Pretreatment process of rice syrup production and analysis of physicochemical properties

Figures & data

Table 1. Orthogonal test design.

Level	Factor
	A. Material ratio (g/mL)	B. Barrel temperature (°C)	C. Screw speed (r/min)	D. Enzyme dosage (U/g)
1	20	85	175	70
2	25	95	210	80
3	30	105	245	90

Figure 1. Influence of extrusion processing conditions on the reducing sugars in resistant starch rice. (a) Influence of material water content on rice reducing sugar. (b) Influence of reaction temperature on rice reducing sugar. (c) Influence of extrusion processing rotation on rice reducing sugars. (d) Influence of extrusion enzyme addition amount on the rice reducing sugars.

Table 2. Results of orthogonal test.

Test No.	Factor level
	A. Material ratio (g/mL)	B. Barrel temperature (°C)	C. Screw speed (r/min)	D. Enzyme dosage (U/g)	Reducing sugar content (%)
1	1	1	1	1	18.3 ± 0.3^b
2	1	2	2	2	16.5 ± 0.59^d
3	1	3	3	3	16.1 ± 0.66^d
4	2	1	2	3	22.6 ± 0.62^a
5	2	2	3	1	17.49 ± 0.15^c
6	2	3	1	2	18.6 ± 0.16^b
7	3	1	3	2	15.7 ± 0.53^d
8	3	2	1	3	18.29 ± 0.17^b
9	3	3	2	1	16.35 ± 0.37^d
K1	16.97	18.87	18.40	17.38
K2	19.56	17.43	18.48	16.93
K3	16.78	17.02	16.43	18.90
R	2.78	1.85	2.05	1.97

All data were expressed as mean and standard deviation of triplicate values. Superscript characters (a–d) indicate significant differences (P < 0.05) in the same column.

Table 3. Main basic composition (the percentage content of dry basis, unit: %).

Sample	Total starch	Resistant starch	Protein	Water content	Fat	Ash	Reducing sugar content
Original rice	69.7 ± 0.5^a	7.82 ± 0.23^a	6.69 ± 0.11^b	11.72 ± 0.26^a	3.2 ± 0.64^a	0.74 ± 0.32^a	0.92 ± 0.19^b
Extruded rice	67.2 ± 0.7^a	7.52 ± 0.13^a	7.37 ± 0.15^a	8.75 ± 0.15^a	2.4 ± 0.28^b	0.96 ± 0.12^a	23.52 ± 0.65^a

All data were expressed as mean and standard deviation of triplicate values. Superscript characters (a and b) indicate significant differences (P < 0.05) in the same column.

Figure 2. Changes in resistant starch rice particles before and after extrusion. a)unextruded resistant starch rice particles. b) Extrusion resistant starch rice powder particles.

Figure 3. X-ray diffraction pattern of starch molecular crystal structure in the resistant starch rice particles before and after extrusion.

Table 4. Changes in thermodynamic properties before and after low-temperature extrusion.

Raw material	T0 (°C)	Tp (°C)	Tc (°C)	∆H (J/g)
Before extrusion	99.97 ± 0.64^b	129.53 ± 0.52^b	177.56 ± 0.38^b	95.63 ± 0.08^b
After extrusion	107.81 ± 0.15^a	139.66 ± 0.36^a	194.99 ± 0.19^a	212.4 ± 0.29^a

Data results indicated the mean ± standard deviation; different letters in the same column indicated significant differences (P < 0.05).

Figure 4. Changes in the solubility of resistant starch rice before and after extrusion.

Table 5. Parallel experimental test results of the color indicator.

Sample	Color index	Parallel 1	Parallel 2	Parallel 3	Parallel 4	Parallel 5	Average value	RSD/%	∆E
Rice syrup	L*	65.46	65.43	65.42	65.41	65.40	65.42	0.036	5.02
	a*	−3.46	−3.51	−3.55	−3.51	−3.53	−3.51	0.955
	b*	6.84	6.84	6.97	6.92	7.03	6.92	2.39
Extruded rice syrup	L*	69.87	69.89	69.90	69.92	69.93	69.90	0.034
	a*	−3.48	−3.46	−3.47	−3.50	−3.51	−3.48	0.658
	b*	4.63	4.61	4.65	4.68	4.66	4.65	0.589

Figure 5. Plot of starch glycohydrodenosis. (a) Shear stress with shear rate. (b) Viscosity with shear rate.