Journal of Food Science & Technology

ISSN: 2472-6419

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Quality Evaluation of Bread Made from Wheat and Tigernut Composite Flour and Substitution of Bakery Fat with African Elemi (Canarium Schweinfurthii) Fruit Oil


F. Lamina1, C. Adah1,2 and D. Enenche1,2

1BSU-CEFTER Benue State University, Makurdi Nigeria

2Department of Chemistry Benue State University, Makurdi Nigeria


FOLASHADE LAMINA, Quality Evaluation of Bread Made from Wheat and Tigernut Composite Flour and Substitution of Bakery Fat with African Elemi (Canarium Schweinfurthii) Fruit Oil(2020)Journal of Food Science & Technology 5(4)


This study examined the proximate and mineral compositions of wheat bread fortified with tigernut flour and substitution of fat with African elemi oil. Non-fortified wheat bread was used as the control. Results of the proximate analysis showed that wheat bread substituted at 20% with tigernut flour had the highest moisture content (20 %), fat content (16 %), and ash content (6.08 %). The protein content of the tigernut flour and African elemi enriched breads decreased at 8.16 %, and later increased subsequently at 8.49 % ,8.95% and 9.33 % respectively. Carbohydrate content decreased in all samples with 100% bread having the highest and 20% substitution the least. Results of the mineral analysis showed the presence of Ca increased by 81% when tigernut was increased, Mg by 98%, K by 150%, Fe by 180% and Na in the bread samples initially increased by 157% but upon successive addition of tigernut it reduced to about 113%. The results showed increase in the mineral content of the bread. The significant increases in amounts of fat and minerals indicated that supplementation of wheat flour with tigernut flour and African elemi oil would greatly contribute to the daily dietary needs and improve the nutritional quality of wheat bread. Fortification of wheat bread with tigernut flour and African elemi oil should therefore be encouraged.

Keywords: Tigernut, African elemi, bread


Food insecurity continues to threaten large proportions of households in low income countries even when the benefit of adequate nutrition for individual development, activity, good health and societal functioning has been emphasized Administrative Committee on Coordination- Subcommittee on Nutrition [ACC/ACS (1991)]. To this end, bread which is a largely consumed food in most cultures can be improved to contain needed nutrients. The consumption of bread in Nigeria cut across all societal strata, ethnicity, political affiliations and economic class. The art of bread making is more than 4000 years old. Though not always in the same form or as we know it today, bread has been a popular staple food for years. The ever-present consumption of bread places it in a position of global importance in international nutrition. (Bauret, 1975; Cauvin, 2004). Bread is however relatively expensive, being made from imported wheat that is not cultivated in many African countries because the generally tropical climate does not encourage commercial wheat cultivation, leading to reliance on wheat importation to support flour milling industries (Olaoye et al., 2006).

There have been reports of bread made from flours of other cereal grains such as rye, maize, barley and oats; roots like cassava in combination with wheat flour and so the idea of substituting part of wheat with other starchy crops is not new. Consequently, these breads are rich in calories but deficient in other nutrients especially protein (Bakke and Vickers, 2007; Jideani and Onwubali, 2009). Previous efforts in Nigeria on the use of composite flour for bread have concentrated on the use of cassava flour. Also, different levels of successes have been recorded with the use of flours from legume, cereals, roots and tubers in baked goods (Basman and Koksel, 2003). The potentials of wheat-based composite flours comprising buckwheat (Lin et al., 2009), plantain (Mepba etal., 2007), modified corn starch (Woo and Seib, 2002), waxy corn starch (Morita et al., 2002; Lee et al., 2001), sunflower flour (Biljan and Bojana, 2008), chick pea (Manuel et al., 2008), bean flour (Hallen, 2008), cowpea flour (Alex et al., 2004), lupin flour (Doxastakis et al., 2002), soybean and plantain flour (Olaoye et al., 2006), for use in bread production have been investigated with promising results showing that partial substitution may be possible.

People now more aware of their health, focus has been shifted to consumption of food products which boost their immune systems. Foods high in protein and fibre content are now mostly preferred by consumers as they have shown to control certain health issues like cardiovascular disease, diabetes and weight gain. Therefore, the need to develop food products that combines health benefits with good sensory properties.

