Unfiltered

olive oil Olive oil is a liquid fat obtained from olives (the fruit of ''Olea europaea''; family Oleaceae), a traditional tree crop of the Mediterranean Basin, produced by pressing whole olives and extracting the oil. It is commonly used in cooking: f ...

(also known as ''cloudy olive oil'', ''veiled olive oil'', or ''olio nuovo'') is an intermediate product of

olive oil extraction Olive oil extraction is the process of extracting the oil present in olive drupes, known as olive oil. Olive oil is produced in the mesocarp cells, and stored in a particular type of vacuole called a lipo vacuole, i.e., every cell conta ...

. It is actually the initial cloudy juice of the

olive The olive, botanical name ''Olea europaea'', meaning 'European olive' in Latin, is a species of small tree or shrub in the family Oleaceae, found traditionally in the Mediterranean Basin. When in shrub form, it is known as ''Olea europaea'' ...

drupe In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part (exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kernel'') ...

s soon after crushing, separation and

decanting Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. The layer closer to the top of the container—the less dense of the two liquids, or the liquid from which the ...

and before final

filtration Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter ...

. The oil is either filtered or stored in tanks to settle for weeks or months to allow sediments to be separated from the oil; this is known as ''racking''. Once opened, unfiltered olive oil has a shorter life because the olive particles continue to ferment in the bottle.

Application

Although most commercially available olive oil in the world market is filtered, unfiltered olive oil is gaining increasing popularity amongst olive oil small scale producers, some chefs, and people who prefer a more "natural" aesthetic. They believe that this oil has superior sensory characteristics compared to filtered olive oil, because it is a less processed product.

Nature of cloudiness

Unfiltered olive has aspects of both a suspension and an

emulsion An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...

. Plant material from olive drupes is suspended in oil due to lack of the filtering step, along with microdroplets of vegetative and non-vegetative

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

in small amounts (0.1–0.3%) forming in a water-oil emulsion. Unfiltered olive oil initially has higher levels of phenolics that form a complex polyphenol-

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

complex. This complex interacts within the suspension/emulsion system and contributes to the formation and maintenance of the physicochemical properties of this oil. However, the presence of water in unfiltered oil leads to a more rapid hydrolysis of these water-associated phenolics, and also to hydrolysis of the triglycerides in the oil, and

enzymes Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

present in particles of olive fruit and pit and pathogens such as

yeasts Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

can accelerate the rate of degradation of the quality of the oil and increase the oil free acidity. The overall effect of filtration on olive oil durability is controversial, with different studies coming to different conclusions, and likely also depends on the specific systems used to filter the oil. The main phenolics found in olive oil are secoiridoids,

hydroxytyrosol Hydroxytyrosol is an organic compound with the formula . Classified as a phenylethanoid, i.e. a relative of phenethyl alcohol, Its derivatives are found in a variety of natural sources, notably olive oils and wines. The compound is colorless solid ...

, and

tyrosol Tyrosol is an organic compound with the formula . Classified as a phenylethanoid, i.e. a derivative of phenethyl alcohol, It is found in a variety of natural sources. The compound is colorless solid. The principal source in the human diet is ol ...

, along with caffeic, vanillic, p-coumaric, syringic and

p-hydroxy benzoic acid 4-Hydroxybenzoic acid, also known as ''p''-hydroxybenzoic acid (PHBA), is a monohydroxybenzoic acid, a phenolic derivative of benzoic acid. It is a white crystalline solid that is slightly soluble in water and chloroform but more soluble in polar ...

s, 3-hydroxyphenylethanol and

3,4-dihydroxyphenylethanol Hydroxytyrosol is an organic compound with the formula . Classified as a phenylethanoid, i.e. a relative of phenethyl alcohol, Its derivatives are found in a variety of natural sources, notably olive oils and wines. The compound is colorless solid ...

.“Polyphenols in olive oils”. T. Gutfinger, ''Journal of the American Oil Chemists' Society'', Volume 58, Number 11, 966–968,

Natural cloudiness versus low-temperature cloudiness

Olive oil cloudiness resulting from sediments discussed in this article is different from the characteristic cloudiness of olive oil due to storage at low temperatures EF This type of cloudiness is the result of congealing of triglycerides. When these oils are returned to room temperature, they become again transparent. Unfiltered olive oil has a cloudy appearance that can persist months after the oil has been returned to room temperature.

Application

Nature of cloudiness

Natural cloudiness versus low-temperature cloudiness

References

Further reading