CHEMICAL ANALYSIS OF OLIVE OIL
1. SENSORY ANALYSIS FROM A TRIAL TEAM
2. ACIDITY:: Parameter defining the olive oil content in free fatty acids
It is expressed in grams of oleic acid per 100g of olive oil MAX 0.8%
and is due to the hydrolysis of the triglycerides of the olive oil by the lipase enzyme resulting in the production of free fatty acids which are responsible for the acidity.
- HEALTHY OLIVE FRUIT (The presence of fruit infested by fruit flies greatly increases the value of acidity)
- OLIVE FRUIT WITHOUT INJURY
- DEGREE OF MATURITY
- WETNESS (The contact of triglycerides with water causes hydrolysis and assists the action of microorganisms and enzymes)
- TEMPERATURE (increase of temperature specifically over 35°C)
- PRESENCE OF ENZYMES-MICROORGANISMS
The acidity occurs primarily at the stage before and during the extraction of olive oil, while after extraction it changes less.
Low acidity oils can be produced when:
- the olive fruit is healthy without having its cells damaged
- the storage time of the olive fruit after the harvest until its return to the olive press as well as the time spent in it until the oil extraction is the minimum possible
- the storage of olive fruit in the olive press until the oil extraction is made in a cool, well-ventilated area.
3. THE NUMBER OF PEROXIDES:It is a way to measure the degree of oxidation of the oil at a primary stage and is used to distinguish edible from inedible oils
They are formed by the effect of O 2 in the olive oil.
It is due to the hydroperoxides which are products of the primary step of oxidation of unsaturated fatty acids of triglycerides.
Oxidation may be chemical or enzymatic.
Lipoxidase enzymes act as oxidants as long as there is contact between the oil and the waste water, either if the cells are broken during the harvest or during the breaking and grinding operations.
The enzymes are removed with the waste water.
ACTIONS: Implementation of best practices in farming – harvesting – storage – crushing of olives – olive oil production
Assisted by the light, high temperature, presence of Ο2,and minerals (iron, copper)
ACTIONS: Avoiding light (storage in a dark place)
temperatures (storage in a cool place)
air (nitrogen tanks)
minerals (storage in tanks of suitable materials that do not release metals)
They help us draw conclusions about the age of oil and the conditions of its preservation.
High number of peroxides shows oxidizing or other lesions and is associated with reduction in the oil’s lifetime.
4. ABSORPTION IN UV
- K270: It is due to secondary oxidation products which can also be produced during the industrial processing of oil
- K232: It is a way of primary oxidation
- CL: It is a measure of discrimination between virgin olive oil and a mixture of virgin olive oil with refined oil.
ABSORPTION K 232
It is due to hydroperoxides produced in the primary stage of oxidation and in conjugated dienes produced during the intermediate stages of oxidation.
K232 is increased:
- When the olives are stored for several days before their elision
- When during the oil extraction in the olive press, there is a long storage time of the olives in the mixer
- When the oil is stored in unsuitable conditions
ABSORPTION 270 K
- It is due to carbonyl groups that are secondary products of oxidation, and conjugated trienes generated when the oil is subjected to industrial processing.
- The price of K270 depends on how fresh the olive oil is. Old oils or mixtures with old olive oils raise the price of K270. In its production, the olive oil has a very low value which increases as the age of the oil increases.
- Increased exposure of the oil to solar radiation and high temperatures accelerate the progress of its aging.
The prolonged storage of olive oil is to be avoided.
During its storage the following must be taken into consideration:
- be protected from the light
- be protected from the air
- be carefully moved during the process of removal of the solid residue which has settled down, avoiding contact with air and light exposure
- not be stored in iron containers
- be kept in cool, clean areas
- and stored in glass containers in a dark place
5. MOISTURE AND VOLATILE SUBSTANCES: Parameters referring to the clarity of oil (clear at 20°C).
6. INSOLUBLE COMPONENTS IN PETROLEUM ETHER: Parameters referring to substances such as phospholipids – oxyacids – soaps. During the buying and selling, it is determined which of them should be considered as foreign substances.
7. SATURATED FATTY ACIDS: Parameter of detection of adulteration with artificial esterification oils (for virgin olive oil <1.3%). 8. FATTY ACIDS: Parameter of detection of other vegetable oils
9. TRANS FATTY ACIDS: Parameter of detection of other vegetable or refined oils
10. FATTY ACIDS IN POSITION b OF TRIGLYCERIDES: Parameter of detection of vegetable oils
11. TRIGLYCERIDES WITH LIQUID CHROMATOGRAPHY: Definition of trinalin for detecting seed oils in olive oil (> 0.5% indicates the presence of vegetable oil).
12. DECN 42: Parameter indicating the presence of other vegetable oils
13. STEROLS: Parameter of detection of vegetable oils
Used to control adulteration with seed oils (sesame oil – cottonseed oil – peanut oil – soybean). The control is based on the fact that the oil has an increased content of b-sitosterol.
b-sitosterol / stigmasterol campestorol
A reduced rate of olive oil sample in b-sitosterol and a small rate of the relationship with respect to the sum of the other two indicates adulteration with a seed oil (if the content of b-sitosterol is increased, the adulteration is possibly from soybean oil).
14. ERYTHRODIOL & UVAOL: Parameters of detection of pomace oil
15. WAXES: Parameter indicating the presence of old olive oils and pomace oils
16. ALIPHATIC ALCOHOLS: Parameter of detection of pomace oil
17. STIGMASTADIENES: Parameter of detection of refined oils
18. UNSAPONOFIABLES (HYDROCARBONS ESPECIALLY SQUALENE – STEROLS – TRITERPENE ALCOHOLS – CAROTENOIDS – TOCOPHEROL – PHENOLIC SUBSTANCES – UNDETERMINED SUBSTANCES):
The amount and composition are mainly influenced by the following factors: the variety of olives – the stage of maturity of the olive fruit – the robustness of trees – the growing conditions and treatments given to the olive grove- the nutritional status – the geographical and climate conditions in the olive grove)
19. DIGLYCERIDES: Parameter related to the age of the oil.
20. TOCOPHEROLS: Natural antioxidants
21. PESTICIDES: Parameter indicating the presence of residues from the use of pesticides.
22. BENZOPYRENE: Parameter indicating the presence of pomace oil (the benzopyrene is neutralized with activated carbon in order to be removed from pomace oil)
23. AFLATOXINS: Group of potent toxic substances produced by fungi (mold) under suitable conditions of dampness and temperature.
24. HEAVY METALS: Parameters related to contamination by metals.
25. PLASTICIZERS: Parameter referring to the olive oil contamination from phthalate esters .