Effects of different heat–moisture treatments on the physicochemical properties of brown rice flour

Abbreviations: 0.1 MPa/5 or 10 min, heat-moisture treatment at 0.1 MPa for 5 or 10 min; 0.2 MPa/5 or 10 min, heat-moisture treatment at 0.2 MPa for 5 or 10 min; 0.3 MPa/10 min, heat-moisture treatment at 0.3 MPa for 10 min; AAC, apparent amylose content; Ad/Tou, adhesion/toughness; Break.d, break down; Cons, consistency; HMT, heat-moisture treatment; KSI, Koshiibuki rice cultivar; KSK, Koshinokaori rice cultivar; Max/Final, maximum/final viscosity; Max/Mini, maximum/minimum viscosity; Past. t, pasting temperature; RS, resistant starch; RVA, Rapid Visco Analyzer; Set/Cons, setback/consistency; Sti/Tou, stickiness/toughness.

Figures & data

Table 1. Component analysis, enzyme activities, and anti-oxidative activity of HMT and untreated brown rice flour.

		Moisture				SD			α-Amylase							SD					Lipase activity								SD				Starch damage								SD							Color difference							SD
		(%)							Activity(CU/g)												(nmol/min/mL)												(%)															ΔE*(ab)
Untreated KSK		12.6a				0.1			0.048a							0.001					5.3a								0.1				7.0a								0.5							23.8a							0.6
0.1 MPa 5 min			12.5a							0.0					0.038b							0.002					4.9a								0.2					7.3ab				0.1					23.8a					1.0
0.1 MPa 10 min		12.7a				0.1			0.017c							0.003					4.9a								0.0				7.7ab								0.1							24.6ab							0.7
0.2 MPa 5 min		12.3a				0.0			0.007d							0.002					5.0a								0.1				8.1ab								0.2							24.9ab							1.7
0.2 MPa 10 min					12.8a					0.3			0.000d							0.000					4.7ab							0.1				9.7c						0.0								26.7b						0.8
0.3 MPa 10 min								12.4a						0.1				0.000d								0.000				4.4b						0.1			14.4 e							0.1						26.9b	0.4
Untreated KSI								12.0a						0.2				0.035a								0.000				6.0a						0.3			9.8a							0.1						27.1a	0.6
0.1 MPa  5 min					12.4a					0.2			0.010b							0.004					6.1a							0.2				9.8a						0.1								28.2a						1.3
0.1 MPa 10 min					12.4a					0.1			0.015b							0.001					5.5b							0.2				11.6b						0.3								28.8ab						0.6
0.2 MPa 5min					12.1a					0.2			0.008c							0.004					5.8a							0.3				12.8c						0.0								29.4b						1.4
0.2 MPa 10 min				12.2a								0.0					0.000c							0.000				5.1b									0.1	15.5d							0.3						31.2b			1.5
0.3 MPa 10 min				11.8a								0.0					0.000c							0.000				4.6b									0.2	17.8 e							0.3						31.4b			0.8
	Dietary fiber						SD				Glucose content								SD				Resistant starch								SD			L-ORAC									SD				H-ORAC										SD
	(g/100g)										(g/100g)												(%)											μmol TE/100gFW													μmol TE/100gFW
Untreated KSK	3.2a						0.1				0.017a								0.002				11.1a								0.1			87.1a									1.0				58.1a										1.5
0.1 MPa 5 min					2.9a									0.1			0.016a				0.001				11.3a					0.1				84.0a						3.3						51.8b				3.6
0.1 MPa 10 min			3.2a						0.2			0.016a								0.001		11.9b							0.1			74.1b						4.5						50.3b								2.2
0.2 MPa 5 min			3.2a						0.0			0.016a								0.001		11.4a							0.1			72.0b						1.5						49.4b								0.4
0.2 MPa 10 min			2.9a						0.2			0.016a								0.001		10.8c							0.1			49.5c						2.1						48.6b								0.1
0.3 MPa 10 min							3.2a								0.1				0.017a			0.000					9.5c					0.2				46.3c						1.3						37.2c		1.3
Untreated KSI							2.8a								0.1				0.024a			0.002					1.5a					0.0				66.3a						0.9						54.0a		2.1
0.1 MPa  5 min	3.2ab			0.1				0.026a											0.004				0.7b								0.0								56.4b								0.9		51.1a		0.1
0.1 MPa 10 min	3.1ab			0.1				0.025a											0.002				0.7b								0.0								38.1c								0.4		51.3 a		1.2
0.2 MPa 5 min	2.9a			0.2				0.026a											0.001				0.6b								0.0								39.0c								4.1		46.7b		1.1
0.2 MPa 10 min						3.0ab							0.2			0.022a					0.000			0.4c					0.0	32.8d					0.7						53.3a		2.1
0.3 MPa 10 min		3.5b								0.1	0.019b							0.001		0.3c						0.0		27.7d					0.6				44.1b								1.4

