Abstract: The effect of cooking methods on some proximate properties of sweet potato (Ipomoea batatas L) was investigated. With the initial properties of the fresh sweet potatoes (sample A) determined, 600g each of samples B, C and D were boiled peeled, boiled unpeeled and roasted unpeeled respectively. The properties determined for the samples are moisture content, ash, fibre, protein, fat, carbohydrate, vitamins A and C. Data collected were analysed statistically to determine the effect of cooking methods on the properties of sweet potatoes. The results show that cooking methods used has no significant effects (p&lt;0.05) on the moisture, ash and crude fibre contents of cooked sweet potato. Cooking generally increases the protein content but decreases the vitamin C and β-carotene content. Cooking of sweet potatoes unpeeled has the highest protein and carbohydrate content, it hence recommended for cooking sweet potatoes

A L Adepoju

B A Adejumo

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INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 4, ISSUE 03, MARCH 2015      ISSN 2277-8616 
146 
IJSTR©2015 
www.ijstr.org 
Some Proximate Properties Of Sweet Potato 
(Ipomoea Batatas L) As Influenced By Cooking 
Methods 
 
Adepoju, A. L., Adejumo, B. A. 
 
Abstract: The effect of cooking methods on some proximate properties of sweet potato (Ipomoea batatas L) was investigated. With the initial properties 
of the fresh sweet potatoes (sample A) determined, 600g each of samples B, C and D were boiled peeled, boiled unpeeled and roasted unpeeled 
respectively. The properties determined for the samples are moisture content, ash, fibre, protein, fat, carbohydrate, vitamins A and C. Data collected 
were analysed statistically to determine the effect of cooking methods on the properties of sweet potatoes. The results show that cooking methods used 
has no significant effects (p<0.05) on the moisture, ash and crude fibre contents of cooked sweet potato. Cooking generally increases the protein 
content but decreases the vitamin C and β-carotene content. Cooking of sweet potatoes unpeeled has the highest protein and carbohydrate content, it 
hence recommended for cooking sweet potatoes.  
 
Keyword: Proximate properties, cooking methods, sweet potato.  
———————————————————— 
 
1. INTRODUCTION 
Sweet potato, Ipomoea batatas is one of the main root and 
tuber crops commonly grown in the tropical and subtropical 
parts of the world. It was described as the seventh most 
important food crop in the world [1, 2]. It originated from 
Central America but is now widely grown and consumed as 
subsistence staples in many parts of Africa (including Nigeria), 
Latin America, the Pacific Islands and Asia. Sweet potato is 
valued for its short growing period of about 3-4 months, high 
nutritional content and its sweetness. Sweet potato is 
considered as an important food security crop, especially in 
Nigeria and is also identified as the least expensive, year 
round source of dietary vitamin A, especially the orange-
fleshed type among the poor [2]. Sweet potatoes are among 
the major tropical staple foods utilized as food as well as 
livestock feed all over the world [3]. In the tropics the fresh 
roots are commonly boiled, fried or roasted and eaten as a 
carbohydrate constituent of the diet [4]. In parts of East Africa 
tubers are sometimes sliced and sun-dried to produce chips, 
which are later ground into flour. In the Northern part of 
Nigeria, a garri-like product from sweet potato has been 
produced and evaluated; it is found it to be in high nutritional 
value [5]. Sweet potatoes are rich source of energy, 
antioxidants and vitamins (especially C) as well as carotenoids 
[6, 7]. They are also an excellent source of fibre and minerals, 
which are important in reducing blood cholesterol and aid 
digestion [8, 9]. The most common methods of cooking sweet 
potato before consumption include boiling (either with the peel 
or without the peel), roasting, frying and baking. Cooking has 
been reported to either be beneficial or detrimental to the 
nutritional content of food [10].  
 
 
 
 
 
 
 
 
 
 
 
 
Cooking helps to improve the microbiological and organoleptic 
qualities of food, increase digestibility and nutrients 
bioavailability, destroy toxins, microbes and antinutritional 
factors in food [11]. Cooking can also cause the loss of some 
micronutrients in the food [12]. Therefore proper attention must 
be given to the method used in cooking foods, especially 
sweet potato. A study on the impact of three cooking methods 
(Steaming, Roasting on Charcoal and Frying) on the β-
carotene and vitamin C contents of plantain and sweet potato 
has been carried out [13]. These nutrients were analysed in 
raw, steamed, roasted and fried plantains and sweet potatoes. 
The results showed there were significant losses in β-carotene 
and vitamin C contents with the cooking methods at p<0.05. 
Losses of β-carotene were higher after frying and vitamin C 
losses were smaller after frying, but higher after roasting. 
Significant losses of total carbohydrate were also observed 
after steaming and frying. On the contrary, total lipids content 
were significantly higher after frying but did not vary with 
roasting or steaming. They concluded that steaming was the 
best cooking method which preserves the β-carotene and 
vitamin C contents in plantain and sweet potato. The aim of 
this study is to determine the effect of cooking methods on 
some proximate properties of sweet potato grown in Minna, 
Niger State Nigeria. 
 