Materials & Methods

2.1 Collection of samples

Fresh fruits of African elemi were collected from a forest reserve in Jos, Plateau State and transported to the laboratory in polythene bags. Dried tigernut, wheat flour and all other materials needed for production of bread was purchased from Wurukum market Makurdi, Benue state, Nigeria.

2.2 Sample preparations

2.2.1 Extraction of African elemi oil

Fresh fruits (5kg) were sorted to remove dirt or foreign matter present in them. They were then washed in cold water to remove any dirt. The fruits were packed in a clean bowl and 1 L of water at 65°C was poured into the bowl and left for 5 min to soften the tissue of the fruits. The seeds were then removed by beating in a mortar with the aid of a pestle. The pulp was ground using the mortar and pestle for 10 min. The obtained pulp was oven dried at 50°C for 24 h to remove moisture. It was then cooled in a desiccator and the oil extracted with n-hexane using a soxhlet apparatus (Abbasi, et al., 2008).

2.2.2 Preparation of Tigernut flour

The method described by Adeyemi, 1988 was used. Dry tigernuts were sorted to remove foreign materials before washing with tap water. The cleaned nuts were sun dried for 24 h to a moisture content of about 13%. The dried nuts were then pulverized using a hammer mill and sieved through a 600 μm aperture sized mesh. The flour was then packed and sealed in a polythene bag until further analyses (Adeyemi, 1988).

2.2.3 Preparation of Sample Blends

Sample blends were prepared by mixing wheat flour to varying proportions of tigernut flour at ratios of 100:0, 90:10, 80:20, 70:30, 60:40 using a simplex lattice mixture design by Ade-Omowaye, et al., (2008).

2.3 Production of bread

The bread was produced using a local recipe described by Ade-Omowaye et al., (2008). Two cups of each sample flour (272 g) was weighed along with the required amount of water to obtain dough, which was kneaded on a pastry-board to smoothen it. The dough was initially fermented for 2 h at room temperature before being subsequently re-kneaded to expel carbon dioxide and tighten-up the dough to improve the texture of the final product. The dough was then sized into baking pans for final proving. The secondary fermentation also lasted for 30 minutes at room temp. Dough baking was carried out in the oven at a temperature of 220oC for 20 minutes. African elemi oil was substituted for baking fat in all blends.

2.4 Analysis of Samples

2.4.1 Characterization of the extracted African elemi oil

Characterization of chemical properties of the oil was done as described by Pearson (1991) including refractive index, acid value, saponification, iodine and peroxide value. Refractive index

An Abbe refractometer was used with a small portion of the oil spotted on the glass slide of the refractometer connected to a power source. The temperature was adjusted according to specification before the sample reading was taken and calculated for using the expression given thus:

Refractive index = scale reading (RI) +[(temperature-20)o C ×0.0000078]


R.I = refractive index obtained before temperature correction was made

T = the temperature at which the measurement was made Acid value

To 1 g of oil sample, 12.5 mL of diethyl ether mixed with 12.5 mL of 98% ethanol in a clean beaker was added in a clean beaker. Again, 1mL of the 1% phenolphthalein indicator solution was added to the mixture and neutralized with few drops of 0.1 M NaOH solution. The solution was then titrated with 0.1 M NaOH solution with continuous shaking until a pink colour persisted for about 15 seconds Pearson (1991). The acid value of sample is calculated thus:

Where; TD= Titre Difference = B – S, B= Titre value blank; S= Titre value with sample N= Normality of titrating solution (KOH used herein) M= Mass of sample (g) Iodine value

The method described by Nadeem et al. (2013) was used. Exactly 0.2g of oil sample was weighed and placed in a 250 mL flask and 20mL of chloroform was then added to the sample. 25mL of Wijs reagent was then added with the aid of a pipette and the resulting mixture stirred and stored in a dark place at 25°C for 30 minutes before 10 mL of 30% potassium iodide was then added to the mixture as well as 100 mL of distilled water. The mixture was then titrated with 0.1N sodium thiosulphate until the yellow colour is almost disappeared. 1 mL of starch solution was then added and the mixture titrated further until the blue starch-iodine colour disappeared. A blank titration was also carried out and the Iodine value calculated using the formula given.

