Defatted melon seed flour as partial replacement of wheat flour in bread making


O.F. Badejo

Department of Food Science and Technology, Rufus Giwa Polytechnic, Owo, Nigeria



In this study which is designed to improve the protein content of bread, wheat flour was blended with defatted melon seed flour at levels of 0, 5, 10, and 15%. The composite flours obtained were manually mixed with bread-making ingredients, mechanically kneaded, proofed beside a mud oven and baked at 180-200oc. The length, width and height of bread loaves produced decreased with increase in level of wheat substitution as follows: length; 15.8 to 15.6cm, width; 10 to 9.6cm and height; 6.9 to 6.7cm.The chemical analysis of the loaves indicated progressive increase from 14.55% (at 0%  level ) to 21.33% ( at 5% ) and then to 21.8% and 22.25% at 10 and 15% levels respectively. Sensory evaluation revealed that the bread loaves from the 5% level of defatted melon seed flour substitution were not significantly different from the control ( bread loaves from 100% wheat flour ) but were different significantly from those from 10 and 15% levels of substitution.


 Keywords: Wheat, flour, blend, melon, substitution



Bread is a popular food item in the Nigeria diet. It is made from wheat flour. Not being a tropical crop, only 3 percent of the county’s total consumption of wheat is locally produced (Agu et al, 2007). Therefore, a large volume of wheat has to be imported annually at great expenditure of foreign exchange. Additionally, the modest protein content of wheat flour- about 9 percent- is not only low in terms of quantity, it suffers from the general inadequacy of plant protein ,in being deficient in one or more essential amino acids (Hoagland, 1978, Kent, 1978). In the developing countries, high quality protein from animal source is beyond the reach of many people because of the general low income (Ihekoronye and Ngoddy,1985) hence the reliance of a greater majority on plant protein inspite of its inadequacy.


However, this inadequacy of plant protein can be ameliorated by supplementing one group of food items with the other. For example cereals which are deficient in one or two amino acids can be supplemented with another such as legumes that are rich in the amino acids. Making food items by partial substitution is not a new idea. Bread has made been by partial substitution of wheat flour with tuber and potato flours that are locally available (Ciacco and Dappolonia, 1978, Yanez,1981). Bread quality has been enhanced by the partial substitution of wheat flour with mango mesocarp flour (Badifu et al., 2005). Furthermore locally available bread fruit flour has been used as partial replacement of wheat flour in the production of biscuit of a higher nutritive quality (Agu et. al., 2007).


Melon seeds are taken in various forms and perhaps the most notable application of the seeds is in their use in the preparation  of the popular egusi soup. They are also used to produce “Igbalo”, “irobo”, “mbam”, “ogiri”, etc (Osagie and Eka, 1998) the use of melon seeds flour in bread production apart from their nutritive value will further diversity its application and promote its cultivation.

The present study was undertaken to investigate the feasibility of using  defatted melon seed flour with a view to: (i) improving the protein content and quality of bread loaves and conveying good quality protein to many homes and (ii) to cutting down wheat importation and saving foreign exchange.


Materials and methods

Collection and treatment of raw materials

Dehulled  melon seed and commercial wheat flour were procured from Oja Oba market Owo, Ondo State of Nigeria. The melon seeds were cleaned dried, milled and defatted at JOF Company Ltd, Owo.



Production of melon seed flour

Extraneous materials such as stones, dust particles and chaff were removed by air blowing and washing with water. The cleaned melon seeds were sun dried for 24 hr, and then milled in an attrition mill. The milled seed was defatted using hexane by the soxhlet method (Pearson 1976). The flour obtained was sun dried to a moisture level of 7.5%. The flow chart for the production of the defatted melon seed is as given in fig.1














Fig 1- Flow chart for the production of melon seed flour.




Preparation of wheat flour/ defatted melon seed flour blends.

Wheat flour/defatted melon seed flour blends at levels of 5, 10 and 15% of defatted melon seed flour were prepared. The 0% level of melon seed flour substitution was used as control.


