Performance of new maize (Zea mays L

Gezira j. of eng. & applied sci.3 (2) :52– 71(2008)

The Chemical Composition of Fenugreek (Trigonella foenum graceum L) and the Antimicrobial Properties of its Seed Oil Abdel Moneim E. Sulieman1, Heba E. Ahmed2and Awad M. Abdelrahim2 1

Department of Food Science and Technology, Faculty of

Engineering and |Technology, University of Gezira, Wad-Medani, Sudan 2

Center of Biosciences and Biotechnology, Faculty of Engineering

and Technology, University of Gezira ,Wad-Medani, Sudan,

ABSTRACT The present study investigated the chemical composition of fenugreek and the antimicrobial characteristics of fenugreek seed oil. The chemical analysis of fenugreek seed showed that the contents of moisture, fiber, ash, protein, fat and carbohydrates were 4%, 6.50%, 3.20%, 28.55%, 4% and 62.48%, respectively. The physiochemical characteristics of fenugreek seed oil were similar to the most edible oils. The inhibitory effect of fenugreek oil was tested against four microorganisms: three bacteria: Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium and one mould: Aspergillus niger The results indicated that the oil has a

Abdel Moneim E. Sulieman , Heba E. Ahmed & Awad M. Abdelrahim

potent antimicrobial activity against all tested microorganisms. The highest antimicrobial activity among the bacteria was detected against E. coli, where the inhibition zone diameter was 20 mm. However, the highest antimicrobial activity against all tested organisms was found against Aspergillus niger where a complete inhibition (100%) was recorded. The study showed the importance of fenugreek seed and its oil as an antimicrobial agent to be used as a food preservative or in medical industries. Keywords: Spices, fenugreek, chemical composition, antimicrobial property.

INTRODUCTION The history of herbs and spices is as long as the history of mankind. People have used these plants since earliest times. Some herbs have the power to change our physiological functioning, they have revolutionized medicine, and created fortunes for those who grow, process and treat them, and in many cases have assumed social and religious significance. Herbs have changed the course of history and in economic term have greater importance as ingredients in food, medicine, perfumery, cosmetics and garden plants (Brown, 1995). Many medicinal herbs are also grown for a range of purposes (Parry, 1969; Andi et al., 1997). 53

Chemical Composition of Fenugreek and the Antimicrobial Properties of its Seed Oil

Spices and herbs are used in foods to improve flavour, pungency and colour. They also have antioxidant, antimicrobial, pharmaceutical and nutritional properties. In addition to the known direct effects, the use of these plants can also lead to complex secondary effects such as salt and sugar reduction, improvement of texture and prevention of food spoilage. The basic effects of spices when used in cooking and confectionery can be for flavouring, deodorizing, masking, pungency and colouring (Ravindran et al., 2002). Some spices such as turmeric and paprika are used more for imparting an attractive colour than for enhancing taste (Ravindran et al., 2002). Fenugreek (Trigonella foenum-graecum) belongs to the family fabaceae. Fenugreek is used both as a herb (the leaves) and as a spice (the seed). It is cultivated world wide as semi-arid crop. In Sudan the seeds have many uses especially in folk medicine. Whole seeds are swallowed as antiacid and against dysentery and stomach disturbances. Also a special porridage (madidat-hilba) is made from wheat flour to which whole or ground fenugreek seeds are added for fattening women. It is also used by lactating women

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in a form of thin porridge (Gorafi, 1983).The objectives of the present study were : 1. To determine the chemical composition of fenugreek seeds grown in Sudan. 2. To evaluate the antimicrobial property of fenugreek seed oil.

MATERIALS AND METHODS The raw material Samples of fenugreek seeds were obtained from Rufa’a local market in (2006). The samples were taken from retailer’s store, in order to avoid the dust, dirt, loss of aroma and colour, which may occur as a result of exposure of the spices to the direct sun light. Proximate analysis The dried fenugreek seed samples were analyzed for the contents of moisture, protein, fiber, ash and fat according to the AOAC (1995) methods, the carbohydrates content was calculated by subtracting the previous components from 100. The experiments were made in triplicates, and then the means were calculated. Extraction of fenugreek oil The fenugreek seed oil was extracted by n-hexane according to AOCS (1971) method using soxhlet apparatus. The experiment was 55


