Numerous attributes of olive oil play a role in determining its overall quality. However, two basic ones are its Peroxide Value, PV and the amount of Free Fatty Acid it contains.
Peroxides are primary oxidation products that are formed when oil is exposed to oxygen, producing undesirable flavours and odours. The Peroxide Value will rise and then taper down while oil is in storage. The unit used for PV is milli-equivalents of active oxygen/kg oil. Virgin olive oils should have a PV of <20.
The Free Fatty Acid value is measured as free acidity expressed in g/100g of oleic acid in the oil. Extra Virgin Olive Oil has not more than 0.8g/100g of free acidity.
The following are test results of Peroxides and Free Fatty Acid for samples of the 2016 and 2017 harvest from Cottage Grove (analysis done by the Far North Enviro Lab Ltd, Taipa).
| 2016 Test Results | Result 1 | Result 2 |
|---|---|---|
| Peroxide mEqO2 | 4.39 | 4.38 |
| Free fatty acid % | 0.11 | 0.11 |
| 2017 Test Results | Result 1 | Result 2 |
|---|---|---|
| Peroxide mEqO2 | 8.42 | 8.40 |
| Free fatty acid % | 0.03 | 0.03 |
Clearly, the olive oil from Cottage Grove passes the Peroxide test with flying colours, although it is interesting that the 2017 PV value is considerably higher than that of 2016. This probably reflects the year standing time of the 2016 vintage before we sent samples for analysis. We would expect the 2017 PV value to fall to a similar low level after another year of storage.
The free acid values of both 2016 and 2017 are much less than 0.8g/100g and therefore both Cottage Grove vintages qualify as extra virgin oil.
General Characteristics of Olive Oil
There is a lot of misinformation about the health and other benefits of olive oil compared to other oils used with food.
Firstly, a comment on terminology: what we refer to as fat is a complex mixture of different molecules, known as lipids or fatty acids. The latter two terms are often used interchangeably.
There are only two or three fats which are truly beneficial to humans, and they are known as Essential Fatty Acids (EFAs). These fats are essential because the human body cannot produce them on its own, so they must come from diet. The two primary EFAs are known as linoleic acid or LA (an omega-6 lipid), and alpha-linolenic acid or ALA (an omega-3 lipid).
Some other fatty acids are sometimes classified as conditionally essential, meaning that they can become essential under some developmental or disease conditions; examples include docosahexaenoic acid or DHA (an omega-3 lipid) and gamma-linolenic acid or GLA (an omega-6 lipid).
Arachidonic acid or AA is not one of the essential fatty acids. However, it does become essential if there is a deficiency in linoleic acid or if there is an inability to convert linoleic acid to arachidonic acid, which is required by most mammals.
The main lipids present in a sample of the Cottage Grove olive oil from the 2016 harvest is given below (analysis by Nutrition Laboratory, Massey University).
Olive oil as a source of Omega 3 fatty acids
The only Omega 3 lipid found in the Cottage Grove olive oil was ALA at a mere 0.82%, which is a typical result for olive oils (see the United States Department of Agriculture Composition Database
USDA). Fish oils are the most common source which is rich in Omega 3 lipids. Some examples are outlined below:
Olive oil is not recommended as a cooking oil
This is because of the low smoke point of olive oil (see Table below). Other oils which have high smoke points (above 200°C/400°F) include avocado oil, almond oil, corn oil, canola oil, grapeseed oil, peanut oil, safflower oil, sesame oil and sunflower oil. These oils are better suited for cooking at higher temperatures.
Saturated and Unsaturated Fats
Saturated fats have no double bond between molecules (the fat is saturated with hydrogen molecules), and they are generally solid at room temperature.
Unsaturated fats have one (monounsaturated) or more (polyunsaturated) double bonds in their molecules and are liquid at room temperature.
The American Heart Association recommends that 25-35% of human total daily calories should consist of fat, and that most of this intake should be from unsaturated fat.
However, accumulating scientific research now suggests that unsaturated fats alone may not be as heart healthy, and consuming saturated fats may not be as dangerous as once thought.
The most common sources of saturated fats include:
The following Table presents the complete lipid analysis carried out on the 2016 vintage from Cottage Grove. ND = Not detected.
Lipid Name Percent
Oleic 76.72
Palmitic 8.96
Linoleic 7.33 LA
Stearic 2.54
Vaccenic 1.17
cis-9,12,15-Alpha linolenic 0.82 ALA
Arachidic 0.40
cis-9-Palmitoleic 0.38
cis-ll-Eicosenoic 0.27
Behenic 0.12
Margaric 0.11
Lignoceric 0.05
cis-ll,14-Eicosadienoic 0.04
Heneicosanoic 0.02
Tricosanoic 0.02
cis-13-Erucic 0.01
Myristic 0.01
Vaccenic 0.01
Total 98.98
As can be seen in these results, Cottage Grove olive oil from the 2016 harvest contains just over 8% of EFA (7.33% LA, and 0.82% ALA). This is very modest, compared with those listed below.
