A Comparative Study on the Physicochemical Properties of Vegetable Oil (Palm Oil, Sesame Oil, Sunflower Oil)
Chapter One
Objective of the study
The research aimed at the following objectives:
- To compare the physicochemical properties of oil produced from some selected seed and kernel (palm, sunflower and sesame)
- To determine the antioxidant (tocopherol content) property in the oil
- To determine the fatty acid composition of the selected vegetable oil
CHAPTER TWO
REVIEWS OF LITERATURES
Sesame (Sesamum indicum, L.) Oil
Sesame (Sesamum indicum, L.) is one of the oldest oilseed crops known to mankind and is the only cultivated Sesamum species. Sesame seed has been considered to be important because of its high oil content (42–56%) and protein (20–25%), and also because it is a good source of minerals, particularly calcium, phosphorus, potassium and iron (Deshpande et al., 2006). Moreover, sesame oil is highly resistant to oxidation and displays several medicinal effects (Kochhar, 2000). For instance, it is written in Chinese ancient books that sesame seeds (called ‘Chih-Ma’ in Chinese) increase energy and prevent ageing. The oil obtained from sesame seeds, called ‘Tila’ in Sanskritor simply ‘Til’ these days, has been used as domestic Ayurvedic medicine in India. Actually the name sesame comes from the Arabic word ‘semsin’. Researchers (Bedigian 2004) now believe that the actual origin of sesame was from Sudan where many wild species are found and not India.
The magic words ‘Open Sesame’ relate to its popularity in Arab countries. The seed colour varies from white through various shades of brown, gold, grey, violet and black. Moreover, because of their characteristic flavour and sweet taste, de-hulled sesame seeds are extensively used in baked goods (as a garnish on top of breads, rolls, bread sticks, buns, and some biscuits, and crackers) and in many confectionery products. In the Middle East and some other countries, sesame seeds are used mainly for preparing ‘tahini’ (sesame butter) and ‘halvah’ (sweet). In many European countries sesame snack bars produced with honey and homous — a dip-in chilled product made from chick pea flour and sesame paste — are being marketed.
As in many common vegetable oils, the lipids of sesame seeds consist mainly of neutral triacylglycerols with small quantities of phospholipids. However, compared with other vegetable oils, sesame oil contains a relatively high per-centage of unsaponifiable matter (1–3%) which includes sterols, sterol esters, (mainly) γ-tocopherol, and unique compounds called sesame lignins (described below). Sesame oil is classified as a polyunsaturated, semi-drying oil containing about 82% unsaturated fatty acids. The major fatty acids, oleic and linoleic, are present in approximately equal amounts in the oil.
World seed production
Sesame, also known as gingelly, beniseed, simsim and sesamum, is an important annual crop of many countries. The sesame plant is cultivated in relatively hot and dry regions because the seeds are adaptable and drought-resistant (Salunkhe et al., 2001). India, China, Myanmar (Burma), Sudan, and Mexico are the major countries involved in the growing of sesame seed and production of sesame seed oil. It is interesting to note that in Myanmar, the sesame crop matures in about 60 days, in Sudan about 80 days, and in the southern US, Mexico, and India about 80–140 days depending upon the variety (Deshpande et al. 2006). The total production of sesame seeds has grown by 57% since2000. This growth is mainly in Asia where China tripled its production from 225,000 to 725,000 tonnes in 2000 (Woltman, 2000). The total production of sesame seed relating to 2000–01 harvest is 3.02 million tonnes. About 20% of this production is exported, particularly to Japan, EU countries, and South Korea. Some of the seed is used as such or in de-hulled form in a variety of exotic products but the bulk (70%) is crushed to yield oil. Most of the oil is consumed in the major producing countries and only a relatively small amount (23,000 tonnes) is exported.