Notes: HMT, heat–moisture treatment at various pressures (0.1, 0.2, or 0.3 MPa) and time (5 or 10 min).

KSK, Koshinokaori rice cultivar, KSI, Koshiibuki rice cultivar.

Means with the same letter are not significantly different (p < 0.05).

Table 2. Analysis of iodine absorption curve and amylose content of HMT and untreated brown rice flour.

	λmax		SD			Aλmax			SD			λmax/Aλmax						SD		Amylose					SD
	(nm)																			(%)
(A)
Untreated KSK	576.5a		2.1			0.42a			0.010			1384.3a						16.1		28.1a					0.4
0.1 MPa  5 min	574.0a		1.4			0.42a			0.000			1361.9a						12.6		28.4a					0.4
0.1 MPa 10 min	575.0a		1.4			0.42a			0.000			1356.1a						1.2		28.3a					0.2
0.2 MPa 5 min		578.0a			2.8			0.44b			0.000			1327.2a			4.3				29.6b			0.0
0.2 MPa 10 min		579.0a			1.4			0.43b			0.000			1340.3a			1.1				29.3b			0.0
0.3 MPa 10 min		576.0a			1.4			0.44b			0.000			1321.2a			16.1				29.6b			0.3
Untreated KSI		562.5a			3.5			0.31a			0.001			1800.0a			15.4				12.7a			0.0
0.1 MPa  5 min		561.5a			0.7			0.30a			0.004			1844.1a			23.7				12.0b			0.1
0.1 MPa 10 min		557.0b			0.0			0.30a			0.002			1885.0b			13.5				10.8c			0.1
0.2 MPa 5 min		559.5b			2.1			0.30a		0.001			1877.6a		16.0				11.4b			0.1
0.2 MPa 10 min		558.0b			0.0			0.30a		0.000			1847.7a		0.0				11.5b			0.1
0.3 MPa 10 min		559.0b			2.8			0.29a		0.001			1907.8c		0.4				10.8c			0.1
(B)
Untreated KSK		577.5a			0.7			0.39a		0.003			1469.5a		8.8				19.4a			0.2
0.1 MPa  5 min		576.5a			0.7			0.40a		0.001			1459.5a		3.4				19.5a			0.1
0.1 MPa 10 min		578.0a		2.8			0.40b			0.001			1432.5a			9.5				20.0a			0.1
0.2 MPa 5 min		576.5a		0.7			0.40a			0.001			1452.1a			3.4				19.7a			0.2
0.2 MPa 10 min		575.5a		3.5			0.41b			0.002			1415.8b			16.1				20.0a			0.2
0.3 MPa 10 min		575.5a		0.7			0.40a			0.002			1455.1a			6.0				19.0a			0.3
Untreated KSI		561.5a		2.1			0.31a			0.003			1835.1a			23.9				11.9a			0.2
0.1 MPa  5min		558.0a		1.4			0.30a			0.003			1872.6b			22.5				11.2b			0.2
0.1 MPa 10 min		559.0a			0.0			0.30a		0.001			1879.0b			4.5				11.2b			0.1
0.2 MPa 5 min		557.5b			0.7			0.30a		0.000			1846.0c			2.3				11.5a			0.1
0.2 MPa 10 min		556.5b			0.7			0.30a		0.001			1848.9c			11.0				11.5a			0.1
0.3 MPa 10 min		558.5a			2.1			0.30a		0.005			1846.5c			23.2				11.2b			0.1

Notes: (A): Initial value. (B): Value following 2 months’ storage at 35 °C.

