How to detect poor quality Olive Oil

Updated: Aug 12



Sensory analysis is the most important type of analysis used to classify olive oil into a quality category.

It is carried out by a “test panel”, i.e. an official tasting group of specialists qualified to use approved methods. A test panel is an essential tool for both checking oil quality and highlighting the uniqueness of the end product. Using only chemical parameters is not sufficient for guaranteeing product quality. Unlike test panels for food, sensory analysis enables an in-depth assessment of olive oil based on olfactory and taste factors.

It is not so widely known that human smell and taste have the precision of a scientific instrument and can recognize properties and defects that are not detectable by chemical analysis.

The olive oil sensory profile is related to enzymatic activities which are, by and large, governed by genetic factors, cultivation practices, ripening state, oil extraction parameters and mode of olive storage. Through sensory analysis, specialists, except for positive and negative attributes, are able to recognize different fruit and vegetable aromas based mainly on the variety of olives. They can identify aromas like tomato, apple, artichoke, banana, pear, peach, grass, almond, vanilla, cinnamon, etc.


Bad quality olive oil will display what is known as ‘defects’, which are commonly caused by poor handling of the olives before and during processing and/or poor handling of the oil after processing/storage.


For olive oil to be Extra Virgin, professional tasters or even consumers, must not perceive any sensory defects. With practice are extremely easy to pick up on once you know what you are smelling for. “Wrong” smells are similar to the smell of paint, nail varnish, a dirty nappy/ diaper, wax crayons, a marshy pond, rotten cheese, metallic, vinegar and so forth. These defects occur because of mistakes made in production, such as leaving the olives to ferment in a bag upon collection, or even beating them out of a tree with a stick, causing them to bruise and rot. A professional taster can tell you the story of the olive’s journey from the tree to the bottle! Once you memorize which smells mean what, you can do it too.

Common causes of defects include:


The length of time and the temperature the fruit is stored before processing

  • Ideally, the fruit should be processed within 4 to 8 hours of harvest

  • Defects caused = Fusty, musty, winey

The condition of the fruit or any damage to the fruit

  • Defects caused = wet hay, stewed fruit, grubby

The time and temperature during processing

  • Defects = burnt, overheated, cooked

The nature of the storage container and the good practices in the storage process

  • Defects = muddy, rancid, metallic

It’s important to note that if an olive oil contains any of the defects listed below, it cannot be called Extra Virgin.


Negative attributes (defects)


Rancid: rancid oils have undergone intense oxidization and are essentially off. This is the most common defect and can be caused by incorrect storage (exposure to heat, light or air) or when the oil has been kept for too long. Some descriptors you might use to describe rancid oil include paint, stale walnuts, old butter, off meat, wax crayons, old lipstick, play-doh.


Fusty – Fustiness occurs in oils made from olives that have been piled or stored for too long before processing, resulting in advanced anaerobic fermentation (fermentation without oxygen). Some descriptors you might use to describe fusty flavored oil include pomace paste, tapenade, olive mill waste pond, mushy black brined olives, rotten cheese and horse poo.


Musty – This is essentially a moldy flavor and happens when the oil is made from moldy olives – often as a result of being stored in humid conditions for too long. Mustiness can also occur when using olives that have been crushed with dirt or mud on them. Some descriptors you might use to describe musty oil include sweaty socks, gym clothes bag, wet carpet, moldy hay, yeasty, and mushroom.


Winey/vinegary – this is usually due to aerobic fermentation (fermentation with oxygen) and results in a sour or vinegar-like taste in the oil. Some descriptors you might use to describe winey/vinegary oil include red apple fermented, nail polish, solvent, yeasty, bad quality wine, apple cider vinegar.


Metallic – a metallic flavor may develop in oils that have been in prolonged contact with metallic surfaces during processing or storage. Some descriptors you might use to describe this defect include metals, tin, rusty nails, grinding dust.


Frozen fruit– this occurs in oils made from olives that have been affected by frost before processing. Some descriptors you might use to describe this defect include vanilla, wet wood, wet hay, stewed fruit.


Burnt/Heated – This occurs when the oil is processed using too high temperatures (more than 30oC). Some descriptors you might use to describe burnt/heated oil include burnt caramel, honey, boiled vegetables.


Dried – this flavor develops in oils made from olives that have been affected by drought, or that have spent extended times refrigerated in a cool room. Some descriptors you might use to describe dried oils include dry hay, pip, wood, moldy straw.


Earthy – This occurs when oils are produced from olives that have been collected with earth or mud on them and not washed. Descriptors you might use to describe this defect include earth, dirty, sandy feeling in the mouth.


Apart from professional olive oil tastings, it is very important for consumers to learn how to taste and select olive oil of good quality since the consumption of olive oil has increased lately due to the need for a better quality of life. Descriptions such as "pure olive oil" or "very good" or "premium" are not enough to determine the quality and consumers should seek deeper knowledge in order to protect their own and their family's health.

Since there are so many mislabeled olive oils in the market, the only way to protect yourself from fraud is to attend an oil tasting workshop where you will be able to learn everything about olive oil. From how to select the best olive oil for your family's needs or those of your taste buds, to how to create extraordinary dishes!



source: Olive Wellness Institute, IOC