Thermal properties of some selected nigerian soups

doi:10.4236/as.2013.45B018

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Vol.4, No.5B, 96-99 (2013) Agricultural Sciences

doi:10.4236/as.2013.45B018

Thermal properties of some selected nigerian soups

Raji Akeem Olayemi1, Akinoso Rahman2

1Department of Food Agric and Biological Engineering, College of Engineering and Technology, Kwara State University, Malete,

Ilorin, Nigeria; [email protected]

2Department of Food Technology, University of Ibadan, Oyo State, Nigeria; [email protected]

Received 2013

ABSTRACT

A preliminary investigation was carried out on the

thermal properties of “Ewedu” (Corchorusolito-

rus), “Ila” (Hibiscus esculentus), “Ogbono” (Irvin-

gi a gabon ensis) and ” Kuka” (Adanso nia digitata)

soups, because information on the thermal prop-

erties of these soups has not been established.

The specific heat capacity, thermal conductivity

and thermal diffusivity parameters were deter-

mined as a function of their proximate composi-

tions by applying additivity principles. The proxi-

mate composition obtained for the soups were:

ewedu (moisture content; 88.60 ± 0.14% , protein;

6.00 ± 0.01%, fat; 1.05 ± 0.05% , ash; 1.81 ± 0.01% ,

crude fiber; 1.47 ± 0.02%, carbohydrate; 1.05 ±

0.04% and energy 34.27 ± 1.89 k/cal/10 g), Ila

(moisture content; 77.25 ± 0.35%, protein; 15.94

± 0.08%, fat; 2.13 ± 0.04%, ash; 1.90 ± 0.14%,

crude fiber; 1.15 ± 0.07%, carbohydrate; 1.48 ±

0.11% and energy 87.61 ± 3.31 k/cal/10 g), Og-

bono (moisture content; 68.87 ± 0.14%, protein;

18.70 ± 0.42% , fat; 6.12 ± 0.11%, ash; 4.55 ± 021% ,

crude fiber; 1.04 ± 0.60%, carbohydrate; 1.90 ±

0.01% and energy; 133.08 ± 0.60 k/cal/10 g) and

Kuka (moisture content; 78.54 ± 0.06%, protein;

8.80 ± 0.41%, fat; 2.29 ± 0.01% , ash; 2.09 ± 0.01% ,

crude fiber; 0.88 ± 0.02%, carbohydrate; 7.42 ±

0.08% and energy 85.64 ± 0.17 k/cal/10 g). The

specific heat capacity, thermal conductivity and

thermal diffusivity for the soups were; ewedu

(3.851 kJ/ kg/K, 0.530 W/m/K and 1.358 x 10-7

m2/s), Ila (3.554 ± 0.01 kJ/kg/K, 0.483 W/m/K and

1.281 x 10-7 m2/s), ogbono (3.332 kJ/kg/K, 0.447

W/m/K and 1.220 x 10-7 m2/s) and kuka (3.586

kJ/kg/K, 0.494 W/m/K and 1.296 x 10-7 m2/s)re-

spectively. The values obtained for the thermal

properties showed that the soups can mildly

retain or dissipate heat during canning and

freezing.

Keywords: Soups; Proximate Composition;

Thermal Properties; Processing

1. INTRODUCTION

Vegetables are important constituents of any type of

diet in many Nigerian homes. Despite that, they add va-

rieties to the menu. As valuable sources of nutrients es-

pecially in rural areas where they con tribute substantially

to protein, mineral, vitamins, fiber and other nutrients

which are usually in short supply in most daily diets [1].

Besides, they add flavour, variety, taste, colour and aes-

thetic appeal to what would otherwise be a monotonous

diet [2,3]. They are mostly in abun dance shortly after the

rainy season but become scarce during the dry season

when cultivated types are used. Some eventually find

their way to urban markets [1].Vegetables have gained a

widespread acceptance as a dietary cons tituent in Nigeria,

generally forming a substantial portion of the diet in the

preparation o f sou ps and stews[3].

Nigeria is a multi-cultural society with different tradi-

tional soups which are indigenous to differen t ethnic groups

and tribes. The soups are consumed along with traditional

dietary staples, obtained from cassava, yam, cocoyam,

sweet potatoes, plantain and maize [4]. Though, there is

no universally accepted short list of such plants men-

tioned above, different tribes in Nigeria have evolved

their preferences and feedi ng habits.

During processing and storage, many foods are either

heated or cooled. Cooling, cooking, pasteurization, de-

hydration, commercial sterilization and freezing involve

heat transfer [5] and the design of such processes re-

quires a detailed knowledge of the thermal properties of

the materials involved.

