







































Agriculture and Food 

Sciences Research 
ISSN(E) : 2411-6653 
ISSN(P) : 2518-0193 
Vol. 3, No. 1, 37-44, 2016 
http://www.asianonlinejournals.com/index.php/AESR 
 

 
 

 

 

 

 

 

37 

 

Evaluation of Porridge Made from Composite Flour of 

Orange-Fleshed Sweet Potato and Enset (Bulla) Flours 

 
Abebe Haile1

     

Martha Geribo2     

Esayas Kinfe3     

1,2,3Hawassa University, Awassa College of Agriculture, 
School of Nutrition, Food Science and Technology,  
Awassa, Ethiopia 
( Corresponding Author) 

 
Abstract 

Bulla is the water insoluble starchy product which is separated from Kocho during the decortications 

process of Enset. However, this extract lacks pro-vitamin A. This study enriched the Bulla with Orange-

fleshed Sweet Potato (OFSP) a plant with high levels of β-carotene that can be useful for combating 

vitamin A deficiency. The porridge was made of composite flours of bulla blended with 30, 35, 40 and 

45% OFSP flours were investigated for proximate composition, β-carotene, functional property and 

sensory acceptability of products using standard methods. The data were analyzed using SAS 1.9 

Software. The composite flours percentage moisture, crude (fiber, protein, fat), ash, carbohydrate, gross 

energy, β-carotene, pH, bulk density and water absorption capacity were found to be in the range of 

29.54 to 40.25, (1.66 to 2.05, 2.11 to 2.55, 0.55 to 0.71), 1.76 to 2.11, 53.86 to 63.31, 227.49 to 268.11 

Kcal/100 g, 386.68 to 558.05 μg/100 g, 4.46 to 5.71, 0.58 to 0.80 and 1.70 to 4.87 ml/g, respectively. 

While, the composite flours porridge percentage moisture, crude fiber, ash, crude protein, crude fat, 

carbohydrate, gross energy, β-carotene, pH and viscosity content found to be in the range from 43.42 to 

58.03, 1.32 to 1.79, 2.39 to 2.78, 2.01 to 2.31, 0.71 to 0.82, 35.21 to 48.63, 155 to 211.11 Kcal/100 g, 

201.46 to 301.50 μg/100 g, 5.71 to 5.82 and 515 to 728 cps, respectively. The porridge OB4PM2 (45% 

OFSP and 55%  Bulla) was most preferred due to its color, odor, flavor and overall acceptability with 

panelist scored value of 4.28, 4.33, 4.39 and 4.45, respectively. Moreover, OB4PM2 porridge was found 

to be good source of ash, energy and β-carotene content.   
 

Keywords: Bulla, Composite flour, Orange-fleshed sweet potato, Porridge, β-carotene, Viscosity. 

 

Contents 
1. Introduction ............................................................................................................................................................................... 38 

2. Materials and Methods ............................................................................................................................................................. 38 

3. Results and Discussions ............................................................................................................................................................ 40 

4. Conclusion .................................................................................................................................................................................. 43 

References ...................................................................................................................................................................................... 43 

 

 
Citation | Abebe Haile; Martha Geribo; Esayas Kinfe (2016). Evaluation of Porridge Made from Composite Flour of Orange-fleshed Sweet Potato and 

Enset (Bulla) Flours. Agriculture and Food Sciences Research, 3(1): 37-44. 
DOI: 10.20448/journal.512/2016.3.1/512.1.37.44           

ISSN(E) : 2411-6653 

ISSN(P) : 2411-6653 
Licensed:  

Contribution/Acknowledgement: 
This work is licensed under a Creative Commons Attribution 3.0 License  

All authors contributed to the conception and design of the study. 

Funding: This study received no specific financial support. 
Competing Interests: The authors declare that they have no conflict of interests. 

Transparency: The authors confirm that the manuscript is an honest, accurate, and transparent account of the study was reported; that 

no vital features of the study have been omitted; and that any discrepancies from the study as planned have been 
explained. 

History: Received: 14 April 2016/ Revised: 6 May 2016/ Accepted: 18 May 2016/ Published: 13 June 2016 

Ethical: This study follows all ethical practices during writing.   
Publisher: Asian Online Journal Publishing Group 

 
 

 

 

 

 

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Agriculture and Food Sciences Research, 2016, 3(1): 37-44 

 

 

 

 

38 

 

1. Introduction 
Bulla is a processed starch made from Enset (Enset ventricosum). It is obtained when the scrapings and pulps 

were squeezed, separating of the liquid. Collecting the pulpy white juice and left for one or two days to settle the 

resultant starch to concentrate into white flour. The starch that separates out from the liquid concentrates into a white 

powder. This product can be either fermented in pit or directly cooked without fermentation [1, 2]. Bulla is a good 

source of calories. It can be prepared as pancake, porridge and made into soup. Bulla fulfills both the nutritional 

requirement and income of the family there by providing household financial security that is by frequent sale of some 

amounts of fermented Bulla from the storage pit. The price of bulla is higher than Kocho even at local market [1]. 

