EXTRACTION AND CHARACTERIZATION OF VEGETABLE OIL USING BREAD FRUIT SEED

EXTRACTION AND CHARACTERIZATION OF VEGETABLE OIL USING BREAD FRUIT SEED.

CHAPTER ONE
INTRODUCTION

1.1 Vegetable oil

A vegetable oil is a triglyceride extracted from a plant. Such oils have been part of human culture for millennia. The term “vegetable oil” can be narrowly defined as referring only to substances that are liquid at room temperature, or broadly defined without regard to a substance’s state of matter at a given temperature. For this reason, vegetable oils that are solid at room temperature are sometimes called vegetable fats. Vegetable oils are composed of triglycerides, as contrasted with waxes which lack glycerin in their structure. Although many plant parts may yield oil, in commercial practice, oil is extracted primarily from seeds.

1.2 Production of Vegetable Oils

To produce vegetable oils, the oil first needs to be removed from the oil-bearing plant components, typically seeds. This can be done via mechanical extraction using an oil mill or chemical extraction using a solvent. The extracted oil can then be purified and, if required, refined or chemically altered.

1.2.1 Mechanical extraction

Oils can also be removed via mechanical extraction, termed “crushing” or “pressing.” This method is typically used to produce the more traditional oils (e.g., olive, coconut etc.), and it is preferred by most health food customers in the United States and in Europe. There are several different types of mechanical extraction: expeller-pressing extraction is common, though the screw press, ram press, and Ghani (powered mortar and pestle) are also used. Oil seed presses are commonly used in developing countries, among people for whom other extraction methods would be prohibitively expensive; the Ghani is primarily used in India.

1.2.2 Solvent extraction

The processing of vegetable oil in commercial applications is commonly done by chemical extraction, using solvent extracts, which produces higher yields and is quicker and less expensive. The most common solvent is petroleum-derived hexane. This technique is used for most of the “newer” industrial oils such as soybean and corn oils. Supercritical carbon dioxide can be used as a non-toxic alternative to other solvents.

1.2.3 Sparging

In the processing of edible oils, the oil is heated under vacuum to near the smoke point, and water is introduced at the bottom of the oil. The water immediately is converted to steam, which bubbles through the oil, carrying with it any chemicals which are water-soluble. The steam sparging removes impurities that can impart unwanted flavors and odors to the oil.

1.2.4 Hydrogenation

Oils may be partially hydrogenated to produce various ingredient oils. Lightly hydrogenated oils have very similar physical characteristics to regular soya oil, but are more resistant to becoming rancid. Hardening vegetable oil is done by raising a blend of vegetable oil and a catalyst in near-vacuum to very high temperatures, and introducing hydrogen. This causes the carbon atoms of the oil to break double-bonds with other carbons, each carbon forming a new single-bond with a hydrogen atom. Adding these hydrogen atoms to the oil makes it more solid, raises the smoke point, and makes the oil more stable.

Hydrogenated vegetable oils differ in two major ways from other oils which are equally saturated. During hydrogenation, it is easier for hydrogen to come into contact with the fatty acids on the end of the triglyceride, and less easy for them to come into contact with the center fatty acid. This makes the resulting fat more brittle than a tropical oil; soy margarines are less “spreadable”. The other difference is that trans fatty acids (often called trans fat) are formed in the hydrogenation reactor, and may amount to as much as 40 percent by weight of a partially hydrogenated oil. Hydrogenated oils, especially partially hydrogenated oils with their higher amounts of trans fatty acids are increasingly thought to be unhealthy.

1.3 Uses of triglyceride vegetable oil

The following are some of the uses of vegetable oils:

1) Culinary uses: Many vegetable oils are consumed directly, or indirectly as ingredients in food – a role that they share with some animal fats, including butter and ghee;

2) Industrial uses: Vegetable oils are used as an ingredient or component in many manufactured products. Many vegetable oils are used to make soaps, skin products, candles, perfumes and other personal care and cosmetic products. Some oils are particularly suitable as drying oils, and are used in making paints and other wood treatment products. Dammar oil (a mixture of linseed oil and dammar resin), for example, is used almost exclusively in treating the hulls of wooden boats. Vegetable oils are increasingly being used in the electrical industry as insulators .

3) Pet food additive: Vegetable oil is used in production of some pet foods. In some poorer grade pet foods though, the oil is listed only as “vegetable oil”, without specifying the particular oil.

4) Fuel: Vegetable oils are also used to make biodiesel, which can be used like conventional diesel. Some vegetable oil blends are used in unmodified vehicles but straight vegetable oil, also known as pure plant oil, needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity. The vegetable oil economy is growing and the availability of biodiesel around the world is increasing. It is believed that the total net greenhouse gas savings when using vegetable oils in place of fossil fuel-based alternatives for fuel production, range from 18 to 100% [10].

1.4 Negative health effects

Hydrogenated oils have been shown to cause what is commonly termed the “double deadly effect”, raising the level of low density lipoproteins (LDLs) and decreasing the level of high density lipoproteins (HDLs) in the blood, increasing the risk of blood clotting inside blood vessels.