2.0 MATERIALS AND METHODS 
The variety of the sweet potato used in this study is the orange 
flesh (Jewel) type and was purchased at the Bosso market in 
Minna, Niger state, Nigeria. The samples were washed with 
clean water to remove dirt and other foreign materials. The 
samples were divided into samples A, B, C and D of 600g 
each. The samples were cooked using the conventional 
traditional methods of cooking sweet potatoes by the Nigerian 
households. Sample A served as the control and were 
analysed raw. Sample B was peeled, washed and boiled with 
about 750ml of water in an aluminum pot for about 10-15 
minutes. Sample C was boiled with about 750ml for 10-15 
minutes unpeeled. 
 
 
 
 
 
___________________________ 
 
 Adepoju, A. L., Adejumo, B. A. 
 Department of Agricultural and Bioresources 
Engineering, Federal University of Technology, Minna, 
Nigeria bolanleadejumo@yahoo.com  
INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 4, ISSUE 03, MARCH 2015      ISSN 2277-8616 
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IJSTR©2015 
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Table 1: Proximate properties of sweet potato samples 
 
 
 
 
 
 
 
 
 
 
 
 
 
Sample D was roasted unpeeled on hot charcoal for about 10-
15 minutes. The samples were turned regularly to ensure even 
roasting. The proximate properties of all the samples were 
determined [14]. The proximate properties determined are 
moisture content, ash content, fibre content, protein, fat, 
carbohydrate, β-carotene and vitamin C. The data obtained 
were analysed statistically to determine the effect of cooking 
methods on the proximate properties of sweet potatoes using 
the SPSS 15.0 statistical package. 
 
3.0 RESULTS AND DISCUSSION 
The effects of cooking methods on the proximate properties of 
sweet potato samples are as presented in Table 1. The results 
show that the moisture content of raw sweet potato (sample A) 
was 68.80% while that of samples B (peeled boiled), C (boiled 
with peel) and D (roasted with peel) was 66.20%, 63.00% and 
67.00% respectively. These moisture contents are found to be 
within the range of values obtained by previous researchers 
[15, 13]. The result shows that there is no significant difference 
(p<0.05) in the moisture contents of the samples. The values 
of the ash and fibre contents of the samples also show that 
there is no significant difference. This implies that the cooking 
methods studied do not actually influence the content of the 
ash and fibre of the sweet potato samples. Sample C (boiled 
with peel) have the highest value of protein which is 0.82%. 
This suggests that the potato peel helps in retaining protein in 
boiled sweet potato. Carbohydrate content increases in the 
cooked samples compared with the raw sweet potato whereas 
previous work [13] shows that there were losses in the 
carbohydrate content of sweet potato after boiling and frying. 
They deduced that these losses might be as a result of 
diffusion of free sugar from food to oil/water during frying and 
boiling. Sweet potato sample boiled unpeeled has the highest 
value of protein, carbohydrate and low value of fat content 
compare with the other samples. The raw sweet potato has 
the highest values of β-carotene (7.68mg/100g) and C 
(0.458mg/100g). These values are similar to 4.99mg/100g (β-
carotene) and 0.50mg/100g (vitamin C) obtained by previous 
work on the effect of cooking and frying on antioxidant present 
in sweet potatoes [10]. 
 
4.0 CONCLUSION 
It concluded that cooking does not have significant effect on 
the moisture content, ash, crude fibre and vitamin C content of 
sweet potatoes. Sweet potato sample boiled unpeeled 
retained nutrients close to the raw sample. It can therefore be 
recommended that potato should be taken raw or boiled 
unpeeled to ensure a considerable intake of these nutrients.  
 
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S/
No  
Moi
stur
e 
(%) 
Ash 
(%) 
Fibre 
(%) 
Prote
in 
(%) 
Fat 
(%)  
CHO%
) 
Beta 
carot
ene 
(mg/
100g
) 
Vit C 
(mg/1
00g) 
A 
69.
80 
1.00 1.00 0.46 1.70 26.84 7.68 0.46 
B 
66.
20 
1.00 0.81 0.78 2.30 28.90 0.48 0.44 
C 
63.
00 
0.81 1.00 0.82 1.00 33.37 4.80 0.37 
D 
67.
00 
1.00 1.00 0.53 3.50 27.00 6.24 0.44 
 
INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 4, ISSUE 03, MARCH 2015      ISSN 2277-8616 
148 
IJSTR©2015 
www.ijstr.org 
 
[13] Gouado, I., Demasse, M. A., Etame, L. G., Meyimgo, 
O. R., Solange, E. A. R. and Fokou, E. (2011). Impact 
of Three Cooking Methods (Steaming, Roasting on 
Charcoal and Frying) on the β-Carotene and Vitamin 
C Contents of Plantain and Sweet Potato. American 
Journal of Food Technology, 6: 994-1001. 
 
[14] AOAC. (2006). Official methods of food Analysis of 
the Association of Official Analytical Chemists 18
th
 
Edition. Washington D.C. 
 
[15] Bahado-Singh, P.S., A.O. Wheatley, M.H. Ahmad, E.Y. 
Morrison and H.N. Asemota. (2006). Food processing 
methods influence the glycaemic indices of some 
commonly eaten West Indian carbohydrate-rich foods. 
British Journal of Nutrition, 96: 476-481. 


Some Proximate Properties Of Sweet Potato (Ipomoea Batatas L) As Influenced By Cooking Methods

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Some Proximate Properties Of Sweet Potato (Ipomoea Batatas L) As Influenced By Cooking Methods

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