Determination of the mineral compositions of some selected oil-bearing seeds and kernels using Inductively Coupled Plasma Atomic Emission Spectrometry ( ICP-AES )

La finalidad del trabajo es establecer el contenido en elementos minerales de semillas oleaginosas tales como ca cahuetes, trementina, avellana, sesamo, maiz, almendras, girasol, utilizando ICP-AES. Se han observado diferencias significativas en la composición de minerales entre cosechas. Todas las semillas contienen cantidades elevadas de Al, Ca, Fe, K, Mg, Na, P y Zn. Los contenidos de B, Cr, Cu, Li, Ni, Sr, Ti y V, sin embargo, fueron bajos. Los contenidos de K y P en todas las semillas estudiadas fueron superiores a las de otras semillas. El contenido medio de K osciló entre 1.701,1 mg/kg (maiz) a 20.895,8 mg/kg (soja), el P entre 3.076.9 mg/kg (trementina) a 12.006.5 mg/kg o 2.617,4 mg/kg (semilla de algodón), y Ca de 68,4 mg/kg (maiz) a 13.195,7 mg/kg (adormidera). Estos resultados indican que los valores obtenidos pueden ser interesantes para deducir informaciones nutricionales de las mismas. En particular, los resultados muestran que las semilla de soja, piña y adormidera representan una buena fuente de K, P y Ca, respectivamente mientras que los piñones tienen un contenido elevado de Zn.


INTRODUCTION
A number of mineral ions are recognized as essential plant nutrients that are directly incorporated into organic compounds sythesized by the plant.Of these, potassium, phosphorus, calcium, magnesium and sodium are the most important quantitatively and are recommended for composition analysis (Anonymous 2004b).Recently, the significance of oil-bearing seeds and kernels in the nutrition of human populations is increasing for several reasons.The seeds of oil-bearing crops (sunflower, corn, peanuts, hazelnut, walnut, mustard, black cumin, soybean, sesame etc.) have several food value and curative properties (Özdemir et al., 2001;Özcan, 2004;Glew et al. 1997;Anonymous 2004a).Sunflower seeds are probably the most familier of all edible seeds.The larger kernels are generally used for edible purposes while the smaller ones for crushing into edible oil.Sunflower was introduced in Europe in the 16th century.Sunflower kernels are well above average in protein, phosphorus and iron concentrations.So, the flour made from sunflower seeds is one of the richest sources of iron in any food.It is, therefore, highly beneficial in the prevention and treatment of anemia (Anonymous 2004a).The phosphorus present is fairly available because of the phytase activity within the grain.The low Ca:P ratio requires the inclusion of ground limestone or similar to supplement the Ca level (Wiseman, 1987).Bas ¸et al.(1986) and Açkurt et al.(1999) reported compositions of major commercial Turkish hazelnut varieties.In addition, Ayfer et al.(1986) and Çalıs ¸kan (1995) reported physical properties of the major commercial Turkish hazelnuts.Pumpkin (Cucurbita sp) and melon (Cirrullus sp) seeds are used directly for human consumption as a snack after salting and roasting in Arabian countries (Al-Khalifa, 1996).Smith et al. (1996) have also reported on the nutritional composition and uses of wild foods common to Burkina Faso and Niger.Moreover, Enujiupha (2003) reported chemical and functional properties of the conophor nut purchased from the Oja-oba market at Akure.Dugo et al. (2004) determined some mineral contents of commercial vegetable oils using derivative potentiometric stripping analyses.
In the earlier part of this century, scientists could qualitatively detect small amounts of several mineral elements in living organisms.The trace elements found in living organisms may be essential, fortuitious reminders of our geochemical origins or indicators of environmental exposure (Macrae et al.1993 a,b).Human, as well as animal, studies originally showed that optimal intakes of elements such as sodium, potassium, magnesium, calcium, manganese, copper, zinc and iodine could reduce individual risk factors, including those related to cardiovascular disease (Anke et al., 1984;Mertz,1982;Sanchez-Castillo et al., 1998).Throughout the world, there is increasing interest in the importance of dietary minerals in the prevention of several diseases.Minerals are of critical importance in the diet, even though they comprise only 4-6% of the human body.The major minerals serve as structural components of tissues and function in cellular and basal metabolism and water and acid-base balance (Macrae et al.1993a;Nielsen,1984;Smith,1988).However, very little information has been reported on the mineral contents of oil-bearing seeds and kernels (Özdemir et al.2001;Enujiugha, 2003;Glew et al.1997;Bas ¸et al.,1986;Açkurt et al.1999;Ayfer et al.,1986;Özcan and Akgül, 1995;Özcan, 2000;Özcan and Seven, 2003;Özcan, 2004).
Therfore, the aim of this work is to established the mineral contents of oil-bearing seeds and kernels via ICP.In addition, other physico-chemical and functional properties of seeds and kernels are also studied.

