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Physicochemical Variability of Shea Butter (Vitellaria paradoxa) from the Regions of Chad

Fidèle Paul Tchobo*, Ali Mahamat Seid, Guevara Nonviho, Reine Zinsou, Mouaimine Mazou, Andriano Jospin Djossou

Unité de Recherche en Génie Enzymatique et Alimentaire, Laboratoire d’Etude et de Recherche en Chimie Appliquée, Ecole Polytechnique d’Abomey-Calavi, Université d’Abomey-Calavi, 01 BP 2009, Cotonou, Bénin

Abstract: Shea seeds were collected in 8 regions of Chad and the butters of their almonds were extracted by refluxing with hexane. The quality index (acid, peroxide, iodine and saponification index), the acylglycerol and fatty acid compositions and the proportions of phenolic compounds and chlorophylls of these various butters were evaluated by standardized conventional methods. Chad Shea almonds are very rich in butters (average of 54.24 ± 4.89%), especially that of Mandoul (61.18%). These Shea butters have excellent quality index and contain high proportions of triacylglycerols (TAG: 76.15 ± 7.33%). The major TAGs are distearylolylglycerol (SOS: 49.17-54.43%), dioleylstearylglycerol (SOO: 32.29-35.70%), and dioleylpalmitylglycerol (POO: 3.57-4.66%). This profile revealed a minor content of Chad Shea butter in arachidic, gadoleic, and linolenic acid. However, Mandoul Region Shea butter has the highest proportion of phenolic compounds (7.24 mg GAE/100 g), relatively no chlorophyll was found.

Keywords: Shea butter, quality index, triacylglycerols, fatty acids, phenolic compounds

Received August 12, 2018; Revised October 03, 2018; Accepted November 12, 2018

Citation: Fidèle Paul Tchobo, Ali Mahamat Seid, Guevara Nonviho, Reine Zinsou, Mouaimine Mazou, Andriano Jospin Djossou, Physicochemical Variability of Shea Butter (Vitellaria paradoxa) from the Regions of Chad. American Journal of Food Science and Technology, 6 (6). 253-257. January 2018. doi:10.12691/ajfst-6-6-4

1. Introduction

In Africa, the forest is a diverse richness of Non-Timber Forest Products (NTFP). These contribute to the population’s food and economic balance. Thus, the Non-Timber Forest Products are traded extensively in local and international markets [1].

Shea butter (Vitellaria paradoxa C. F. Gaertn., or Butyrospermum paradoxum C. F. Gaertn or Butyrospermum parkii G. Don) is a Non-Timber Forest Products of the Sapotaceae family, known for its butter extracted from almonds. It exists under two subspecies: V. paradoxa Nilotica Kotschy (usually found between Sudan and Uganda, via the Democratic Republic of Congo) and V. paradoxa Paradoxa (C.F. Gaertner) Hepper. (Found in West Africa and in the southern reaches of Central Africa) [2].

The subspecies Vitellaria paradoxa paradoxa is widespread in Chad, where it plays a very significant socio-economic and nutritional role [3]. The transformation of Shea fruits into butter is mainly done through traditional methods and remains the main activity of women. This butter has a fatty acid profile identical to that of Pentadesma butyracea butter but different from the latter in unsaponifiables [4].

Given its physicochemical qualities sought in the fields of agri-food, the parapharmaceutical industry, cosmetics and soap, Shea butter are increasingly sought on the international market [5]. For this purpose, buyers’ requirements in terms of quality are based on certain parameters that make it possible to define their use [6,7]. As a result, the characterization of Shea butters and their functionality has attracted interest in scientific and technical research in many countries [8]. But, very few studies are done on Shea butter produced in Chad. To meet the requirements of the markets, it becomes imperative to conduct the study of the physico-chemical quality of Shea butter in this country. It is for this reason that the present study has set the overall objective of contributing to a better knowledge of the quality of Shea butter extracted from kernels from different regions of Chad.