A high consumption of omega-6 polyunsaturated fatty acids (PUFAs), which are found in most types of vegetable oil (e.g. soyabean oil, corn oil– the most consumed in USA, sunflower oil, etc.) may increase the likelihood that postmenopausal women will develop breast cancer. A similar effect was observed on prostate cancer in mice. Plant based oils high in monounsaturated fatty acids, such as olive oil, peanut oil, and canola oil are relatively low in omega-6 PUFAs and can be used in place of high-polyunsaturated oils.

1.5 Uses/Importance of Vegetable oils
1.5.1 Margarine

Margarine originated with the discovery by French chemist Michel Eugene Chereul in 1813 of margaric acid (itself named after the pearly deposits of the fatty acid from Greek (margaritēs / márgaron), meaning pearl-oyster or pearl, or (margarís), meaning palm-tree, hence the relevance to palmitic acid). Scientists at the time regarded margaric acid, like oleic acid and stearic acid, as one of the three fatty acids which, in combination, formed most animal fats. In 1853, the German structural chemist Wihelm Heinrich Heintz analyzed margaric acid as simply a combination of stearic acid and of the previously unknown palmitic acid.

Emperor Louis Napoleon III of France offered a prize to anyone who could make a satisfactory substitute for butter, suitable for use by the armed forces and the lower classes. French chemist Hippolyte Mege-Mouries invented a substance he called oleomargarine, the name of which became shortened to the trade name “margarine”.

Mège-Mouriès patented the concept in 1869 and expanded his initial manufacturing operation from France but had little commercial success. In 1871, he sold the patent to the Dutch company Jurgens, now part of Unilever. In the same year the German pharmacist Benedict Klein from Cologne founded the first margarine factory “Benedict Klein Margarinewerke”, producing the brands Overstolz and Botteram.

Margarine is a semi-solid emulsion composed mainly of vegetable fats and water. While butter is derived from milk fat, margarine is mainly derived from plant oils and fats and may contain some skimmed milk. In some locales it is colloquially referred to as oleo, short for oleomargarine. Margarine, like butter, consists of a water-in-fat emulsion, with tiny droplets of water dispersed uniformly throughout a fat phase which is in a stable crystalline form. Margarine has a minimum fat content of 80%, the same as butter, but unlike butter reduced-fat varieties of margarine can also be labelled as margarine. Margarine can be used both for spreading or for baking and cooking. It is also commonly used as an ingredient in other food products, such as pastries and cookies, for its wide range of functionalities.

1.5.1.2 Manufacture of Margarine

The basic method of making margarine today consists of emulsifying a blend of hydrogenated vegetable oils with skimmed milk, chilling the mixture to solidify it and working it to improve the texture. Vegetable and animal fats are similar compounds with different melting points. Those fats that are liquid at room temperature are generally known as oils. The melting points are related to the presence of carbon-carbon double bonds in the fatty acids components. Higher number of double bonds give lower melting points.

Partial hydrogenation of a typical plant oil to a typical component of margarine, makes most of the C=C double bonds be removed in this process, which elevates the melting point of the product. Commonly, the natural oils are hydrogenated by passing hydrogen through the oil in the presence of a nickel catalyst, under controlled conditions. The addition of hydrogen to the unsaturated bonds (alkenic double C=C bonds) results in saturated C-C bonds, effectively increasing the melting point of the oil and thus “hardening” it. This is due to the increase in van der Waals’ forces between the saturated molecules compared with the unsaturated molecules. However, as there are possible health benefits in limiting the amount of saturated fats in the human diet, the process is controlled so that only enough of the bonds are hydrogenated to give the required texture. Margarines manufactured in this way are said to contain hydrogenated fat.

This method is used today for some margarines although the process has been developed and sometimes other metal catalysts are used such as palladium. If hydrogenation is incomplete (partial hardening), the relatively high temperatures used in the hydrogenation process tend to flip some of the carbon-carbon double bonds into the “trans” form. If these particular bonds aren’t hydrogenated during the process, they will still be present in the final margarine in molecules of trans fats, the consumption of which has been shown to be a risk factor for cardiovascular disease. For this reason, partially hardened fats are used less and less in the margarine industry. Some tropical oils, such as palm oil and coconut oil, are naturally semi solid and do not require hydrogenation.

Three types of margarine are common:

1.     Soft vegetable fat spreads, high in mono- or polyunsaturated fats, which are made from safflower, sunflower, soybean, cottonseed, rapeseed or olive oil.

2.     Margarines in bottle to cook or top dishes

3.     Hard, generally uncolored margarine for cooking or baking.

1.5.2 Soap

In chemistry, soap is a salt of a fatty acid. Soaps are mainly used as surfactants for washing, bathing, cleaning, in textile spinning and are important components of lubricants. Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strongly alkaline solution. Fats and oils are composed of triglycerides; three molecules of fatty acids are attached to a single molecule of glycerol. The alkaline solution, which is often called lye, (although the term “lye soap” refers almost exclusively to soaps made with sodium hydroxide) brings about a chemical reaction known as saponification. In saponification, the fats are first hydrolyzed into free fatty acids, which then combine with the alkali to form crude soap. Glycerol (glycerin) is liberated and is either left in or washed out and recovered as a useful byproduct, depending on the process employed.

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