**Evaluation of the Contamination by Herbicides in Olive Groves**

Antonio Ruiz-Medina and Eulogio J. Llorent-Martínez *University of Jaén Spain* 

#### **1. Introduction**

The application of phytosanitary products on the ground is one of the main employed procedures to solve the problems of plagues and diseases in olive groves. As a result, there is an increasing unease related to the possible presence of residues from these products in the olive-derived foods. Recent studies have shown that these residues can be found in olives and olive oil (mainly insecticides and fungicides) due to the lipophillic nature of the used plaguicides. This is also the effect that has been observed with the introduction of herbicides in this cultive. However, the detected levels of all these phytosanitary products are usually below the maximum residue limits (MRLs) established.

Herbicides are used by olive farmers to weed olive plantations with two essential goals: (1) eliminate the competition for water resources between olive trees and weeds, especially in particular moments of the productive cycle; and (2) keep the soil clean around the olive tree (in that way, the harvest of the olive fruits is easier if they fall off the tree after maturation is over). The main herbicides commonly used in olive groves are triazines (simazine, atrazine, trietazine, terbuthylazine and terbutryn), phenylurea diuron and phenylether oxifluorphen. All of them are directly applied on the ground of the plantation and nowadays widely used in intensified-traditional and modern-intensive olive groves. Herbicide residues remain highly concentrated in the top 5-15 cm of soil, even after several months. This fact presents two main consequences. First, herbicide residues are washed into streams, rivers and reservoirs with the soil that is eroded in heavy rains, polluting surface waters. Second, when harvesting is done using various devices to shake the olives off the trees without extending nets under the tree, olives come in contact with the herbicides present in the soil. This constitutes a risk of these herbicides being incorporated in olives and, consequently, olive oil.

Olive oil is a very important commodity in the Mediterranean basin. This product has a great importance in the sustainable economy of important regions from the main olive oil producers in the world: Spain, Italy and Greece. Due to the facts that virgin olive oil production has increased in recent years and that it is being exported to different countries, exhaustive quality controls are required. Different regulations regarding MRLs in olives and olive oil have been established by the European Union and the Codex Alimentarius of the Food and Agriculture Organization of the United Nations. In addition, new regulations will be established in following years with MRLs of 10 µg/kg.

Evaluation of the Contamination by Herbicides in Olive Groves 209

pressure and increases the bone mass. Moreover, olive oil has a favorable effect on the development of the central nervous and vascular systems, in brain development as well as

The human body easily absorbs olive oil. This means that the body absorbs the good ingredients such as vitamin E and phenols, which have anti-oxidizing properties and prevent the oxidization of fatty tissue, therefore helping to delay the aging process. In addition, it is not only easy to digest but it also helps the digestion of other fatty substances because it helps the secretions of the peptic system and stimulates the pancreatic enzyme lipase. On the other hand, olive oil consumption has a very positive effect on blood cholesterol (limits the oxidizing of bad cholesterol because it is rich in anti-oxidizing agents,

Olive oil, as any fatty substance, deteriorates during the frying process, especially if it is used over and over and if the frying temperature is very high. High temperature destroys the good ingredients of any oil while it creates harmful agents for the liver, the arteries and the heart. However, it is important to take into consideration that these harmful agents are less likely to be created in olive oil than in all other known vegetable oils because of the different composition. Olive oil contains a high percentage of oleic acid, which is much more resistant to oxidization than polyunsaturated acids (found in large amounts in seed oils). As a result, olive oil is the most stable fat and it stands up well to high frying temperatures.

Taking into account all the procedure in order to obtain the oil, edible olive oil is marketed in accordance with the following designations and definitions (International Olive Council,

1. Virgin olive oil: it is the oil obtained from the fruit of the olive tree solely by mechanical or other physical means under conditions, particularly thermal conditions, that do not lead to alterations in the oil, and which have not undergone any treatment other than washing, decantation, centrifugation and filtration. The virgin olive oils that are fit for consumption are extra virgin olive oil and virgin olive oil, presenting a free acidity, expressed as oleic acid, of not more than 0.8 and 2 grams per 100 grams, respectively. They also have to fulfil different quality criteria that, according to the IOC, include good