2. Material and Methods

2.1. Plant Material

Shea fruits were collected in 8 regions in the southern part of Chad. These are Tandjile (Tan), Mandoul (Man), Logone Oriental (Lor), Logone Occidental (Loc), Mayo Kebbi West (Mao), Mayo Kebbi East (Mae), Moyen Chari (Moc) and N’Djamena (Chari-Baguirmi) (Ndj).

2.2. Methods

2.2.1. Oil Extraction and Quality Index

Samples of ground kernels (50g) were weighed and extracted four times with hexane (7 h) using a continuous Soxhlet extractor. The fat content was gravimetrically measured after removal of the solvent by rotary evaporation under vacuum. Extraction was run in triplicate (three times on 50g sample each) on the original iso kernels. For determination of acid, peroxide, iodine and saponification index, standard IUPAC methods were used.

2.2.2. Fatty Acid Analysis and Tryaclglycerols Profiles

Fatty acids and tryaclglycerols profiles were determined by the methods described by [9].

2.2.3. Acylglycerol Profile Determination

The acylglycerols were determined by the method described by [10] and using an automatic depositor (ATS4 Camag, Muttenz, Switzerland). Several standard concentrations of mono, di, triacylglycerols and free fatty acids were used for quantification.

The samples were deposited on silica plates (HPTLC, 20 × 10 cm, silica gel 60F). Elution was done with hexane/diethyl ether / acetic acid 70: 30: 1 (v/v/v) and developed using copper sulfate / acid / methanol / water solution (10: 1). 8: 5: 78, v/v/v/v) and heating the plate at 180 ° C for 10 min. The different compounds have been quantified at 550 nm with a TLC3 scanner (CAMAG, Muttenz, Switzerland).

2.2.4. Phenolic Content

To extract the phenolic compounds, 1 g of the oil was introduced into a tube, supplemented with 2 ml of n-hexane and 2 ml of 60% ethanol-water mixture. After homogenization, the mixture was centrifuged for 5 min at 3000 rpm. The hydroalcoholic phase containing the polyphenols was recovered. This procedure was repeated twice to exhaust the oil.

Total phenolic compounds were determined according to method used by [11] and gallic acid as a standard.

2.2.5. Determination of Chlorophyll Content

The chlorophyll pigments were determined by the method described by [12]. Thus, 7.5 g of the oil was weighed and dissolved in 25 ml of cyclohexane. Then the reading was made spectrophotometer at 670 nm.

3. Results and Discussion

3.1. Butter Extraction Yield and Their Quality Index of Butters

Table 1 shows the extraction yield, the quality index (acid, peroxide, iodine and saponification index) of the different Shea kernels of Chad.

The Shea kernels of the Chad regions have oil contents ranging from 44.42% (N’Djamena kernels) to 61.18% (Mandoul kernels) with an average of 54.24%. This value is higher than that reported by [13] for kernels (43.86%) from parts of Chad between 14º 19’34 “East, 9º 36’30" North and 18º 2’19 “East, 9º 3 ’56" North. It is also higher than that of kernels from Cameroon (29.7%) [14]. These variations in butter content may depend on factors such as the morphological characteristics of the kernels and their drying time [15].

The acid and peroxide index provided information on the degradation and conservation qualities of vegetable oils. If the acid number indicates the degree of degradation of the triglycerides during their storage, the peroxide index reflects their auto-oxidation and therefore their ability to preserve. The acid values of Shea butter from all eight regions of Chad are all low and below 0.25 mg KOH/g of butter. The highest value of these index was obtained with the Mayo Kebbi West sample (0.52 ± 0.00 meq O2/kg) and the lowest with the Logone Occidental sample (0.13 ± 0.02 meq O2/kg).

These Shea butters in Chad have acid and peroxide levels that are in line with the WAEMU standards for unrefined Shea butter [15].