Although the recipe and nutritional contents of stews

and soups commonly consumed in Nigeria had been es-

tablihed in order to serve as a reference for interested

individuals, corporate organizations, researchers, medical

practitioners, nutritionists and dieticians, public health

workers and food technology programmes [6], informa-

tion on the thermal p r op erties of these so up s has not been

established. The parameters stated above will serve as a

R. A. Olayemi, A. Rahman / Agricultural Sciences 4 (2013) 96-99 97

basis for future research in canning of Nigerian soups

and also establish the possibilities of extending the shelf

life of the local soups under frozen storage. Soups to be

considered are chosen because they are popularly

consumed along with staple foods from the three major

tribes in Nigeria and these are prepared from “Ewedu”

(Corchorusolitorus), “Ila” (Hibiscusesculentus), “Og-

bono” (Irvingiagabonensis) and ” Kuka” (Adansoniadig

itata).

2. MATERIALS AND METHODS

2.1. Materials

The ingredients used for the preparation of the above

soups were purchased from Local markets at Ipata and

Ago in Ilorin, Kwara State Nigeria.

2.1.1. Preparation of Soups

Selected Nigerian soups mentioned above were pre-

pared using facilities of the department of Food Agric

and Biological Engineering, Kwara State University Ni-

geria. The preparation methods used for the selected

soups were those earlier established by recipe book of

the Federal Institute of Industrial Research, Oshodi [6].

Each dish was prepared in triplicates and analyses were

carried out on wet basis.

2.1.2. Sample Collection and Preparation

Each soup was cooled to room temperature and equal

portions of the dishes were homogenized with a warring

blender.

2.2. Proximate Composition Analysis

Each sample was analysed for moisture, ash, crude fat,

and crude fiber using the methods of the Association of

Official Analytical Chemists[7]. Nitrogen was deter-

mined by Kjeldahl method and percentage nitrogen was

converted to crude protein by multiplying the value with

6.25[8]. Carbohydrate was determined by the difference

of the sum of all the proximate compositions from 100%.

The energy value was calculated using the Atwater fac-

tors 0f 4, 9, and 4 for protein, fat, and carbohydrate re-

spectively [9].

2.3. Determination of Thermal Properties

The specific heat capacity, thermal conductivity and

thermal diffusivity of the soups were determined as a

function of their proximate compositions by applying

additivity principles.

2.4. Specific Heat Capacity (Cp) and

Thermal Conductivity (K)

The above parameters were determined based on weight

fraction of water, fat, ash, protein and carbohydrate com-

ponent of food using the equations stated below[10].

1.424 1.5491.6750.8374.187

pcpf a

CXXXX w





0.580.1550.25 0.160.135

wpcf

kXXX Xa





2.5. Thermal Diffusivity

This was determined based on weigh t fraction of water,

fat, protein and carbohydrate component of food using

the equation stated below [11].

0.146 100.10 10

0.075 100.08210

DXX



 



X was the fraction of food component, and the sub-

scripts; w, f, p, c and a represented water, fat, protein,

carbohydrate and ash respectively.

St atistical Analysis

Data were reported as mean ± standard deviation. Sta-

tistical analyses were carried out using SPSS for Win-

dows, version14.0 (SPSS Inc. Chicago, IL.USA).

3. RESULTS

Table 1. Proximate composition of some selected nigerian soups.

Soups MC% CHON% Fat% Ash% CF% CHO% E(k/cal/10 g)

Ogbono 68.70 ± 0.14 18.70 ± 0.42 6.12 ± 0.11 4.55 ± 0.21 1.04 ± 0.60 1.90 ± 0.01 133.08 ± 0.60

Ewedu 88.60 ± 0.14 6.00 ± 0.01 1.05 ± 0.05 1.81 ± 0.01 1.47 ± 0.02 1.05 ± 0.04 34.27 ± 1.89

Ila 77.25 ± 0.35 15.94 ± 0.08 2.125 ± 0.04 1.90 ± 0.14 1.15 ± 0.07 1.475 ± 0.11 87.61 ± 3.31

Kuka 78.54 ± 0.06 8.80 ± 0.14 2.29 ± 0.01 2.09 ± 0.01 0.875 ± 0.02 7.415 ± 0.08 85.64 ± 0.17

MC = Moisture Content(% wb); CF = Crude Fibre(% wb); CHON = Protei n Content(% wb); E = Ener gy,k/cal/10 g.