Bulla can be stored for a long period of time without spoiling. The shelf life of Bulla depends on the age of the 

harvested Enset plant and the way of packing system. Proper packaging is needed to protect the spoilage. If there are 

pockets of air, or exposed to air, molds and other spoilage organisms can grow and soften the product.  Due to its 

moisture content there will be taste and color change happen to the product [3].  

Bulla was considered the best quality Enset food. However, it is low in protein, fat content and has no adequate 

pro-vitamin A for the daily requirement of a normal person. According to the study of Minaleshewa [2] and Tilahun, 

et al. [4] protein and fat content of Bulla were renged from 0.4-0.8 and 0.2-0.4g, respectively. The Vitamin “A” 

content of Enset products record was 0-0.2% [4]. As a result, it is a problem for those people who use Enset product 

(Bulla) as staple or co-staple food have a chance of being affected by vitamin A deficiency.  

Orange-fleshed Sweet Potato (Ipomoea batatas ) is an important tuber crop grown in the tropics, sub-tropics and 

warm temperate regions of the world for its edible roots crop. The roots contain significant amount of carbohydrate 

constitute mainly in the forms of starch, sugar and dietary fibers, which play an important role of providing low-cost 

energy in the diet of consumers. Beside carbohydrate, it contains high levels of ß-carotene and appreciable amount of 

minerals. Orange-fleshed Sweet Potato (OFSP) varieties are being promoted as food based intervention to combat 

vitamin A malnutrition [5]. The flesh color of the root varies from various shades of white, cream, yellow to dark-

orange depending upon the carotenoids content [6].  Carotenoids have been linked with the enhancement of immune 

system and decreased risk of degenerative diseases such as cardiovascular problems. Dietary fiber has the potential 

to reduce the incidence of a variety of diseases in man including colon cancer, diabetes, heart diseases and digestive 

disturbances [7]. The primary role of enriching the Enset product (Bulla) with Orange-fleshed Sweet Potato was to 

upgrade the Vitamin A content of the products. It is the intervention falls in the latter category of food based 

approaches which is particularly suited for rural areas where the Enset products used as a staple food. A food based 

strategy has the advantage of bringing more nutrients, vitamin “A” and more sustainable approach. Enriching the 

indigenous root crop Enset product (Bulla) by mixing with orange-fleshed sweet potato can be a good solution to 

improve the nutritional quality of household diets.   

Vitamin A is a fat-soluble vitamin that was needed in small quantities for several metabolic activities in the 

body. When vitamin A intake is below required levels, a number of manifestations collectively known as vitamin A 

deficiency (VAD) disorders occur. This vitamin deficiency has manifested as blindness, increased susceptibility to 

infection and closely associated with increased mortality and morbidity [8]. The causes of VAD occurs when vitamin 

A intake or liver stores fail to meet daily metabolic requirements and the most common cause is a persistently low 

intake of vitamin A-rich foods. Therefore, the objective of this study is enriching of Enset product (Bulla) flour with 

Orange-fleshed Sweet Potato to prepare porridge of having high vitamin A content from the blended flours. 

Moreover, to determine the physicochemical, β-carotene content and sensory acceptability of the products. 

 

2. Materials and Methods 
2.1. Sample Collection 

Raw Bulla sample was purchased from Hawassa local market. Raw Orange-fleshed Sweet Potato of Tulla variety 

(CIP-420027) was collected from Southern Agricultural Research Center of Primary Quality Sweet Potato Vine 

Multiplication Center (Wondo Genet Farm). All the samples were properly packed and transported to the laboratory 

of Food Science and Technology, Hawassa University. The OFSP was stored at -18 0C (Haier chest freezer Model 

HCF 588) to protect spoilage. While Bulla was stored at dry and ambient temperature until further processing.  

 

2.2. Bulla Flour Preparation 
Bulla sample was prepared according to procedure outlined by Minaleshewa [2]. The semi dried bulk Bulla 

sample was spreaded on clean dry wood board and the long fibers were removed manually. The sample was then 

sieved through 500µm sieve (FRITSCH, test sieve, Made in German) to remove the hard particles and made it 

uniform size and the contents were mixed. Bulla flour was packed by polyethylene bag and stored at room 

temperature.  