The saponification index of butters varies from 144.85±1.39 (Moyen Chari) to 228.87±1.40 mg KOH/g (Mandoul). With the exception of the values of Moyen Chari (144.85), Tandjile (208.56), Mandoul (228.87) and Logone Occidental (228.67), all the others are close to the values obtained from butters. Marketed in Benin (186.43 to 193.74 mg KOH/g), and in Uganda (192.15 ± 1.99 mg KOH/g) [17].

The butters of Chad is therefore low in free fatty acids and can be used as raw material for the manufacture of foaming soaps as the oils of copra (max = 264) and palm kernel (max = 254) commonly used for these uses. The iodine index of Shea butter range from 29.73 ± 0.43mg I₂/100g (N’Djamena) to 30.64 ± 0.44g mgI₂/100g (Mayo Kebbi East).

Table 1. Extraction yield and quality index of Shea butter from the regions of Chad

Compared to commercialized Shea butters in Benin (48.07 to 50.26mg I₂/100g) [18] and those obtained by “Tchabal” manufacturing processes (71.9 mgI₂/100g) in Cameroon (58.8 mgI₂/100g), iodine levels of Shea butters in Chad are low and very close to those of cocoa butters (36.1 mgI₂/100g), Shea butter from Uganda (36, 6 ± 1.15 mgI₂/100g) and shea butter marketed in Ivory Coast (28.53 to 31.78 mgI₂/100g). They further show that Shea butters in Chad is highly saturated [17].

3.2. Acylglycerol Compounds, Triacylglycerols and Fatty Acid Profiles

The proportions of fatty acids (FA), monoacylglycerols (MG), diacylglycerols (DG) and triacylglycerols (TG) of the various butters samples were made by elution on TLC and the results obtained are shown in Table 2. Shea butters from Chad contain a high proportion of triacylglycerols TG (63.6-86.1%). The proportions of fatty acids vary from 6.2 (Moyen Chari) to 22.8% (Logone Oriental). Monoacylglycerols (3.4-8.0%) and diacylglycerols (0.4-3.6%) are present in relatively low proportions. The strong presence of TGs confirms the good conservation qualities previously observed for these butters based on their quality index.

Table 2. Proportion of fatty acids (FA), monoacylglycerols (MG), diacylglycerols (DG) and triacylglycerols (TG)

The compositions of these TAGs are defined in Table 3. It is observed that the Shea butters of the different regions studied contain ten molecular species of TAG (SLL, OOO, SLO, POO, POP, SOO, OOS, POS, SOS, SSO). In order of quantitative importance, we find the distearylolylglycerol whose rate is very high (SOS, Mayo Kebbi East: 49.17 at Moyen Chari: 54.43% with an average of 52.75±2.00%), the dioleylstearylglycerol (SOO, average of 34.12±1.20%) and dioleylpalmitylglycerol (OOP, average of 4.03 ± 0.39%).

Gunstone, [19] reported the proportions of SOS (42%) and SOO (26%) of lower Shea butter but the proportions of POP (3%), POS (6%), SOL (5%), and OOO. (6%) are higher. Similarly, Di-Vincenzo et al., 2005 mentioned that the proportions of SOS (Mali: 35.51-45.78%, Burkina Faso: 38.78-43.82%, Nigeria: 42.97-44, 59% and Uganda: 19.87%) and SOO (Mali: 23.74-29.07%, Burkina Faso: 26.02-29.32%, Nigeria: 24.18-26.02 % and Uganda: 33.39%) were still lower than those of Shea butter in this study.

There is evidence that the most important feature of cocoa butter use in chocolate is its important TG composition such as POP, POS, SOS [20]. Considering their rather diversified composition in TG, a study of a use of Shea butters of Chad as equivalents of cocoa butter in chocolate; could be initiated. Since the TG proportions of these Shea butter are close to those of P. butyracea butters “SOO” (35 and 45%), “SOS” (30.5-61.4%), “OOP” (0.2 -2.5%) [4].

