Feasibility of ultrasound-assisted optimized process of high purity rice bran protein extraction

Bernardi, Sílvia; Kalschne, Daneysa Lahis; Menegotto, Anne Luize Lupatini; Flores, Eder Lisandro Moraes; Barin, Juliano Smanioto; Fuchs, Renata Hernandez Barros; Colla, Eliane; Canan, Cristiane

doi:10.1590/0103-8478cr20200012

ABSTRACT:

Rice bran is a by-product of the rice milling process, found worldwide in abundance and highlighted due its protein content. This study optimized the conditions for ultrasonic-assisted extraction of protein from defatted rice bran (DRB) and characterized the rice bran protein concentrate (RBPC). A sequential strategy of experimental design was employed; the effect of pH, temperature, ultrasound exposure time, and amplitude were evaluated regarding the percentage of protein extraction by a Full factorial design (FFD) with a fixed frequencies (FFD-A: 37 kHz; FFD-B: 80 kHz). Subsequently, the percentage of protein extracted was optimized employing a Central composite rotatable design (variables: pH and ultrasound exposure time) and RBPC obtained was characterized regarding chemical and functional properties. The pH and ultrasound exposure time had positive effect (P ≤ 0.05) on percentage of protein extraction; moreover, 37 kHz frequency was more effective in protein extraction. The optimized condition (frequency: 37 kHz; temperature: 30 °C; pH: 10; ultrasound exposure time: 30 min; and amplitude: 100%) allowed 15.07% of protein recovery and the RBPC presented 84.76 g 100 g^-1 of protein. Magnesium and copper were the main mineral in RBPC (34.4 and 25.5 µg g^-1, respectively), while leucine was the limiting amino acid (0.42) and threonine presented the highest chemical score (1.0). The RBPC solubility was minimal at pH 4 and higher at pHs 6-10; the water and oil absorption capacity were higher than bovine serum albumin (BSA) and the emulsifying capacity was comparable to BSA, with a suitable stability. It was possible to obtain a higher purity RBPC than described in the literature, due to the optimization in the extraction process steps, with functional properties suitable for application in food products, especially emulsified ones.

Key words:
amino acid; alkaline extraction; by-product; defatted rice bran; functional properties; sequential strategy of experimental design

[1] E-mail: canan@utfpr.edu.br. ^*Corresponding author

Run	x1	x2	x3	x4	FFD-A	FFD-B
					y1^*	y2^*
1	-1 (8)	-1 (25)	-1 (5)	-1 (40)	1.83^a ± 0.09	1.50^b ± 0.02
2	+1 (10)	-1 (25)	-1 (5)	+1 (100)	2.09 ^a ± 0.03	1.53 ^b ± 0.07
3	-1 (8)	+1 (45)	-1 (5)	+1 (100)	1.80 ^a ± 0.02	1.51 ^b ± 0.02
4	+1 (10)	+1 (45)	-1 (5)	-1 (40)	2.15 ^a ± 0.00	1.89 ^b ± 0.04
5	-1 (8)	-1 (25)	+1 (30)	+1 (100)	1.83 ^a ± 0.03	1.70 ^b ± 0.04
6	+1 (10)	-1 (25)	+1 (30)	-1 (40)	2.14 ^a ± 0.01	2.00 ^b ± 0.03
7	-1 (8)	+1 (45)	+1 (30)	-1 (40)	1.86 ^a ± 0.04	1.69 ^b ± 0.04
8	+1 (10)	+1 (45)	+1 (30)	+1 (100)	2.52 ^a ± 0.09	2.16 ^b ± 0.03
9	0 (9)	0 (35)	0 (17.5)	0 (70)	2.02 ^a ± 0.06	1.79 ^b ± 0.03
10	0 (9)	0 (35)	0 (17.5)	0 (70)	2.12 ^a ± 0.03	1.85 ^b ± 0.03
11	0 (9)	0 (35)	0 (17.5)	0 (70)	2.08 ^a ± 0.01	1.75 ^b ± 0.01