Oil composition
The fatty acids in sesame seed oil are mainly equal proportions of oleic acid and linoleic acid, with small amounts of saturated acids, and only a little linolenic acid. Several researchers have reported the fatty acid composition of sesame oils from Sesamum indicum seeds (Yermanos et al., 2002; Eltinay et al., 2006; Spencer et al., 2006; Brar, 2002; Abdel Rahman, 2004). The fatty acids of the oilare mainly oleic acid (18:1, 33–54%) and linoleic acid (18:2, 35–59%), together with palmitic acid (16:0, 8–17%) and stearic acid (18:0, 3–9%). Kamal-Eldin and co-workers (2002b) compared the fatty acid composition and triacylgycerol profiles of different varieties of the cultivated sesame, S. indicum with three wild species, (S. alatum, S. angustifolium and S. radiatum) growing in Sudan, using capillary column GC and HPLC.
The oil content of the wild species (29–36%) was much less than that in the cultivated varieties (47–54%). The reported percentage fatty acid ranges of 16:0, 18:0, 18:1 and 18:2 in the S. Indicum varieties were 9.2–10.9, 5.2–6.7, 36.1–41.3 and 41.3–46.7, and that in wild species 8.7–11.5, 5.6–9.9, 36.3–44.2 and 36.9–44.8 respectively. The fatty acid composition of sesame oil was only slightly affected by genotype, agroclimatic conditions, and stages of ripening (Brar 2007, 2000; Lee and Kang 2000; Sekhon and Bhatia 2002). The triacylglycerol composition of the S. indicum variety comprised 1.5% monounsaturated, 7.7% di-unsaturated and 90.8% polyunsaturated triacylglycerols (Kamal-Eldin et al. 2002b).
The major triacylglycerols were found to be 25.4% LLO, 19.6% LLL, 15.1%LOO, 1.8% PLL and 8.1% PLO (L=linoleic, O=oleic, P=palmitic and each three letter symbol represents all the triacylglycerols containing the three acids indicated). Oil from cultivated S. indicum comprised 88.9% triacylglycerols, 6.5% diacylglycerols, 1.2% free fatty acids, 2.8% polar lipids, and 0.6% sterolesters (Kamal-Eldin and Appelqvist, 2004a). Fatty acids composition is often used to characterize individual oils, including sesame oil. Sesame oil is dextro-rotatary, which is unusual for the glycerol esters lacking any optically active fatty acid. Minor components of the unsaponifiable fraction of sesame oil are probably responsible for the optical rotation of the oil.
CHAPTER THREE
MATERIALS AND METHODS
Materials
Various vegetable oils (Sesame oil, Palm oil and sunflower oil) were purchased from Oja Oba in Owo, Ondo State Nigeria, while Sunflower oil was purchased in Shoprite, Akure in Ondo State. Various chemicals Hydrochloric acid (HCl), sodium hydroxide (NaOH), potassium hydroxide (KOH), idobromine (IBr), sodium thiosulphate (Na2S2O3), potassium iodide (KI), and acetic acid (CH3COOH) were used to determine the physico-chemical properties of the oil, the analysis was carried out in chemistry laboratory of Food Science and Technology, Rufus Giwa Polytechnic Owo, Ondo State, Nigeria.
CHAPTER FOUR
RESULTS AND DISCUSSION
Results
Table 1: Reference Table for Edible Oil
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
Conclusion
From the study above the physicochemical properties of the seed oil studied are in agreement with those of conventional seed oils and they all meets the standard for all edible oil according to FAO/WHO (2009). Palm oil have the highest value for saponification, free fatty acid and peroxide followed by sunflower oil (saponification and free fatty acid), sesame oil have higher value compared to sunflower oil in terms iodine value and peroxide value. The specific gravity for the oil samples has similar values. The oils revealed high content representing a potential source of oil rich in oleic, palmitic, linoleic and stearic fatty acid. It was concluded that all the 3 valuable seeds have valuable oil content that have numerous properties for application at home and industry level. The analysis indicated that all the products are within the permissible range of a certified food organization. Oils are rich source of energy and other essential nutrients that will benefit the human health. The presence of reasonable amount of tocopherol with both saturated and unsaturated fatty acid makes the oil to have good shelf life as well as a good raw material for processing at the food, pharmaceutical, nutraceutical and cosmetic industries.
Recommendations
According to this project work it was recommended that either of the oils can be used for fortification or enrichment due to their tocopherol content, for example with high content of gamma and alpha tocopherol in the oil, there was presence of quantity antioxidant capacity.
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