R. A. Olayemi, A. Rahman / Agricultural Sciences 4 (2013) 96-99

Table 2. Thermal properties of some selected nigerian soups.

Soups CP( kJ/kg/K) K(W/m/K) D(m2/s)

Ogbono 3.3315 ± 0.00 0.4470 ± 0.00 1.22E-07

Ewedu 3.8505 ± 0.00 0.5295 ± 0.00 1.36E-07

Ila 3.5535 ± 0.01 0.4825 ± 0.00 1.28E-07

Kuka 3.5860 ± 0.00 0.4935 ± 0.00 1.30E-07

Cp = Specific Heat Capacity, KJ/ Kg/K; K= Thermal Conductivity ,W/m/K;

D=Thermal Diffusivity,m/s2

4. DISCUSSION

The results of the proximate compositions and thermal

properties of some selected nigerian soups were pre-

sented in Tables 1 and 2. The moisture content of the

soups determine their suitability to microbial attack and

hence spoilage [12]. The moisture content of “Ogbono”

(68.70 ± 0.14%) is lower than those of “Ila”,

“Ewedu”and “Kuka. This indicated that Ogbono with

lower moisture content, might have storage advantage

over others. Ash content is an index of mineral contents

in biota[13]. The observed ash content from the present

study ranged between 1.81 ± 0.01 to 4.55 ± 0.21%, with

Ogbono having the highest ash content. This could mean

that the minerals in Ogbono are higher th an that of others.

Proteins are important in the body due to their numerous

roles[14,15]. The protein content of the soups ranged

from 6.00 ± 0.01 to 18 .70 ± 0.42%, and Ogbono had th e

highest. Ewedu and Kuka with lower protein content

(6.00 ± 0.01% and 8.80 ± 0.14%) might not be able to

contribute significantly to the daily protein requirements

of 22 - 56 g [16]. Fats are saturated lipids at room tem-

perature[17,15] which are known to play protective roles

in the body system[12]. Some important fatty acids such

as omega-3-fatty acid, etc, are derived from fats. These

fatty acids are noted for their roles in the body system

[18].The crude fat content of the soups were in the range

of 1.05 ± 0.05 to 6.12 ± 0.11%. Variation in the fat con-

tents might be as a result of different quantities of exter-

nal red oil added to the soups as stated in the recipe book.

Adequate intake of dietary fiber can lower the level of

serum cholesterol and reduce the risk of developing hy-

pertension, constipation, diabetes, colon, cancer and

coronary heart disease [19]. The fiber content of the

soups ranged between 0.875 ± 0.02 to 1.47 ± 0.02%,

with having the highest fiber content. The recommended

dietary allowance (RDA) values of carbohydrate for

adults, pregnant and lactating mothers are 130 g, 175 g,

and 210 g respectively [15]. The carbohydrate content

and the estimated calorific value of the soups were very

low, but this is not a concern since they are been con-

sumed along with starch based dietary staples[4].

The thermal properties express the reaction of a sub-

stance when a change in temperature occurs. Specific heat

capacity determines the amount of heat a substance can

absorb [10]. The specific heat capacity obtained ranged

from 3.3315 ± 0.00 to 3 .8505 ± 0.00 kJ/kg/K. These val-

ues are slightly below the specific h eat capacity of water.

It has been proved that there is direct correlation between

the specific heat capacity and moisture content of food

product [20]. This implies that as the moisture content

increases, the specific heat capacity increases. This was

noticed in the soup samples, with Ewedu having the

highest moisture content and specific heat capacity. The

thermal conductivity of a material is a measure of its

ability to transmit heat[21,10].The thermal conductivity

estimated ranged between 0.4470 ± 0.00 and 0.5295 ±

0.00 W/m/K. Highest value was reported for Ewedu.

This connotes that ewedu will have a greater advantage

of absorbing and dissipating heat during processing and

storage than others. It was observed that thermal conduc-

tivity of food depended on the structure and chemical

composition of the sample and it increased with increas-

ing water content for all food products at temperature

above freezing [19]. Similar results were obtained in this

study for the thermal conductivity of soups. The thermal

diffusivity quantifies a material`s ability to conduct heat

relative to its ability to store heat [11].The results ob-

tained indicated that thermal diffusivity increased with

increase in moisture content, as it was observed in ther-

mal conductivity and specific heat capacity of the soup

samples.

5. CONCLUSIONS

The present study shows that the chemical composi-

tions and water fractions greatly influence the thermal

properties of sou ps.

The values of the thermal properties obtained shows

that the soups can considerably retain or dissipate heat

during canning and freezing.

