Structural properties of sweet potato starch and its vermicelli quality as affected by heat-moisture treatment

Figures & data

Figure 1. X-ray diffraction patterns of the native starch and the heat-moisture treated sweet potato starch at different water levels

Table 1. RVA pasting parameters of native starch and the heat moisture-treated sweet potato starch at different water levels

Sample	PT(/°C)	PV(/cp)	HPV(/cp)	BD(/cp)	FV(/cp)	SB(/cp)
Native	79.25 ± 0.03e	5 227 ± 52a	2 464 ± 54d	2 764 ± 20a	3 220 ± 42e	756 ± 57e
HMT22%	83.40 ± 0.04d	4497 ± 25d	3817 ± 40c	680 ± 17b	5188 ± 67d	1371 ± 43d
HMT26%	84.05 ± 0.06c	4 600 ± 53c	3 904 ± 10b	696 ± 60b	5 522 ± 60c	1618 ± 70c
HMT30%	85.36 ± 0.05b	4 815 ± 43b	4 103 ± 42a	711 ± 28b	5 959 ± 27b	1 855 ± 20b
HMT34%	85.96 ± 0.06a	4 771 ± 24c	4 119 ± 28a	652 ± 7c	6 386 ± 46a	2 267 ± 18a

Data were reported in means ± standard deviation. Values followed by the same letter in each column are significantly different (p < .05). PV = peak viscosity, HPV = Hot paste viscosity BD = breakdown, FV = final viscosity, SB = setback, PT = pasting temperature.

HMT = heat-moisture treatment

Table 2. DSC thermal characteristics of native starch and the heat-moisture treated sweet potato starch at different water levels

Sample	To (°C)	Tp (°C)	Tc (°C)	∆T (°C)	∆H (J/g)
Native	69.10 ± 0.56c	79.04 ± 0.36d	86.87 ± 0.74c	17.77 ± 0.90a	10.34 ± 0.14c
HMT22%	72.92 ± 0.47b	81.38 ± 0.82c	89.54 ± 0.86b	16.62 ± 0.17b	13.11 ± 0.15a
HMT26%	72.41 ± 0.81b	81.50 ± 0.11c	88.86 ± 0.38b	16.45 ± 0.67c	11.37 ± 0.12b
HMT30%	74.06 ± 0.72a	84.97 ± 0.23b	90.27 ± 0.53a	16.21 ± 0.81d	10.74 ± 0.21c
HMT34%	74.78 ± 0.58a	86.27 ± 0.19a	90.53 ± 0.33a	15.75 ± 0.69e	10.44 ± 0.14c

Data were reported in means ± standard deviation. Values followed by the same letter in each column are significantly different (p < .05). To = onset temperature, Tp = peak temperature, Tc = conclusion temperature, ∆T = temperature range (Tc-To), ∆H = enthalpy of gelatinization

HMT = heat-moisture treatment

Table 3. Herschel-Bulkley parameters of the native starch and the heat-moisture treated sweet potato starch at different water levels

Sample	Flow curve
	σ0/Pa	k/Pa·s^m	n	R^2
Native	186.9 ± 1.75a	38.63 ± 0.77e	0.47 ± 0.0a	0.999
HMT22%	162.90 ± 1.47b	71.38 ± 0.82c	0.44 ± 0.00b	0.997
HMT26%	153.60 ± 2.72c	67.16 ± 0.43d	0.39 ± 0.00c	0.995
0HMT30%	134.20 ± 1.13d	89.14 ± 0.22b	0.38 ± 0.00c	0.998
HMT34%	90.16 ± 1.02e	108.40 ± 1.52a	0.32 ± 0.00d	0.999

Data were reported in means ± standard deviation. Values followed by the same letter in each column are significantly different (p < .05). σ₀ = yield stress, k = consistency coefficient, n = flow behavior index, R² = determination coefficient; HMT = heat-moisture treatment

Figure 2. Steady shear flow curves parameters of the native starch and the heat-moisture treated sweet potato starch at different water levels

Table 4. Vermicelli texture parameters of the native starch and the heat-moisture treated sweet potato starch at different water levels

Sample	Native	HMT22%	HMT26%	HMT30%	HMT34%
Hardness (g)	490.50 ± 22.30a	734.40 ± 28.60b	920.80 ± 42.20c	1079.90 ± 58.40d	1332.30 ± 30.30e
Springiness (mm)	0.91 ± 0.00a	0.93 ± 0.05ab	0.92 ± 0.02a	0.94 ± 0.01ab	0.95 ± 0.01b
Chewiness	366.90 ± 12.30a	423.50 ± 12.60b	553.30 ± 8.90c	723.40 ± 15.10d	953.20 ± 18.50e

Data were reported in means ± standard deviation. Values followed by the same letter in each line are significantly different (p < .05). HMT = heat-moisture treatment

Figure 3. Dynamic mechanical spectra as a function of frequency of the native starch and the heat-moisture treated sweet potato starch at different water levels (Closed symbols represent G′, open symbols represent G”)

Figure 4. Tanδ as a function of frequency of the native starch and the heat-moisture treated sweet potato starch at different water levels

Figure 5. Creep test curves of the native starch and the heat-moisture treated sweet potato starch at different water levels