Rheological Characterisation of Malaysian Varieties of Sweet Potato Doughs Using Large and Small Deformation Measurements

Figures & data

FIGURE 1 Schematic diagram of forces acting on dough and the length of dough during tensile test at the extensibility rig.

TABLE 1 Proximate compositions of sweet potato flours

Parameter	VitAto	Bukit Naga	Okinawan
Moisture (g/100 g)	4.60 ± 0.00^b	4.40 ± 0.14^b	5.15 ± 0.07^a
Ash (g/100 g)	3.15 ± 0.07^a	3.20 ± 0.00^a	2.75 ± 0.07^b
Crude protein (g/100 g)	5.70 ± 0.00^a	3.85 ± 0.07^a	3.50 ± 0.00^b
Fat (g/100 g)	0.20 ± 0.00^a	0.70 ± 0.00^a	0.20 ± 0.00^b
Dietary fiber (g/100 g)	14.80 ± 0.00^a	11.20 ± 0.00^c	11.30 ± 0.00^b

All means present the average of two independent replications. Values followed by the different superscript in each row are significantly different (P < 0.05).

FIGURE 2 Dough microscopic changes at various stages of development associated with (a) undermixed; (b) optimally mixed; and (c) overmixed doughs.

FIGURE 3 Graph of large deformation test of sweet potato doughs mixed at 5 min mixing time for (a) measured force-hook displacement curves and (b) stress-strain curves.

FIGURE 4 Graph of small deformation test of sweet potato doughs mixed at 5 min mixing time for (a) modulus of storage, G’; (b) modulus of loss, G” and; (c) tan δ.

FIGURE 5 The effect of mixing time in large deformation tests to sweet potato doughs at (a) length at fracture; (b) failure strain; (c) failure stress; (d) coefficient k; and (e) index, n.

TABLE 2 Extensibility parameters of sweet potato and wheat doughs at fracture at various mixing time

Flour	Mixing time (min)	yt (mm)	Fm (N)	lt (mm)	Fa (N)	ϵH	σ(Nmm^−2)
VitAto	2	42.63	0.914	98.33	0.462	1.653	0.0045
	5	48.63	0.994	110.22	0.502	1.767	0.0054
	8	43.25	0.916	99.56	0.463	1.666	0.0045
	11	42.89	0.919	98.85	0.465	1.659	0.0045
	14	42.99	0.921	99.05	0.466	1.661	0.0045
Bukit Naga	2	40.52	0.785	94.16	0.397	1.610	0.0035
	5	42.63	0.814	98.33	0.412	1.653	0.0038
	8	40.35	0.789	93.83	0.400	1.606	0.0035
	11	39.95	0.791	93.04	0.401	1.598	0.0035
	14	39.86	0.795	92.86	0.403	1.596	0.0035
Okinawan	2	35.72	0.694	84.69	0.352	1.504	0.0028
	5	37.23	0.706	87.67	0.358	1.539	0.0030
	8	35.52	0.694	84.30	0.352	1.499	0.0028
	11	35.41	0.696	84.08	0.354	1.497	0.0028
	14	34.81	0.699	82.90	0.355	1.483	0.0028
*Wheat	2	136.1	1.400	287.00	0.710	1.930	0.0489
	5	136.1	1.410	287.00	0.710	1.930	0.0491
	8	172.2	1.430	358.70	0.720	2.150	0.0618
	11	140.3	1.360	295.30	0.690	1.950	0.0490
	15	137.5	1.490	289.80	0.770	1.930	0.0523

*Adapted from Abang Zaidel et al.^[17] as a comparison.

FIGURE 6 The effect of mixing time in small deformation tests to sweet potato doughs at (a) modulus of storage, G’; (b) modulus of loss, G”; and (c) tan δ.

TABLE 3 Pearson correlation of the large and small dough rheological properties for sweet potato at various mixing time

	G’	G”	ϵH	σmax
G’	1
G”	0.9942	1
ϵH	0.9090	0.9272	1
σmax	0.8269	0.8480	0.9744	1

Abang Zaidel, D.N.; Chin, N.; Abdul Rahman, R.; Karim, R. Rheological characterisation of gluten from extensibility measurement. Journal of Food Engineering 2008, 86 (4), 549–556.

 Web of Science ®Google Scholar