Properties of Chocolate Bars Produced by Partial Replacement of Cocoa with Bambaranut Flours

 

 

K. S.  Abasiekong and D. I. Ibe

 

Department of Food Science and Technology,

Michael Okpara University of Agriculture, Umudike, Nigeria

 

Abstract

Cocoa powder (Theobromo cacao) and bambaranut (Voandzeasubterranea) flours blended at 100:0, 90:1, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80 and 10:90 ratios were used for the production of chocolate bars. Qualities which included sensory properties (appearance, flavour, texture, mouthfeel and general acceptability), proximate, mineral (zinc, copper, calcium, magnesium and iron) and vitamin (thiamin, riboflavin, niacin and pyridoxine) composition were evaluated. Levels of moisture (7.35 – 9.60%) and protein (16.01 – 22.27%) in the bars were adequate to enhance shelf life stability and good nutritional quality respectively. The bambaranut bars compared favourably with the control (100: 0 cocoa: bambaranut bar) in most of the properties evaluated moreover the overall acceptability of the 60:40 and 70:30 cocoa: bambaranut bars were significantly higher (p<0.05) than the control.

 

Key Words: Chocolate bars, bambaranut, properties

 


Introduction

Bambaranut (Voandzeia subterranean L thours) is an indigenous African legume which belongs to the family leguminosae. It ranks third after groundnut (Arachis hypogea) and cowpea (Vigna unguiculata) as the most consumed legume (Omoikhoje, 2008). It is a common indigenous delicacy in Nigeria especially the South Eastern part where it is prepared in the form of paste known as Okpa. The fleshly harvested pods are cooked and eaten as vegetable snack while the dry seeds are eaten roasted. It is also used for the fortification of maize meals in some parts of the country.

Bambaranut is the only legume whose seeds are considered as complete food as it contains adequate amounts of protein, carbohydrate and fats (NRC, 2006). Nutritional profile of bambaranut includes carbohydrate (46.50 – 65.0%) and a protein (15 – 18%) rich in lysine and methionine (Bandoin and Mergeai, 2001; Okonkwo and Okpara, 2010). It has gross energy that is greater than other pulses such as cowpea, lentils and pigeon pea (FAO, 1982), and is richer than groundnut in essential amino acids such as isoleucine, leucine, lysine, methionine, phenylalanine, threonine and valine (Ihekoronye and Ngoddy, 1985). Despite the crop’s agronomic characteristics such as drought tolerance, high yield, and ability to recover from effect of water stress after rainfall, it is not utilized beyond local applications.

Cocoa on the other hand is the basis of chocolate and has high nutritional value with vital importance in nutritional medicine. Cocoa powder contains about nineteen percent protein and other essential elements such as flavonoids, magnesium which have beneficial cardiovascular effect on health. Chocolate has become a favourite of persons in every rank of life. Several authors such as Biehl and Ziegleder (1993), and Potter and Hotchkiss (1995) have recommended the substitution of chocolate with legume. The substitution of cocoa with bambaranut will create variety in bambaranut utilization as well as enhance its industrialization and consumption beyond local limits.

The objective of this work was to produce chocolate bars from mixtures of cocoa and bambaranut and to assess their properties. 


 


Materials and Methods

Preparation of samples

The bambaranut was obtained from local farmers in Enugu while cocoa powder was purchased from a sales outlet in Aba, South East Nigeria. Essentially the method of Ijarotimi et al.(2009) was adopted for the processing of bambaranut. Four kilograms of bambaranut was cleaned and steeped in potable water for 48 h to loosen the seed coat for ease of dehulling, then dried, roasted and milled into flour. The flour was sieved with a 300µm sieve.