Percent EFA lipids ALA AL
Chia seed oil 64 18
Flax/linseed seed oil 40 31
Hemp oil 19 56
Walnut oil 0.4 59
Avocado oil 0.8 15
Grapeseed oil 0.1 73
For clarity, the species names of these plants are: chia, Salvia hispanica; common flax or linseed, Linum usitatissimum (not to be confused with NZ flax, Phormium tenax); hemp, Cannabis sativa; walnut, Juglans regia; avocado, Persea americana; grape, Vitis vinifera.
The main Omega 3 fatty acids are: 18:3 Alpha-Linolenic acid (ALA); 20:5 Eicosapentaenoic acid (EPA); and 22:6 Docosahexaenoic acid (DHA).
Fish Oils % EPA DHA ALA
Salmon oil 13 18 <1
Sardine oil 10 11 <1
Cod liver 7 11 <1
Avocado oil 271°C
Ghee (clarified Butter) 252°C
Soybean oil (refined) 238°C
Peanut oil 232°C
Coconut oil (refined) 232°C
Corn oil 227°C
Grapeseed oil 216°C
Canola oil (refined) 204°C
-------------------------------------
Olive oil (virgin) 199°C
Olive oil (extra virgin) 191°C
Lard 188°C
Vegetable shortening 182°C
Coconut oil (extra virgin) 177°C
Sesame oil (unrefined) 177°C
Butter 120-150°C
Flax seed oil 107°C
The most common sources of unsaturated fats include:
Animal meat including beef, poultry, pork
Certain plant oils such as palm kernel or coconut oil
Dairy products including cheese, butter, and milk
As can be seen from the above, olive oil is a monounsaturated fat, and as a result is considered by many to be a more healthy source of dietary fat than many others available. However, the scientific literature relating to the hazards and benefits of consuming different types of fats in diet is far too complex (and in some places contradictory) to be summarised here. One suggestion is that whatever modest health benefits that might be associated with consuming olive oil could be largely due to the beneficial plant chemicals, such as polyphenols and plant sterols, found in the extra virgin olive oils. In addition, these plant chemicals are largely lost in the more processed ‘light’ cheaper olive oils available in supermarkets. Clearly, Cottage Grove extra virgin oil might therefore have a lot to recommend it.
Monounsaturated fats canola oil and olive oil
Polyunsaturated fats safflower oil, sunflower oil, and corn oil
| Lipid Number | Fatty Acid Name | Percent | |
|---|---|---|---|
| C6:0 | Caproic | ND | |
| C8:0 | Caprylic | ND | |
| Cl0:0 | Capric | ND | |
| Cll:0 | Undecanoic | ND | |
| C12:0 | Lauric | ND | |
| C13:0 | Tridecanoic | ND | |
| C14:0 | Myristic | 0.01 | |
| C14:1n5 | cis-9-Myristoleic | ND | |
| C15:1n5 | cis-l0-Pentadecenoic | ND | |
| C16:0 | Palmitic | 8.96 | |
| C16:1n7 | cis-9-Palmitoleic | 0.38 | |
| C17:0 | Margaric | 0.11 | |
| C17:1n7 | cis-l0-Heptadecenoic | ND | |
| C18:0 | Stearic | 2.54 | |
| C18:1n9t | Elaidic | ND | |
| C18:1n7t | Vaccenic | 0.01 | |
| C18:1n9c | Oleic | 76.72 | |
| C18:1n7c | Vaccenic | 1.17 | |
| C18:2n6t | Linolelaidic | ND | |
| C18:2n6c | Linoleic | 7.33 | |
| C20:0 | Arachidic | 0.40 | |
| C18:3n6 | cis-6,9,12-Gamma Linolenic | ND | |
| C20:1n9 | cis-ll-Eicosenoic | 0.27 | |
| C18:3n3 | cis-9,12,15-Alpha Linolenic | 0.82 | |
| C21:0 | Heneicosanoic | 0.02 | |
| C20:2n6 | cis-ll,14-Eicosadienoic | 0.04 | |
| C22:0 | Behenic | 0.12 | |
| C20:3n6 | cis-8,ll,14-Eicosatrienoic | ND | |
| C22:1n9 | cis-13-Erucic | 0.01 | |
| C20:3n3 | cis-ll,14,17-Eicosatrienoic | ND | |
| C20:4n6 | cis-5,8,ll,14-Arachidonic | ND | |
| C23:0 | Tricosanoic | 0.02 | |
| C22:2n6 | cis-13,16-Docosadienoic | ND | |
| C24:0 | Lignoceric | 0.05 | |
| C20:5n3 | cis-5,8,ll,14,17-Epa | ND | |
| C24:1n9 | cis-15Nervonic | ND | |
| C22:5n3 | cis-7,10,13,16,19-DPA | ND | |
| C22:6n3 | cis-4,7,10,13,16,19-DHA | ND |