Compositional Characterization of Endosperm (Guar Gum) of Six Guar (Cyamopsis tetragonoloba) Genotypes Grown in Sudan

Compositional Characterization of Endosperm (Guar Gum) of Six Guar

(Cyamopsis tetragonoloba) Genotypes Grown in Sudan

* Murwan K. Sabahelkheir and ** Abdelwahab H. Abdalla

* Department of Biochemistry, School of Biotechnology, Faculty of Science and Technology, Al Neelain University, Sudan

** Department of Agronomy, Faculty of Agriculture, University of Khartoum,

Sudan.

Abstract: This study was conducted in 1999, University of Khartoum. Six guar genotypes were selected from 45 genotypes grown in Sudan for study. The results revealed that the chemical compositions of endosperm of guar seed are as follow: 4.8-8.7% moisture, 3.5-5.0% protein, 0.5-0.9% ether extract, 0.5-0.8% ash, 1.4- 2.0% crude fiber and 83.3-87.5% carbohydrates while physical characters are:1.2337 refractive indices, 0.20-0.47 relative viscousty (distilled water as solvent), 0.37-.56 relative viscousty (4% NaCL as solvent), 5.0-7.0 pH, +20  to +76 specific rotation and 0.035-.0.050 optical density. Ash compositions of endosperm are: 13.000-19.000 ppm Potassium, 55.000-100.000 ppm Sodium, 2.500-13.000 % Magnesium, 15.000-22.000 % Phosphorus and 11.000-38.000 ppm Iron. The total available carbohydrates as mannose and galactose were ranged 67-73% and 28-33%, respectively. Ratio of mannose to galactose in the endosperm was 2:1.

Keyword: Guar, Endosperm, Mannose and Galactose.

1.0 Introduction

Guar seed (Cyamopsis tetragonoloba) composed of the hull (30 -33%), endosperm (27 -30%) and germ (43 -47%). The germ and hull of the guar seeds are known as guar meal, which rich in protein, hence used for the cattle feed. The germ has toxic effect but recently advanced research has been made on the germ to reduce its toxic effect and to make it suitable of animal consumption as a rich source of the protein (Murwan, 1999). The endosperm is commercially important part in the guar seed, as it is converted into powder gum. It contains 41% of the dry weight and acetone insoluble solids of the seed,

3 – 11% of the nitrogen and phosphorus. At least 75% of acetone insoluble solids of the endosperm are galactomannose and 12% being accounted for as pentosan, protein, pectin, phytin, ash and dilute acid insoluble residue (John, 1976).The guar crop is acquired an economic importance after the discovery of the gummy substance (Galactomannan) in its endosperm (Murwan, 2008) Galactomannans are composed of a b 1 – 4 mannan backbone with varying degree of  a 1 - 6 galactose substitution and are found in the cell wall of legume endosperm(Marten et al., 2001). Guar seeds are a rich source of mucilage or gum which forms a viscous gel in cold water and used as an emulsifier, thickener, stabilizer in a wide range of food and industrial application (Marina et al, 2007).Guar galactomannan has a mannose to galactose( M:G) ratio of  6:1 (Edwards et al, 1992). The pure mannan without galactose is completely insoluble in the water and the increasing of galactose substitution increase the solubility of the polymer by allowing it to become attended (Noble, 1986 and Stephen, 1983). The mannose to galactose ratio is 2:1, guar gum is insoluble in organic solvent, molecular weight range is 50.000 – 80.000 and gum is a white to yellowish white, nearly odourless, free flowing powder with a bland taste (Yoko, 2008). Objectives of this study were estimated the proximate analysis, physical characters, minerals contents, mannose, galactose, ratio of mannose to galactose and tannin content of endosperm of sex guar genotypes grown in Sudan.

2.0 Materials and methods

2.1 Collection and preparation of samples: Sex guar genotypes (X1H6, X1H7, X2H0, X2H4, X2H6 and X2H8) were collected from the Department of Agronomy, Faculty of Agriculture, and University of Khartoum, Sudan. The seeds of the sex guar genotypes were soaked in water for 12 hours and then hand pounded to separate the endosperm from the hull and germ. The separated endosperms were then dried at 105oC and then ground to pass 0.2 mm screen.