Bread making

Four batches of bread were produced at the Rufus Giwa Baking unit.  The levels of substitution of wheat flour by melon seed flour were 0, 5, 10 and 15%. The straight dough method of break making was used ( Pyke, 1976 ). The flour blends were properly mixed manually in a wooden mixer. The dough obtained from the blends were kneaded in a kneading machine. Portions of 300g each of the dough were cut, moulded between the palms and put in baking pans and allowed to ferment beside the mud oven for about 90 minutes. The loaves were baked for 10minutes at a temperature of 1600C in the mud oven.


The bread making formula used was 100g wheat flour or blend, 0.45g yeast, 1.65g table salt, 12g sugar, 1g margarine, 0.1g vitamin C tablet (white) and about 41cm3  water.



Chemical analysis

Moisture, protein, fat, ash and fibre of the flours, and their bread loaves were determined according to the procedure in AOAC (1984).

Physical properties of bread loaves

The mean weights of the loaves were determined with a weighing scale. Average length, width and height of the loaves were carefully measured with a ruler and the volume calculated by length x width x height.


Sensory evaluation.

Sensory evaluation of the bread sample were carried out by 10 untrained panelists that are familiar with bread. The quality attributes assessed were taste flavour, texture, crust. crumb and overall acceptability. A five point hedonic scale was used in which 5 was like extremely and 1 was dislike extremely.


The results of the sensory evaluation were subjected to analysis of variance (Akinjayeju, 2002).


Results and discussion

Physical properties of dough and Bread loaves.

The experimental baking did not reveal any serious difficulty in kneading and moulding. However some degree of stickiness of dough with increasing levels of defatted melon seed flour was noticed. The volume of water absorbed decreased slightly as level of defatted melon seed flour in the blends increased. This may be due to the lower water absorbing capacity of the melon flour. The physical characteristics of the bread loaves were as shown in Table 1.The mean height for the control bread loaves was 6.9cm. The values of 6.9, 6.7, and 6.6cm were recorded for the 5, 10 and 15% levels of defatted melon seed flour substitution respectively. Average length of bread loaves obtained from 100% wheat flour was 15.8cm while 15.55, 15.60 and 15.6cm were recorded for the different levels of substitution at 5, 10 and 15%. The specific volume of the control loaf was 4.11cm3/g . This value decreased slightly to 3.74, 3.39 and 3.12cm3/g for the 5, 10 and 10% defatted melon seed flour substitution respectively.  Tsen et al. (1971) reported a decrease in loaf volume for protein fortified breads as the level of substituent increased.


In contrast the weight increased gradually from 265.5g for the control to 316g obtained for the 15% level of defatted melon seed flour substitution. Badifu et al (2005) reported a similar increase in the weight of bread loaves with increase in the proportion of mango flour substitution. This may have the advantage of promoting sales as there is a customer preference for heavier loaves.


Chemical composition of wheat flour, defatted melon seed flour and bread loaves.

The chemical analysis results of the wheat flour and the defatted melon seed flour were as shown in Table 2. Protein content recorded for wheat flour was 13.65% (N X6.25) and 35.16% for the defatted melon seed flour. Result of the bread loaves from the different blends were as shown in Table 3. Bread loaf made from wheat flour only was used as control. The fat content of the control loaf which was 17% increased through 18 to 19% at the 15% level of defatted melon seed flour substitution. This is not unexpected as the residual oil in the defatted melon seed flour could have accounted for this apart from the added margarine. The protein content increased significantly from 14.55% in the control loaf to 21.33, 21.8 and 22.25% in the 5, 10 and 15% levels of substitution respectively. These translate  to 46-53% increase in protein content. Agu et al (2007) found out that bread-fruit had a significant effect on the nutritional quality of biscuit most especially the protein content which was highest in 60:40% bread-fruit/wheat flour biscuit. The outcome of this work is also in conformity with Edema et al (2005) that protein content in bread from maize-meal-soy flour blends increased with increase in the level of soy flour substitution.


