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European Journal of Applied Sciences – Vol. 9, No. 6
Article Received: Sep 27, 2021
Article Published: Dec 25, 2021
DOI:10.14738/aivp.96.10989. N’dri, A. G. E. Y., Kouadio, I. A., & Koffi, M. K. (2021). Physicochemical Characterization of Agricultural By-Products: Case of the
Peelings of Varieties of Yams Produced in Côte d’Ivoire. European Journal of Applied Sciences, 9(6). 54-65.
Services for Science and Education – United Kingdom
Physicochemical Characterization of Agricultural By-Products:
Case of the Peelings of Varieties of Yams Produced in Côte
d’Ivoire
Armand Gildas Elvis Yao N’dri
Laboratory of Biotechnologies, Agriculture and Biological Resources
UFR Biosciences, University Felix HOUPHOUËT-BOIGNY
22 BP 582 Abidjan 22 Côte d’Ivoire
Irène Ahou Kouadio
Laboratory of Biotechnologies, Agriculture and Biological Resources
UFR Biosciences, University Felix HOUPHOUËT-BOIGNY
22 BP 582 Abidjan 22 Côte d’Ivoire
Mathias Kouamé Koffi
Laboratory of Biotechnologies, Agriculture and Biological Resources
UFR Biosciences, University Felix HOUPHOUËT-BOIGNY
22 BP 582 Abidjan 22 Côte d’Ivoire
ABSTRACT
In this study, the physicochemical characteristics of the peelings of three varieties
of yam commonly called "Bètè Bètè". "Krenglè" and "Kponan" which are the most
consumed in Côte d'Ivoire were evaluated in order to contribute to the
determination of the nutritional value of this fraction of these yams which is very
often thrown away as household waste. Known standard methods were used for this
physicochemical characterization. The results obtained show that the peelings of
the variety "Kponan" are the richest in fat (2.33% ± 0.02), carbohydrates (82.95%
± 0.02) and fiber (1.58 % ± 0.01). On the other hand, the highest proteins content
(8.05% ± 0.1) was observed in those of the variety “Bètè Bètè”. This protein content
is also higher than those observed in the flesh of yams. For major minerals such as
magnesium and iron, the highest levels were observed in the peelings of the variety
“Krenglè”. Those of the variety “Kponan” are the richest in potassium. On the other
hand, the peelings of the variety “Bètè Bètè” are the richest in calcium. These yam’s
peelings could thus be transformed for use in times of scarcity to fight against
Hunger.
Keywords: Yam, peelings, dry matter, moisture, macronutrients, micronutrients
INTRODUCTION
Yam is a tuberous plant of the botanical genus Dioscorea, containing more than 600 species
present in tropical zones [1]. World production was estimated at 71 million tons in 2017 [2]. It
represents the staple food for over 500 million people in various tropical countries in Africa,
the Caribbean, Oceania and Latin America [3]. This world production of yam is dominated by
farmers from West Africa (Nigeria, Ivory Coast, Ghana, Benin and Togo) [4]. Indeed, they
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N’dri, A. G. E. Y., Kouadio, I. A., & Koffi, M. K. (2021). Physicochemical Characterization of Agricultural By-Products: Case of the Peelings of Varieties
of Yams Produced in Côte d’Ivoire. European Journal of Applied Sciences, 9(6). 54-65.
URL: http://dx.doi.org/10.14738/aivp.96.10989
produce more than 90% of the yams cultivated in the world [4]. This tuber is one of the most
popular main foods in West Africa [5]. It is the leading food crop in the Ivory Coast with an
annual production estimated at 7.148 million tons [2]. This country is also the second largest
producer of this commodity in the world after Nigeria [6]. Thus, despite the importance of post- harvest losses, yams and cassava are the only food crops for which Côte d’Ivoire can display a
status of food self-sufficiency [7].
This production is generally intended for human consumption in various forms (porridge,
mash, fried and braised). The consumption of this tuber in Côte d’Ivoire is high and is estimated
at 120 kg / inhabitant / year [8]. However, the various forms of yam consumption do not involve
its peelings. They are classified as household waste. They represent a loss of 18 to 30% of the
weight of fresh yam. Despite the wide availability of yam peelings, the lack of interest shown in
this fraction of this tuber limits the scientific data and the fields of use of the latter. To make up
for this deficit, specific studies on yam peelings are necessary with a view to enhancing the
value of this fraction of this tuber. In this perspective, studies have shown the use of yam
peelings in sheep farming in Benin [9] and in Côte d'Ivoire [10].
The present study thus proposes to determine the physicochemical characteristics of the
peelings of three varieties of yams widely consumed in Côte d'Ivoire in order to help determine
the nutritional value of this fraction of this tuber thrown as household waste.
MATERIAL AND METHODS
Biological Material
The biological material was the peelings of yams. For this study, three varieties of yam more
consumed in Côte d’Ivoire were used [11]. Two of these varieties namely «Kponan» and «
Krenglè » belong to the species Dioscorea cayenensis-rotundata and the other one namely «Bètè- bètè» belongs to the species Dioscorea alata (Figure 1). For each variety of yam three samples
of 1 kg each were taken and the peelings were collected to form batches of peelings. These
batches were analyzed to determine their physicochemical characteristics.
