Effect of microwave treatment on the cooking and macronutrient qualities of pulses

Figures & data

Table 1. Cooking times of untreated and microwave treated pulses.

			Moisture content (%)
	Microwave powerlevel (W)	Exposure time (s)	10	14	18
Red lentil	Control	0	13.09 ± 0.14	11.31 ± 0.24	10.66 ± 0.46
	400	14	13.08 ± 0.08	11.87 ± 0.40	10.48 ± 0.48
		28	12.69 ± 0.45	11.30 ± 0.15	10.70 ± 0.30
		56	12.09 ± 0.36	10.41 ± 0.18	10.41 ± 0.55
	500	14	12.65 ± 0.35	11.36 ± 0.42	11.06 ± 0.32
		28	11.92 ± 0.80	10.59 ± 0.38	10.51 ± 0.42
		56	11.36 ± 0.31	9.75 ± 0.28	9.49 ± 0.33
	600	14	12.01 ± 0.43	10.59 ± 0.37	9.56 ± 0.39
		28	11.33 ± 0.15	9.02 ± 0.42	9.78 ± 0.64
		56	11.78 ± 0.37	8.39 ± 0.16	9.45 ± 0.26
Chickpea	Control	0	85.58 ± 0.48	83.45 ± 0.55	80.52 ± 0.58
	400	14	85.11 ± 0.40	82.52 ± 0.58	79.16 ± 0.50
		28	83.58 ± 0.37	80.75 ± 0.40	76.50 ± 0.43
		56	82.55 ± 0.53	77.95 ± 0.25	73.98 ± 0.53
	500	14	79.41 ± 0.69	75.52 ± 0.53	69.14 ± 2.13
		28	76.30 ± 1.08	73.93 ± 0.58	69.82 ± 1.46
		56	73.45 ± 0.59	72.20 ± 0.88	66.17 ± 0.88
	600	14	73.21 ± 1.66	71.59 ± 0.49	64.47 ± 0.64
		28	72.50 ± 0.53	69.22 ± 0.99	63.61 ± 0.56
		56	71.07 ± 0.98	66.70 ± 0.62	62.94 ± 0.51
Pigeon pea	Control	0	25.83 ± 0.50	24.74 ± 0.62	25.12 ± 0.60
	400	14	25.64 ± 0.65	24.78 ± 0.25	24.39 ± 0.61
		28	24.67 ± 0.57	24.31 ± 0.10	24.47 ± 0.65
		56	24.35 ± 0.39	24.75 ± 0.52	23.78 ± 0.40
	500	14	25.31 ± 0.41	24.67 ± 0.36	23.77 ± 0.39
		28	25.28 ± 0.58	23.89 ± 0.18	22.98 ± 0.43
		56	24.90 ± 0.18	23.74 ± 0.33	22.57 ± 0.47
	600	14	24.30 ± 0.47	23.64 ± 0.59	22.44 ± 0.28
		28	23.57 ± 0.44	22.61 ± 0.45	21.66 ± 0.33
		56	23.3 ± 0.2	22.80 ± 0.42	21.27 ± 0.30
Mung bean	Control	0	13.41 ± 0.30	12.91 ± 0.24	12.49 ± 0.47
	400	14	13.48 ± 0.20	13.4 ± 0.08	13.17 ± 0.15
		28	13.53 ± 0.04	13.28 ± 0.11	12.52 ± 0.22
		56	12.22 ± 0.13	12.69 ± 0.83	11.74 ± 0.28
	500	14	11.76 ± 0.67	11.61 ± 0.47	11.87 ± 0.31
		28	11.08 ± 0.32	11.54 ± 0.50	13.05 ± 0.22
		56	11.05 ± 0.24	10.32 ± 0.26	11.59 ± 0.55
	600	14	10.92 ± 0.37	9.29 ± 0.15	10.87 ± 0.37
		28	10.27 ± 0.32	9.67 ± 0.43	9.94 ± 0.33
		56	9.93 ± 0.42	8.54 ± 0.33	9.55 ± 0.45
Pinto bean	Control	0	56.70 ± 0.44	47.22 ± 0.79	50.17 ± 0.98
	400	14	58.32 ± 0.26	47.53 ± 1.34	49.91 ± 0.56
		28	57.76 ± 0.50	46.81 ± 0.45	49.68 ± 0.40
		56	57.51 ± 0.42	45.41 ± 0.43	47.53 ± 1.34
	500	14	56.05 ± 0.09	43.52 ± 0.62	46.35 ± 0.17
		28	54.54 ± 0.52	43.57 ± 0.40	44.26 ± 0.13
		56	52.65 ± 0.45	43.27 ± 0.20	49.44 ± 0.58
	600	14	53.85 ± 0.70	42.33 ± 0.35	46.50 ± 0.52
		28	51.41 ± 0.70	41.78 ± 0.33	45.83 ± 0.61
		56	48.67 ± 0.53	40.84 ± 0.65	46.05 ± 0.78

Table 2. Characteristic bands of different functional group observed in the mid infrared spectra of pulses.^[31,³²,^39]

Peak position (cm^−^1)	Assignment bands
3300	O-H stretching
3010	HC=CH stretching
2956	CH(CH3) asymmetric stretching
2871	CH(CH3) symmetric stretching
2926	CH(-CH2-) asymmetric stretching
2855	CH(-CH2-) symmetric stretching
1745	-C=O stretching
1650	-C=O- and -C=N- stretching (amide I)
1540	N-H bending (amide II)
1388	C=O, C-N-C stretching
1240	-C-O, -CH2- stretching and bending
1160	-C-O, -CH2- stretching and bending
1080	C-C stretching
1050	C-OH bending
1020	C-O stretching

Figure 1. The average and area normalized FTIR spectra of the five pulses at 10% m.c. Inserts show the expanded view of lipid and protein regions. RL: Red lentil; CP: Chickpea; PP: Pigeon pea; MB: Mung bean; PB: Pinto bean.