REFERENCES

[1] Mepba, H.D., Eboh, L. and Banigo, D.E.B. (2007) Effects

of processing treatments on the nutritive composition and

consumer acceptance of some Nigerian edible leafy

vegetables. African Journal of Agricultural Nutrition and

Development, 7, 1-18.

[2] Shiundu, K.M. (2002) Role of african leafy vegetables

(ALVs) in alleviating fFood and nutrition insecurity in af-

rica. AJFNS, 2, 96-97.

[3] Hart, A.D., Azubuike, C.U., Barimalaa, I.S. and Achi-

newhu, S.C. (2005) Vegetable consumption pattern of

R. A. Olayemi, A. Rahman / Agricultural Sciences 4 (2013) 96-99 99

households in selected areas of the old Rivers State in

Nigeria. African Journal of Food, Agriculture, Nutrition

and Development, 5, No. 1.

[4] Kayode, F.O., Ozumba, A.U., Ojeniyi, S. Adetunji, D.O.

and Erukainure, O.L. (2010) Micronutrient content of se-

lected indigenous soups in nigeria. Pakistan Journal of

Nutrition, 9, 962 - 965. doi:10.3923/pjn.2010.962.965

[5] Oyelade, O.J., Odugbenro, P.O., Abioye, A.O. and Raji,

N.L. (2005) Some physical properties of African star ap-

ple (Chrysophyllum alibidum) seeds. Journal of Food

Engineering, 67, 435-440.

doi:10.1016/j.jfoodeng.2004.05.046

[6] FIIRO, (2006) Soup Recipe Book. Federal Institute of

Industrial Research, Oshodi, Nigeria.

[7] Association of Official Analytical Chemists (1990): Offi-

cial Methods of Analysis, Association of official chem-

ists,15th Edn.,Washington DC., Association of Official

Analytical Chemists, 10-30.

[8] Pearson, D. (1976) Chemical Analysis of Foods. 7th Edn.,

Church Hill Livingstone, London, UK., 72-73, 138-143,

488-496.

[9] Onwuka, G.I. (2005) Food analysis and instrumentation

(Theory and practice). 1st edn, Napthali prints, Surulere,

Lagos – Nigeria. 140-160.

[10] Singh, R.P. and Heldman, D.R. (2000) Introduction to

Food Engineering, Third Edition.Academic Press.

[11] Stroshine, R., Hamann, D.D.(1994) Physical properties of

agricultural materials and food products. Course manual,

Purdue University, USA.

[12] Olusanya, J.O. (2008) Essential of food and Nutrition.1st

edition Apex book limited, 36-76.

[13] Akubugwo, I.E., Obasi, N.A., Chinyere, G.C. and Ug-

bogu A.E. (2007) Nutritional and chemical value of ama-

ranthus hybridusL. leaves from Afikpo, Nigeria. African

Journal of Biotechnology, 6, 2833-2839.

[14] Uwakwe, A.A. and Ayalogu, E.O. (1998) Proteins, In:

Biochemistry (A tropical approach), FIUS Publishers,

Port Harcourt, 2, 44-45.

[15] Duru Majesty, K.C., Agomuo E.A. and Amadi, B.A.

(2012) Nutrient composition of “Nduduagworagwo”, a

traditional food of Akokwa people in Ideato North L.G.A

of Imo State, Nigeria.

[16] National Research Council (1975) Recommended daily

dietary allowance. Nutr. Rev, 31, 373-395.

[17] Kritchevsky, D. (1996) Food lipids and artherosclerosis.

Food lipids and health. Dekker, New York, 18-24.

[18] Obidoa, O., Joshua, P.E. and Eze, N.J. (2010) Phyto-

chemical analysis of Cocos nicifera L. Journal of

Pharmacy Research, 3, 280-296.

[19] Ishida, H., Suzuno, H., Sugiyama, N., Innami, S., Todoro,

T. and Maekawa, A. (2000) Nutritional evaluation of

chemical components of leaves, stalks and stem of sweet

potatoes (Ipomea betatas poir). Food Chemistry, 68,

359-367. doi:10.1016/S0308-8146(99)00206-X

[20] Lewicki, P.P. (2004). Water as the determinant of food

engineering properties. A review. Journal of Food Engi-

neering, 61, 483-495.

doi:10.1016/S0260-8774(03)00219-X

[21] Butts, C.L., Mishoe, J.W. and Chau, K.V. (1990) Meas-

uring the thermal diffusivity of soil. Transaction of ASAE,

33, 179-184.