Sensory evaluation of bread loaves

Results of the sensory evaluation were as shown in Table 4. There  was no significant difference (p>0.05) in all characteristics between the control (i.e. bread loaves from 100% wheat flour) and loaves produced from wheat flour blend at the 5% level of defatted melon seed flour substitution. Bread loaves from composite flour at the level of 10% defatted melon seed flour substitution did not differ significantly (p>0.05) in crumb colour and texture from the control. However taste, flavor, crust colour and overall acceptability differ significantly (p< 0.05) at this level. This may be due to the maillard browning between the carbohydrate and the epsition –NH2 group of lysine in the defatted melon seed flour (Ihekoronye, 1985). This reaction is responsible for tastes, colours and aromas of food and although desirable in baking process, it does lead to reduction in nutritive value of foods. Sugar-protein compounds may be formed which can not be readily attacked by digestive enzymes or can only be split very slowl and are therefore nutritionally lost (Helmann,1989, Berk, 1979). The 15% defatted melon seed flour blend gave bread product significantly different from the control and of the lowest consumer acceptability. This implies that there is a limit to the level of defatted melon seed substitution.



The results seem to support the feasibility of the incorporation of defatted melon seed flour in bread making. The substitution of wheat flour with defatted melon seed  flour at the 5% level did not indicate any significant difference in consumer acceptability. On the other hand it beefed up the protein content by about 46%.  Fortifying a popular food item like bread is an inexpensive way of   addressing the problem of supplying protein to 60% of the world population that cannot afford a good source of it (Ihekoronye et al 1985). The concomitant diversification  of the use of melon away from its limited traditional use will trigger demand which will in turn promote a more profitable cultivation of this crop. Its industrial use as an ingredient in bread making will reduce the dependence on imported wheat, save foreign exchange and boost economic growth.


Table 1: Result of the chemical analyses of the wheat flour and the defatted

    melon seed flour

Characteristics ( % )                                      Wf,                Dmf.

Moisture                                                        6.00              7.50

Protein  ( N x 6.25 )                                     13.65            35.16

Fat                                                                2.50              10.5

Ash                                                               1.00              6.50

Fibre                                                             1.75              6.50

Carbohydrate *                                            75.1             33.84

*By calculation

Wf.   =  Wheat flour

Dmf   =   Defatted melon seed flour.











Table 2. Chemical analysis results of the bread loaves produce from the different blends

Characteristics ( % )                 Wf:Dmf           Wf:Dmf                   Wf:Dmf   Wf:Dmf

                                                100: 0              95 :      5                      90 :10              85 :15


Moisture                                  18.56               18.60                           18.55               18.7

Protein (N X6.25)                     14.55              21.33                           21.80               22.25

Fat                                           17.00               18.5                             18.55               19.00

Ash                                          2.00                 3.00                             1.00                 2.00

Fibre                                        0.88                 0.60                             0.5                   0.6

Carbo   hydrate *                     47.07               39.7                             40.7                 37.75


*By calculation

Wf       wheat flour

Dmf     Defatted melon seed flour.


Table 3. The physical properties of the bread loaves from the different blends.

Flour and their blends (g)

Characteristics             Wf :Dmf          Wf:Dmf           Wf:Dmf           Wf:Dmf

                                    100 :0              95:  5               90:10               85:15

Length (cm)                 15.8                 15.55              15.6                 15.60

Width (cm)                  10.00               9.70                 9.70                 6.60

Height (cm)                  6.90                 6.90                 6.70                 6.60

Volume (cm3)              1090.2             1040.               1003.3             9          983.27

Weight (g)                    265.5               278.3               296                  315

Specific volume           4.11                 3.74                 3.39                 3.12



Table 4. Sensory evaluation of bread loaves from wheat flour and its blends.


Flour blends (g)



Wf  Dmf

Wf  Dmf

Wf  Dmf

Wf  Dmf



95 :5

90 :10

85 :15

Crumb colour

3 .90 a

3.70 a

3 .30 a

2 .00b


3 .90 a

3 .50 a

3. 40 a

2 .30 b


3 .90 a

3. 0 ab

2.30 b

1.90 c


4 .00 a

3 .30a

3.00 ab


Crust colour

4 .30a

3.50 a

3 .2 a

2 .90 b

Overall acceptability

4.60 a

4.10 a

2 .90 b

1.90 c


Means with different subscripts in a row are significantly different (p>0.05)

Scale    1-5 was used where

1          -           dislike extremely

2          -           dislike

3          -           neither like nor dislike

4          -           like

5          -           like extremely.

Wf = Wheat Flour, Dmf = Defatted melon seed flour



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