From Amanda Bailey
In the industry at the moment there seems to be confusion about olive oil tests. What tests are required and what does all the terminology mean?
Harvest time is a busy time for growers and processors alike. However, as we get caught up in the haste of the season, the way in which olives have been handled pre- through to post-production will certainly show up in chemical testing results. I know we always harp on improving quality, however, ensuring you are keeping to quality parameters at all times is not just something you need to keep in mind but practice day-to-day. Don’t worry if your results aren’t the shining light you hoped for this season, but think of this as an opportunity to improve your processes. Sometimes there are circumstances that you have no control over but which nonetheless can have an impact on quality.
Here is a list of most tests available in accredited Australian Laboratories and what they are for:
| TEST NAME | IOC Range | Description |
|---|---|---|
| FFA Free Fatty Acid | 0.0-0.8% | is a common test for trade classification. Free fatty acid is expressed as percent of oleic acid (the predominant fatty acid in olive oil). |
| PV Peroxide Value | 0-20meq O2/kg | is a primary measurement of oxidation in oil. Oils which present higher values are not as stable and certainly have a much-reduced shelf life. Higher values could indicate improper handling of oil and/or fruit. PV’s of 13 or more are said to be rejected by the buyer. |
| FAP Fatty Acids Profile | Fatty acid composition as determined by gas chromatography (% m/m methyl esters):
| is a test performed to detect adulteration with other oils and also determines the monounsaturated (the best type of fat), polyunsaturated (lower levels desired) & saturated (lower levels desired) profile of your oil. A vast range of fatty acids are tested from Myristic acid to Lignoceric Acid. This test shows the allowable range for the scope of fatty acids including Linoleic acid (or Omega 6) & Palmitic acid (which can be in higher concentrations in warmer areas and you may find higher levels of this acid during warmer seasons). |
| PP Total Polyphenols | Expressed as mg caffeic acid/kg oil. | This test is useful in determining the stability of olive oil, however, there is a correlation between the number of total polyphenols and the resistance to oxidation over time. Polyphenol content decreases with prolonged storage. |
| Rancimat - Induction Time | is used as a primary measure of stability. The analysis gives an indication of shelf life of your oil. | |
| UV absorption | a secondary indicator of oxidation and is used to test old oils or refined oils. Refined oils have higher values. Higher values could also indicate adulteration. | |
| Sterols |
Total sterol content (mg/kg)
| this test is used in detecting adulteration. Olive oil has a fairly stable sterol composition. This test is normally needed if you are exporting. |
| Alpha Tocopherols | are polyphenols and are the principle form of vitamin E. It is used as a measure of quality and stability. | |
| Moisture Content | Virgin oils exhibit a certain percentage of moisture in suspension of oil and should not exceed 0.2%. If this test shows a higher result this can lead to storage problems and the source of the moisture should be determined. Usually, the source of the moisture indicates a malfunctioning vertical separator. | |
| Stigmastadienes | Stigmastadiene content (mg/kg)
| this is a test that detects bleaching during a refining process. When sterol components are exposed to high temperatures stigmastadienes are formed. High levels are a good indicator of the presence of refined oil(s). |
| Trans fatty acids |
| Trans fats occur when an oil is hydrogenated means to add hydrogen and turn a product into a solid (which you would find in the spreadable olive oil/margarine section of your supermarket). |
| TAGs: Tri acyl glycerides Composition & ECN42 (Equivalent Carbon Number 42) | Maximum difference between the actual and theoretical ECN 42 triacylglycerol content:
| When other vegetable oils have a similar fatty acid (like sunflower, rapeseed and grape seed) to olive oil, this test is used to detect adulteration. (See also DAG) |
| Unsaponifiable matter | Unsaponifiable matter (g/kg)
| The fraction of substances in oil & fat which is not saponified by caustic alkali, but is soluble in ordinary fat solvent is called unsaponifiable matter. A characteristic feature of unsaponifiable matter in olive oil is its content of squalene, which is higher than that of other vegetable oils. |
| Waxes | Wax content C40 + C42 + C44 + C46 (mg/kg)
| The levels of waxes and diols (erthrodiol and uvaol) are found in higher levels of solvent-extracted (or refined) olive oils. When the oil has a wax content between 300 mg/kg and 350 mg/kg it is considered a lampante virgin olive oil if the total aliphatic alcohol content is < 350 mg/kg or the erythrodiol + uvaol content is < 3.5%. |
| Oil & moisture by cold press extraction, solvent extraction or NIR | Cold press or Partial Extraction NIR Solvent Extraction | In order to take out some of the guesswork when the optimal harvest time should be, these tests can be carried out in one of three ways. This test shows the level of oil accumulation and indicates that when oil accumulation is around its peak, the harvest should be conducted. |
| DAG: Di-acyl Glycerides | Fresh extra virgin olive oil contains a high proportion of 1,2-diacylglycerols to 1,2- and 1,3-diacylglycerols, while olive oil from poor quality fruits and refined olive oil have elevated levels of 1,3- diacylglycerols. | is a test that is required to determine adulteration and authenticity. An elevated level of DAGs indicates oxidized of poor quality, and/or adulterated with cheaper refined oils. During the breakdown of triacylglycerols, diacylglycerols are formed. |
| Pyropheophytin a | PPP | “Pyro” meaning heat and “pheophytin” meaning chlorophyll. Pyropheophytins occur when oil has been subjected to heat or age-related degradation. |
| Heavy Metals & Pesticide Residues | Maximum permissible concentration Lead (Pb) 0.1 mg/kg Arsenic (As) 0.1 mg/kg | these tests are required for export and wholesaler determination of olive oils. The limits are set by Codex Alimentarius Commission. |
Sensory tests
| Organoleptic test | Positive descriptors are; fruity, green, citrus, spicy, fragrant, tropical, soft, over-ripe, bitter and pungent, and they are determined by the quality of fruit produced on the tree. Negative descriptors are caused by human error and include; fusty, musty, muddy, winey, metallic, rancid, burnt and others. | The sensory characteristics are the primary indicators of EVOO. However, even the most sensitive palate cannot detect every case of adulteration. All EVOO oils must be free of defects. The sensory components of olive oil are; Aroma, Flavour Profile, Fruitiness, Pungency & Bitterness. |
Olive oil tests for specific purposes
Exporting your olive oil
Determining authenticity of oils may require a number of tests. The laboratories normally have packages which include IOC and adulteration tests to ensure that oils meet IOC standards. Depending on where you are exporting to there may be further requirements than the standard tests.
Code of Practice
As the new standards have just been adopted, you may need to consult your laboratory on the tests now required..
Contacting a laboratory:
- DPI Wagga Wagga, Phone: 02 6938 1957
- Modern Olives Laboratory Services
PO BOX 92. Lara, VIC 3212.
Phone: 03 5272 9570
Fax: 03 9272 9599
Email:lab@modernolives.com.au
References
- Codex Alimentarius – Olive Oil
- Trade standard applying to olive oils and olive pomace oils, IOC
- Websites for DPI Wagga Wagga & Modern Olives Laboratory