Figure 2. The PCA of the FTIR spectra of the five pulses in the lipid (a: 3100–2700 cm⁻¹) and fingerprint (c: 1800–800 cm⁻¹) regions of five pulses at 10% m.c. and the respective loading plots (b and d). RL: Red lentil; CP: Chickpea; PP: Pigeon pea; MB: Mung bean; PB: Pinto bean.

Table 3. Integrated absorption band area of lipids (3000–2840 cm^–1), carbonyl ester (1760–1720 cm⁻¹), amide I (1700–1600 cm^–1), and carbohydrates (1005–945 cm^–1).

	3000–2840 cm^−^1	1760–1720 cm^−^1	Integrated area 1700–1600 cm^−^1	1005–945 cm^−^1	Lipid/protein
Red lentil
10% m.c.	328.9 ± 3.7	54.9 ± 2.1	814.5 ± 8.8	581.5 ± 6.2	0.067
10%-600 W*	334.1 ± 3.6	65.6 ± 2.3	780.6 ± 7.9	561.3 ± 5.9	0.083
18% m.c.	343.2 ± 4.8	58.6 ± 2.1	832.1 ± 8.1	580.5 ± 6.4	0.07
18%-600W	323.1 ± 4.3	62.3 ± 1.8	759.3 ± 7.7	552.2 ± 6.6	0.082
Chickpea
10% m.c.	453.2 ± 7.3	88.9 ± 2.2	605.6 ± 7.3	589.1 ± 6.1	0.147
10%-600 W	445.8 ± 5.4	90.7 ± 1.8	571.2 ± 6.7	589.3 ± 5.3	0.159
18% m.c.	444.9 ± 8.1	86.3 ± 1.7	626.2 ± 7.7	538.9 ± 5.6	0.138
18%-600W	450.1 ± 5.7	100.3 ± 2.5	578.5 ± 7.4	622.1 ± 4.8	0.173
Piegon pea
10% m.c.	334.2 ± 3.1	62.9 ± 1.9	777.8 ± 7.9	557.2 ± 5.1	0.081
10%-600 W	340.5 ± 3.6	65.3 ± 2.1	792.5 ± 8.2	554.8 ± 4.7	0.082
18% m.c.	366.3 ± 3.9	60.3 ± 1.7	695.3 ± 7.8	562.8 ± 6.5	0.086
18%-600W	326.1 ± 4.2	76.2 ± 1.6	805.5 ± 8.4	517.5 ± 6.2	0.095
Mung bean
10% m.c.	321.9 ± 3.4	65.7 ± 2.1	786.6 ± 5.3	560.4 ± 4.4	0.082
10%-600 W	367.9 ± 2.9	75.2 ± 1.8	800.3 ± 5.1	615.5 ± 4.8	0.093
18% m.c.	320.5 ± 4.8	60.2 ± 2.3	753.5 ± 6.4	564.7 ± 4.3	0.079
18%-600W	352.3 ± 5.1	69.1 ± 2.6	804.5 ± 4.5	600.5 ± 5.7	0.091
Pinto bean
10% m.c.	371.8 ± 4.6	80.8 ± 1.5	939.3 ± 8.6	573.4 ± 6.1	0.086
10%-600 W	386.5 ± 4.3	85.1 ± 1.8	977.1 ± 8.9	585.4 ± 6.4	0.087
18% m.c.	347.8 ± 4.1	74.1 ± 2.2	941.8 ± 9.1	545.7 ± 5.8	0.079
18%-600W	355.5 ± 3.9	82.2 ± 1.9	940.2 ± 9.3	556.7 ± 6.6	0.087

*Time of microwave treatment was 56 s.

Figure 3. Second derivatives of the FTIR spectra of control and microwave treated pulses in the lipid A: (3000–2840 cm⁻¹) and amide I B: (1710–1600 cm⁻¹) regions. Each spectrum is the average of five independent spectra. a: red lentil; b: chickpea; c: pigeon pea; d: mung bean; and e: pinto bean.

Table 4. The integrated absorbance area of β-sheets (1639 cm⁻¹: 1648–1622 cm⁻¹), aggregates (1630 cm⁻¹: 1635–1622 cm⁻¹), and the percentage change of β-sheets to aggregates derived from second derivative spectra.

	Pulses
Treatments	Red lentil	Chickpea	Pigeon pea	Mung bean	Pinto bean
10% m.c. (β-sheets)	0.164	0.128	0.162	0.178	0.234
10% m.c.-600 W-56 s (aggregates)	0.11	0.061	0.148	0.088	0.223
% change of β-sheet	33	52	9	50	5
18% m.c. (β-sheets)	0.166	0.122	0.153	0.172	0.226
18% m.c.-600 W-56 s (aggregates)	0.113	0.040	0.079	0.102	0.179
% change of β-sheet	32	67	48	40	21

Figure 4. The SEM micrographs of untreated and microwave (18% m.c., 600 W, and 56 s treated) A: chickpea and B: mung bean.

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