Olive Oil Quality Criteria
22-06-2023
11:55
Photograph: Olive Oil Tasting Glass, International Olive Oil Council; COI/T.20/Doc. no. 5, “Glass for Oil Tasting”; internationaloliveoil.org
Society's demand for olive oil is related to more than one factor, regionally and traditionally; culinary culture, taste habits and desire to consume healthy food. Policies should be developed to prevent the misdirection of consumers as well as to ensure the purity of olive oil products in terms of content. By guaranteeing the reliability of olive oils offered to the market, it should be aimed to protect consumer rights and to improve individual and public health. In addition to its cultivation and production costs, natural olive oil is more expensive than many other vegetable oils due to its unique qualities, especially its organoleptic qualities and the phytochemicals it contains as a functional food.
The quality criteria of olive oil are made according to some chemical and physical measurements objectively, and subjectively according to the taste evaluation of experts (Sensory Properties/Panel tests).
a. Measurable Criteria (Analytical Properties)
Although it is not the subject of this article, one of the features analyzed is the examination of whether olive oil is pure or not. Because olive oil may be mixed with seed oils or olive pomace oil. Whether the olive oil is pure; fatty acids composition and transfatty acids, sterol composition, ECN 42 difference amount, determination of erythrodiol and uvaol amount from triterpenic alcohols, amount of waxy substances can be understood.
The first criterion to be used for objective evaluation at the beginning of the century is the “percentage of free fatty acidity” value in terms of oleic acid. The acidity of the highest quality olive oil is between 0.1% and 1%. As the value increases, a quality defect called "rancidity" or "bitterness" occurs.
Another criterion that has started to be used for objective evaluation in olive oil is “lipid peroxidation measurement”. It is the total number of active oxygen in one kilogram of olive oil (peroxide value, meq active oxygen/kg). Throughout the oil production process and storage process, it constantly undergoes a chemical reaction with oxygen in the air, called oxidation. Peroxides appear in the first step of oxidation. The maximum number of peroxides in an extra virgin olive oil is 20. The lower the peroxide value, the higher the quality of the olive oil. It gives information about the degree of deterioration of the oil and how long it can be stored.
“Specific Cooling Values in UV Light” or specific absorbance for short; It is an important quality parameter used as a measure of resistance to oxidation. It is done by using a spectrophotometer device. It is an analysis method that works with the principle of oil absorbing light at different wavelengths in ultraviolet light. Specific absorption measurement in ultraviolet light at 232 - 270 nm is one of the objective methods used to determine the purity and quality of olive oil. R=K232 /K270 value; It is between 10-15 for good quality natural oils, not above 20 is an indication of good quality.
“Moisture and Volatile Matter Measurement”; It is made by oven drying method in order to determine the water and volatile substances that pass into the oil from the olive tissues during the extraction of olive oil. Values of 0.2% and below are good quality indicators.
“Ether-Insoluble Impurities”; It is the measurement of the total impurities other than the volatile substances in olive oil. It is done to investigate the presence of undesirable particles and inappropriate applications during production. Substances insoluble in petroleum ether or n-hexane, soil, sand and similar substances, mineral substances, oxidized fatty acids, mineral substances, carbohydrates, nitrogenous substances, some resins and some of calcium and alkali soaps are tried to be measured. The value is given in %m/m, values below 0.1% m/m are indicative of good quality.
"Heavy metals"; The presence and amount of these metals are investigated with atomic absorption spectrophotometer devices. First of all, the total amount of iron and copper contained in the oil is determined. Heavy metals are indicators of contamination of catalysts and/or soil bleaches. It can also be found in olive oil as a result of contamination from storage and processing equipment.
Fatty acid composition measurement, triglyceride composition (gas chromatographic method), Pyropheophyt A percentage, and 1.2 diglyceride amount measurements in percent are other measurable objective analysis methods used in quality assessment today, although they are less common.
b. Immeasurable Sensory Measures (Sensory Analysis, Taste and Smell Perception)
Despite the above objective measurable criteria, it is a fact that it is always possible to come across natural olive oils that are defective or insufficient in terms of sensory (smell and taste) even though they have full analytical properties. Therefore, sensory properties are as important as analytical properties in the evaluation of natural olive oils. Since it is not an objectively measurable criterion, it is a difficult assessment to standardize.