This composition of TG prefigures a composition of Shea butter rich in oleic acids. This is evidenced by the results in Table 4

Table 3. Triacylglycerol (TAG) profiles of various Shea butter

Table 4 presents the proportions of 8 Shea Butters harvested in Chad in fatty acids. Shea butters from Chad is indeed rich in oleic acids (47.25%-55.21%), stearic (29.74%-39.48%), linoleic (6.01-8.64%) and palmitic (4.47% - 6.44%). Minor proportions of arachidic acids (1.03% - 1.54), gadoleic (N’Djamena 0.22% - 0.44%) and linolenic (0.10% - 0.19%) were also reported. The proportions of fatty acids <0.10% is considered as traces. These are unusual fatty acids in Shea butter like the heptadecanoic fatty acid (C17). Their proportion could be confirmed by complementary analyzes.

This fatty acid profile (mainly oleic-stearic and palmitic) of Shea butter from southern Chad is typical of this plant species harvested in Africa. However, the oleic acid content of the butters samples from Chad is lower than that of the samples extracted in Uganda (57.76%), but higher than those of the Shea butter of Mali, Burkina Faso and Nigeria which vary from 42 and 46.2% [21]. According to Derya, [22], these variations are due to the degree of maturity, genetic variation, climatic conditions, soil type and chemical compositions by Shea fruits.

Table 4. Fatty acid composition of shea butter from the Chad Regions

3.3. Levels of Phenolic Compounds and Chlorophylls

Phenolic compounds pass into butters during extraction [23]. Their presence is considered as natural antioxidants that protect the butters against oxidation since they give them a better stability during storage [24].

The content of phenolic compounds (Figure 1) expressed as a percentage of gallic acid (R2 = 0.9999, y = 0.0075x + 6E-05) of Shea butter varies from 1.62 to 7.24 mg. 100 g. The variations observed at these levels vary from 1.62 ± 0.00 to 7.24 ± 0.00 mg GAE/100g.

This phenolic content of Shea butter is similar to that found in some seeds [25].

3.4. Chlorophyll Content

The color of butters comes from natural substances such as carotene, xanthophyll and chlorophyll. These play an important role in determining the physical quality of the butter. They make it possible to characterize and estimate the level of purity of butters. Chlorophylls specifically are pigments related to oxidative phenomena by their catalytic actions, pro-oxidant (in the presence of light) and antioxidant (in the dark) [26]. The chlorophyll content of the butter samples from Chad is shown in Figure 2.

Unlike the higher proportion of this butter in phenolic compounds, Mandoul Shea butter has relatively no chlorophyll. The chlorophyll content therefore varies from 00 ± 0.00 to 0.12 ± 0 mg/kg (Logone occidental). There is a great variability of this chlorophyll composition from one region to another. This variation would depend on the stage of maturity of the seeds before harvest [22]. Because the concentration of pigments of the seeds would decrease with the ripening of the fruits [27].

Figure 1. Phenolic compound content of Shea butters (Tan: Tandjilé; Man: Mandoul, Lor: Logone oriental, Loc: Logone occidental, Mae: Mayo Kebbi Est, Mao: Mayo Kebbi Ouest, Ndj: N’djamena, Moc: Moyen Chari)

Figure 2. Chlorophyll content of Shea butter extracted from kernels harvested in Chad (Tan: Tandjilé; Man: Mandoul, Lor: Logone oriental, Loc: Logone occidental, Mae: Mayo Kebbi Est, Mao: Mayo Kebbi Ouest, Ndj: N’djamena, Moc: Moyen Chari)

4. Conclusion

Shea butter is a vegetable fat extracted from the fruit kernels of Vitellaria paradoxa, an oilseed that grows wild in the semi-arid areas of sub-Sahelian Africa. It is of great socio-economic and nutritional importance linked to its many virtues widely exploited locally and globally in the fields of agribusiness, cosmetics and traditional medicine. The evaluation of the physicochemical quality of butters from Vitellaria paradoxa seeds collected in Chad allowed us to characterize these different butters in order to meet the requirements of the markets and to solve the problem of lack of awareness of the quality potential of Shea butter in this country.