 

2.3. Orange-fleshed Sweet Potato Flour Preparation 
Orange-fleshed sweet potato flour was prepared according to the procedure outlined by Owori, et al. [9]. The 

OFSP was taken out from deep freezer and kept on the laboratory table for four hours until its temperature was raised 

to room temperature. The OFSP was washed with potable water to remove any foreign bodies and then the outer skin 

was peeled by peeling machine (Robot coupé H. Biaugeaup Model CL 30). The remaining unnecessary parts were 

removed manually and rinsed by clean potable water. The OFSP was chopped to minimize the size for the slicer 

machine. The chopped sweet potato was then sliced to a uniform size of 3 mm by the slicer machine (H. Biaugeaup 

Model W1 9901). The slices were soaked in 1% w/v sodium chloride solution for 30 minutes. The function of salt is 

to inhibit the growth of microorganisms on the slices while drying. The slices were dried on the flat racks of solar 

dryer. The dried sample was milled by electronic grinder and sieved by 500µm sieve (FRITSCH, test sieve, Made in 

German). The flour obtained was double packed by dark polyethylene bags stored in dry and dark place to protect 

oxidation of ß- carotene. 



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39 

 

2.4. Preparation of OFSP Added Bulla Composite Flour  
The formulation of OFSP with Bulla for porridge making were done based on the recommended dietary intake 

(RDI) of adult person to maintain a healthy life. It also allows creating unique and delicious recipes based on the 

acceptability of the users, see Table 1 below. 

 
Table-1. Proportion of OFSP powder used to formulate the composite flour 

 Bulla composition /Kg 

 OB4PM1 OB3PM1 OB2PM1 OB1PM1 B1PM1 

OFSP  45%  40%  35% 30% - 

Bulla 55%  60%   65% 70% 100% 

Total 1Kg 1Kg     1Kg 1Kg 1Kg 
                      Note: * PM1→ is the code of treatments before cooking 
 

Table-2. Proportion of ingredients used to prepare porridge 

                                            Bulla composite flour porridge /kg  

 OB4PM2 OB3PM2 OB2PM2 OB1PM2  B1PM2 

OFSP   45%  40%  35% 30% - 

Bulla 55%  60%  65% 70 100% 

Water (mL/kg) 1500    1500  1500 1500 1500   

Oil (mL/kg)    20 20 20 20                  20 
                   Note: *PM1→ treatments before cooking, *PM2 → treatments after cooking. 

 

B1PM1=100% of Bulla flour, OB1PM1=30% OFSP + 70% of Bulla, OB2PM1=35% OFSP + 65% of Bulla, 

OB3PM1=40% OFSP + 60% of Bulla and OB4PM1=45% OFSP + 55% of Bulla composite flour; B1PM2=100% Bulla 

porridge, OB1PM2=30 % OFSP + 70% Bulla, OB2PM2=35% OFSP + 65% of Bulla, OB3PM2=40% OFSP + 60% 

Bulla and OB4PM2=45% OFSP + 55% Bulla composite flour porridge.  

 

2.5. Porridge Preparation 
Bulla based porridge was prepared using the methods outlined by Yewelsew, et al. [10]. One kilogram of 

composite flours was mixed with 1500 mL/kg of water, kneaded well in the pot, and boiled until all particles became 

soluble while boiling 20mL oil was added. Then the composite flour porridge was cooked at the temperature of 100 
0C for 10 minutes. 

 

2.6. Chemical Analysis  

2.6.1. Determination of ß-carotene Contents  
ß-carotene content in the food was determined as the procedure outlined by Rodriguez, et al. [11] based on 

Spectro-photometric test. 

 

2.6.2. Determination of Proximate Composition 

The Proximate composition of flour and composite flour porridge were determined by using the standard method 

of Association of Official Analytical Chemists (AOAC) [12]. The total carbohydrate amount in the sample was 

determined by difference: 

Total c𝐚𝐫𝐛𝐨𝐡𝐲𝐝𝐫𝐚𝐭𝐞 % = 𝟏𝟎𝟎 − (𝐏 + 𝐅 + 𝐀 + 𝐌) 

Whereas:  P = the mass percentage of crude protein,  

                 F = the mass percentage of crude fat 

                A = the mass percentage of ash, 

                M = the mass percentage of moisture 

 

2.6.3. Determination of Gross Energy 
The energy value was determined by calculation using the relationship from fat, carbohydrate and protein 

contents of the Atwater’s Conversion Factors; (4kcal/g) for protein, (9kcal/g) for fat and (4 kcal/g) for carbohydrates 

and expressed in calories.  

Gross energy (kcal/g) = (4 × protein) + (4 × carbohydrate) + (9 × fat) 

 

2.7. Determination of Physical and Functional Properties 

2.7.1. pH Value  
The pH of the samples was determined from 1/10 dilution of sample by glass electrode attached to digital pH 

meter as their combination ratio before cooking and after cooking of each composite flours samples were done 

according to the method described by Yirmaga [13]. The pH meter (MP 511 Lab. pH meter, China) was calibrated 

using pH 4.0 and 7.0 buffers prior to determination of the pH of the samples. 