Run	x1	x2	y1^*	y2
1	-1 (8.3)	-1 (19)	1.91^d ± 0.05	1.99
2	1 (9.7)	-1 (19)	2.25^b ± 0.03	2.23
3	-1 (8.3)	1 (41)	2.05^c ± 0.01	2.11
4	1 (9.7)	1 (41)	2.16^bc ± 0.03	2.35
5	-1.41 (8)	0 (30)	2.01^cd ± 0.02	2.00
6	1.41 (10)	0 (30)	2.37^a ± 0.01	2.34
7	0 (9)	-1.41 (15)	2.08^c ± 0.05	2.08
8	0 (9)	1.41 (45)	2.37^a ± 0.01	2.25
9	0 (9)	0 (30)	2.19^b ± 0.01	2.17
10	0 (9)	0 (30)	2.23^b ± 0.03	2.17
11	0 (9)	0 (30)	2.21^b ± 0.08	2.17

Factor	------------FFD-A: 37 kHz ultrasound frequency------------					--------FFD-B: 80 kHz ultrasound frequency--------
	Effect	Standard error	t (6)	p - value	Effect	Standard error	t (6)	p - value
Mean	2.04	0.03	64.86	0.0000^*	2.17	0.02	115.48	0.0000^*
x1	0.39	0.07	5.34	0.0018^*	0.28	0.04	6.34	0.0007^*
x2	0.11	0.07	1.50	0.1852	0.03	0.04	0.75	0.4802
x3	0.12	0.07	1.67	0.1464	0.12	0.04	2.69	0.0362^*
x4	0.07	0.07	0.90	0.4038	0.04	0.04	0.97	0.3706

Parameters	DRB	RBPC
---------Centesimal composition (g 100 g^-1; dry basis)---------
Protein	16.75 ± 0.29	84.76 ± 0.29
Lipids	1.88 ± 0.04	9.40 ± 0.38
Carbohydrate	68.65	ND
Ash	12.72 ± 0.64	5.71 ± 0.37

Parameters	RBPC
-------------Mineral composition (µg g^-1; dry basis)-------------
Mg	34.4 ± 2.78
Cu	25.5 ± 1.85
Zn	13 ± 0.44
As	2.7 ± 0.24
Ni	2.4 ± 0.10
Mo	1.96 ± 0.09
Sr	1.5 ± 1.11
Co	0.95 ± 0.06
Pb	0.46 ± 0.02
Cr	0.32 ± 0.02
Sb	ND
Se	ND
Sn	ND
---------------------------Color parameters--------------------------
L^*	60.42 ± 2.15
a^*	-1.31 ± 0.53
b^*	20.29 ± 1.39

Brasil

Brasil

Feasibility of ultrasound-assisted optimized process of high purity rice bran protein extraction

Viabilidade do processo otimizado assistido por ultrassom para extração de proteína de farelo de arroz de alta pureza

ABSTRACT:

Amino acid	RBPC (current study)	RBPC†	RBPC‡	BSA§	Requirements of preschool children^*		RBPC amino acid chemical score
------------------------------------------------------------------------------Essential----------------------------------------------------------------------------
Leucine (Leu)	28	79	77	120	-	73^*	0.38
Lysine (Lys)	25	52	46	127	52∂	64^*	0.48
Threonine (Thr)	27	37	37	58	27∂	37^*	1.00
Phenylalanine (Phe)	17	50	82f	69	-	69^*∫	0.43∫
Tyrosine (Tyr)	13	38	82f	50	-	69^*∫	-
Valine (Val)	23	69	55	58	-	43^*	0.53
Histidine (His)	16	31	45	39	-	-	-
Isoleucine (Ile)	13	45	36	26	-	31^*	0.42
Methionine (Met)	8.0	-	27ǂ	8	26∂ǂ	27^*ǂ	0.77ǂ
Cysteine (Cys)	12	-	27ǂ	48	-	27^*ǂ	0.44
Tryptophan (Trp)	-	-	12	6	7.4∂	14^*	-
--------------------------------------------------------------------------Nonessential---------------------------------------------------------------------------
Glutamic acid (Glu)	88	176	-	178	-	-	-
Arginine (Arg)	56	98	-	55	-	-	-
Aspartic acid (Asp)	41	109	-	119	-	-	-
Glycine (Gly)	28	58	-	23	-	-	-
Serine (Ser)	23	45	-	46	-	-	-
Proline (Pro)	15	-	-	49	-	-	-
Alanine (Ala)	30	71	-	62	-	-	-