Hard-to-cook phenomenon in bambara groundnut (Vigna subterranea (L.) Verdc.) processing: Options to improve its role in providing food security

Figures & data

Table 1. Proximate composition of bambara groundnut seeds.

Proximate composition
Parameter	Minimum	Average	Maximum	References
Moisture (g/100 g)	5.8	8.6	11.5	(45, 53, 64, 125, 138–140)
Crude protein (g/100 g)	17.1	18.9	22.9	(7, 14, 25, 45, 53, 64, 125, 140–143)
Crude lipid (g/100 g)	2.9	6.3	9.2	(7, 14, 25, 45, 53, 64, 125, 140–143)
Ash (g/100 g)	2.9	3.7	5.1	(7, 14, 25, 45, 53, 64, 125, 140–143)
Crude fiber (g/100 g)	1.4	4.0	7.2	(7, 14, 25, 45, 53, 64, 125, 140–143)
Acid detergent fiber (g/100 DM)	8.0	8.3	8.6	(14, 143)
Neutral detergent fiber (g/100 DM)	10.8	15.5	20.1	(14, 143)
Carbohydrate (g/100 g)	55.8	61.7	68.0	(7, 25, 45, 53, 64, 138, 141, 142)
Energy (kcal/100 g)	367	385	395.3	(7, 45, 140)
Dry matter (%)	89.1	90.9	93.0	(14, 43, 141, 143)
Acid detergent lignin (g/100 DM)	0.3	1.6	3.4	(14)
Tannin (g CE/100 g)	0.25	0.90	2.27	(20, 41, 45)
True protein digestibility (%)	na	77	na	(141)

DM, dry matter; CE, catechin equivalent; na, not available.

Table 2. Mineral composition of bambara groundnut seeds.

Mineral composition
Parameter	Minimum	Average	Maximum	References
K (mg/100 g)	470	1234	2200	(25, 144, 145)
P (mg/100 g)	33.3	317	613	(25, 45, 140, 143, 144)
Ca (mg/100 g)	37	56	70	(25, 45, 140, 143, 144)
Na (mg/100 g)	0.9	5.3	20.2	(25, 143, 144, 145)
Mg (mg/100 g)	57.1	184.0	335	(143–145)
Fe (mg/100 g)	1.2	3.1	7.0	(140, 143, 144)
Zn (mg/100 g)	0.6	1.1	1.2	(125, 143)
Mn (mg/100 g)	1.0	1.8	5.5	(125, 143)
Cu (mg/100 g)	0.2	0.6	1.3	(125, 143, 144)

Table 3. Vitamin composition of bambara groundnut seeds.⁽¹⁴⁰⁾

Vitamin composition
Parameter	Minimum	Average	Maximum
Thiamine (mg/100 g)	0.22	0.47	0.62
β-Carotene (mg/100 g)	na	0.01	na
Riboflavin (mg/100 g)	0.14	0.15	1.12
Niacin (mg/100 g)	0.6	1.8	2.4
Ascorbic acid	na	Trace	na

na, not available.

Reprinted from⁽¹⁴⁰⁾ with permission from Elsevier. © Elsevier. Reproduced by permission of Elsevier. Permission to reuse must be obtained from the rightsholder.

Table 4. Physical characteristics of bambara groundnut seeds.

Parameter	Minimum	Average	Maximum	References
Length (mm)	11.5	11.9	12.7	(20, 54, 59, 60)
Width (mm)	9.4	9.8	10.6	(20, 54, 59, 60)
Thickness (mm)	9.2	9.9	10.5	(20, 54, 59, 60)
Germ length (mm)	6.5	7.1	7.9	(20)
Germ width (mm)	4.7	5.5	6.6	(20)
True density (kg/m^3)	1003	1174	1295	(54, 59, 60)
Bulk density (kg/m^3)	745	805	895	(54, 59, 60)
Porosity (%)	22.7	32.6	43.8	(54, 59, 60)
Sphericity (%)	85.5	86.9	88	(54, 59, 60)
Geometric average diameter (mm)	9.8	10.4	11.1	(54, 59, 60)
Seed coat thickness (mm)	0.11	0.16	0.20	(20)
Test weight (kg/hL)	89	91.1	92.8	(20)
1000 seed weight (g)	543	670	816	(54, 59)

Figure 1. Overview of HTC development in legumes and mechanism of cooking time reduction.

Table 5. Composition of nonstarch polysaccharides (NSP) of bambara groundnut.⁽⁴³⁾

Parameter	Composition
Total NSP % DM	12.78 ± 0.32
Insoluble NSP % total	57.42 ± 5.13
Soluble NSP % total	42.58 ± 5.13
NCP % total	53.48 ± 3.41
Cellulose % total	36.04 ± 2.16
Wt NSP % DM	25.62 ± 0.47
Reside % DM	12.84 ± 0.69

Total NSP, insoluble NSP; NCP, noncellulosic NSP; Wt NSP, dry weight of NSP following enzymatic hydrolysis

©John Wiley and Sons. Reprinted with permission of John Wiley and Sons. Permission to reuse must be obtained from the rightsholder.

Table 6. Composition of sugar constituents of nonstarch polysaccharides (NSP) of bambara groundnut.⁽⁴³⁾

Sugar	Total	Insoluble	Soluble	NCP	Cellulose
Rhamnose	1.13 ± 0.08		1.13 ± 0.08
Arabinose	38.7 ± 1.38	15.54 ± 1.59	23.16 ± 0.08	42.38 ± 3.14
Xylose	16.69 ± 0.26	9.05 ± 0.98	7.64 ± 1.10	19.15 ± 1.38
Mannose	1.51 ± 0.22	0.52 ± 0.02	0.99 ± 0.43
Galactose	5.94 ± 0.18	2.59 ± 0.18	3.35 ± 0.31	5.37 ± 0.18	0.57 ± 0.28
Glucose	50.44 ± 1.81	45.19 ± 2.88	5.25 ± 1.05	3.07 ± 0.70	47.37 ± 1.26
Uronic acids	14.47 ± 0.15	1.09 ± 0.21	13.38 ± 0.25	11.16 ± 0.44
Total	128.88 ± 4.08	73.98 ± 5.86	54.9 ± 3.30	81.13 ± 5.84	47.94 ± 1.54

©John Wiley and Sons. Reprinted with permission of John Wiley and Sons. Permission to reuse must be obtained from the rightsholder.

Figure 2. Percentage cooking time reduction of cowpeas soaked and cooked in water, cooked in sodium chloride, ⁴kanwa, alkali potash, citrate buffer, and alkali buffer solutions.^{(137) 4}Kanwa = natural rock salt used as cooking aid in West Africa.

Figure 3. Percentage cooking time reduction of bambara groundnut soaked (0, 3, and 6 hours) and cooked in water, 0.3% ⁴kanwa and 0.5% kanwa solutions.^{(2) 4}Kanwa = natural rock salt used as cooking aid in West Africa.

Figure 4. Percentage cooking time reduction of cowpeas cooked in sodium bicarbonate and ⁴kanwa solutions.^{(111) 4}Kanwa = natural rock salt used as cooking aid in West Africa.

Figure 5. Percentage cooking time reduction of cowpeas cooked in ⁴kanwa, potassium carbonate, calcium carbonate, sodium carbonate, and sodium bicarbonate solutions. ²CaCO₃ = –11%.^{(114) 4}Kanwa = natural rock salt used as cooking aid in West Africa.

Figure 6. Overview of processing techniques for HTC bambara groundnut.

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