2.2 Chemical analysis: Protein, moisture, ether extract, ash, and crude fiber contents were determined as described by AOAC (1984).Carbohydrates content was determined by difference.

2.3 Physical analysis: Refractive indices, specific rotation, relative viscousty, pH value ad optical density were determined as described by AOAC (1990).

2.4 Ash composition: Minerals contents of endosperm were extracted according to method described by Pearson (1970).The measurement of minerals was done by using atomic absorption.

2.5 Total available carbohydrates: Total available carbohydrates content of endosperms were determined as described in Anthrone method by Clegg (1958).

Galactose and mannose dilution: 100mg of galactose were dissolved in 100 ml distilled water (1mg = 10 ml).Then 10 ml of strong galactose solution was dissolved in 100 ml distilled water to make the dilute galactose solution. The same procedure was done to make the dilute mannose

Anthrone reagent (0.1%):100 mg Anthrone was dissolved in 100 ml sulphuric acid (270 ml concentrated H2SO4 was dissolved in 300 ml distilled water).

Procedure: One ml from each dilute sample, galactose and mannose was pepetted into a series of test tubes 1, 2, and 3, respectively. Then 5 ml of the Anthrone reagent was added to each test tube, then content of each test tube was heated in water bath for 12 minutes and allow cooling to room temperature. Spectrophotometer was set up at 360 nm, so that the scale read zero with distilled water. Then the dilute sample, galactose and mannose were read.

CHO as galactose (mannose) % =    25 X B

S X A

Where: B = Reading of dilute sample, A = Reading of dilute galactose (mannose) and S = Weight of origin sample

2.6 Tannin content: Quantative estimation of tannin for each separated- endosperm was carried out using the modified vanillin-HCL in methanol method as described by Price et al (1978). A standard curve was prepared expressing the results as Catechin equivalent, i.e. amount of the catechin (mg/ml) which gives a colour intensity equivalent to that given by tannins after correction for blank.

2.7 Statistical analysis: A test of homogeneity for error variance for each variable was done according to Gomez and Gomez (1984).

3.0Results and discussion

3.1 Chemical composition: Table 1 illustrated the proximate composition of endosperm of six guar genotypes seeds. The moisture content of endosperm ranged from 4.8 – 8.7%, which is higher than those reported by Thomas (1980) and lower than those given by Stein, Hall and Co. (1962). The results revealed that there is highly significant difference in moisture content at level (p ?0.05).Protein content ranged 3.5 – 5.0%.The findings are in agreement with results given by Thomas (1980).These results indicated there is significant difference in protein content at level (p ?0.05).Ether extract of endosperm ranged from 0.5 – 0.9%, which within the range reported by Maria (1988).The findings indicated that there is significant difference at level (p ?0.05).The ash content ranged from 0.5 – 0.8%, which falls within range reported by Stein, Hall and Co. (1962).

The results revealed there is significant difference at level (p ?0.05).Crude fiber contents ranged from 1.4 – 2.0%, which is online with those range that given by Stein, Hall and Co. (1962).In addition to that there is no significant difference at level (p ?0.05).

Carbohydrates contents were varied from 83.3 – 87.5%, which is higher than values reported by Thomas (1980). The results revealed there is significant difference at level

(p ?0.05).

3.2 Physical characters: Table 2 illustrated the physical characters of endosperm of six guar genotypes seeds. The mean values of refractive indices are 1.2337. The results indicated that there is no variation in refractive indices at concentration 0.1mg/ 100 ml for the overall endosperms. Relative viscousty of endosperm ranged from 0.20 – 0.47(used water as solvent) and varied from 0.37 – 0.65 (used 4% NaCL as solvent).

It was found that relative viscousty, when 4% NaCL used as solvent, is higher than when distilled water used as solvent. This findings indicated that the relative viscosity is effected by the types of solvents The results indicated that there is significant difference in both distilled water and 4%NaCL at level (p ?0.05).pH values varied from 5.0 – 7.0, which fell within range reported by Whistler (1954).The findings indicated that there is significant difference at level (p ?0.05). Specific rotation ranged from + 20 to + 76.

In addition to that there is significant difference at level (p ?0.05). Optical density ranged from 0.035 – 0.050. The results revealed that there is significantly difference at level (p ?0.05).