HMT, heat–moisture treatment at various pressures (0.1, 0.2, or 0.3 MPa) and time (5 or 10 min).

KSK, Koshinokaori rice cultivar, KSI, Koshiibuki rice cultivar.

Means with the same letter are not significantly different (p < 0.05).

Table 3. Physical properties of gelatinous HMT and untreated brown rice flour.

	Hardness			SD				Toughness				SD			Adhesion			SD	Stickiness					SD	Adhesion/toughness						SD				Stickiness/toughness					SD
	(gw/cm^2)							(gw/cm^2)							(gw/cm^2)				(gw/cm^2)
(A)
Untreated KSK	0.21a			0.07				8.51a				0.51			50.75a			2.54	92.40a					3.45	5.97a						0.12				10.88a					0.39
0.1MPa 5 min	0.19a			0.06				10.10b				0.39			48.59b			3.64	79.48b					6.67	4.83b						0.59				7.88b					0.87
0.1 MPa 10 min	0.22a			0.05				9.16c				0.76			53.87a			1.54	94.57a					3.69	5.92a						0.58				10.37a					0.66
0.2 MPa 5 min		0.12b				0.01				8.50a			0.44			54.28a				4.03		90.87a				2.77		6.39a				0.51				10.72a			0.85
0.2 MPa 10 min		0.19a				0.01				9.71c			1.12			52.40a				2.46		85.92c				7.98		5.46c				0.67				9.01c			1.82
0.3 MPa 10 min		0.14b				0.01				7.64a			1.01			51.84a				1.39		86.04c				4.74		6.88a				0.82				11.48d			2.07
Untreated KSI		0.04a				0.01				4.15a			0.21			61.83a				2.03		49.48a				1.17		14.94a				0.59				11.96a			0.45
0.1 MPa  5 min		0.05a				0.01				4.29a			0.23			67.47b				5.69		46.61b				0.58		15.82b				2.26				10.90b			0.71
0.1 MPa 10 min		0.05a				0.01				4.24a			0.22			68.04b				1.21		49.83a				0.84		16.08b				0.67				11.78a			0.54
0.2 MPa 5 min		0.04a			0.01				4.02a				0.11			63.90a				8.27		48.50a				2.21			15.88b				2.01				12.08a		0.62
0.2 MPa 10 min		0.04a			0.01				4.15a				0.16			71.41c				1.13		50.44a				1.28			17.23c				0.57				12.18a		0.67
0.3 MPa 10 min		0.04a			0.01				3.93b				0.12			86.33d				1.48		49.78a				0.59			21.97e				0.95				12.66a		0.28
(B)
Untreated KSK		0.08a			0.02				7.33a				0.82			68.67a				5.30		89.04a				2.76			9.52a				1.79				12.29a		1.47
0.1 MPa  5 min		0.09a			0.01				6.55b				1.05			67.67a				3.19		86.43b				3.63			10.52b				1.36				13.34a		1.59
0.1 MPa 10 min	0.09a			0.01				6.06b				0.93			66.63a			4.50	87.39b					3.64	11.17b						1.48				13.83a					0.89
0.2 MPa 5 min	0.08a			0.01				5.42c				0.28			70.22b			1.58	85.94b					3.38	12.99b						0.92				15.86b					0.47
0.2 MPa 10 min		0.09a			0.01				5.77c				0.19			64.13c				2.36		86.99b				1.59		11.12b				0.42				15.11b			0.84
0.3 MPa 10min		0.07a			0.01				6.35b				0.68			56.79e				3.12		79.65c				3.21		9.09a				1.57				12.71d			1.74
Untreated KSI		0.06a			0.02				5.01a				0.23			72.91a				4.89		67.58a				1.15		14.55a				0.51				0.89a			0.39
0.1 MPa  5 min		0.05a			0.00				4.73b				0.36			65.38b				2.35		63.47b				0.88		13.82a				1.61				0.80a			0.87
0.1 MPa 10 min		0.06a			0.01				4.54b				0.17			76.28c				2.74		62.31b				1.78		16.80b				0.99				0.49b			0.66
0.2 MPa 5 min		0.05a			0.01				4.87b				0.59			70.85a				4.90		62.99b				2.03		14.55a				3.07				1.43c			0.85
0.2 MPa 10 min			0.04b				0.01				4.63b			0.56			75.15c				4.76		56.27c				1.17			16.23b				2.25				1.84d	1.82
0.3 MPa 10 min			0.02c				0.00				3.72c			0.07			82.59d				3.84		47.24d				2.06			22.20d				1.66				0.88a	2.07