Chocolate bar production

The formula included each blend of cocoa: bambaranut (100:0, 90:1, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80 or 10:90) and a constant proportion of sugar (200g), powdered milk (120g), water (20ml), margarine (20g), gelatin (10ml), glucose syrup (10ml) and flavouring agent (10ml). A total of 10 samples were prepared with the 100:0 cocoa: bambaranut used as control. Margarine and sugar were mixed in a bowl and creamed until the mixture became light and fluffy. Milk powder was then added with flavour while mixing. After 15 minutes of mixing, water, glucose syrup and gelatin were added slowly into the mixture. The dough like substance obtained was then heated for 10 minutes and emptied into a mould and allowed to cool.

Sensory evaluation

Sensory evaluation was carried out using a 25 man semi trained sensory panel based on a nine point hedonic scale (Iwe, 2002).

Chemical analysis

The proximate analysis was determined using AOAC (1990) methods described in NAFDAC (2011) while the functional properties were determined using the methods described in Onwuka (2005). The flame method for Atomic Absorption Spectrophotometer (AAS Model-6800 Perkin Elmer) (AOAC, 2006) was used in the determination of the mineral content (calcium, potassium, zinc, iron, magnesium, lead and copper) while the vitamins (thiamin, riboflavin, niacin and pyridoxine) analyses were done using the high performance liquid chromatographic technique (NAFDAC, 2012).

 

 


 

 

Results and Discussion

The proximate composition is presented in Table 1. Moisture content (9.60 - 7.35%) was low enough in most of the products to fall within limits(≤ 9% moisture) acceptable for low-fat cocoa powders and low-fat cocoa by the Codex Alimentarius Commission (FAO/WHO, 1981). Low moisture content enhances shelf life stability. The ash content of 60:40 cocoa: bambaranut bar was exceptionally high (7.44 %) which implies high mineral content. Also, the protein

 

 

content of the products were generally high compared to the values in Fox and Cameron (1982) for milk chocolate. The crude fibre levels were quite low (5.63 - 6.20 %). Although low crude fibre has been attributed to better processing (Onimawo et al., 2007), fibre is essential in foods as roughages for easy bowel movement. Fat was in the range of 15.30 – 17.82% in the products. Fat is of great importance as flavour retainer and for increase in mouth-feel of the foods (Onimawo and Akubor, 2005). Carbohydrate levels were quite high and compares with those of Onwuka and Abasiekong (2006) for legume based chocolate bars.


 

 

 

 

 

 

 

Table 1: Proximate composition of bambaranut chocolate bars

Chocolate Bars

Moisture

(%)

Ash

(%)

Protein

(%)

Crude

Fiber (%)

Ether Extract

(%)

Carbohy-

drate (%)

100:0

9.56a±0.93

3.77b±0.08

22.27a±1.51

5.63e±0.01

15.70de±0.85

43.08b±3.20

90:10

8.76a±1.34

3.64c±0.02

17.17bcd±0.21

5.76cd±0.03

15.35e±0.65

49.33b±1.77

80:20

8.03a±1.39

3.57c±0.04

15.89e±0.11

5.69de±0.07

15.30e±0.28

59.08a±9.43

70:30

8.25a±1.58

3.40d±0.01

16.01de±0.01

5.64e±0.05

17.20ab±0.28

49.52b±1.92

60:40

7.35a±1.41

7.44a±0.05

16.54cde±0.18

6.20a±0.01

16.84bc±0.23

45.65b±1.90

50:50

8.30a±0.13

2.88e±0.06

17.45bc±0.04

5.81c±0.01

17.82a±0.02

47.76b±0.27

40:60

8.16a±1.44

1.93h±0.01

16.42cde±0.03

5.99b±0.01

17.76a±0.05

49.76b±1.54

30:70

9.06a±1.39

1.57i±0.01

16.16de±0.01

5.75cd±0.01

17.76a±0.01

49.72b±1.35

20:80

9.39a±1.22

2.72f±0.02

17.17bcd±0.02

6.20a±0.01

16.23cd±0.03

48.31b±1.22

10:90

9.60a±1.29

2.34g±0.03

18.32b±0.03

6.02b±0.01

16.42bcd±0.02

47.31b±1.29

Means with the same superscripts within each column are not significantly different (P>0.005).

