Influence of Acid Treatment on Physicochemical Properties of Aged Rice Flour

Figures & data

TABLE 1 pH, total acidity, and chemical composition of rice flour without and with citric acid (C) and ascorbic(A) acid solutions

Sample	Treatment	pH	Total acidity (g/100 g)	Moisture**	Protein*	Fat*	Ash*
0.7 month	Native	6.38 ± 0.03^a	0.00 ± 0.00^b	10.32 ± 0.04^f	8.13 ± 0.03^a	0.34 ± 0.01^a	0.29 ± 0.02^a
	Control	6.08 ± 0.01^c	0.00 ± 0.00^b	11.20 ± 0.00^d	8.02 ± 0.00^a	0.31 ± 0.01^a	0.21 ± 0.01^b
12 months	Native	6.22 ± 0.00^b	0.00 ± 0.00^b	11.13 ± 0.11^d	8.04 ± 0.04^a	0.30 ± 0.01^a	0.28 ± 0.01^a
	Control	5.98 ± 0.01^d	0.00 ± 0.00^b	10.90 ± 0.00^e	7.81 ± 0.00^b	0.27 ± 0.00^b	0.20 ± 0.00^b
	C 0.1%	4.06 ± 0.00^f	0.01 ± 0.00^b	11.72 ± 0.11^ab	6.65 ± 0.02^d	0.17 ± 0.01^c	0.17 ± 0.01^bc
	C 0.2%	3.81 ± 0.00^h	0.01 ± 0.00^b	11.41 ± 0.02^c	5.95 ± 0.10^g	0.17 ± 0.00^c	0.17 ± 0.01^bc
	C 0.3%	3.69 ± 0.00^i	0.02 ± 0.00^b	11.84 ± 0.03^a	5.28 ± 0.03^h	0.16 ± 0.05^c	0.17 ± 0.01^bc
	C 0.9%	3.58 ± 0.00^j	0.05 ± 0.01^a	11.84 ± 0.05^a	4.55 ± 0.04^j	0.16 ± 0.03^c	0.18 ± 0.01^bc
	A 0.1%	4.23 ± 0.00^e	0.00 ± 0.00^a	11.44 ± 0.00^c	7.18 ± 0.01^c	0.14 ± 0.02^c	0.15 ± 0.01^bc
	A 0.2%	3.95 ± 0.01^g	0.01 ± 0.00^a	11.44 ± 0.02^c	6.49 ± 0.01^e	0.15 ± 0.00^c	0.14 ± 0.02^c
	A 0.3%	3.93 ± 0.01^g	0.01 ± 0.00^a	11.58 ± 0.01^bc	6.23 ± 0.02^f	0.15 ± 0.02^c	0.15 ± 0.01^bc
	A 0.9%	3.81 ± 0.00^h	0.02 ± 0.01^a	10.76 ± 0.02^e	4.88 ± 0.00^i	0.14 ± 0.01^c	0.16 ± 0.01^bc

Data are shown as mean ± standard deviation.

^a-lMeans with different letters in the same column are significantly different (p ≤ 0.05). The calculation of total acidity as citric acid for 12 month aged rice flour treated with citric acid solution and total acidity as ascorbic acid for 12 month aged rice flour treated with ascorbic acid solution.

^*,**Unit: % of dry basis and wet basis, respectively.

FIGURE 1 A: WAI; B: WSI; and C: swelling power of 0.7 month rice flour (0.7M) and 12 month aged rice flour (12M) without and with citric acid (12M+C) and ascorbic acid (12M+A) solutions. The data are shown as means ± SD (bars).

TABLE 2 Pasting properties of the rice flour without and with citric acid (C) and ascorbic (A) acid solutions

Sample	Treatment	Viscosity (RVU)					Pasting temperature (°C)
		Peak	Tough	Breakdown	Final	Setback
0.7 month	Native	156.88 ± 2.30^c	132.42 ± 0.47^a	24.46 ± 2.77^h	235.09 ± 0.36^b	102.67 ± 0.84^b	86.15 ± 0.00^b
	Control	164.09 ± 1.38^ab	107.34 ± 1.91^c	56.75 ± 1.47^e	182.54 ± 0.65^e	75.21 ± 1.26^e	84.55 ± 1.19^bcd
12 months	Native	139.09 ± 1.53^e	123.82 ± 2.57^b	15.27 ± 1.03^i	247.80 ± 0.12^a	123.98 ± 1.69^a	88.20 ± 1.13^a
	Control	155.21 ± 0.30^d	104.21 ± 1.71^cd	51.00 ± 1.87^f	225.29 ± 1.62^c	121.08 ± 1.54^a	86.20 ± 1.13^b
	C 0.1%	158.79 ± 1.77^c	93.09 ± 1.50^e	65.71 ± 1.73^d	177.54 ± 1.81^f	84.46 ± 1.30^d	84.48 ± 0.74^bcd
	C 0.2%	161.75 ± 1.55^b	83.75 ± 1.45^f	78.00 ± 1.90^b	157.59 ± 1.87^h	73.84 ± 1.42^e	83.83 ± 0.49^cd
	C 0.3%	166.42 ± 1.14^a	76.50 ± 1.36^g	89.92 ± 1.50^a	133.21 ± 1.68^j	65.21 ± 0.30^f	83.20 ± 1.13^cde
	C 0.9%	115.54 ± 1.62^f	42.46 ± 1.66^i	73.08 ± 1.96^c	92.88 ± 1.36^l	50.42 ± 1.70^g	82.95 ± 0.07^e
	A 0.1%	140.34 ± 1.76^e	101.71 ± 1.49^d	38.63 ± 1.27^g	202.21 ± 0.31^d	100.50 ± 1.36^b	85.68 ± 0.46^bc
	A 0.2%	114.50 ± 1.51^f	75.75 ± 1.06^g	38.75 ± 1.45^g	168.79 ± 1.00^g	93.04 ± 1.06^c	85.23 ± 0.32^bc
	A 0.3%	106.54 ± 1.39^g	65.21 ± 1.37^h	41.33 ± 1.02^g	141.92 ± 1.43^i	76.71 ± 1.80^e	84.68 ± 0.95^bcd
	A 0.9%	96.88 ± 1.72^h	40.09 ± 0.12^i	56.79 ± 1.60^e	102.96 ± 1.24^k	62.88 ± 1.36^f	84.20 ± 1.70^bcd