Notes: (A): Initial value. (B): Value after 2 months’ storage at 35 °C.

HMT, heat–moisture treatmentat at various pressures (0.1, 0.2, or 0.3 MPa) and time (5 or 10 min).

KSK, Koshinokaori rice cultivar, KSI, Koshiibuki rice cultivar.

Means with the same letter are not significantly different (p < 0.05).

Table 4. Pasting properties of HMT and untreated brown rice flours.

	Maxi.vis.			SD			mini.vis.			SD			Break.d			SD				Final.vis				SD				Setback				SD			Past.t			SD	Consis							SD	Setback/consis					SD			Max/mini			SD		Max/Final			SD
	(RVU)						(RVU)						(RVU)							(RVU)								(RVU)							°C				(RVU)
(A)
Untreated KSK	389.8a			0.4			166.0a			3.0			223.7a			3.4				405.5a				2.2				15.7a				2.6			72.7a			0.0	239.4a							0.8	0.1a					0.0			2.3a			0.0		1.0a			0.0
0.1 MPa  5 min	385.0a			0.9			164.3a			1.6			220.7a			0.6				399.7a				2.1				14.7b				1.2			75.1b			0.2	235.4b							0.5	0.1a					0.0			2.3a			0.0		1.0a			0.0
0.1 MPa 10 min	388.5a			5.7			167.5a			2.8			221.0a			2.9				402.5a				3.6				14.0b				2.1			75.7b			0.1	235.0b							0.8	0.1a					0.0			2.3a			0.0		1.0a			0.0
0.2 MPa 5 min		351.5b			0.8			155.6b			1.4			195.9b			2.2				377.2b				0.6				25.7c					1.4			75.9b					0.0			221.6c				0.8		0.1b			0.0			2.3b		0.0		0.9a	0.0
0.2 MPa 10 min		364.8b			0.4			160.8a			1.1			204.0b			0.7				387.5b				2.8				22.8c					2.5			76.1b					0.2			226.8c				1.8		0.1b			0.0			2.3b		0.0		0.9a	0.0
0.3 MPa 10 min		282.9c			1.1			129.6d			0.2			153.3c			1.4				319.4c				1.2				36.5e					2.4			76.0b					0.0			189.8e				1.0		0.2d			0.0			2.2d		0.0		0.9c	0.0
Untreated KSI		396.4a			0.2			137.0a			1.4			259.4a			1.2				259.5a				1.0				−136.8a					0.8			67.5a					0.0			122.5a				0.4		−1.1a			0.0			2.9a		0.0		1.5a	0.0
0.1 MPa  5min		423.9b			3.8			139.1a			3.2			284.8b			0.6				256.0a				3.7				−167.9b					0.2			67.6a					0.4			116.9b				0.4		−1.4b			0.0			3.0a		0.0		1.7b	0.0
0.1 MPa 10 min		446.7c			1.0			146.3b			0.8			300.5c			1.8				266.9a				0.8				−179.8c					1.8			68.3b					0.1			120.7a				0.0		−1.5b			0.0			3.1a		0.0		1.7b	0.0
0.2 MPa 5 min		436.0b			4.5			142.0b			1.9			294.0c			2.5				261.1a				1.8				−174.9c					2.7			68.0b				0.0			119.2a					0.1		−1.5b			0.0			3.1a		0.0		1.7b	0.0
0.2 MPa 10 min		449.9c			0.8			150.3b			0.9			299.7c			1.8				280.3b				1.4				−169.6b					2.2			68.4b				0.0			130.1c					0.5		−1.3c			0.0			3.0a		0.0		1.6b	0.0
0.3 MPa 10 min		330.2d			0.4			143.2b			0.5			187.0d			0.1				278.2b				0.6				−52.0e					0.2			62.2c				0.9			135.0c					0.1		−0.4d			0.0			2.3b		0.0		1.2c	0.0
