Evaluation of Antioxidant Potential of Monodora Myristica (African Nutmeg)
Chapter One
SIGNIFICANCE OF RESEARCH
The aim and objective of this research is to:
- To carry solvent extraction of Monodora myristica
- To investigate the antioxidant effect of Monodora myristica extract on palm kernel oil and palm oil at different environmental conditions.
CHAPTER TWO
LITERATURE REVIEW
AFRICAN NUTMEG
Scientific Classification
Kingdom: Plantae
Phylum/Division: Spermatophytae
(unranked): Angiosperms
(unranked): Magnoliids
Order: Magnoliales
Family: Annonaceae
Genus : Monodora
Species: myristica
Binomial name
Monodora myristica (African nutmeg)
Habitat/Ecology of Monodora myristica
Monodora myristica is tropically distributed. It is cultivated in East India, Malaysia, Sri Lanka, West lndies and Africa. It could be propagated by stem culturing and budding (Okafor, 2003). The Monodora species are also found in West Africa and are cultivated in the southern parts of Nigeria. The trees are very common in Anambra, Abia, Delta, and Enugu States.
Local Names
The plant is usually called Orchid flower and is also referred to as and called:
Ehuru – lgbo name
Ehinawosin – lkale name
Lakosin – Yoruba name
Uyenghen – Edo name
(Keay, 1989)
Characteristics/Morphology of Monodora myristica
Monodora myristica, commonly known as calabash nutmeg, ehuru, Jamaican nutmeg, nuscade de Calabash, ariwo, airama, African nutmeg and African orchid nutmeg is a tropical shrub of the Annonaceae or custard apple family of flowering plants (Okafor, 2003). The flowers of Monodora myristica look very much like those of an orchid (hence the common name of ‘African orchid nutmeg’), and the fruit is a nearly spherical drupe about the same size as an orange. The seeds and seed coats of the plant are used as a spice. The fruit contains a number of these aromatic seeds embedded in a yellow pulp (Oguntinein et al., 1999).. The seeds and their seed coat are removed and dried giving a heart-shaped spice some 3cm long and 2cm broad at its widest part. Once dried these have an aroma reminiscent of nutmeg and are sold whole to be grated as a nutmeg substitute (Talalaji, 1999).. At one time it was widely sold as an inexpensive substitute for nutmeg, although this practice is less common today outside its region of production (Nigeria). Calabash nutmeg has a nutmeg-like flavour with a pungent overtone. The whole seed coat and seed is either ground and used as a seasoning for West African soups or stews or is ground and used as a nutmeg-like flavouring in cakes and desserts. As well as yielding calabash nutmeg the seed coat is often removed and the inner true seed is sold as ehuru or ehiri (its name in igbo language, a Nigerian language).
CHAPTER THREE
MATERIALS AND METHODS
Equipments / Apparatus Maker
weighing balance (triple beam balance) Larle ®
Analytical balance, Ohaus scale corporation
Labouratory dry oven (hot air oven) DHG 9101 Model
Uv-Vis Spectrophotometer Lemfield
Water bath 801A Model
Volumetric flask Permagold
Measuring cylinder, Beaker, Simax
Cornical flask, burette
Soxhlet extractor, Heating mantle, Pyex
Extraction thimble, Condenser,
pH meter Hannah microprocessor
Filter paper Whatman
Mortar and pestle
Procedurement Of Raw Materials
The selected indigenous spice, African nutmeg (Monodora myristica) was purchased from ogbete main market in Enugu state of Nigeria and identified by Dr. B.C. Ndukwu (a plant taxonomist) of department of plant science and biotechnology, University of Port Harcourt and was furtherly authenticated by Dr Charles N. Ishiwu of Department Of Food Science And Technology, University of Nigeria, Nsuka and also a senior lecturer in Biochemistry Department of Caritas University, Enugu state.