Material
Oil-seeds and kernels (Table 1) were purchased from bazaar in Konya in Turkey in August 2003.The materials were transported in polypropylene bags and held at room temperature.Materials were cleaned by a combination of manual and mechanical means to get rid of all foreign matter as well as crushed or immature fruits.

Determination of mineral contents
About 0.5 g dried and ground materials was put into a burning cup and 15 ml of pure HNO 3 were added.The sample was incinerated in MARS 5 Microvawe Oven at 200 o C temperature and the solution was diluted to the desired volume with water.Concentrations were determined with an ICP-AES (Skujins, 1998).

RESULTS AND DISCUSSIONS
The mineral contents of oil-bearing seeds and kernels are presented in Table 2. Mineral values were established to vary widely depending on the different seeds and kernels.
Results have shown that Al, Ca, Fe, K, Mg, Na, P and Zn were major minerals of all oil-bearing seeds and kernels (Fig 1).B, Cr, Cu, Li, Ni, Sr, Ti and V contents of crops were found to be very low.Mn was not established in cotton seed, turpentine, pistachio nut, sesame, aspir, corn, almond or apricot.In addition Sr was not determined in corn or pistachio nut, respectively.The levels of K and P of all crops in this study were found to be higher than those of other seeds and kernels.The potassium content was high in most cases and ranged from 1701.08 mg/kg corn to 20895.78 mg/kg soybean.The phosphorus content ranged from 3076.87 mg/kg turpentine to 12006.46 mg/kg pistachio nut (Fig 1).The magnesium content varied from 1153.99 mg/kg in corn to 2617.38 mg/kg in cotton seed.The Lithium contents of seeds and kernels were found in similarly small percentages in all the species analyzed, ranging from 1.63 mg/kg soybean to 2.76 mg/kg black cumin.Ca was found to be high, ranging from 68.40 mg/kg in corn to 13195 mg/kg in poppyseed.Cr content was found to be very similar to those of other crops.Fig 1 provides evidence that Ca is present in very low amounts but poppy seed presented the highest mean concentrations of Ca 13195.67 mg/kg.Pine stone kernels also presented the highest average amounts of zinc (85.57mg/kg) and turpentine fruit the lowest (8.29 mg/kg).Copper concentrations found in this work were lower than those published for black cumin, whereas the levels of B and Zn are similar to those determined in black cumin (Özcan,2004).
Minerals are of interest due to their pro-oxidant activity and health benefits (Alphan et al.,1996;Pala et al., 1996;Parcerisa et al.,1995;Pesrshern et al.,1995).Özdemir (1985) and Özdemir et al.(2001) determined the Fe, Cu, Mn, K, Zn, Na, Mg and Ca contents of some commercial and new hybrid hazelnut varieties, and Ca, Mg and K contents were found higher than those of other elements.Hazelnut was rich in mineral matters such as Ca (209.0 mg/100 g), Mg (162.5 mg/100 g), P (337.0 mg/100g) and K (704.0 mg/100 g) (S ¸ims ¸ek and Aslantas ¸,1999).From a human nutritional point of view, hazelnut is rich in Ca, K, Mg and P. The seeds of Sorghum vulgaris contain relatively large amounts of Mg (1520 µg/g), P (3030 µg/g),Ca (202 µg/g) and Fe (35 µg/g).
We concur, too, with their?results that dried sesame, copper, mustard and peanut contain high concentrations of Cu, Mg, Z and Fe.Our data on mineral contents are in accordance g with their?data in that we found that soybean contains large quantities of Al, Ca, K and Ni.
It is noteworthy that trace minerals are important not only for human nutrition, but for plant nutrition as well.Mineral-efficient varieties of plants are more drought resistant and require less irrigation (Botta and Giovanni,1996;Bouis,1996;Glew et al.,1997).
The Mg, Fe, K, Ca and P levels are adequate.Inorganic elements which may contribute to biological processes, but which have not been established as essential, are B and Li (Macrae et al.,1993a).Lithium is another element with beneficial pharmacological properties; it has been used effectively in the treatment of manic depressive disorders.There is evidence to suggest that lithium is also an essential element (Macrae et al.1993b).