(B)
Untreated KSK		282.2a			2.6			145.8a			3.6			136.4a			1.0				483.0a				1.2				200.8a					3.8			77.0a				0.9			337.2a					4.8		0.6a			0.0			1.9a		0.0		0.6a	0.0
0.1 MPa 5 min		283.4a			4.9			138.5a			1.6			144.9b			3.4				434.5b				3.2				151.0b					1.7			77.7a				0.1			295.9b					1.6		0.5b			0.0			2.0a		0.0		0.7b	0.0
0.1 MPa 10 min			284.3a			0.3			140.3a			0.9			144.0b			1.2				415.4c				0.4				131.1c			0.6			78.0a				0.2			275.1c					0.6		0.5b			0.0			2.0a			0.0		0.7b	0.0
0.2 MPa 5 min			266.7b			0.6			140.2a			0.6			126.5c			1.2				419.3c				1.6				152.6b			2.2			78.4a				0.1			279.1c					1.0		0.5c			0.0			1.9a			0.0		0.6b	0.0
0.2 MPa 10 min			223.4c			0.1			125.0b			1.1			98.4d			0.9				315.6d				0.4				92.2d			0.5			78.7a				0.2			190.6d					1.5		0.5b			0.0			1.8b			0.0		0.7c	0.0
0.3 MPa 10 min			146.1d			7.4			90.5c			0.8			55.6e			6.5				199.0e				1.8				52.9e			5.6			79.3a				0.1			108.5e					0.9		0.5b			0.1			1.6c			0.1		0.7c	0.0
Untreated KSI			340.7a			1.5			128.7a			0.4			212.0a			1.9				300.2a				1.4				−40.5a			2.9			68.5a				0.0			171.5a					0.9		−0.2a			0.0			2.6a			0.0		1.1a	0.0
0.1 MPa  5 min			374.8b			1.5			130.6a			0.9			244.2b			0.6				285.5b				2.1				−89.3b			0.6			69.5a				0.2			154.8b					1.2		−0.6b			0.0			2.9a			0.0		1.3b	0.0
0.1 MPa 10 min		373.5b			4.8			136.7b			1.3			236.8b					3.5				291.5b				0.1				−82.0b			4.7			70.6a				0.1			154.8b					1.2		−0.5b			0.0			2.7a		0.0		1.3b	0.0
0.2 MPa 5 min		364.6b			0.3			136.2b			0.1			228.5ab					0.2				292.0b				0.5				−72.6c			0.2			70.4a				0.0			155.9b					0.4		−0.5b			0.0			2.7a		0.0		1.2b	0.0
0.2 MPa 10 min		308.3c			1.8			130.3a			1.0			178.0c					2.8				273.4c				2.2				−34.9d			4.0			70.8a				0.1			143.1c					1.2		−0.2a			0.0			2.4b		0.0		1.1a	0.0
0.3 MPa 10 min		195.8d			5.3			113.3c			0.2			82.5d					5.5				232.5d				0.4				36.8e			5.7			69.0a				0.0			119.3d					0.1		0.3c			0.0			1.7c		0.1		0.8c	0.0

Notes: (A):Initial value. (B): Value after 2 months’ storage at 35 °C.

HMT, heat–moisture treatmentat at various pressures (0.1, 0.2, or 0.3 MPa) and time (5 or 10 min).

KSK, Koshinokaori rice cultivar, KSI, Koshiibuki rice cultivar.

Means with the same letter are not significantly different (p < 0.05).

Table 5. Correlation between fat acidity, fatty acid composition, pasting properties, physical properties and iodine absorption curve of HMT and untreated brown rice flour.