One purchase, the spices (seeds) were collected into sterile glass desiccators and stored in an oven maintained at 70ºC until use.The spices (dried samples) were estimated to have been in the market for 6-7days before purchase.
CHAPTER FOUR
RESULTS AND DISCUSSION
The mean acid value (AV) for free fatty acid and thiobarbituric acid (TBA) values of tested oil sample are shown in Table 3 – 6, respectively. Data for the tested oil samples were obtained by measuring samples from the same producer in triplicate. Mean values in Table 3 – 6 are followed by lists those pairs of weeks, between which statistically significant difference exists.
Tables 3 and 4 respectively showed the Acid Values (AV) of free fatty acid, while tables 5 and 6 showed the thiobarbituric acid values (TBA) of crude palm kernel oil and palm oil stored with varying concentration of 0.2%-1.0% of n-hexane extract of Monodora myristica seed, stored in the sun and in the room. The trend observed above for AV was also the same with that of TBA in all the storage conditions only that the AV values were higher than that of TBA. Ihekoronye and Ngoddy (1985) reported that the AV of any lipid were both measure of hydrolytic rancidity and that the lower their values, the slower was the rate of hydrolytic rancidity. Hence crude palm oil stored with varying concentration of 0.2%-1.0% extract of Monodora myristica seeds were less prone to oxidative rancidity. This showed that the extracts at varying concentration demonstrated high antioxidant activity. However the antioxidant activity was higher as concentration of Monodora myristica extract increases at both environmental conditions.
CHAPTER FIVE
SUMMARY AND CONCLUSION
The study results favoured the highest concentration of treatment and storage of the tested oil samples at the different environmental conditions.
Recently, the determination of PV in commercial oils was assessed by the modern Infrared Spectroscopy (IR) (Yildiz et al., 2002); which can also be extended to the determination of AV in butter. The theoretical principle of IR had been reported earlier (Koczoñ et al., 2001, 2003, 2006) and the technique finds application in the food analysis (Ismail et al., 1993; Chippie et al., 2002; Guillen and Cabo, 2002; Tay et al., 2002; Van de Voort et al., 2004) and significantly less number for monitoring of chemical changes in foods (Quilitzsch et al., 2005).
Fats and oils are quite unstable substances. When stored for any considerable length of time, especially when the temperature is high and the air has free access to them, they deteriorate and spoil. In this respect different fats differ markedly. Some spoil very much more rapidly than others. Among the various fats, spoilage takes the form of rancidity. The fat acquires a peculiarly disagreeable odor and flavor. A vast amount of scientific research has been carried on to determine the cause and nature of rancidity, but investigators are far from agreement on the subject. For present purposes it is sufficient to point out that spoilage of a fat, usually identical with rancidity, is accompanied by partial splitting of the fat into glycerin and fatty acids. The glycerin disappears, or at any rate is unobjectionable, but the fatty acids remain dissolved in the fat, give it an acid reaction, and contribute to its objectionable rancid flavor. The rancidity of a given parcel of fat is not necessarily the result of long storage under unfavorable conditions. The fat may have been spoiled and rancid from the moment of its production. This will inevitably be true when the materials from which it was produced have undergone decomposition. Thus the fat obtained from putrefying carcasses will be rancid and so will the oil expressed from fermented cottonseed. In other words, to obtain a sound and sweet fat, the raw material must be sound and sweet; it must be worked up speedily before it has had time to decompose; and this must be done under clean and sanitary conditions. The fat thus obtained must be stored under favorable conditions and its consumption cannot be too long delayed. These conditions it is difficult to obtain in many of the less civilized portions of the world, especially in the tropics, where many fat- and oil-yielding raw materials are produced. Hence fats and oils made at the source of the raw materials may be less sound than those produced at or near the place of consumption.