Where: TD = titre difference, M = weight of oil measured Saponification value

2.0g of extracted oil was weighed into a flask and 25mL of alcoholic KOH solution added. The solution was then heated under reflux on a boiling water bath for 1 h before adding 1 mL of 1% phenolphthalein indicator. The mixture was then titrated with 0.5 M HCl solution while still warm. A blank analysis was carried out before the saponification value was calculated thus:


b = titre value of the blank; a = titre value of the oil+ reagents; 28.05 = constant Peroxide value (PV)

Peroxide value was determined according to the method described by Morris (1999). 5g of oil was dissolved in 30 mL of solvent mixture consisting of 60% glacial acetic acid and 40% chloroform and 0.5 mL of saturated solution of potassium iodide (KI). The flask was shaken until clear by giving a rotary motion to the flask. After exactly 2 minutes from time of the KI, 30 mL of water was added and the liberated iodine was titrated with 0.1 N sodium thiosulphate solution. The flask was shaken vigorously to remove any traces of iodine from the chloroform layer. A blank titration was also done. The result was expressed in terms of miliequivalents per 1000g of oil using the following formula:

Where, mL = vol of sodium thiosulphate solution, N = normality of sodium thiosulphate solution, g = weight of oil

2.4.2. Proximate composition of Flours and bread samples

Proximate analyses were carried out on the samples using standard AOAC (2005) methods. Moisture content was determined using a hot air oven, by drying the sample at 105 °C± 2 °C until a constant weight was obtained. Total fat was determined by Bligh and Dyer method using chloroform/methanol (1/1, v/v). Crude protein content was determined by converting the nitrogen content obtained by Kjeldahl's digestion method (N = 6.25). Ash content was determined after combustion for 20 h at 550 °C. Total carbohydrate was determined by difference (Ihekoronye and Ngoddy, 1985).

2.4.3. Sensory Evaluation

Five bread samples were evaluated for color, aroma, taste, colour and overall acceptability. Thirty untrained panelists familiar with consumer bread were randomly selected. The samples were coded and randomly presented to the panelists in similar trays with water provided to rinse the mouth between evaluations. A 9-point Hedonic scale was used for the evaluation where 1 represented “dislike extremely” and 9 “like extremely” (Ihekoronye and Ngoddy, 1985). The evaluation for aroma and taste were done under amber light while appearance was under bright illumination.

2.5. Statistical Analysis

All the results expressed are the mean of three measurements. Data were presented as mean ± standard deviation. To test the differences between species, one-way ANOVA was performed. Significance was established at P >  0.05. Statistical analyses were performed using SPSS 16.0 for windows (SPSS, Chicago, IL, USA).


Table 1 presents the physiochemical properties of the African elemi. The colour was greenish yellow. The refractive index was found to in range of about 1.4403±0.03, the acid value was about 3.95±0.15, Iodine value was 184.9±3.09. Again, Saponification value was 243.061±5.53 while peroxide value was 3.5±0.01. The physicochemical properties of the oil are similar to the recommended codex standard for vegetable oil (Agu et al., 2008). The refractive index for the oil was within the range of values reported for some common seed oils, refractive index is used to check purity and to follow and control hydrogenation and isomerization processes. According to Ikhuoria and Maliki (2007), iodine value gives an indication of the degree of unsaturation of oils, higher iodine values can be attributed to high unsaturation. The iodine value for the oil also known as African black olive is much higher than the standard olive oil. Therefore, based on this fact, the oil can keep for a time without adverse deterioration in quality of the oil.  The saponification value reported by Agu et al., (2008) (150.40) was much lower than the present study (243.06) possibly because of the method of extraction employed. The bright greenish yellow colour of the oils can attract consumers easily thereby creating market for the product.

Table 1: Physiochemical content of African elemi oil


African elemi oil


Greenish yellow

Refractive Index


Acid value (mg/KOH/g)


Iodine value


Saponification value


Peroxide value (Meq/kg)