	Fat acidity					Palmitic acid							Oleic acid			Linoleic acid							α-linolenic acid							Oleic acid/Linoleic + α-linoleic														Linoleic acid/α-linolenic acid
Fat acidty	1.00
Palmitic acid	0.97**					1.00
Oleic acid	0.86**					0.83**							1.00
Linoleic acid	−0.97**					−0.98**							−0.91**			1.00
αｰlinolenic acid	−0.59					−0.57							−0.45			0.55							1.00
Oleic/Lino + αｰlino							0.97**								0.97**							0.94**							−1.00**								−0.55						1.00
Linoleic/α-lino							−0.89**								−0.91**							−0.88**							0.94**								0.23						−0.94**					1.00
Maxi.vis.							−0.60								−0.59*							−0.51							0.58*								0.13						−0.58*					0.63*
Mini.vis.							0.64								0.58*							0.43							−0.56								−0.62*						0.54					−0.40**
Break.d							−0.76**								−0.74**							−0.62*							0.73**								0.29						−0.72**					0.73**
Final.vis							0.95**								0.92**							0.79**							−0.92**								−0.66*						0.91**					−0.80**
Setback		0.97**							0.94**								0.81**							−0.93**								−0.52						0.92**								−0.88**
Past.t		0.84**							0.90**								0.87**							−0.93**								−0.47						0.93**								−0.89**
Consis		0.98**							0.96**								0.84**							−0.96**								−0.64*						0.95**								−0.85**
Set/Cons		0.96**							0.93**								0.79**							−0.92**								−0.52						0.91**								−0.86**
Max/Mini		−0.90**							−0.87**								−0.69*							0.84**								0.45						−0.83**								0.79**
Max/Final		−0.96**							−0.94**								−0.79**							0.93**								0.52						−0.92**								0.87**
Hardness			0.93**							0.91**									0.87**								−0.93**							−0.58*						0.93**						−0.84**
Toughness			0.97**							0.95**									0.87**								−0.97**							−0.51						0.96**						−0.92**
Adhesion			−0.75**							−0.79**									−0.88**								0.85**							0.43						−0.86**						0.81**
Stickiness					0.96**							0.97**						0.88**								−0.98**							−0.70*						0.97**						−0.85**
Ad/Tou					−0.90**							−0.92**						−0.92**								0.96**							0.53						−0.96**						0.90**
St/Tou					−0.71**							−0.68*						−0.66*								0.70*							0.14						−0.69*						0.75**
λmax				0.96**							0.96**										0.93**							−0.98**							−0.57						0.99**						−0.91**
Aλmax				0.96**							0.98**										0.91**							−1.00**							−0.55						0.99**						−0.93**
λmax/Aλmax								−0.96**						−0.98**						−0.91**					1.00**						0.56					−0.99**						0.93**
AAC								0.97**						0.98**						0.91**					−1.00**						−0.56					1.00**						−0.93**

Notes: Correlation significant at 5%* or 1%** by t-test.

Fig. 1. Fat acidity of HMT and untreated brown rice flour during 2 months’ storage at 35 °C.

Notes: (A) KSK samples. (B) KSI samples. HMT, heat–moisture treatment; KSK, Koshinokaori rice cultivar; KSI, Koshiibuki rice cultivar. The same letters indicate no significant difference.

Fig. 2. Formula for estimating the fat acidity based on the iodine absorption curve and pasting properties of retrograded brown rice flour.

Notes: (A) Fat acidity values based on the iodine absorption curve. Estimation formula: Fat acidity (mgKOH⁻¹ 100 g⁻¹D.W.) = 2.15 × λmax/A_λmax + 111.25 × AAC – 5202.78. The equation has a determination coefficient (R²) of 0.90. (B): Fat acidity values based on the pasting properties. Estimation formula: Fat acidity (mgKOH⁻¹ 100 g⁻¹D.W.)=4.74 × Setback + 1071.77 × Max.vis – 624.09 × Break.d – 288.39 × Past.t – 176.10 × Mini.vis + 132.19. The equation has a determination coefficient (R²) of 0.99.