2. Olive oil: it is the oil consisting of a blend (approximately 80:20 v:v) of refined olive oil and virgin olive oils fit for consumption as they are. It has a free acidity, expressed as oleic acid, of not more than 1 gram per 100 grams and its other characteristics

3. Olive pomace oil: it is the oil obtained by treating olive pomace with solvents or other physical treatments, to the exclusion of oils obtained by re-esterification processes and of any mixture with oils of other kinds. The marketed olive pomace oil is the oil comprising the blend (approximately 80:20 v:v) of refined olive-pomace oil and virgin olive oils fit for consumption as they are. It has a free acidity of not more than 1 gram

Chemical processing may improve high acidity olive oil and make it edible; however, it takes away some extremely valuable ingredients such as vitamins and phenols. As a result, processed olive oil (refined) lacks the desirable properties and characteristics that can be

organoleptic characteristics (taste and aroma) and low peroxide value.

correspond to those fixed for this category in this standard.

normal child development (Cicerale et al., 2010; El & Karakaya, 2009).

as it was indicated before).

per 100 grams.

found in abundance in (extra) virgin olive oil.

2010):

There are alternative methods available for the analysis of herbicides in different kinds of samples. However, the common methods of analysis for their determination are Gas Chromatography (GC) and Liquid Chromatography (LC). GC is usually the chosen technique due to the high separation efficiency and compatibility with a wide range of detection techniques. Our research group has performed thorough investigation over the analysis of herbicides in soils, olive fruits and virgin olive oils. In particular, we have developed different GC analytical methods with mass spectrometric detection for the analysis of all the main herbicides used in olive groves. In this way, sensitive and reliable procedures can be implemented for the quality control of olives and olive oils in the industry. These methodologies, together with the obtained results over real samples from Spain, will be commented in this chapter.

### **2. Composition and properties of olive oil. Classification**

Olive oil is composed mainly of triglycerides (98-99% of the olive oil) and contains small quantities of free fatty acids (FFA), being the proportion of FFA variable and related to the degree of hydrolysis of the triglycerides. The composition of fatty acids in the oil depends on the variety of the olive tree, climatic conditions and geographical localization of the grove. Both the International Olive Council (IOC) and the Codex Alimentarius Comission have established maximum and minimum percentages for each fatty acid in the composition of the olive and pomace-olive oils. Olive oil is basically composed of mono-insaturated fatty acids. Regarding the degree of insaturation, fatty acids composition is as follows: 72% mono-insaturated, 14% poli-insaturated and 14% saturated.

There are also minor components in olive oil, which are specific markers of its physicochemical authenticity and they also add unique sensory and biological characteristics:


Virgin olive oil is the most digestible of the edible fats and it helps to assimilate vitamins A, D and K. It contains essential acids that cannot be produced by our own bodies and slows down the aging process. It also helps bile, liver and intestinal functions. It is noteworthy that olive oil has a beneficial effect in the dietary treatment of diabetes. In addition, it helps to control blood

There are alternative methods available for the analysis of herbicides in different kinds of samples. However, the common methods of analysis for their determination are Gas Chromatography (GC) and Liquid Chromatography (LC). GC is usually the chosen technique due to the high separation efficiency and compatibility with a wide range of detection techniques. Our research group has performed thorough investigation over the analysis of herbicides in soils, olive fruits and virgin olive oils. In particular, we have developed different GC analytical methods with mass spectrometric detection for the analysis of all the main herbicides used in olive groves. In this way, sensitive and reliable procedures can be implemented for the quality control of olives and olive oils in the industry. These methodologies, together with the obtained results over real samples from

Olive oil is composed mainly of triglycerides (98-99% of the olive oil) and contains small quantities of free fatty acids (FFA), being the proportion of FFA variable and related to the degree of hydrolysis of the triglycerides. The composition of fatty acids in the oil depends on the variety of the olive tree, climatic conditions and geographical localization of the grove. Both the International Olive Council (IOC) and the Codex Alimentarius Comission have established maximum and minimum percentages for each fatty acid in the composition of the olive and pomace-olive oils. Olive oil is basically composed of mono-insaturated fatty acids. Regarding the degree of insaturation, fatty acids composition is as follows: 72%

There are also minor components in olive oil, which are specific markers of its physicochemical authenticity and they also add unique sensory and biological characteristics:

 Squalene is the major olive oil terpenoid hydrocarbon (300-700 mg L-1), whereas βcarotene, biological precursor of vitamin A, is found in small quantities (mg L-1). Triterpenoids alcohols (24-methylenecycloartanol, cycloartenol, α-amirine and βamirine) are especially important from the biological point of view. Eritrodiol is also important from the analytical perspective, because it can be used to detect the presence

 Sterols can be used to construct a fingerprint in order to authenticate the olive oil, specifically using the β-sitosterol content, which represents around 93% of the total

Tocopherols, especially α-tocopherol or vitamin E (150-300 mg L-1) are important

Phenolic compounds, some of them contribute to the characteristic flavor of olive oil,

 Approximately one hundred aromatic compounds are also present, being the exact chemical composition dependent on the variety, climatic conditions and quality of the

Virgin olive oil is the most digestible of the edible fats and it helps to assimilate vitamins A, D and K. It contains essential acids that cannot be produced by our own bodies and slows down the aging process. It also helps bile, liver and intestinal functions. It is noteworthy that olive oil has a beneficial effect in the dietary treatment of diabetes. In addition, it helps to control blood

Spain, will be commented in this chapter.

of pomace-olive oil.

content of sterols.

antioxidants.

oil.

**2. Composition and properties of olive oil. Classification** 

mono-insaturated, 14% poli-insaturated and 14% saturated.

increase the antioxidant properties of the oil.

pressure and increases the bone mass. Moreover, olive oil has a favorable effect on the development of the central nervous and vascular systems, in brain development as well as normal child development (Cicerale et al., 2010; El & Karakaya, 2009).

The human body easily absorbs olive oil. This means that the body absorbs the good ingredients such as vitamin E and phenols, which have anti-oxidizing properties and prevent the oxidization of fatty tissue, therefore helping to delay the aging process. In addition, it is not only easy to digest but it also helps the digestion of other fatty substances because it helps the secretions of the peptic system and stimulates the pancreatic enzyme lipase. On the other hand, olive oil consumption has a very positive effect on blood cholesterol (limits the oxidizing of bad cholesterol because it is rich in anti-oxidizing agents, as it was indicated before).

Olive oil, as any fatty substance, deteriorates during the frying process, especially if it is used over and over and if the frying temperature is very high. High temperature destroys the good ingredients of any oil while it creates harmful agents for the liver, the arteries and the heart. However, it is important to take into consideration that these harmful agents are less likely to be created in olive oil than in all other known vegetable oils because of the different composition. Olive oil contains a high percentage of oleic acid, which is much more resistant to oxidization than polyunsaturated acids (found in large amounts in seed oils). As a result, olive oil is the most stable fat and it stands up well to high frying temperatures.

Taking into account all the procedure in order to obtain the oil, edible olive oil is marketed in accordance with the following designations and definitions (International Olive Council, 2010):


Chemical processing may improve high acidity olive oil and make it edible; however, it takes away some extremely valuable ingredients such as vitamins and phenols. As a result, processed olive oil (refined) lacks the desirable properties and characteristics that can be found in abundance in (extra) virgin olive oil.

Evaluation of the Contamination by Herbicides in Olive Groves 211

The process of releasing the oil from the plant tissue begins by milling the olives to tear the flesh cells in order to let the oil run out of the vacuoles. This is followed by stirring the olive paste to permit the formation of large drops of oil and to break up the oil–water emulsion. In so-called "dual-phase decanters" the oil is then separated by direct continuous centrifugation from the pomace, which consists of vegetable matter and water. The yield of oil varies from 80 to 90% of the total oil content of the olives, because the oil in the olive paste is only partially free to escape and part of it remains in the unbroken cells or is

After the extraction of virgin olive oil from the olives, the remaining paste is called pomace and still contains a small quantity (2-6%) of oil that can only be extracted with chemical solvents. This is done in specialized chemical plants, not in the oil mills and the obtained oil

trapped in the tissues of the cytoplasm, or is emulsified in the aqueous phase.

Air Cleaners

Washing device

Air cleaners

Olives carried towards the cleaners

Fig. 1. Cleaning steps for olive fruit.

Fig. 2. Washing step for olive fruit.

**3.1.3 Preparation** 

is called pomace oil.