Chocolate bars – cocoa: bambaranut


 


The results of the sensory assessment of the bars (Table 2) showed that most of the products were rated higher (p<0.05) than the 100:0 cocoa: bambaranut (control) in appearance. While the 10:90 bar was rated low in all the sensory properties assessed except appearance, 70:30 and 60:40 bars were rated high in appearance, flavour, mouth-feel and general acceptability.


 

 

 

 

 

 

 

 

 

 

 

Table 2: Sensory scores of bambaranut chocolate bars

Chocolate Bars

Appearance

Flavour

Texture

Mouth feel

General

Acceptability

100:0

6.40c±1.12

6.84abcd±1.18

6.12cd±1.05

6.40bc±0.90

6.84ab±0.94

90:10

7.24ab±1.13

6.96abc±1.02

6.68abc±1.07

6.80ab±1.04

6.76ab±1.01

80:20

7.40ab±1.29

7.00ab±1.50

7.48a±1.30

7.12ab±1.30

6.96ab±1.46

70:30

7.68a±1.11

6.84abcd±1.46

7.20ab±1.29

7.44a±1.29

7.16a±1.28

60:40

7.88a±0.97

7.20 a±1.12

6.84abc±1.43

7.08ab±1.61

7.28 a±1.34

50:50

6.16c±1.65

5.96cd±2.26

5.56d±2.20

5.60c±5.60

6.12 b±2.01

40:60

6.60bc±1.38

6.12bcd±1.45

6.36bcd±1.52

6.28bc±1.34

6.92ab±1.29

30:70

6.72bc±1.21

5.88d±1.69

6.12cd±1.78

6.12bc±1.74

6.88ab±1.36

20:80

6.40c±1.47

5.88d±1.79

5.92cd±1.94

6.12bc±1.83

6.48ab±1.56

10:90

6.16 c±1.84

4.72e±2.32

3.56e±2.39

4.12d±2.44

5.16c±2.06

Means with the same superscripts within each column are not significantly different (P>0.005).

Chocolate bars – cocoa: bambaranut

 

 


Mineral evaluation (Table 3) of the products revealed high levels of zinc as compared to the RDA of 11mg/day for zinc (Byham-Gray et al., 2014). Zinc is essential due to its role in enzyme activity and normal growth moreover the body has no specialized zinc storage system besides zinc absorption is often affected by iron (Barth and Schlimme, 1989).Also important is the high levels of copper in the product which is needed for the prevention of copper deficiency which has been linked to zinc intake in foods. The values of calcium in the bars was not surprising as there are high calcium deposits in bambaranut (Igbedioh et al., 1994) as well as cocoa. Whereas magnesium was low, iron was high compared to the RDA (8 mg). Iron is essential in the prevention of iron deficiency anemia a serious public health problem.


 

 

 

 

Table 3: Mineral profile of bambaranut chocolate bars

Chocolate Bars

Zinc

(mg/l)

Copper

(mg/l)

Calcium

(mg/l)

Magnesium (mg/l)

Iron

(mg/l)