3.3 Ash composition: Table 3 illustrated the ash composition of endosperm of six guar genotypes seeds. The mean value of Potassium ranged from 13.000 – 19.000 ppm.The findings indicated that there is no significantly difference at level (p ?0.05). Sodium content varied from 55.000 – 100.000 ppm. The findings revealed that there is highly significant difference at level (p ?0.05). Calcium mean ranged from 3.500 – 5.500 ppm, the results indicated that there is significant difference at level (p ?0.05). Magnesium content varied from 2.500 – 13.000 %. It indicated that there is highly significant difference at level (p ?0.05). The mean values of Phosphorus ranged from 15.500 – 22.000 %.The results revealed that there is highly significant difference at level

1. (p ?0.05). Iron content varied from 11.000 – 38.000 ppm. It was   revealed that there is highly significant difference at level (p ?0.05).

3.4 Total available Carbohydrates and tannin contents: Table 4 illustrated the total available carbohydrates and tannin content of endosperm of sex guar genotypes seeds. Total available carbohydrates as mannose ranged from 67 – 73% while the total available carbohydrates as galactose ranged from 28 – 33%. These results indicated that the mannose to galactose ratio is 2: 1, which is similar to those values given by Whistler (1954), Painter (1979) and (Yoko, 2008), but it is differ to value given by (Edwards et al, 1992).The tannin content ranged from 445 – 450 mg/100g. The similar results were reported for guar seeds soaked in water for different time intervals (Majed et al.2006).

1. In addition to that there is no significant difference at level (p ?0.05).

Conclusion: It is concluded that the variation in chemical, physical, ash composition, total available carbohydrate and tannin content is controlled by genetic or environment factors under which plant material were tested  

Acknowledgement: Authors extremely indebted to the soul of Dr. Karmalla K.A., Department of Food Science and Technology, Faculty of Agriculture, University of Khartoum, Sudan, to whom we express our enormous gratitude for his patience continuos guidance, meticulous and fundamental throughout this study.

Reference:

1. AOAC (1984). Official methods of Analysis.14th edition. Published by AOAC Inc. IIII North 19th Street.210 Arlington, Virginia 22209 USA.

2. A.OAC. (1990). Official Methods of Analysis 15th ed., Association of Official and Analytical Chemists. Washington, D.C.

3. Clegg K.M. (1958). In total available carbohydrates (Anthrone method) J.Sci.Agric., 7:40.

4. Edwards M. E., C.Scott, M.J.Gidley and J.S. Reid (1992). Control of mannose / galactose during galactomannan formation in developing legume seeds. Planta 1992; 187:67 -74, doi10; 1007/BF00201625.

5. Gomez T.P. and A.A.Gomez (1984). Statistical Procedure for Agriculture Research .John Wiley and Sons Inc.  New York, USA.

6. John H. M., G.N. William and F.W.Herman (1976).The Role of the Endosperm in the Germination of Legumes: Galactomannan, Nitrogen, Phosphorus Change in the Germination of Guar (Cyamopsis tetragonoba; Leguminosae). American Journal of Botany, 63(6), pp 790 – 797.

7. Majed B.A., A.H Rashed, E.A. Mohamed, B.H.Amro and E.B. Elfadil (2006) Proximate Composition , Ant nutritional Factors and Protein Fractions of Guar Gum Seeds as influenced by processing Treatment. Pakistan Journal of Nutrition 5(5):481 -484.

8. Marina N., I.T.Jerez, S.A., J.I.He, P.X.Zhao, R.A.Dixon, and G.D.May (2007). Analysis of cDNA libraries from developing seeds of guar (Cyamopsis tetragonoba (L.) Taub). BMC Plant Biology 7:62 doi:10.1186/471-2229-/7/62.

9. Marten J. J. Marcussen and J.Brunstedt (2001). In vivo modification of the cell wall polysaccharide galactomannan of guar transformed with a ? –galactosidase gene from senna.Molecular Breeding 7:211 – 219.

10. Murwan K.S. and A.H. Abdalla (2008). Yield and Yield Components of Forty Five Guar (Cyamopsis tetragonoba) Genotypes Grown in Sudan. Nile Basin Research Journal, 11(4); 48 -54.

12. Murwan K.S (1999).Improvement of Yield and Quality of Guar (Cyamopsis tetragonoba).Ph.D. Thesis, Department of Biochemistry, Faculty of Agriculture, University of Khartoum, Sudan.

