Contribution to the Physicochemical and Organoleptic Study of Two Olive Oils of Traditional and Industrial Extraction of the Wilaya of Tlemcen ()
1. Introduction
Olive oil is the Mediterranean product par excellence. It is found throughout history, from Greek civilization to the present day. It is the main source of fat from the Cretan diet or the Mediterranean diet that are well known for their beneficial effects on human health. Olive oil is an interesting product from a nutritional point of view, but first for its fatty acid composition. Indeed, it is largely unsaturated and contains a small part of essential fatty acids [1] .
The quality of olive oil varies not only according to the variety, the soil and the climatic conditions but also with many factors relating to the cycle of production, processing and marketing of olives and oils [2] .
Our study is based on the comparison between two olive oils of industrial and traditional extraction from the point of view physicochemical and organoleptic, by specifying their advantages and disadvantages, as well as the good quality management of the oils produced.
The samples were taken from different regions of the wilaya of Tlemcen: Sabra, Ain Defla and Benisnouss. Compliance of oil with C.O.I. (International Olive Oil Council) and C.A. (Codex Alimentarius) requires the determination of certain physical parameters (Potential hydrogen, Water content, Absorbance in the ultra violet), chemical (acid index, saponification index, peroxide index, iodine index, ester index) and organoleptic.
2. Materials and Methods
2.1. Origin of Samples
The olive oils studied come from three different oil mills: Sabra, Ain defla, Tafessra, some of which are artisanal and some industrial, these three regions represent the most important olive oil production sites in the wilaya of Tlemcen.
2.2. Physicochemical Characterization
2.2.1. Acid Index
The acid index (IA) is the number of milligrams of potassium hydroxide required for the neutralization of free acids contained in one gram of fat [3] .
2.2.2. Saponification Index
The saponification index (IS) corresponds to the number of milligrams of potash required to saponify the fatty acids contained in one gram of fat. This value is all the higher than the fatty acids are of lower molecular weight [4] .
2.2.3. Peroxide Index
The peroxide index (IP) is a measure for estimating the amount of peroxide present in a fat [3] . A sample is dissolved in a mixture of acetic acid and chloroform, then treated with a potassium iodide solution. The liberated iodine is treated with a solution of sodium thiosulfate in the presence of starch stains (colored indicator) [5] .
2.2.4. Iodine Index
Iodine index (II) generally measures the degree of unsaturation of a fat by determining the number of grams of iodine binding to the double bonds present in 100 g of lipids [3] .
2.2.5. Absorbance by Spectrophotometry
Extinction at 232 nm and 270 nm of a crude fat can be considered as an image of its oxidation state; more the extinction at 232 nm is strong, the more olive oil is rich in secondary oxidation product [6] .
2.2.6. Water Content
It consists of causing water to start by heating a known quantity of oil until the water is eliminated completely [7] .
2.2.7. Hydrogen Potential
Hydrogen potential (PH) gives an indication of the acidity or alkalinity of the medium, it is determined from the amount of free hydrogen ions (H+) contained in the olive oil [8] .
2.3. Sensory Analysis
The organoleptic characteristics of olive oil are related to the variety of fruits, their degree of maturity, at harvest time, ecological factors, variations in harvesting and fruit storage operations, and the variability of extraction and storage processes of olive oil [9] .
The test used sets the different tasting criteria: taste, color, appearance and smell according to C.O.I. Candidates must taste the samples submitted to them and see how they find the product by checking the statement.
3. Results and Discussion
3.1. Results of Physico-Chemical Analyzes
Traditional olive oils represent higher acidity compared to industrial olive oils (Figure 1 and Figure 2), but remain fit for consumption, certainly due to the prolonged storage of olives in the open, the lack of washing and sorting, the lack of mastery of the techniques of purification and incomplete separation of the fruit juice of the margines alters the taste of the oil and increases its acidity.
The results show that all analyzed samples have varying saponification (Figure 3). The impurity percentage, Peroxide and iodine indices meet the standards too (Figures 4-6), which allows us to consider them as being of good quality. On the other hand, oil of Ain Defla region is a little higher than the norms which imply that it is easily alterable and less stable, which will facilitate their rancidity.
The absorbance in the ultraviolet, the water content and the pH of our samples is in the norms (Figures 7-9 ).
The detailed numerical values of these results are shown in Table 1, Table 2 gives the values according to the standards.
3.2. Sensory Results
The tasting analysis highlights a superiority of the traditional extraction olive oil characterized by a low fruity taste and an acceptable odor. The acceptability of it by the taster is well appreciated, contrariwise all tasters criticize this one for being too strong. On the other hand, olive oil of industrial extraction, presents a normal coloring, but a taste and an unacceptable odor. Its acceptability by the taster is not well appreciated.
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Figure 9. Absorbance spectrophotometer at 232 nm and 270 nm.
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Table 1. Summary table of different chemical and physical characteristics of the seven samples studied.
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Table 2. Normal values of physicochemical characteristics.
4. Conclusions
The good quality of olive oil depends on several factors, first the good quality of the olive species, picking, transporting it to oil mills, the manufacturing process used as well as the preservation and packaging.
In this study, the quality of olive oil is measured by physicochemical and organoleptic characteristics, mainly related to the raw material (olive) and the extraction process.
The results obtained showed that among the oils analyzed, some are impure and have high levels of acidity that do not meet standards, which is certainly due to the geographical origin of the olives, lack of attention to the harvest, as well as the conservation and processing of olives.
For this, the quality department should oblige the olive oil seller to guarantee the purity and to improve the packaging of his product, and this is certainly not due to a requirement, but for one’s own consumption from the nutritional point of view.