100:0

75.19a±0.01

58.629a±0.01

666.09h±0.01

109.55h±0.01

308.84a±0.01

90:10

28.95c±0.01

24.853b±0.01

668.09h±0.01

105.44e±0.01

106.02b±0.01

80:20

25.71 a±0.01

22.320e±0.01

905.45e±0.01

109.27b±0.01

88.03c±0.01

70:30

24.09f±0.01

20.707b±0.01

1083.88b±0.01

107.35c±0.01

77.80e±0.01

60:40

24.60e±0.01

22.291d±0.01

1047.58d±0.01

106.98d±0.01

82.31d±0.01

50:50

30.14b±0.01

16.981i±0.01

774.08g±0.01

76.66j±0.01

67.40f±0.01

40:60

16.54i±0.01

19.564g±0.01

800.29f±0.01

100.59g±0.01

53.97g±0.01

30:70

12.70j±0.01

20.222f±0.01

597.78i±0.01

95.31i±0.01

26.59j±0.01

20:80

18.22g±0.01

16.029j±0.01

1110.17a±0.01

103.92f±0.01

39.37h±0.01

10:90

18.05h±0.01

16.994h±0.01

1082.88c±0.01

98.78h±0.01

29.83i±0.01

Means with the same superscripts within each column are not significantly different (P>0.005). Chocolate bars – cocoa: bambaranut

 

 


Vitamins evaluated in the bars as shown in Table 4include thiamin, riboflavin, niacin and pyridoxine. Thiamin was not detected in the products, a condition which may be attributed to processing as the vitamin is very unstable during processing. Thiamin is quite essential in energy metabolism and is a component of the coenzyme thiamine diphosphate (TDP), and deficiency causes beriberi hence the need for thiamin fortification of the products. Niacin profile was lower than the RDA in the bars. Niacin plays an important role in metabolism, unlike other water soluble vitamins, it can be synthesized by the body from tryptophan. Pyridoxine is important for healthy immune system through the production of white blood cells. The RDA is 1.3 for adult and its profile across the products showed that eight of the products exceeded the RDA. This is quite essential as it also plays important role in energy production besides its role in the conversion of tryptophan to niacin.


 

Table 4: Vitamin profile of the bambaranut chocolate bars

Chocolate Bars

Thiamine

(B1) (mg/l)

Riboflavin

(B2) (mg/l)

Naicin (B3)

(mg/l)

Pyridoxine

 (B6) (mg/l)

100:0

ND

0.042a±0.001

0.812h±0.001

10.233a±0.001

90:10

ND

0.043 a±0.001

3.474a±0.001

9.898a±0.001

80:20

ND

0.043a±0.001

3.201b±0.001

8.423b±0.001

70:30

ND

0.043a±0.002

0.938g±0.001

4.449c±0.001

60:40

ND

0.039b±0.001

2.078e±0.001

3.610d±0.001

50:50

ND

0.032c±0.001

2.839c±0.001

2.014e±0.001

40:60

ND

0.28d±0.001

1.598f±0.001

1.912e±0.017

30:70

ND

0.022e±0.001

2.450d±0.001

2.092e±0.774

20:80

ND

0.016f±0.001

0.825h±0.001

0.855f±0.001

10:90

ND

0.009g±0.001

0.724i±0.001

0.478f±0.298

Means with the same superscripts within each column are not significantly different (P>0.005). Chocolate bars – cocoa: bambaranut. ND – Not Detected.

 

 

 

 

 

 

 

 

 

 

 

 


 

Conclusion

The bambaranut chocolate bars were adequate in most of the properties assessed with the sensory properties showing high level of acceptability.

 

The 70:30 and 60:40 cocoa: bambaranut chocolate bars were exceptional among the bars, implying that the partial replacement of cocoa with bambaranut in chocolate bar production is best at 30 or 40 percent. These levels of substitution are therefore recommended.


References

AOAC (1990). Official Methods of Analysis. 15th Edition. Association of Official Analytical Chemists, Washington DC.

AOAC (2006). Official Methods of Analysis.18th Edition. Association of Official Analytical Chemists, Washington DC.

Bandoin, J. P. and Mergeai, G. (2001). Grain Legumes. In: Raemaeker, R., Ed., Crop Production in Tropical Africa, Directorate Generale for International Cooperation, Brussels, pp. 313-317. 

Barth, C. A. and Schlimme, E. (1989). Milk Proteins: Nutritional, Clinical, Functional and Technological Aspects. Springer - Verlag, New York, pp. 89.