 

2.7.2. Bulk Density 
The bulk density of OFSP added Bulla composite flours were determined by using method [14].  

 



Agriculture and Food Sciences Research, 2016, 3(1): 37-44 

 

 

 

 

40 

 

2.7.3. Water Absorption Capacity 
Water absorption capacity OFSP added Bulla composite flours were determined using the method [15]. 

 

2.8. Viscosity 
The viscosities of the composite flours porridge were measured using the method of [16]. 

 

2.9. Sensory Evaluation  

Sixty-two panelists who were the students of the School of Nutrition, Food Science and Technology, Hawassa 

University did the consumer acceptability of composite flour porridge. The panelists ranked the color, odor, flavor, 

and overall acceptability of composite flours porridge using a five point hedonic scale (5 Extreme like, 4 Like very 

much, 3 Like, 2 Dislike and 1 Dislike very much). The composite flours porridge samples were presented in 

triplicate. Samples were being ordered on the table without providing any information to the panelists. A bottle of 

tape water with white plastic cups was given to rinse their mouth after each test. They use their observation and sense 

organ on making decisions, and they interpret the nature of a sample. The results were recorded and analyzed to 

determine the significance of variations of sensory attributes of the products average scores.   

 

2.10. Ethical Approval  

The study protocol was approved by the ethical committee of Hawassa University College of Medicine and 

Health Science for sensory evaluations. 

 

2.11. Statistical Analysis 
The data were analyzing using the SAS 9.1 Software. Analysis of variance (ANOVA) was used for the analysis. 

Fisher`s Least Significance Difference (LSD) test was used to determine the significance of mean differences of the 

results. The level of statistical significance was set at (p<0.05). 

 

3. Results and Discussions 
3.1. Proximate Composition, Physicochemical and Functional Properties  
 

Table-3. Proximate composition (%) of OFSP added Bulla composite flours and porridge. 

Treatment Moisture content Crud fiber  Ash       Crude protein   

Composite flours     

B1PM1 48.25±0.01d 0.39±0.01i 1.26± 0.01i 1.06±0.01h 

OB1PM1 40.38± 0.00g 1.66±0.01e  2.11±0.01g  1.76± 0.01g 

OB2PM1 33.72± 0.01h 1.81±0.00c 2.24± 0.01f 1.88±0.01e 

OB3PM1  31.62±0.01i 1.92±0.01b 2.38±0.01e 2.01±0.01d  

OB4PM1 29.54±0.01j 2.05±0.01a 2.55±0.00c 2.11±0.01c  

Porridge       

B1PM2 60.30±0.01a 0.12± 0.01j 2.00±0.01h 1.90±0.00f 

OB1PM2 58.03±0.01b 1.32± 0.01h 2.39±0.01e 2.01±0.00d 

OB2PM2 50.11±0.01c 1.49± 0.01g 2.51±0.01d 2.12±0.01c  

OB3PM2 46.75±0.01e 1.62± 0.01f 2.62±0.01b 2.21±0.01b 

OB4PM2 43.42±0.00f 1.79± 0.01d  2.78±0.01a 2.31±0.01a  
                      Note: *PM1→ treatments before cooking, *PM2 → treatments after cooking.  

 

B1PM1 = 100% of Bulla flour, OB1PM1 = 30% OFSP + 70% of Bulla, OB2PM1 = 35% OFSP + 65% of Bulla, 

OB3PM1=40% OFSP + 60% of Bulla and OB4PM1=45% OFSP + 55% of Bulla composite flour; B1PM2 = 100% 

Bulla porridge, OB1PM2 = 30 % OFSP + 70% Bulla, OB2PM2 = 35% OFSP + 65% of Bulla, OB3PM2 = 40% OFSP + 

60% Bulla and OB4PM2 = 45% OFSP + 55% Bulla composite flour porridge. Means ± SD, values within the same 

column with different superscript letters are significantly different from each other (p<0.05).  

Table 3 shows that the moisture content of  OFSP and Bulla composite flours and porridges were ranged from 

31.62-48.25% and 43.42-60.30 %, respectively. The highest moisture content observed in B1PM2 (60.30%) followed 

by OB1PM2 (58.03%) and the least was for the OB4PM1 (29.54%). Moisture content of OFSP and Bulla composite 

flour and porridge were significantly different (p<0.05) to each other. According to Kalekristos [3] the moisture 

content of Bulla bought from Addis Ababa supper market was found in the range of 44 to 57%,  that was contain 

more moisture than the present study. There were significant differences in moisture content between the treatments, 

before and after cooking of the porridge. The highest moisture content of composite flours and porridges scores were 

(OB1PM1) 40.38% and OB1PM2 (58.03%), respectively. The difference might be due to addition of more water while 

cooking the porridge. As the amount of OFSP flour increases in the composite flours, the moisture content of flour 

and porridge were decreased gradually.  

