In vitro digestion, physicochemical and morphological properties of low glycemic index rice flour prepared through enzymatic hydrolysis

Figures & data

Table 1. Physicochemical and in vitro digestion properties of low glycemic index (GI) rice flour.

	Untreated rice flour	Low GI rice flour
Physicochemical properties
Water activity	0.66 ± 0.00^a	0.09 ± 0.00^b
Moisture (%)	10.36 ± 0.06^a	8.94 ± 0.07^b
Crude protein (%)	6.41 ± 0.01^a	22.31 ± 0.02^b
Crude fiber (%)	0.73 ± 0.05^a	2.22 ± 0.03^b
Dietary fiber (%)	3.61 ± 0.02^a	4.30 ± 0.01^b
Ash (%)	0.8 ± 0.20^a	1.08 ± 0.02^a
Crude fat (%)	0.56 ± 0.20^a	6.90 ± 0.03^b
Carbohydrates (%)	81.11 ± 0.33^a	58.53 ± 0.17^b
Total sugars (%)	0.4 ± 0.05^a	23.58 ± 0.06^b
Reducing sugars (%)	ND	12.18 ± 0.03
Energy (Kcal/100g)	355.20 ± 1.23^a	385.48 ± 0.4^b
In vitro digestion properties
Total starch (%)	82.14 ± 0.61^a	36.63 ± 0.15^b
Very rapidly digestible starch (%)	1.45 ± 0.01^a	0.64 ± 0.01^b
Rapidly digestible starch (%)	77.95 ± 0.23^a	37.67 ± 0.05^b
Slowly digestible starch (%)	12.20 ± 0.03^a	36.09 ± 1.60^b
Resistant starch (%)	8.42 ± 0.17^a	25.6 ± 1.55^b
Digestible starch (%)	91.58 ± 0.17^a	74.41 ± 1.55^b
Starch hydrolysis rate (%)	260.3 ± 2.52^a	151.32 ± 1.07^b
Starch digestible index	94.88 ± 0.91^a	102.85 ± 0.41^b

Values are presented as mean± standard deviation and are the average of triplicates.

Values with different superscripts within the row differ significantly (p ≤ 0.05) from each other.

ND: Not detected

Table 2. Apparent amylose, amylopectin, glycemic load, sweetness index, total sweetness index and sugar profile of low glycemic index (GI) rice flour.

	Untreated rice flour	Low GI rice flour
Apparent amylose (%)	17.11 ± 0.02^a	7.45 ± 0.15^b
Amylopectin (%)	82.88 ± 0.02^a	92.55 ± 0.15^b
Glycemic load*	67.5 ± 0.2^a	20.03 ± 0.20^b
Sweetness index	ND	12.78 ± 0.03
Totals sweetness index	ND	9.25 ± 0.02
Sugar profile
Glucose (%)	ND	12.78 ± 0.03
Fructose (%)	ND	ND
Sucrose (%)	ND	ND
Maltose (%)	ND	1.32 ± 0.00
Lactose (%)	ND	0.4 ± 0.00

Values are presented as mean± standard deviation and are the average of triplicates.

Values with different superscripts within the row differ significantly (p ≤ 0.05) from each other.

*Glycemic load (GL) was calculated from the equation, GL = Glycemic index (GI) × Available carbohydrate/100; where available carbohydrate = Total carbohydrate – Dietary fiber

Figure 1. Thermal decomposition behavior of low glycemic index (GI) rice flour (A): Thermal gravimetric analysis (TGA) of untreated and low glycemic index (GI) rice flour (B): Differential thermal gravimetric (DTG) of untreated and low glycemic index (GI) rice flour.

Figure 2. Particle size distribution of untreated and low glycemic index (GI) rice flour.

D[2,3] = surface area mean (Sauter Mean Diameter)D[3,4] = volume moment mean (De Brouckere Mean Diamater) – particles constituting the bulk of the sample volumeDv (90) = the diameter where 90% of the population lies below this value and 10% above thisDv (50) = the diameter where 50% of the population lies below this value and 50% above thisDv (10) = the diameter where 10% of the population lies below this value and 90% above this.

Figure 3. Scanning electron micrographs of low glycemic index rice flour.

Figure 4. X-ray diffractrometry of low glycemic index rice flour showing ln(counts) at each Bragg’s angle (2θ).