All oils are fats, but not all fats are oils. They are very similar to each other in their chemical makeup, but what makes one an oil and another a fat is the percentage of hydrogen saturation in the fatty acids of which they are composed. The fats and oils which are available to us for culinary purposes are actually mixtures of differing fatty acids so for practical purposes we’ll say saturated fats are solid at room temperature (20C) and unsaturated fats we call oils are liquid at room temperature. For dietary and nutrition purposes fats are generally classified as saturated, monosaturated and polyunsaturated, but this is just a further refinement of the amount of saturation of the particular compositions of fatty acids in the fats.
Connoisseurs of good edible palm oil know that the increased FFA only adds ‘bite’ to the oil flavour. At worst, the high FFA content oil has good laxative effects. The free fatty acid content is not a quality issue for those who consume the crude oil directly, although it is for oil refiners, who have a problem with neutralization of high FFA content palm oil.
Oxygen is eight times more soluble in fats than in water and it is the oxidation resulting from this exposure that is the primary cause of rancidity. The more polyunsaturated a fat is, the faster it will go rancid. This may not, at first, be readily apparent because vegetable oils have to become several times more rancid than animal fats before our noses can detect it. An extreme example of rancidity is the linseed oil (flaxseed) that we use as a wood finish and a base for oil paints. In just a matter of hours the oil oxidizes into a solid polymer. This is very desirable for wood and paint, but very undesirable for food.
Antioxidants are often added to fat-containing foods in order to retard the development of rancidity due to oxidation. Natural anti-oxidants include flavonoids, polyphenols, ascorbic acid (vitamin C) and tocopherols (vitamin E).
Synthetic antioxidants include butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl 3,4,5-trihydroxybenzoate also known as propyl gallate and ethoxyquin.
The natural antioxidants tend to be short-lived, so synthetic antioxidants are used when a longer shelf life is preferred.
The effectiveness of water-soluble antioxidants is limited in preventing direct oxidation within fats, but is valuable in intercepting free radicals that travel through the watery parts of foods.
A combination of water-soluble and fat-soluble antioxidants is ideal, usually in the ratio of fat to water.
In addition, rancidification can be decreased, but not completely eliminated, by storing fats and oils in a cool, dark place with little exposure to oxygen or free radicals, since heat and light accelerate the rate of reaction of fats with oxygen. (Oxidative rancidity or autooxidation is a chemical reaction with a low activation energy consequently the rate of reaction is not significantly reduced by cold storage)
LIMITATIONS
There were limitations to the present study which were barriers in achieving ideal experimental conditions.
The current study was conducted on limited parameters of tested intervals and constant temperature, the ranges for the interval for test at the tropical environmental conditions may have been varied. Therefore the present study did not show the significant stability of the tested oil samples.
FUTURE RECOMMENDATIONS
- PalmOilTester which is a fast, user-friendly and reliable testing system for crude and refined palm oil is recommended as it enables the determination of acidity (FFA), DOBI & Carotene content, the values of Peroxide (PV), anisidine (AnV) and iodine (IV) in few minutes.With its simplicity, PalmOilTester is ideal to performe analysis during every production stages in palm oil industry to monitor the quality of oil in real time, from the oil mill to the refinery plant, during the acceptance and storage phases, as well as during trading of finished products.Several comparative studies have demonstrated that the analytical accuracy of PalmOilTester matches that of AOCS/MPOB reference methods, with the advantages that PalmOilTester is easier to use and outputs results much faster.
- The use of apparatus called Rancimat is recommended to calculate effect of antioxidant on oil and fat, though other methods like used for determination of rancidity are Peroxide value ( Primary Oxidation) and Anisidine value( Secondary Oxidation) in fat or oil .Peroxide value provides the extent of rancidity present in the oil.Peroxi de value is found by formation of iodine when oil or fat are
reacts with iodine ion. Totox value are also used to check the quality of oil and fat . Totox Value = Anisidine value + 2x Peroxide value. Thiobarbituric acid value also provides useful information on oxidative level of rancid oil.
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