ¹HNMR diagram of natural (a) and enzyme-modified kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h

The right numbers refer as α-1, 6 glycosidic linkage.

Figure 4. XRD diagram of natural (a) and enzyme-modified kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h

The right numbers represent relative crystallinity.

Figure 5. Apparent viscosity versus shear rate of native (a) and enzyme-modified kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h

Figure 6. The elastic modulus (G′) and the viscous modulus (G″) as a function of angular frequency (ω) of native (a) and enzyme-modified kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h

Figure 7. The loss tangent (Tan δ) and complex viscosity (η*) as a function of angular frequency (ω) of native (a) and enzyme-modified kudzu starches of (b) BE; MA→BE (different BE time): (c) 1 h; (d) 3 h; (e) 6 h; (f) 9 h; (g) 12 h