Data are shown as mean ± standard deviation.

^a-lMeans with different letters in the same column are significantly different (p ≤ 0.05).

TABLE 3 Thermal properties of the rice flour without and with citric acid (C) and ascorbic (A) acid solutions

Sample	Treatment	Gelatinization				Amylose-lipid complex				Retrogradation
		To (°C)	Tp (°C)	Tc (°C)	ΔH (J g^–1 dry basis)	To (°C)	Tp (°C)	Tc (°C)	ΔH (J g^–1 dry basis)	To (°C)	Tp (°C)	Tc (°C)	ΔH (J g^–1 dry basis)
0.7 month	Native	62.4 ± 0.2^b	69.6 ± 0.0^b	76.6 ± 0.2^b	9.08 ± 0.27^d	91.4 ± 0.1^a	96.6 ± 0.1^a	103.8 ± 0.8^a	0.74 ± 0.05^b	45.5 ± 1.2^b	56.2 ± 0.5^b	62.1 ± 0.1^b	1.89 ± 0.01^b
12 months	Native	66.2 ± 0.4^a	73.8 ± 1.1^a	81.1 ± 1.1^a	10.47 ± 0.04^c	91.1 ± 0.7^a	97.3 ± 0.4^a	104.4 ± 0.7^a	1.53 ± 0.07^a	49.7 ± 0.9^a	57.9 ± 0.5^a	63.8 ± 0.0^a	3.03 ± 0.14^a
	C 0.2%	52.9 ± 0.0^cd	69.2 ± 0.1^b	76.7 ± 0.3^b	11.74 ± 0.05^b	91.4 ± 0.0^a	96.6 ± 0.4^a	104.2 ± 0.1^a	1.48 ± 0.01^a	45.8 ± 0.6^b	56.5 ± 0.3^b	61.5 ± 0.6^b	2.03 ± 0.14^b
	C 0.9%	52.8 ± 0.3^cd	69.2 ± 0.1^b	76.6 ± 0.5^b	10.66 ± 0.16^c	91.5 ± 0.5^a	96.8 ± 0.1^a	105.1 ± 0.4^a	1.46 ± 0.07^a	45.5 ± 0.4^b	56.2 ± 0.2^b	61.2 ± 0.5^b	1.58 ± 0.16^c
	A 0.2%	52.8 ± 0.1^cd	69.7 ± 0.4^b	77.5 ± 0.7^b	12.26 ± 0.11^a	90.6 ± 0.8^a	96.3 ± 0.1^a	104.4 ± 0.1^a	1.53 ± 0.01^a	46.7 ± 0.7^b	56.5 ± 0.5^b	63.1 ± 0.7^a	1.08 ± 0.17^d
	A 0.9%	52.3 ± 0.4^d	69.4 ± 0.2^b	77.4 ± 0.0^b	11.56 ± 0.14^b	90.4 ± 0.6^a	97.5 ± 0.4^a	104.5 ± 0.7^a	1.51 ± 0.07^a	45.8 ± 0.3^b	56.4 ± 0.6^b	61.8 ± 0.6^b	0.91 ± 0.05^d

Data are shown as mean ± standard deviation.

^a-lMeans with different letters in the same column are significantly different (p ≤ 0.05). T_o, T_p, T_c: Onset, peak, and conclusion temperature, respectively; ΔH: enthalpy.

FIGURE 2 SDS-PAGE of 0.7 month rice flour (0.7M) and 12 month aged rice flour (12M) without and with citric acid (12M+C) and ascorbic acid (12M+A) solutions. A: without β-ME; B: with β-ME. β: beta-mercaptoethanol.

TABLE 4 Hardness (N) of rice flour gels without and with citric acid (C) and ascorbic (A) acid solutions

Sample	Treatment		Hardness (N)
		Fresh	Cycle 1	Cycle 5
0.7 month	Native	0.72 ± 0.04^bcC	0.93 ± 0.08^bB	1.65 ± 0.03^bA
12 months	Native	1.02 ± 0.06^aC	1.57 ± 0.10^aB	3.15 ± 0.25^aA
	C 0.1%	0.71 ± 0.10^bcB	0.88 ± 0.00^bB	1.56 ± 0.04^bcA
	C 0.2%	0.44 ± 0.05^dB	0.55 ± 0.06^cB	1.09 ± 0.12^cA
	A 0.1%	0.82 ± 0.09^bcB	0.91 ± 0.07^bB	1.65 ± 0.09^bA
	A 0.2%	0.68 ± 0.05^cB	0.81 ± 0.05^bB	1.40 ± 0.37^bcA

Data are shown as mean ± standard deviation.

^a–cMeans with different letters in the same column are significantly different (p ≤ 0.05).

^A–CMeans with different letters in the same row are significantly different (p ≤ 0.05).