Distinguishing the quality of olive oil
(1) General principles
1. Good olive oil has the following characteristics:
The characteristics of olive oil are closely related to the oil-making technology. High-quality olive oil is prepared by cold pressing, and it needs to be separated from low pressure to high pressure. The low-pressure virgin olive oil is light yellow in color, which is the most ideal cold oil and cooking oil.
observation: the oil body is bright and thick, showing light yellow, yellow-green, blue-green, blue and black. Dark olive oil has high acid value and poor quality. The pigment and other nutrients in refined oil are destroyed.
Smell: There is a fruity smell. Different tree species have different fruity smells. The oil taster can even distinguish 32 different olive fruit smells such as licorice, cream, fruit and chocolate.
taste: the taste is smooth, slightly bitter and spicy, with obvious feeling at the back of the throat, and the spicy feeling is lagging behind.
2. Bad olive oil has the following characteristics:
View: the oil is mixed and lacks bright luster, indicating that it has been left for a long time and begins to oxidize. Light color, thin feeling, not strong, indicating refined oil or blended oil.
smell: stale, musty, muddy, sour wine, metallic, and spicy. It indicates deterioration, or there is something wrong with the raw materials of olive fruit, or improper storage.
taste: it smells bad, or it doesn't taste at all. Explain deterioration, or refined oil or blended oil.
(II) Specific operation
1. Look at the product name and classification
Theoretically, according to the Trade Standard of Olive Oil and Olive Fruit Residue issued by international olive oil council in 28, the name of olive oil can only be divided into super virgin olive oil (or extra virgin olive oil) and virgin olive oil according to its grade. The so-called fruit residue is the oil extracted from olive pomace. The quality of this oil is relatively low. According to the international olive oil council standard, it can't be called "olive oil" under any circumstances.
pure olive oil is made of refined oil mixed with extra virgin olive oil, and the acidity of the oil does not exceed 1.5g/1g. This kind of oil is widely used in the cooking field, but many unscrupulous merchants are confused and often produce pure olive oil in the form of blending soybean oil and sunflower oil, so dealers and consumers must carefully read the test report of this product before distributing and buying it. Fake pure olive oil test report, regular pure olive oil test report. From the comparison of these two test reports, it can be seen that the fatty acid composition of fake so-called pure olive oil is basically the same as that of soybean oil. Unfortunately, some regional agents and distributors in China are selling fakes on the pretext of catering to the market demand.
There are also some labels on the market in China that indicate olive oil, or cooking olive oil, which is actually fruit residue or pure olive oil. Consumers and distributors must carefully identify the name on the product label.
there are two kinds of fruit pressed olive oil, a kind of fruit pressed olive oil and b kind of fruit pressed olive oil. Over-ripe, spoiled, insect-bitten, and cracked olives can also be squeezed out like good olives, but these oils are of poor quality and inedible. Before 19, this oil was only used for lighting oil lamps. To this day, this oil is still called "lamp oil". At the beginning of 19th century, some chemists discovered a refining method, which can make olive oil into odorless, colorless and tasteless edible oil. In the olive oil trade, this refined olive lamp oil is called Class A refined olive oil. The refining process destroyed the taste of olive oil and the basic polyphenol antioxidants. After adding 3%-1% virgin (or virgin) olive oil to this refined olive lamp oil, it was grandly named "1% pure olive oil" in the market. Pure olive oil and "light" olive oil are actually a mixture of Class A refined olive oil and virgin olive oil (not super virgin olive oil). This mixed oil has the same calories as other grades of olive oil. Most blended oils contain 1% virgin olive oil and 9% Class A refined olive oil. This 9-1 model is usually called "Rivera mixing method" or "classic mixing method".
The peel and core of normal olive fruit still contain 3-4% oil, but it can't be extracted by cold pressing. At this time, the oil needs to be extracted by ultra-high temperature, hexane solvent and alkali, and then the harmful substances in the oil are removed by decoloration, winterization and deodorization. Finally, the "produced" oil is tasteless and odorless, which is a class B refined olive oil. Mixing refined olive oil of Class B with a small amount of real olive oil is edible olive fruit residue. It is illegal to call this fat-free oil "olive oil" in many countries.
2. Look at the quality inspection report
By understanding the main physical and chemical indicators of olive oil, we can also identify the authenticity and quality of olive oil. According to international olive oil council's Trade Standard of Olive Oil and Olive Fruit Residue, Analytical Method of Olive Oil by Ultraviolet Spectroscopy and China's Professional Standard of Olive Oil and Olive Fruit Residue, the main physical and chemical indexes of olive oil include acid value, peroxide value, fatty acid composition and ultraviolet absorbance. Usually, regular foreign olive oil manufacturers will issue a quality inspection report with each batch of olive oil.