13. Noble O., D.Perez, C.Rochas and F. Travel (989). Optical rotation of branched polysaccharides. Polymer Bulletin, 16:175 -180, doi, 10;1007/BF00955488./

14. Painter T.J, J.J. Gonzalez and P.C. Hemmer (1979).In study distribution of D- galactosyl in Guaran. Carbohyd. Res.69:2.

15. Pearson D. (1970). The Chemical Analysis of Food.Edn.by Egon H.., Kirk R.S., Sawyer, New York.

.16. Price M.L. and L.C. Butler (1980).Tannin and Nutrition .Station Bulletin No.272.Adriculture Experiment Station .Purdue University, West Lafayette.Indian

17. Stein, Hall and Co (1962). Jaguar guar gum Stein, Hall and Co, New York.

18. Stephen A. M., (1983).Other polysaccharides .In Aspinal G.O editor.

The polysaccharides, Vol. 2.New York Academic Press 1983; pp.97 -195.

19. Thomas T.A., B.S. Dabas and D.D.Chopra (1980).Guar gum has many uses. Indian Farming, 32(4): 7 – 10.

20. Whistler R.L. (1954).Guar gum, Locust bean, and others. In: Natural Plant Hydrocolloids. Pp. 45 – 50. American Chemistry Society, Washington, D.C.

21.. Yoko K. (2008). Guar Gum, Chemical Technical Assessment (CTA), 2008- Page 1(4).Ph.D. 69TH JECFA.

Table1: Proximate analysis of an endosperm (Guar Gum) of sex guar genotypes.

Parameters / Samples

Moisture

%

Protein

%

Ether extract

%

Ash

%

Crude fiber

%

Carbohydrates

%

X1H6

6.5

3.5

0.5

0.5

1.5

87.5

X1H7

7.4

4.5

0.9

0.5

1.4

85.3

X2H0

4.8

4.4

0.8

0.8

1.9

87.3

X2H4

8.7

4.0

0.7

1.3

2.0

83.3

X2H6

7.8

5.0

0.7

0.8

1.9

83.8

X2H8

6.8

5.5

0.7

1.0

1.4

84.6

* Each value is average of two replicates expressed on dry weight basis.

Table 2: Physical characters of endosperm (Guar Gum) of sex guar genotypes

Parameters / Samples

Refractive indices

Relative viscousty

pH

Specific rotation

Optical density

(water)

(4% NaCL)

X1H6

1.2337

0.47

0.48

5.0

+ 36

0.035

X1H7

1.2337

0.29

0.65

5.0

+ 76

0.035

X2H0

1.2337

0.33

0.45

5.0

+ 59

0.035

X2H4

1.2337

0.25

0.37

7.0

+ 75

0.050

X2H6

1.2337

0.47

0.64

6.0

+ 17

0.040

X2H8

1.2337

0.20

0.45

5.0

+ 20

0.040

* Each value is average of two replicates expressed on dry weight basis.

Table 3: Mineral contents (K, Na, Ca, Mg, P and Fe) of endosperm (Guar Gum) of sex guar genotypes

Parameters / Samples

K ppm

Na ppm

Ca ppm

Mg %

P %

Fe ppm

X1H6

16.000

65.000

5.500

7.500

15.500

11.000

X1H7

19.000

100.000

3.500

7.500

22.000

26.000

X2H0

19.000

65.000

3.500

2.500

19.000

11.000

X2H4

13.000

85.000

3.500

4.000

18.000

37.000

X2H6

16.000

75.000

4.500

13.000

17.000

38.000

X2H6

18.000

55.000

3.500

2.500

19.000

15.000

*Each value is average of two replicates expressed on dry weight basis.

Table 4: Mannose, galactose and ratio of mannose to galactose of endosperm (Guar Gum) of sex guar genotypes

Samples

X1H6

X1H7

X2H0

X2H4

X2H6

X2H6

Mannose (M) %

70

71

67

73

70

71

Galactose(G) %

30

33

33

28

30

29

M : G  ratio

2:1

2:1

2:1

2:1

2:1

2:1

Tannin content mg/100 g

445

450

450

445

430

450

* Each value is average of two replicates expressed on dry weight basis.