In view of the results, Chad’s Shea butter extracted by solvent has acid, peroxide and saponification iodine index in accordance with the standards of the West African Economic and Monetary Union (WAEMU) for non-Shea butters refined. These Shea butters from the point of view of fatty acid content, triacylglycerols, phenolic compounds, chlorophylls, unsaponifiables are very rich. Their presence in the Shea butters of Chad determines their stability and their antioxidant properties. From these results it can be concluded that Shea butters from Chad can be classified in the first quality that is to say, they are better able to meet the needs of the cosmetics, pharmaceutical and agribusiness industries and also be consumed directly.

References

[1]   | Tabuna, H, Le marché des Produits Forestiers Non Ligneux de l’Afrique Centrale en France et en Belgique: produits, acteurs, circuits de distribution, et débouchés actuels, CIFOR Occasional paper, 1999, (9). 32 P.
[2]   | Seid Ali, M., Tchobo, F.P., Maoudombaye, T., Mahamat Nour, S, Production process on the artisanal extraction output of Vitellaria paradoxa Gaaerterner butter in the southern part of Chad. International Journal of Innovation and Applied Studies, 2018, (23). 22-32.
[3]   | Hall, J.B., Aebischer, Tomlinson, D.P., Osei-Amaning, H.F.E., Hindle, J.R, Vitellaria paradoxa: A monograph, School of Agricultural and Forest Sciences, University of Wales, Bangor, U.K, 1996, 105. Pp.
[4]   | Tchobo, F.P., Natta, A.K., Barea, B., Barouh, N., Piombo, G., Pina, M., Villeneuve, P., Soumanou, M.M., Sohounhloue, D.C.K, Characterization of Pentadesma butyracea sabine Butters of Different Production Regions in Benin, J. Am. Oil Chem. Soc, 2007, (84), 755-760.
[5]   | Compaoré, P.N, Femmes, développement et transfert de technologies. Le cas des presses à karité au Burkina Faso. Montréal, Université de Montréal, Département de sociologie, thèse de doctorat non publiée, 2000.
[6]   | Lovett, P.N, Spécifications techniques et test au laboratoire pour le beurre de karité et les produits cosmétiques. Karité 2006, Explorting and qualitity 16-19 Aout 2006.
[7]   | Kassamba, Synthèse des techniques connues d’extraction et de conditionnement du beurre de karité au Burkina Faso, Rapport final ; projet filière karité du CECI / IRSAT, Ouagadougou, 1990, pp.3-9.
[8]   | N’koumam, Conservation des fruits du karité (Vitellaria paradoxa Gaertn.) et de l’aiéle (Canarium Schmeinfuurthii Engl.). Isothermes de sorption d’eau et extraction des matières grasses des fruits stockés, 2007.
[9]   | Tchobo, F.P., Natta, A.K., Barea, B., Barouh, N., Piombo, G., Pina, M., Villeneuve, P., Soumanou, M.M., Sohounhloue, D.C.K, Characterization of P. Butyracea sabine Butters of Different Production Regions in Benin. Journal of American Oil Chemistry Society, 2007, (84). 755-760.
[10]   | Kouteu, P.A.N., Blin, J., Bare, B., Barouh, N., Villeneuve, P, Solvent-Free Biodiesel Production Catalyzed by Crude Lipase Powder from Seeds: Eﬀects of Alcohol Polarity, Glycerol, and Thermodynamic Water Activity, J. Agric. Food Chem, 2017, (65). 8683-8690.
[11]   | Vasquez, R., Janer Del valle C., Janer Del Valle, M.L, Détermination de la teneur en polyphénols totaux dans l’huile d’olive, Grass y Aceites, 1973, (24). 350-357.
[12]   | Minguez, M.I., Rejano, J.L., Gandul, B., Higinio, A., Garrido, J, Couleur pigment correlation in virgin olive oil, Journal of the american oil chemists society, 1991, (68). 669-671.
[13]   | Akihisa, T., Kojima, N., Katoh, N., Ichimura, Y., Suzuki, H., Fukatsu, M., Maranz, S., Masters, E.T, Triterpene alcohol and fatty acid composition of shea nuts from seven African countries, J. oleo Sci, 2010, (59). 351-360.
[14]   | Maranz, S., Wiesman, Z., Bisgaard, J., Bianchi, G, Germplasm resources of Vitellaria paradoxa based on variation in fat composition across the species distribution range Agrofor, Sys. 2004, (60). 61-69.
[15]   | Womeni, H.M., Ndjouenkeu, R., Kapseu, C., Mbiapo, F.T., Parmentier, M., Fanni, J, Effet de la cuisson et du séchage des noix de karité (Butyrospermum parkii (G. Don Kotschy) sur la qualité du beurre, Tropicultura, 2006, (24). 175-182.
[16]   | Anonyme, Compte rendu de la réunion régionale inter gouvernementale et des experts sur l’établissement et l’harmonisation de normes régionales de l’Afrique pour l’amande et le beurre de karité, « Prokarité » 2006, pp 1-8.
[17]   | Ahouannou, C., Tchobo, P.F., Toukourou, C., Kougbadi, F., Soumanou, M.M, Influence des opérations thermiques impliquées dans les procédés traditionnels d’extraction du beurre de karité au Bénin, int. J. Biol. Chem. Sci, 2013, (7). 2151-2164.