The person who will perform the sensory analysis should be educated and experienced, concentrate at the time of tasting, focus, feel good psychologically and physiologically, have a cold, etc. It is desirable not to have a disease. Must not have smoked, must not have used perfume, make-up or scented soap. The most suitable analysis times are around 10.30 and 14.30. At least one hour of fasting is required, ideally two hours, because it may take two hours for the stomach to completely empty depending on the content of the food taken.
The environment where the tasting will take place should be spacious and calm, and should be free from all kinds of odors and noise as much as possible. A sufficient level of daylight should be preferred in terms of illumination. Ambient temperature should be kept between 20 – 22 °C, relative humidity should be kept under control as 60-70%.
The characteristics of the container containing oil to be tasted are important. The container should have a stable design that will not deteriorate, it should be narrow in order to allow the concentration of volatile compounds and odors, and it should be colored so that the oil does not show its color. It is preferred that it is made of durable glass, has smooth and smooth edges, has reached room temperature, and is resistant to temperature changes. It should have a 15ml indicator line on it.
The container to be tasted is covered by hand, it is rotated around its axis and shaken slightly; The hand is pulled over the glass to smell the aroma of the oil, and a small sip is taken and thoroughly circulated in the mouth. If more than one oil tasting is to be performed, the oil in the mouth should be cleaned by chewing a slice of apple before tasting the next oil. Three or at most four different oils should be tasted at a time. Sweet-soft oils are tasted first, bitter-hard oils are tasted last.
According to the International Olive Oil Council, during the evaluation of sensory properties, each sample is graded out of 10 or 5, and positive or negative characterization is made regarding the taste and smell of olive oil. Any of the negative features should not exceed 2.5 out of 10.
Definitions of Negative Sensory Traits:Negative characterizations; almond (in sweet oil with a bland smell), sour, bitter, burnt, cushion or mat, bland, grease, rusty or metallic, vinegary or wine-like, musty or musty smelling, etc. is defined as.
Metallic: A taste reminiscent of metal is felt, it occurs when the oil is in contact with the metal surface for a very long time during the production process or during storage.
Bitter: It is the taste of oil under the effect of oxidation. It should not be confused with the burning sensation in the throat.
Heated or Burnt: The taste of the oil produced under unsuitable conditions and temperatures, especially from the olive paste called pomace, which is left after the oil is separated from the olive.
Straw – Wood/Woody: It is used for the taste of oil produced from completely dried olives. It is used to taste the oil produced from olives that are very small, underdeveloped and whose water needs are not met.
Hard/Rough: Used for oils that are thick/dense, with a doughy feel.
Oily: Oil with the flavor of diesel, oil or mineral oil.
Positive Sensory Trait Descriptions:
positive characterizations; It is expressed with definitions such as fruity, apple, almond/walnut, artichoke, banana, melon, herb-scented, leaf-scented, dried herb scented, sour, bitter (peppery), sweet and bitter. The bitterness in the positive qualities is one of the characteristics of freshly squeezed olive oil, it contains the very intense taste and smell of the fruit.
Fruit Taste: Defines the characteristic, bulky oil odor characteristics coming from firm, fresh, ripe or not fully ripe olives, can be felt directly or under the nose.
Bitter: It is used to describe the aroma of oil that has not reached full maturity (not completely black). The bitterness that burns the throat is an indication that olive oil contains a high amount of phenolic substances.
Sharp Bitter: The taste of oil obtained from the first or never ripe olives of the season. It is an indicator of high amount of phenolic substance content.
Compiled by: Uğur Saraçoğlu (ugisaracoglu@yahoo.com.tr)
Resources:
1. World Olive Encyclopedia; International Olive Council; Fausso Luchetti, 1997.
2. Olive oil; Fahrettin Göğüş, Mücahit Taha Özkaya, Semih Ötleş, Eflatun Publishing House, 2009.
3rd Izmir Olive Symposium; In Search of the Immortal Tree/Don't Touch My Olive, 2-3 September 2015.