Methods
Determination of the physicochemical characteristics of yam’s peelings
Determination of the moisture content and dry matter content of yam’s peelings
The moisture content and that of the dry matter were determined according to AOAC Standard
950.01 [12]. The yam peelings were grated using a stainless steel knife and then mixed to obtain
a homogeneous sample. From this, a test sample of 100 g was placed in a box of mass (m0) and
the whole was weighed to give the mass (m1). The box containing the sample was then placed
in a MEMMERT brand oven at 105 ° C +/- 5 ° C until a constant mass was obtained. After baking,
the sample was allowed to cool before being reweighed to give the mass (m2). This same
operation was carried out for the three varieties of yams studied.
The results were calculated for three replicates and were expressed in g / 100 g. The humidity
content was given by the following formula:
Dry matter content:
Humidity = [(m1 – m2) / (m1 – m0)] × 100
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European Journal of Applied Sciences (EJAS) Vol. 9, Issue 6, December-2021
Services for Science and Education – United Kingdom
m0 = mass of the box
m1 = mass (box + sample) before baking
m2 = mass (box + sample) after baking
Determination of proteins content of the peelings of yam
The method used for the determination of proteins content was the standard ISO 5983-1:2005
[13] (method of Kjeldahl). This analysis consisted in digestion by heating the sample (leaves or
leaves fortified by peanut paste) in the presence of sulfuric acid, anhydrous sodium sulfate and
copper. The solution in the digestion flask is then made alkaline by addition of sodium
hydroxide. The nitrogen content is then estimated by titration of the ammonium borate formed
with standard sulfuric. The nitrogen concentration of the sample was determined using the
following equation:
Where vs and vb are the titration volumes of the sample and blank, and 14g is the molecular
weight of nitrogen N. Once the nitrogen content has been determined, it is converted to a
protein content:
Three essays were done.
Determination of raw ash content of the peelings of yam
The raw ash contents was determined by method ISO 2171:2007 [14]. The sample (leaves or
leaves fortified by peanut paste) was dried in an incubator at 103 ̊C until constant weight. The
dried sample was then burned at 500 °C. Three essays were done. The ash content was
expressed on dry basis:
MASH is the mass of ash and MDRY is the mass of dried sample obtained after drying until constant
weight of the sample.
Determination of fibers content of the peelings of yam
The method used for the determination of the fibers content was the standard NF V 03-
040:1993 [15]. This method consisted firstly in enzymatic digestion of the sample (peelings of
yam) by α-amylase. The homogenate obtained was precipitated and filtrated. The residue
obtained was used for ash analysis.
The fibers content = Weight (residue) – Weight (ash + proteins). Three essays were done.
Determination of lipids content of the peelings of yam
The lipids content was determined by the method of the settlement CE N° 152/2009 of
European Union [16]. The extraction was made in Soxhlet extractor used hexane at 68 °C for 12
Dry matter content (%) = 100 - Humidity
% proteins = F. % N. Where F=
6.25.
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N’dri, A. G. E. Y., Kouadio, I. A., & Koffi, M. K. (2021). Physicochemical Characterization of Agricultural By-Products: Case of the Peelings of Varieties
of Yams Produced in Côte d’Ivoire. European Journal of Applied Sciences, 9(6). 54-65.
URL: http://dx.doi.org/10.14738/aivp.96.10989
hours. The solvent was then removed from the extract in a rotary evaporator at 40 °C under
vacuum. The amount of lipid recovered was determined as below:
Mass of lipid = (weight of the flask + boiling chips + extracted oil) − (weight of the flask + boiling
chips).
The lipids content was then determined as below:
Lipid content (%) = mass of lipid extracted (g)/sample weight (g) × 100.Three essays were
done.
Determination of carbohydrates content of the peelings of yam
The carbohydrates content of the peelings of yam was obtained by the difference between the
dry matter content and the sum of the protein, lipid, fibers and raw ash contents of the sample
[17].
Determination of the minerals content of the peelings of yam
The atomic absorption spectrometric method (standard ISO 6869: 2000) [18] was used for the
determination of calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn),
potassium (K), sodium (Na), Cobalt (Co), Chrome (Cr) and zinc (Zn) ). For this study, the
samples were digested by microwave. The contents of minerals were determined by
Absorption/flame atomic emission spectrometer VARIAN Spectra AA 110. The standard
minerals from Central Laboratory of Food Hygiene of LANADA (Abidjan, Côte d’Ivoire) were
used for quality control. For each mineral, three essays were done.
Statistical analysis
The statistical analysis of data was made by Analysis of Variance (ANOVA) using 5% level of
significance. The statistical package used was IBM SPSS Statistics version 20. Tukey's Multiple
Comparison test was used to identify these differences.
RESULTS AND DISCUSSION
Physicochemical characteristics of the peelings of the three varieties of yam
Physiques characteristics
Peelings yield of obtained
The peelings yield obtained for the three varieties of yam are similar. Indeed, the statistical
analysis carried out showed no significant difference between these yields (P> 0.05). The values
obtained were, 25% ± 1, 25% ± 1 and 24% ± 1 respectively for the peelings of the varieties of
yam "Bètè Bètè", "Krenglè" and "Kponan" (Table I).
Moisture content and dry matter content of yam’s peelings
The moisture content of the peelings determined are significantly different (P <0.05). These
humidity levels are 5.94% ± 0.03, 7.88% ± 0.03 and 4% ± 0.02 respectively for the peelings of
the varieties "Bètè Bètè", "Krenglè" and "Kponan" ( Table I). Moreover, the peelings of the
variety "Krenglè" have the highest moisture content. These results show that the peelings of
yam are poor in water unlike whole tubers. Indeed, some authors have shown that yam tubers
have a high moisture content [17]. These authors obtained a moisture content of 77.3% in fresh
tubers of yam of D. alta and 65.7% in fresh tubers of yam of the species D. cayenensis-rotundata