[18]  
Honfo, F.G., Kerstin, H., Coulibaly, O., Tenkouano, A, Effet des conditions de stockage sur les qualités sanitaires et physicochimiques du beurre de karité. Présentation des résultats du projet amélioration de la qualité des produits agricoles au Bénin : Cas de l’anacarde et du karité. Cotonou, Benin, 2012.

[19]   | Gunstone, F.D, Vegetable Oils in Food Technology Composition, Properties and Uses, second ed. Willy-Blackwell, CRC Press, 2011, 291–343.
[20]   | Lipp, M., Anklam, E, Review of cocoa butter and alternative fats for use in chocolate part a. compositional data. Food Chemistry, 1998, (62). 73-97.
[21]   | Di-Vincenzo, D., Maranz, S., Arnaldo, S., Vito, R., Wiesman, Z., Bianchi, G, Regional Variation in Shea Butter Lipid and Triterpene Composition in four African Countries, J. Agric. Food Chem, 2005, (53). 7473-7479.
[22]   | Derya, O, Classification of Turkish virgin olive oils based on their phenolic profiles, Thesis (139 pages), Master of Science In Food Engineering Graduate School of Engineering and Science, Izmir institute of technology Turkish July 2008.
[23]   | Tanouti, K, Serghini-Caid, H, Amélioration qualitative d’huiles d’olive produites dans le Maroc oriental. Les technologies de laboratoires, 2011 Volume 6, n°22.
[24]   | Olivier, D., Boubault, E., Pinatel, C., Souillot, S., Guérère, M., Artaud, J, Analyse de la fraction phénolique des huiles d’olives vierges J. Annales des falsifications de l’expertise chimique et toxicologique, 2004, (965). 169-196. (Confirmer si l’auteur est Olivier dans le texte ou Ollivier).
[25]   | Maranz, S., Wiesman, Z., Garti, N, Phenolic Constituents of Shea (Vitellaria paradoxa) Kernels, J. Agric. Food Chem, 2003, 51). 6268-6273.
[26]   | Ranelli, B, Analytical evaluation of virgin olive oil of first and second extraction,, J. Agric. Food Chem, 1981, (47). 417-424.
[27]   | Grati, K.N., Khlif, M., Ayad, M., Rekik, H., Rekik, B., Hamdi, M.T, Evolution of oil characteristics with maturity of olives in Sfax: Chemlali variety, Acta Horticulturae, 1999, (474). 701-704.