Acidity is an index used to measure the proportion of Free Fatty Acids in every 1 grams of oil. Free fatty acids, also known as free fatty acids, are the "restless" fat components in oil. Too high acidity will easily lead to oxidation, which will lead to rancidity and inedible oil. According to the standards of international olive oil council and EU, the oleic acid content of super virgin olive oil is lower than .8, and that of virgin olive oil is lower than 2.. Therefore, the acidity of super virgin olive oil and virgin olive oil is natural acidity, while the acidity of refined olive oil is artificially interfered acidity. From the point of view of natural acidity, the lower the quality of olive oil, the better.
Peroxide value refers to the total peroxide content in oil. The peroxide value is the hydroperoxide produced by the oxidation of oil and oxygen in the air, which is the primary product of automatic oxidation of oil. It is highly active and can continue to change rapidly, decomposing into aldehydes, ketones and oxides, which leads to rancidity and deterioration of oil. Therefore, hydroperoxide is a sign of the initial oxidation degree of oil. Hydroperoxide is harmful to human health, and oils with excessive peroxide value cannot be eaten. China's standards are usually expressed in millimoles (m mol/kg), while international olive oil council and the European Union use (meq O2/kg). The acidity of super virgin olive oil and virgin olive oil should be less than 2(meq O2/kg, international) or 1(m mol/kg, domestic) according to international and domestic standards, and the refined olive oil with manual intervention should be less than 5 (international and domestic). Like acidity, if the peroxide value on the quality inspection report is too low, the product does not belong to super virgin olive oil or virgin olive oil. If the peroxide value is higher than the standard, it means that the product has been stored for too long and the olive oil has begun to deteriorate.
ultraviolet absorbance (Absorbency in ultra-voilet) refers to the spectral values of oils and fats irradiated by ultraviolet rays with different wavelengths. The determination of ultraviolet spectrum of olive oil is very helpful to understand the quality, storage state and change of olive oil. It usually indicates the grade and fresh-keeping ability of olive oil. There is no relevant ultraviolet absorbance standard in the Professional Standard of Olive Oil and Olive Fruit Residue of the People's Republic of China, so some dealers deliberately conceal this test result.
Fatty Acid Composition is one of the most important physical and chemical indexes of olive oil, which reveals the authenticity of olive oil and its nutritional value. Fatty acid is the basic unit of fat, and it is one of the most important nutrients in human body like vitamins and amino acids. In biology, fatty acids are divided into saturated fatty acids and unsaturated fatty acids, and unsaturated fatty acids are divided into monounsaturated fatty acids and polyunsaturated fatty acids. The biggest difference between olive oil and traditional oils and fats is that the unsaturated fatty acid content of olive oil is the highest among all oils and fats, and monounsaturated fatty acids can reduce the contents of serum cholesterol and low-density lipoprotein cholesterol without changing (even increasing) high-density lipoprotein cholesterol, thus preventing and preventing the formation of cellulite and preventing cardiovascular diseases. Polyunsaturated fatty acids include linoleic acid (C18: 2), which is omega-6 fatty acid, linolenic acid (C18: 3), which is omega-3 fatty acid and other essential fatty acids that cannot be synthesized by human body.
In addition, the ratio of linoleic acid to linolenic acid in fatty acid composition is also an important indicator. Generally speaking, the ratio of linoleic acid to linolenic acid in extra virgin olive oil is lower than 2: 1. Theoretically, the ratio can reach the ideal 4: 1. In fact, olive oil that can reach this ratio is very rare, and olive oil with good quality can reach 6: 1 to 12: 1.
the quality inspection report of olive oil is just like a "physical examination" report, and it is clear at a glance whether it is healthy or not, good or bad, true or false, and good or bad. However, the quality appraisal of olive oil should be comprehensively evaluated, instead of amplifying a certain index alone (for example, exaggerating the low acidity and peroxide value of the product without looking at the fatty acid composition and ultraviolet absorbance of the product). At the same time, it should be evaluated in combination with the sensory indexes of olive oil. Only in this way can we not be blinded by one leaf and be a smart consumer.