Crud fiber contents of Bulla 0.39%, OFSP added Bulla composite flour ranged from 1.66 to 2.05%, while Bulla 

porridge ranged from 0.12 to 1.79%. There were significant difference (p<0.05) among the treatments. Higher crude 

fiber (2.05%) content was obtained in Bulla based composite flour OB4PM1, while the lowest (0.12%) was obtained 

for porridge B1PM2. According to the previous reported literature, Bulla was the decanted fluid of the decortications 

processing of Enset plant and it is very poor in fiber content of recorded values were in the range from 0.6 to 0.8% 

[3].  As the amount of OFSP flour increases in the composite flours, the fiber content increased gradually. This might 

be due to the crude fiber content of OFSP more than Bulla flour.  However, the fiber content of OFSP added Bulla 

composite flours were not fulfilling the RDA of fiber for healthy adult.  According to FAO Food Standards Program 



Agriculture and Food Sciences Research, 2016, 3(1): 37-44 

 

 

 

 

41 

 

[17] of the RDA of fiber for healthy person set at 25 to 38 g/day which was significantly different from the present 

study. Hence, Bulla composite flours porridge needs additional fiber source of food.                                                                                                                              

Ash actually a much more general term that can refer to a number of substances in the food. The ash is residue 

that remains after heating and removing water or it refers to any inorganic material present in food [18]. The ash 

content of OFSP added Bulla composite flour and porridge were ranged from 1.26-2.55% and 2.39 - 2.78%, 

respectively. According to Minaleshewa [2] and Yirmaga [13] the ash content of Bulla was found 0.2 and 2.39 %, 

respectively. The highest ash content was observed for OB4PM2 (2.78%) whereas the least for B1PM1 (1.26%).  The 

ash content of composite flours and porridges were significantly different (p<0.05) to each other. It might be due to 

the leaching of some minerals from cooking utensils. As the amount of OFSP flour increased in the composite flours, 

the crude ash content increased. The increment of ash content show that the increasing the density of inorganic 

material such as minerals present in food.  

The protein value for different Bulla based composite flour and porridge were presented in Table3 shows that the 

highest protein record was for OB4PM2 (2.31%) and the least was observed for B1PM1 (1.06%). There were 

significant different (p<0.05) observed among protein content except for OB4PM1 and OB3PM1. The crude protein 

content of Bulla was recorded 1.6g/100 g while the protein content of OFSP added Bulla composite flour was in the 

range of 1.76 to 2.11%. These, value were greater than the crude protein content of Bulla reported values of 0.6 and 

0.4-0.8 g/100g by Tilahun, et al. [4] and Minaleshewa [2] respectively. The highest protein content of Bulla 

composite porridge score was (2.31%) observed in OB4PM2. When the percentage of OFSP increases, the protein 

content of composite flour increased gradually. This might be due to relatively higher protein content of OFSP 

compared to Bulla. However, protein contents of the composite flours were not enough for daily requirement of 

healthy person which was in the range of 0.80 to 1.52 g/kg/d [17, 18]. 
 

Table-4. Proximate composition (%) of crude fat, carbohydrate, energy and β-carotene of composite flours and porridges 

           Note: *PM1→ treatments before cooking, *PM2 → treatments after cooking (porridge). 

 

B1PM1=100% of Bulla flour, OB1PM1=30% OFSP + 70% of Bulla, OB2PM1=35% OFSP + 65% of Bulla, 

OB3PM1=40% OFSP + 60% of Bulla and OB4PM1=45% OFSP + 55% of Bulla composite flour; B1PM2=100% Bulla 

porridge, OB1PM2=30 % OFSP + 70% Bulla, OB2PM2=35% OFSP + 65% of Bulla, OB3PM2=40% OFSP + 60% 

Bulla and OB4PM2=45% OFSP + 55% Bulla composite flour porridge. Means ± SD, values within the same column 

with different superscript letters are significantly different from each other (p<0.05).  

As it is indicated in Table 4 the fat content of OFSP added Bulla composite flour and porridge were ranged from 

0.26 - 0.70 % and 0.22- 0.82%, respectively. The present studied samples were slightly different from Minaleshewa 

[2] fat content observed value ranged from 0.2 to 0.4 g/100 g. The fat content of the OFSP added Bulla composite 

flours and porridges were significantly different (p<0.05) to each other. The highest and lowest fat content values 

were observed for OB4PM2 (0.82%) and B1PM2 (0.22%), respectively. However, fat content of Bulla composites 

were not enough to satisfying the daily requirements of adult person. The results indicating that both Bulla and OFSP 

are poor sources of crude fat. 

