Physico-chemical Properties of Olive Oil
Objective of the Study
With this background, the research was undertaken with main objective to study the physical and chemical properties of olive oil.
The Origin and Distribution of Olive Tree and Olive Crop
The olive tree is one of the most ancient cultivated fruit trees (Elbaum et al., 2006), and the use of olives has been ascertained in the late Stone Age at the Kfar Samirin site in Israel (Galili et al., 1997). Cultivated olive (Olea europaea L.) was developed by domesticating wild olives, Olea europaea L. subsp. oleaster (Hoffmanns. & Link) Negodi, with which it shares close genetic affinities (Zohary and Hopf, 1993); it is no accident that domestic olive tends to regress towards oleaster when it reverts to the wild.
The crop was known to all ancient Mediterranean civilizations and it probably originated independently in several different areas. The olive variety we know today is the result of selective breeding which began about 6,000 years ago (Guerci, 2005) when Syrian and Palestinian farmers, and probably also those in the vast area stretching from the Southern Caucasus to the Iranian plateaus (Guerci, 2005), managed to obtain one or more varieties with fruits containing plenty of oil, but without the thorns of the wild variety. The original wild olive probably originated in Asia and was quite widespread at this time, but difficult to exploit for food or ritual purposes because of its hard thorns and small olives with a low oil content.
Up to this point the olive had moved slowly westward, and it was thanks to the ships of Phoenician merchants – and later of Greek traders – that olive spread to many places around the Mediterranean, including Spain, southern France and North Africa. Roman armies conquered all the lands around the Mediterranean creating one vast empire, so that communications and trade links became safer and more intense. The Romans took olive-growing into new areas and encouraged it in places where it languished in order to supply the growing internal demand.
Olive-growing became more important and reached its high point in the 2nd and 3rd centuries, especially in the north (Imberciadori, 1983), but also in Spain, in Dalmatia and in Provence; there is evidence of the oil trade with Sicily, Magna Graecia, Athens and Marseille (Sterpellone, 1990). After the fall of the Roman Empire, historical data about olive become much scarcer. Olive-growing lost its former importance, caused also by the population decrease and abandonment of vast areas during the early Middle Ages. The crop remained important in the Arab-dominated territories, to the point that in occupied Sicily it was forbidden to grow olives, the aim being that of protecting the economy of North Africa, then the main olive-growing area.
In Europe, on the other hand, olive oil consumption was limited, and only began to assume more importance in about the 15th-17th centuries. This was when oil once more became important for Venetian traders, who imported it into Europe from their lands on the Aegean (Cyprus, Crete and Corfu). It is worth remembering that oil was not used just as a foodstuff: it was just as important as a fuel for lighting, as oil used for massages, for soap manufacture and for processing wool.
It quickly became important again, and olive-growing spread anew throughout its traditional areas and remains there to this day. At the same time, North Africa witnessed a decline in olive-growing almost everywhere, and this tendency has only recently changed. Olives were taken to Peru from Spain in 1560 (Valdizàn and Maldonado, 1992), and it also arrived in Egypt following the Asian invasions of the 17th century B.C. (Guerci, 1994). Spanish missionaries took the olive tree to California in about 1850 and Italian immigrants were responsible for its introduction into Argentina. Attempts to spread olive-growing in Australia have so far met with little success.
The Olea L. genus includes around 40 specific and sub-specific taxa (Besnard et al., 2001), equivalent to approximately 805 million individual plants, distributed across four continents (Africa, Asia, Europe and Oceania) (Besnard et al., 2001), 98% of which grow in the Mediterranean basin, where six sub-species of O. europaea L. are recognized (Médail et al., 2001; Green, 2002). Sub-spp. europaea and oleaster occupy substrates of various kinds at altitudes not generally above 1000 m, and are present in almost all Mediterranean countries (Green, 2002), while the other sub-species have more limited ranges.
Olive oil is a major component of the diet of the countries surrounding the Mediterranean Sea. For the people living in this region, olive oil is the main source of fat in their cuisine. In the past few years the oil has also become more popular among consumers in Northern Europe, the US and Canada, in particular, although these new consumers are not always familiar with the properties and characteristics of this natural product. Growing enthusiasm for the Mediterranean diet and for olive oil is due largely to studies indicating that this diet plays a positive role in the prevention of certain diseases, especially coronary heart disease.
Chemical and analytical work to elucidate the structure and to quantify minor constituents of olive oil is now progressing rapidly. Much work has been also carried out by nutritionists on the key functional components. This chapter examines what makes olive oil chemically different from other culinary fats. The discussion does not cover olive oil chemistry and technology completely. It aims to highlight the issues related to production, compositional characteristics and properties that make this oil so distinct.
MATERIALS AND METHODS
Two bottles of olive oil (virgin and refined) were puchased from Oja Oba in Owo, Ondo State Nigeria. 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.
Determination of Physico-chemical Properties of Olive Oil
The determinations of physicochemical parameters of seeds (Olive) oils for Acid value, Iodine value, Saponification value, Peroxide value, and Specific gravity were carried out according to the methods of AOAC (1990).
RESULTS AND DISCUSSIONS
Table 4.1: Physicochemical Properties of Olive oil
It reveals that olive oil is rich, it can be used for edible purposed as well as industrial. It was recorded that refinery of olive oil degrade the value both for physcicochemical properties and in tocopherol content hence these is little change delta tocopherol either total tocopherol has decrease with approximately 50.7%.
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