Chemistry of Premium Olive Oils
Guide to Assess the Purity of Olive Oils
Understanding the chemistry of premium olive oils begins with two essential methods of assessment: chemical analysis and organoleptic analysis. While chemical testing offers objective data, sensory evaluation provides a deeply personal experience. Together, these approaches help determine the quality and character of extra virgin olive oil.
Through laboratory testing, we measure beneficial compounds such as polyphenols and oleic acid, along with indicators of deterioration like free fatty acids and peroxide levels. These results reveal the nutritional value and freshness of the oil. However, lab results alone cannot capture the sensory pleasure of using fresh, well-crafted olive oil.
That’s where organoleptic analysis comes in. This process happens through the senses—your nose and mouth detect fruity, grassy, nutty, or peppery notes, each contributing to the oil’s complexity. Although science can identify the chemical compounds responsible for flavor and aroma, the human sensory system remains the most effective tool for experiencing and evaluating premium olive oil.
Therefore, to truly understand the chemistry of premium olive oils, we encourage you to taste a wide variety of oils. As your palate develops, you’ll begin to recognize the subtle differences that set exceptional oils apart. This hands-on exploration not only enhances your appreciation but also helps you choose the olive oil that brings the most satisfaction to your cooking and wellness routine.
Types of Olive Oil
Before choosing a bottle, it’s essential to understand the different types of olive oil. Each type offers unique health benefits—and the chemistry of premium olive oils plays a key role.
Olive oil supports digestion, reduces inflammation, helps prevent cancer, and moisturizes skin and hair. However, only high-quality oils, like extra virgin, deliver the full range of nutrients and antioxidants.
By learning more about the chemistry of premium olive oils, you can choose the right type for your health, cooking, and personal care needs.
This oil comes exclusively from virgin oil production and contains no more than 0.8% acidity. Additionally, experts judge it to have a superior taste. In fact, extra virgin olive oil makes up less than 10% of the oil produced in many countries.
Producers create this oil using only physical methods, avoiding chemical treatment entirely. It contains less than 2% acidity and is considered to have good taste. However, more than 50% of the oil produced in the Mediterranean region is of such poor quality that refiners must process it to make it edible. Following these two grades are blended oils, which typically consist of up to 90% refined oil mixed with virgin olive oil.
Producers typically label oils as Pure Olive Oil or Olive Oil when they blend refined oil with virgin production oil. In fact, over 50% of the oil made in the Mediterranean region is of such poor quality that refiners must treat it to make it edible. Although they don’t use solvents to extract the oil, they do refine it using charcoal along with other chemical and physical filtration methods.
Producers blend virgin and refined production oils to create this oil, which contains no more than 1.5% acidity. As a result, it has a mild taste and lacks strong flavor.
Producers refine pomace olive oil and sometimes blend it with virgin production oil to create this product. Although it is safe to consume, regulations do not allow it to be labeled simply as olive oil. Instead, manufacturers typically reserve olive-pomace oil for restaurant use, especially for specific types of cooking, and rarely sell it at retail.
Refiners obtain this oil from virgin olive oils using methods that preserve the original glyceride structure. It contains no more than 0.3 grams of free acidity per 100 grams (0.3%), expressed as oleic acid, and meets all characteristics defined for this grade. To create it, producers refine virgin oils with high acidity or noticeable organoleptic flaws, which the refining process eliminates. In fact, more than 50% of the oil produced in the Mediterranean region requires refining before it becomes edible. Although no solvents are used during extraction, producers refine the oil using charcoal and other physical and chemical filtration techniques. Previously, the industry referred to this category as “pure olive oil.”
Producers consider this oil unsuitable for consumption because it typically comes from spoiled or insect-damaged olives. The name “lampante” refers to its traditional use in oil-burning lamps. Today, manufacturers primarily use lampante oil in industrial markets. Before anyone can consume it, refiners must chemically treat it. After processing, the resulting product is called A-Refined or Refined-A olive oil. Technically, it does not qualify as true “olive oil.” Instead, manufacturers use it as the main component in a new blend marketed as “Pure Olive Oil.”
Because the United States is not a member of the International Olive Oil Council (IOOC), its retail grades carry no legal weight in the country. As a result, producers may use terms like “extra virgin” without regulatory restrictions.
Since 1948, the U.S. Department of Agriculture (USDA) has defined four olive oil grades based on acidity, odor, flavor, and absence of defects:
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U.S. Grade A or U.S. Fancy must have a free fatty acid content no greater than 1.4% and be “free from defects.”
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U.S. Grade B or U.S. Choice must not exceed 2.5% acidity and be “reasonably free from defects.”
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U.S. Grade C or U.S. Standard may contain up to 3.0% acidity and be “fairly free from defects.”
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U.S. Grade D or U.S. Substandard has more than 3.0% acidity and “fails to meet the requirements of U.S. Grade C.”
Because these grading terms vary and offer limited detail, the best way to evaluate olive oil quality is by tasting it yourself. Always consider freshness, flavor, and the levels of beneficial antioxidants and nutrients when choosing a high-quality olive oil.