Table 4 show that the carbohydrate content of OFSP added Bulla composite flour ranged from 48.78 to 63.31%, 

while that of porridge ranged from 35.00 to 48.63%. The highest and lowest carbohydrate content values were 

observed for composite flour OB4PM1 (63.31%) and porridge B1PM2 (35%), respectively. According to Minaleshewa 

[2] the carbohydrate content of Bulla recorded to be 43.6 to 55.4g/100g, which was less than from the present study 

finding. There were significant difference (p<0.05) observed between carbohydrate content of the composite flours 

and porridges. Due to the dilution of more water for porridge processing, the sample contained high amount of water. 

On the other hand as the percentage of OFSP is increased the carbohydrate content of both the composite flours and 

porridges were significantly increased. The carbohydrate content of the Bulla composite flour products were 

somehow enough for satisfying daily requirements of adult person. The findings indicating both Bulla and OFSP 

were good sources of carbohydrate. The RDA of carbohydrate for healthy person was found to be 130 g/day [18].                                                                                                                  

The gross energy content of OFSP added Bulla composite flours and porridges were ranged from 201.07 - 

268.11 and 149.58-211.11Kcal/100gm, respectively. The highest gross energy content was found for OB4PM1 

(268.11 Kcal/ 100gm), while the least was for B1PM2 (149.58Kcal/ 100gm). The gross energy content were 

significantly different from each other (p<0.05). 

According to the study of Almaz [19] and Minaleshewa [2] the energy content of Bulla was scored 1860 and 

1410 -1950 kJ/kg, respectively which were different from present study. The highest energy content of composite 

flour and porridge were scored for OB4PM1 (268.11 Kcal/100g) and OB4PM2 (211.11 Kcal/100g), respectively. 

There were significant difference (p<0.05) between the energy content of composite flour and porridge. When the 

percentage of OFSP increases in the composite flour, the energy content of composite flour and porridge were 

Treatment Crude fat   Total  carbohydrate  Gross energy, Kcal/100gm β-carotene, μg/100gm 

Composite flours  
 

  

B1PM1 0.26±0.00h 48. 78±0.02e 201.07±0.00f Nil 

OB1PM1 0.55±0.01g 53.86±0.01d  227.49±0.07d  386.68±0.04d 

OB2PM1 0.59±0.01f 60.09±0.01c 253.19±0.04c 451.13±0.02c 

OB3PM1  0.64±0.00e 61.73±0.02b 260.33±0.61b 515.58±0.03b 

OB4PM1 0.71±0.01d 63.31±0.00a 268.11±0.05 a  558.05±0.00a 

Porridges   
 

  

B1PM2 0.22±0.01i 35.00±0.00h 149.58±0.05 j Nil 

OB1PM2 0.71±0.01d 35.21±0.00h 155.27±0.00i 201.46±0.34h 

OB2PM2 0.74±0.01c   42.71±0.02g 185.98±0.05 h 231.54±0.03g 

OB3PM2 0.78±0.00b 45.71±0.02f 198.72±0.06g 265.71±0.01f 

OB4PM2 0.82±0.01a  48.63±0.01e  211.11±0.07e 301.50±0.02e 



Agriculture and Food Sciences Research, 2016, 3(1): 37-44 

 

 

 

 

42 

 

enhanced gradually. This might be due to the relatively higher energy content of OFSP compared to Bulla. The 

results indicate that the composites are good source of energy. 

As mentioned on the previously reported literatures, Bulla was poor in β-carotene content. Therefore, it can be 

enhanced by the application of β-carotene rich food items to improve the β-carotene of the diet. The effect of 

addition of OFSP on β-carotene content of Enset (Bulla) based composite flour and porridge is shown in Table 4.  

The β-carotene content of solar drayed OFSP powder was scored 1280 μg/100g, while the β-carotene content of 

OFSP added Bulla composite flour values were ranged from 386.68 to 558.05 μg/100g. Similarly, the β-carotene 

content of the OFSP added Bulla composite porridge values were ranged from 201.46 to 301.50 μg/100g. The 

highest β-carotene content observed for the composite flour OB4PM1 (558.05μg/100gm) followed by OB3PM1 

(515.58μg/100gm) and the least was observed for porridge OB1PM2 (201.46μg/100gm). The β-carotene content of 

composite flours and porridge were found to be significantly different (p<0.05) to each other. According to the study 

of Stella [6] and Aurélie [20] the β-carotene content of raw OFSP was observed in the ranged values from 1,255 to 

2,400 and 1,596 to 2,382 μg /100g of edible portion, respectively which is different from present study. The β-

carotene content of raw OFSP flour comparing with the composite four was significantly different (p<0.05). This 

might be due to the degradation of β-carotene in the drying process and mixing with food having none β-carotene. 