repeated many times until reasonable amount was collected for further tests. Physicochemical properties of fenugreek oil The physicochemical analysis of fenugreek seed oil were determined according to the Standard Methods For Analysis of Fats, Oils and Derivatives (1979). These analysis included: acid value, saponification number (mg KOH/g of oil), ester value, free fatty acids (Oleic acid/ 100g oil) and the refractive index at 37°C. Antimicrobial property of fenugreek seed oil Sample preparation Different concentrations of fenugreek seed oil: hexane were prepared by dissolving the oil in n-hexane. These concentrations included 100% oil, 90% oil and 50% oil. Tested organisms The fenugreek oil was tested against one- gram positive bacterium Staphylococcus aureus, two gram negative bacteria Escherichia coli and Salmonella typhimurium, and one mould Aspergillus niger. The tested microorganisms were obtained from the Food Microbiology Laboratory, University of Gezira. Antibacterial property tests The cup – plate agar diffusion method (Kavanagh, 1972) was used 56


for the cultural test of fenugreek oil antibacterial property with minor modifications. Two ml of a standardized bacterial cells suspension (109 /ml) were thoroughly mixed with 200 ml of sterile molten nutrient agar, which was maintained at 40ºC, and then the medium was pouered into sterile Petri dishes, and left to solidify at room temperature. Sterile Whatman glass fiber filter discs were cut using a cork borer (No. 4) and saturated with the oil at different concentrations (50%, 90% and 100%) and placed centrally on the surface medium. Control discs were only saturated with sterile distilled water. The plates were then incubated at room temperature for 72 hours and the inhibition zones were measured each 24 hours as was described by Barry et al. (1970) and Cruikshank et al. (1975). Three replicates were carried out for each treatment. Antifungal property The method used was as described by Abdel-Rahim, et al. (1997).The potato dextrose agar (PDA) medium was dispensed in 100 ml conical flasks. The medium was sterilized by autoclaving, then poured in Petri–dishes and left to solidify at room temperature. Each solidified Petri dish was inoculated by a fungal growth disc cut by a sterile cork borer (8 mm diameter) from the edge of an actively growing culture of Aspergillus niger growth on 57


PDA. The inoculated Petri dishes were then incubated at room temperature for 3 days and every 24 hours the diameter of growth was measured. All treatments were done in triplicates.

RESULTS AND DISCUSSION Chemical composition of fenugreek seeds The proximate chemical composition of fenugreek seeds is shown in Table 1. The moisture content of fenugreek seeds was found to be 4.00%, this result is lower than that reported by Mounir et al. (1978) who found a value of 9.3%, and higher than the values reported by both Abdel Aal et al. (1985) and Pudayasekhara and Sharma (1987), who reported 3.4% and 2.4%, respectively. The variations in moisture content reported by various investigators could be attributed to the differences in the environmental conditions, the time of harvesting and the storage conditions as stated by Sulieman (1995). The crude fiber content of fenugreek seeds was 6.50%. This value is lower than the range 9.3%–11.97% and the value 10.4% reported by Haram (1991) and

Shankaracharya and Nalarjan

(1972), respectively. In contrast, the value found in the present study was nearly similar to that reported by Nour and Magboul

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(1986) who reported a value of 6.7% crude fiber content in Sudanese fenugreek seeds. The ash content of the fenugreek seeds was found to be 3.20%. This value was in a close agreement with that reported by Shankaracharya and Nalarjan (1972) which was 3.15%. On the other hand, the ash content obtained in the present work was lower than that recorded by Abdel Hamid et al. (1984) for the Egyptian fenugreek seed which was 7.6%. The variation in the ash content could be due to the variety of fenugreek or the soil conditions (Sulieman1995). The fenugreek seeds protein content was 28.55 %. This value was higher than reported by Wunschendroff (1919) and Shankaracharya and Nalarjan (1972) who found a value of 27% and 24.7%, respectively .These variations in the protein contents could be attributed to different cultural practices, soil and environmental conditions (Sulieman, 1995). The fat content of fenugreek seeds was found to be 4.00%. This result was lower than that reported by Abdel Hamid et al. (1984), Abdel Aal et al. (1985) and Sulieman (1995) who reported 7%, 7.6% and 8.04%, respectively.

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Fenugreek seed contained about 46.25% carbohydrates. This value was higher than that reported by Abdel Aal and Rahma (1986) and Haram (1991), who reported total carbohydrates in fenugreek seeds was 40.6 %, and 44%, respectively, and much lower than that reported by Yousif et al. (1973) who determined 60.01% carbohydrates in fenugreek seeds. Physico-chemical characteristics of fenugreek seed oil The physico-chemical characteristics of fenugreek seed oil are shown in Table 2. The acid value was found to be 4.75, the saponification value was found to be 195, the ester value was found to be (190.25), and the free fatty acids content was (2.38) The refractive index of fenugreek oil was found to be (1.4640). These values indicate that fenugreek seed oil can serve as an edible oil if its sharp odour being minimized. Table 1. Proximate chemical composition of the dried fenugreek seeds Parameter (%) Protein 28.55 Fat 4.00 Fiber 6.50 Ash 3.20 Moisture 4.00 Carbohydrates 46.25