3. Look at the processing technology
If it is extra virgin olive oil (or extra virgin olive oil), there is a method of cold pressing (Cold Pressed or Cold Extracted will be marked on the label), that is, the olive fruit is squeezed directly by physical machinery, which is the same as the principle that some families apply juice presses to squeeze juice. The olive oil extracted by this method is natural and pure, and its nutrition has not been damaged. Another method is Refined, which is actually chemical leaching method.
4. Look at the place of origin
The place of origin has a great influence on the price and quality. At present, among the main producers of olive oil, Spain accounts for one-third of the world total, Italy for one-fourth and Greece for one-fifth. Other oil-producing countries include Turkey, Syria, Portugal, France and Egypt. According to statistics, the proportion of super virgin olive oil in Greece accounts for 75% of the country's olive oil production, 5% in Italy and only 3% in Spain. The reasons for good quality are tree species, climate, latitude and other geographical conditions.
5. Look at the bottled place
At present, the vast majority of olive oil sold in China market depends on imports. There are two kinds of imported olive oil: original and sub-packaged. Originally, the bottle of olive oil was canned in the factory in the exporting country. Large foreign professional olive oil manufacturers usually have low-temperature tanks for storing more than 1, tons of olive oil, and the whole process from harvesting to squeezing and bottled transportation has passed HACCP hazard analysis and key point control certification and ISO91 quality management certification in the food industry. Therefore, the probability of original olive oil safety is very high.
6. Look at the packaging
There are many kinds of packaging for olive oil. At present, the main types of packaging we have seen are transparent glass bottles, dark glass bottles, transparent plastic spatula, transparent plastic bottles, cartons, metal TIN containers and so on. Olive oil has high antioxidant content, which can be stored in a cool and dark place for 24 months, which is incomparable to any other oil and natural juice. However, olive oil is sensitive to light, and it is easy to be oxidized if the light is continuous or intense. Therefore, it is recommended to buy dark glass bottles or containers that are not easy to transmit light, so that the storage time will be longer and the nutrition in olive oil will not be destroyed easily. In addition, in addition to small packaging, the international standard packaging of olive oil is: 25 ml, 5 ml, 75 ml, 1 liter, 3 liters, 5 liters and so on. It should be noted that there are some packages that are short of weight in the market.
7. Look at the certificate
Olive oil legally imported from China should have a series of official certificates of exporting countries, quality certificates and China's official certificates and quality certificates, including imported food label audit certificates, official inspection reports of exporting countries, laboratory reports of exporting countries, hygiene certificates, quality certificates, China's laboratory inspection reports and hygiene certificates. In addition, the quality certification of foreign manufacturers is also very important. Dealers should ask for series certificates, and consumers can check them online if conditions permit. Some general olive oil distributors in China do not have these certificates, or the certificates are incomplete. What is more serious is that some general olive oil distributors import from country T, but they are branded as country G.. Dealers and consumers need to distinguish carefully.
8. The quality of
olive oil is good. On the one hand, it is some internal physical and chemical indicators, on the other hand, it needs to be determined by the senses. For this reason, international olive oil council promulgated the Method of Sensory Analysis of Olive Oil and Sensory Evaluation of Original Olive Oil. If conditions permit, consumers should taste it in person to judge the basic quality of the product. In western countries, like wine tasters, there are also oil tasters who specialize in tasting olive oil.
Usually, the oil taster evaluates olive oil according to the following steps:
1) Note: It is best to evaluate 3 or 4 kinds at a time. According to the smell, it's best to taste light first and then strong. Do not use perfume, deodorant, soap, lipstick, smoke, eat sweets or drink coffee 3 minutes before or during the tasting.
2) Pour the olive oil that needs to be evaluated into small glasses in turn. Pick up a cup at a time, put your palm close to the bottom of the cup, gently shake it, and slowly heat the olive oil with the temperature of your palm, so that the fragrance of the oil can be fully emitted. Meanwhile, observe the color and transparency of the oil.
3) Keep your nose as close to the olive oil as possible, and slowly inhale deeply for two or three consecutive times. Pay attention to the smell. If necessary, do it again in a minute.
4) There are two ways to taste olive oil, one is to pour it on unsalted white bread, and the other is to drink it directly. When drinking directly, drink 2-3 ml each time, and moisten the oil to all parts in the mouth.
5) Open your mouth slightly, inhale continuously and quickly for two or three times, spray the oil into mist, and let the air and oil mix and touch your tongue and palate. Spit out the oil. You can repeat it if necessary. However, before repeating, you need to rinse your mouth with clear water, or eat an apple, then rinse your mouth and taste it.