 The β-carotene content of composite flour is significantly higher than bulla based porridge (p<0.05). This might 

be due to the effect of cooking temperature on β-carotene content in the preparation of the porridge. On the other 

hand when the percentage of OFSP increases, the β-carotene content of composite flour and porridge enhanced 

gradually. This is due to the higher β-carotene content of OFSP compared to Bulla. The results indicate that the 

composites were good source of β-carotene even though it is less than the one indicated by Stella [6] and Aurélie 

[20].  

According to Kósambo [21] the average β-carotene loss on the finished products of porridge made from OFSP 

flour was 65%. In the present study the loss of β-carotene content during cooking process of OFSP and Bulla 

composite flour porridge was 256.55 μg/100g (45.97%). The finding show that the β-carotene degradation decreased. 

This might be due to short cooking time, temperature and genetic variation of the crop.   

A person who eats 45% OFSP and 55% Bulla composite  porridge he/she gain 301.50μg that was (33.5%) of the 

daily requirement of adult. The daily requirement of β-carotene of healthy person range between 250 to 900µg/day 

[17, 18].  

 

3.2. Physical and Functional Properties Composite Flours or/and Porridge 

 
Table-5. Physical and functional properties, and pH of bulla based composite flours and porridge 

 

Treatment  pH /100mg Bulk density, g/ml WAC, g/ml3 Viscosity, cps 

Composite flours     

B1PM1 4.0±0.01c 0.92±0.01a 0.76±0.00e  

OB1PM1  4.46±0.01c 0.80±0.01b 1.70±0.10d - 

OB2PM1  5.27±0.01b  0.69±0.02c   3.07±0.12c - 

OB3PM1   5.64±1.15b 0.61±0.01d 4.00±0.00 b - 

OB4PM1  5.71±0.03a 0.58±0.01e 4.87±0.15a - 

Porridge      

B1PM2 5.13±0.01c   515±1.00e 

OB1PM2 5.71±0.00a - - 525.67±0.58d 

OB2PM2 5.73±0.01a - - 553.00±1.00c 

OB3PM2 5.77±0.01a - - 624.67±0.58b 

OB4PM2 5.82±0.02a - - 728.00±1.73a 
                             Note: *PM1→ treatments before cooking, *PM2 → treatments after cooking. 

 

B1PM1=100% of Bulla flour, OB1PM1=30% OFSP + 70% of Bulla, OB2PM1=35% OFSP + 65% of Bulla, 

OB3PM1=40% OFSP + 60% of Bulla and OB4PM1=45% OFSP + 55% of Bulla composite flour; B1PM2=100% Bulla 

porridge, OB1PM2=30 % OFSP + 70% Bulla, OB2PM2=35% OFSP + 65% of Bulla, OB3PM2=40% OFSP + 60% 

Bulla and OB4PM2=45% OFSP + 55% Bulla composite flour porridge. Means ± SD, values within the same column 

with different superscript letters are significantly different from each other (p<0.05). WAC-water absorption 

capacity, cps-centi pose second. 

The pH value of Bulla was 4.00/100mg; OFSP added Bulla composite flour and porridge were found in the range 

from 4.46-5.82/100mg as presented in Table 5. The highest pH value observed for bulla based porridge OB4PM2 

(5.82/100mg), while the least value was seen for composite flour B1PM1 (4.00/100mg). This might be due to cooking 

temperature increases the pH value of the samples by denaturing the amino acids in the food. As the percentage of 

OFSP increases, the pH value of composite flour and porridge were enhanced.   

The composite flour pH values were significantly different (p<0.05) to each other. While the pH values for 

porridges were not significantly different (p>0.05) to each other. According to the study of Kalekristos [3] Bulla 

bought from Addis Ababa supper market pH value was 4.9/100mg which was less acidic compared to present study. 

As mentioned in previous sections, the bulk density of a powder depends on how closely individual particles 

packed together and it play important roles during mixing in dough formation [14]. The bulk densities for Bulla was 

0.92 g/ml, OFSP added Bulla composite flour were ranged from 0.58-0.91g/ml. The highest bulk densities was 

observed for B1PM1 (0.92g/ml) while the least was for OB4PM1 (0.58g/ml). The bulk densities of OFSP added Bulla 

composite flours were significantly different from each other (p<0.05). As the amount of OFSP powder increases in 

the composite, the bulk density decreased gradually. This is due to particle size of OFSP is less than Bulla.  

The water absorption capacity of flour indicates how much water to add during food preparation and interrelated 

to gelatin properties. Hence, the low water absorption capacity recorded by the flours could explain the less gel 

formation capacity [16]. The finding of the water absorption capacity of Bulla in this study was 0.76 ml/g, while the 



Agriculture and Food Sciences Research, 2016, 3(1): 37-44 

 

 

 

 

43 

 

water absorption capacity of OFSP added Bulla composite flours were ranged from 1.70 to 4.87 ml/g as shown in 

Table 5. As the amount of OFSP flour increases in the composite, the water absorption capacity increased gradually. 