Biehl, B. and Ziegleder, G. (1993). Cocoa – chemistry of processing/production, products, and use. In: Macrae, R., Robinson, R. K. and Sadler, M. J. (eds) Encyclopedia of Food Science, Food Technology and Nutrition, Vol. 2. Academic Press, London, pp. 1073 – 1097.

Byham-Gray, L. D., Burrowes, J. D. and Chertow, G. M. (2014). Nutrition in Kidney Disease. 2nd Edn. Springer, New York.

FAO (1982). Legumes in Human Nutrition. 2nd Edn. Food and Agricultural Organization of the United Nations, Rome, ISBN: 92-5-101181-8, pp. 37-126.

FAO/WHO (1981). Codex Standard for Cocoa Powders (COCOAS) and Dry Mixtures of Cocoa and Sugars - Codex Stan 105 – 1981, Codex Alimentarius Commission, Rome.

Fox, A. and Cameron, G. A. (1982). Food Science - A Chemical Approach. 4th Edn. Hodder and Stoughton Education, London, England, pp. 84-224.

Igbedioh, S. O., Olugbemi, K. T. and Akpapunan, M. A. (1994). Effects of processing methods on phytic acid level and some constituents in Bambara groundnut (Vigna subterranean) and pigeon pea (Cajanuscajan). Food Chem., 50: 147 – 151.

Ihekoronye, A. I. and Ngoddy, P. O. (1985). Integrated Food Science and Technology for the Tropics. Macmillan Education Ltd, London.

Ijarotimi, O. S., Oyewo, M. T. and Oladeji, B. S. (2009). Chemical, functional and sensory properties of roasted Bambara groundnut (Voandzeia subterranean L thours) and cooking banana (Musa spp., ABB genome) weaning diet. African J. of Food Science 3(5): 139-146.

Iwe, M. O. (2002). Handbook of Sensory Methods and Analysis. 1st Edn. Academic Publisher, Nsukka, Nigeria, pp. 32.

NAFDAC (2011). Standard Operating Procedure (SOP) for HPLC Laboratory. National Agency for Food Drug Administration and Control, Abuja, Nigeria. 

NAFDAC (2012). Standard Operating Procedure (SOP) for Laboratory. National Agency for Food Drug Administration and Control, Abuja, Nigeria.

NRC (2006). “Bambara bean” lost crops of Africa: Vol. II: vegetable lost crop of Africa. National Academic Council. ISBN 978-0.309-10333-6.

Okonkwo, S. I. and Okpara, M. F. (2010). The Analysis of Bambaranut (Voandzeia subterranean L thours) for sustainability in Africa. Research Journal of Applied Sciences 5(6):394-396.

Omoikhoje, S. O. (2008). Assessment of the nutritive value of Bambara groundnut as influenced by cooking time. Livest. Res. Rural Dev., 20 (4).

Onimawo, I. A. and Akubor, P. I. (2005). Food Chemistry - Integrated Approach with Biochemical Background. AMBIK Press, Benin City, Nigeria, pp. 157-167.

Onimawo, I. A., Ibekwe, J. O., Uchechukwu, N. and Emebu, K. P. (2007). Functional properties and production of improved biscuits from sorghum (Sorghum bicolor) and fermented Bambara groundnut (Vigna subterranean) flour blends. Nig. J. Nutr. Sci. 28(1): 90-98.

Onwuka, G. I. (2005). Food Analysis and Instrumentation Theory and Practice. Naphthali Prints, Lagos, Nigeria.

Onwuka, U. N. and Abasiekong, K. S. (2006). Production and evaluation of chocolate bars from roasted and unroasted African breadfruit and Bambara groundnut flours. J. of Food Processing and Preservation. Blackwell Publishing 30: 534-548.

Potter, U. N. and Hotchkiss, J. (1995). Food Science. 5th Edn. Chapman and Hall, USA, pp 402-407.