Table 2: Proximate composition of flour composition


Composition %

Tigernut flour

Refined Wheat flour














Crude Fat




Moisture Content







The proximate composition of the tigernut flour and wheat flour is given in Table 2 with tigernut flour showing higher contents of ash, fibre and fat while wheat flour showed higher contents of protein, carbohydrate and moisture content. The proximate composition of bread from wheat and tigernut composite flour and African elemi oil are shown in Table 3. The bread produced from 40% tigernut flour substitution had the highest crude protein content of 9.33%, although lower than 100 % wheat bread which contained 10.4 % protein. The bread produced from 100% refined wheat flour had an ash content of about 2.4% which was significantly different (p<0.05) from the ash content of all samples produced with composite flours. There was an increase in ash content of bread as the ratio of tigernut substitution increased with sample E (60:40 wheat to tigernut flour) at 4.8% having the highest amount of ash content. The ash content is generally used as a quality measure for the assessment of the functional properties of foods (Nwachukwu et al., 2017). There was a decrease in carbohydrate content as refined flour is further substituted with tigernut flour from 66.90% < 63.14% < 57.71% < 50.40% and the bread containing 60% refined wheat flour recording the lowest carbohydrate at 43.89 %. This trend is similar to reports given by Ade-omowaye et al., 2008) using tigernut flour. We also see a significant difference in the composition of the bread samples as regards to the fat content with 100% refined wheat bread having the lowest fat content of about 4.8 % while sample B had 8.3 % sample C had 10.4 % sample D with 13.1 % and sample E with the highest at 16.0 %. A much lower fat increase of 0.52 to 5.44 % was recorded for bread substituted with tigernut flour and moringa flour (Chinma et al., 2012). Likewise, moisture and fibre content were seen to increase as the wheat replacement with tigernut flour increased. The fibre content compared favourably to bread produced from composite flours of honey beans (5.73 %) (Nwachukwu et al., 2017). Schneeman (2002) stated that the metabolic and gastrointestinal system function well with a good intake of crude fibre. The differences in percentage moisture content of the bread could also attributed to the degrees of exposure to heat which led to moisture evaporation during baking.

Table 3: Proximate composition of Bread from composite flours



Ash %

Crude Fibre%

Crude Fat%

Moisture Content %

Carbohydrate %










































Table 4 shows the composition of some minerals such as Na, Mg, Ca, Fe, and K contained in milligrams per grams in the bread produced.   Addition of tigernut flour to wheat flour increased mineral content of the bread samples from 8.57 to15.54 µg, 5.78 to 16.06µg, 28.92 to 61.66µg, 200.58 to 515.39 µg and 23.73 to 47.12 µg for Ca, Fe, Na, K and Mg respectively. The high amount of Fe, Ca, Na and Mg in the bread samples is of nutritional importance. The result of mineral contents of bread indicates that bread samples prepared from the composite blends contain appreciable levels of minerals and could contribute to mineral intake of consumers, because a deficiency of any one of the minerals can result in severe metabolic disorders and compromise the health of the individual. The mineral composition obtained in this study is higher than the value reported by Chima et al., (2012) and those of Charoenthaiki et al., (2012) for wheat-germinated brown rice flour bread.

Table 4: Mineral composition of Bread from composite flours











































The sensory evaluation of bread from the various composite samples as compared to the control bread as shown in Table 5. The data revealed that incorporation of tigernut flour and substitution of fat with African elemi oil drastically affected the colour, flavour and taste. The samples had appreciable ratings for colour, flavour, taste and texture all except 20%. Omeire and Onyenagorom (2007) reported a similar result where the peculiar flavour of walnut was said to affect the flavour of African walnut-wheat flour composite flour bread. The colour scores showed that there was significant difference (p>0.05) among samples. The scores for the sample which contained 10 % and 20% tigernut flour compared well with that of the 100% wheat flour sample. Sample B to E showed lower ratings in appearance. Its crust (the outer later) was observed to be brown in color while the crumb (the inner part) was light brown in colour. This was attributed to the greenish colour of the African elemi oil which changed the loaves to an unfamiliar colour. Onuegbu et al. (2004) reported a similar result where the blue-green color of the African pear (Dacryodes edulis) fruit pulp/oil used as a replacement for bakery fat was said to affect the appearance of the bread.

Table 5: Sensory Scores of Bread from composite flours






Overall Acceptability

































Inclusion of tigernut flour and African elemi oil in wheat flour used for bread production at levels of up to 40% resulted in notable increase in fibre and ash contents while protein content decreased. The significant increase in the fibre content could be nutritionally advantageous in Nigeria, where white bread is one of commonest staples among all classes of people. Also, the consumption of wheat-tigernut flour and African elemi oil bread is advocated for groups with special caloric and glycaemic requirements, such as obese or diabetic people owing to the reasons of low carbohydrate content.


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