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Table 2. Physico-chemical properties of fenugreek oil Acid value mgKOH/g of oil Saponification value mgKOH/g of oil Ester value Free fatty acid value (Oleic acid) /100g oil Refractive index (at 370C)

4.75 195 190.25 2.38 1.4640

Antimicrobial property of fenugreek oil The average of the diameters of the growth inhibitions zone obtained is shown in Tables 3 and 4. The results indicated that fenugreek oil has an antimicrobial activity against all tested microorganisms, because all of them were sensitive to fenugreek essential oil. Antibacterial property of fenugreek oils Fenugreek seed oil showed its higher antibacterial property against Escherichia coli (Table 3) where the inhibition zones were 20 mm when the concentration of fenugreek seed oil was 100%, while at 50% and 90% concentrations the antimicrobial activity was not detected (ND). We could’nt find reports in the literature regarding the effects of fenugreek oil as antibacterial agent. However, there are some reports about the effects of clove and ginger, James et al. (1999) reported that E.coli was sensitive to ginger and clove oil, while Krishna and Banerjee (1999) also reported that ginger, clove, cinnamon, cumin, onion and garlic 61


inhibited the growth of E.coli. They also stated that the bacterium ferments undigested carbohydrates causing flatulence. Badreldin (2006) reported that ginger oil inhibited the growth of E.coli with an inhibition zone of 23 mm which was higher than the inhibition zone of fenugreek essential oil. The present study showed that fenugreek seed oil has a potent antibacterial property against Staphylococcus aureus where the inhibition zone diameters were ND, ND and 15mm at 50%, 90% and 100% oil concentrations, respectively. The bacterial species of the genus staphylococci are widely distributed in the environment, these species cause food poisoning, such as cooked meat, eggs, fish, milk and milk products (Gugnani and Ezenwamze, 1985). Ginger oil showed antimicrobial activity against Staphylococcus aureus (Badreledin, 2006). While, ELboshra (2005) reported that Staphylococcus aureus was sensitive to clove oil, the inhibition zone was 22mm which was lower than that reported for the oil in the present study. The fenugreek oil was also found to inhibit Salmonella typhimurium, the inhibition zone diameters were ND , ND and 15 mm when the oil concentrations were 50 %, 90% and 100%, respectively. We could’nt find reports in the literature regarding the 62


effects of fenugreek oil against this bacterium, however, ginger oil and clove oil were reported to be effective against this bacterium (James et al., 1999; Badreldin, 2006; Elboshra, 2005). Table 3. The antibacterial property of fenugreek oil against the standard organisms. Oil concentration 50% 90% 100% S.a: Staphylococcus aureus. E.c: Escherichia coli. S.t: Salmonella typhimurim ND = Not detected

Inhibition zone Diameter (mm) S.a E.c S.t ND ND ND ND ND ND 10 20 15

Antifungal activity of fenugreek oil The results presented in Table 4 indicate that fenugreek seed oil caused complete inhibition (100%) of the growth of Aspergillus niger. Although no much work was reported in the literature, the present result is in harmony with many reports published by many workers about the use of essential oils as antifungal compounds. Hoffmans and Evans, (1911) were among the first to describe the preservation action of cinnamon and clove, these authors as well as others (Subba et al. (1967); Alderman and Marth, 1976; AbdelRahimi and Mohammed (2002) found that cinnamon, clove, lemon and oregano oils have inhibitory effect against Aspergillus 63


paraciticus, and Aspergillus niger was one of the most common species of the genus Aspergillus. It causes black mould on certain types of fruits. Table 4. The anti fungal activity of fenugreek oil on Aspergillus niger. Oil concentration 50% (w/v) 90% (w/v) 100% (w/v) ND = Not detected

Inhibition zone diameter (mm) ND ND Complete inhibition zone

CONCLUSION The chemical analysis carried out in this study showed that fenugreek seed contains high contents of protein and carbohydrates and low contents of fiber, ash and moisture. The microbiological analysis indicated that fenugreek oil has high antimicrobial activity against the tested organisms, especially Escherichia coil (among bacteria). On the other, the highest inhibitory effect of fenugreek oil was found against the fungus Aspergillus niger. However the inhibitory effect against the tested organisms was with the concentrated oil only. Therefore, it is highly recommended to use fenugreek seed oil in the food industry to improve the shelf-life of food as well as its use in medicinal and chemical industries.

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