This might be due to the water absorption capacity of OFSP powder was higher compared to Bulla flour. The highest 

water absorption capacity of OFSP added Bulla composite was for OB4PM1 (4.87 g/ml3) and the least was for B1PM1 

(0.76 g/ml3). There were significantly different from each other (p<0.05). 

The value of viscosity of Bulla porridge was 515.00 c.p.s, OFSP added Bulla composite flours porridge were 

ranged from 525.67-728.00 c.p.s. (see above Table 5). The highest viscosity value was observed for OB4PM2 (728.00 

c.p.s) followed by OB3PM2 (624.67) and the least for B1PM2 (515.67 c.p.s.). There were significantly difference 

(p<0.05) between each treatment. As the amount of OFSP flour increases in the composite flours, the viscosity of the 

porridge was also increased. This might be due to the water absorption capacity of the OFSP flour. The higher the 

viscosity is a desirable quality attribute of flour for cooking purpose. Liquids make up of small molecules have a low 

viscosity and liquids with long chain molecules have a much higher viscosity [22]. 

 

3.3. Sensory Evaluation of Bulla Based Composite Flours Porridge 
 

Table-5. Organoleptic evaluation score of OFSP added Bulla composite flours porridge 

 

 

 

 

 

 
 

 

Note: *PM1→ treatments before cooking, *PM2 → treatments after cooking.  

 

B1PM1= 100% of Bulla flour, OB1PM1=30% OFSP + 70% of Bulla, OB2PM1=35% OFSP + 65% of Bulla, 

OB3PM1=40% OFSP + 60% of Bulla and OB4PM1=45% OFSP + 55% of Bulla composite flour; B1PM2=100% Bulla 

porridge, OB1PM2=30 % OFSP + 70% Bulla, OB2PM2= 35% OFSP + 65% of Bulla, OB3PM2=40% OFSP + 60% 

Bulla and OB4PM2=45% OFSP + 55% Bulla composite flour porridge. Means ± SD, values within the same column 

with different superscript letters are significantly different from each other (p<0.05). 

The porridges were prepared by blending of OFSP and Bulla in different combination were analyzed for various 

sensorial attributes for their acceptance by using 5 point hedonic scale. When you are offering a new product or 

changing ingredients of food items, it is important to know what likely the consumer reaction is to be to the 

characteristics of your product. At the present study all panelists were instructed to make their own individual 

assessments, according to the evaluation criteria provided for each samples on the basis of, color, odor, flavor and 

overall acceptability. The organoleptic evaluation of OFSP and Bulla composite flours porridge score values ranged 

from 1.05-4.28, 1.00-4.33, 1.3-4.39 and 1.25-4.45 for attributes of color, odor, flavor and overall acceptability, 

respectively as indicated in above Table 6. There were Significant difference (p<0.05) was observed among the 

treatments. The highest preferences of Bulla composite porridge by color, odor, flavor and overall acceptability were 

scored 4.28, 4.33, 4.39 and 4.45, respectively.  It was observed that the Bulla based porridge sample OB4PM2 ,  

prepared by addition of 45% OFSP flour was liked most by sensory panelist as compared to the other combinations. 

The least preferred Bulla composite porridge OB1PM2 was scored 1.05, 1.00, 1.30 and 1.25 for color, odor, flavor 

and overall acceptability, respectively. The evaluation results of the panelist’s preferences were increases as the ratio 

of OFSP increases in the composite flours. 

 

4. Conclusion 
As Orange-fleshed Sweet Potato (OFSP) percentage increased in the composite flours and porridge; gross 

energy, β-carotene content, pH, water absorption capacity and viscosity were enhanced. However, an increased 

amount of OFSP in Bulla flour and its corresponding products do not made them to be good source of crude fiber, 

protein and fat. The composite flours porridge OB4PM2 was preferred by panelists in terms of the sensory attributes 

of color, odor, flavor and overall acceptability.  

 

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Parameters 

Porridge Color Odor Flavor Overall acceptability 

B1PM2 1.05±0.12e  1.00±00 e 1.30±1.00 e 1.25±0.30 e 

OB1PM2 2.63±1.08d 2.62±1.09d 2.60±1.06d 2.58±0.99d 

OB2PM2 2.80±0.78c 2.84±0.85c 2.83±0.80c 2.89±0.77c 

OB3PM2 3.36±0.92b 3.36±0.95b 3.37±1.05b 3.53±0.94b 

OB4PM2 4.28±0.87a 4.33±0.82a 4.39±0.83a 4.45±0.76a 



Agriculture and Food Sciences Research, 2016, 3(1): 37-44 

 

 

 

 

44 

 

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