Interpreting Olive Oil Chemistry
admin | August 29, 2013So what do all those chemical analyses found in lab reports mean?
There are dozens of them. Some have been accepted as indicators of quality, others suggest how long an extra virgin olive oil will survive on the shelf, while other analyses tell a story about the taste style of the oil (and therefore how it is best used in the kitchen). However, most have been developed in an effort to identify olive oils that have been adulterated with other oils. However, as these limits are necessarily arbitrary, they only suggest rather than prove adulteration.
I have provided some ranges and averages that typify good to excellent extra virgin olive oil in addition to the official limits which are often set to accommodate the constraints of the big EU packers to produce quality olive oil.
Analysis
|
IOOC limit for EVOO |
Average |
Effect |
Comments |
Common Analysis | ||||
Free fatty acidity | 0.8% | 0.192% a
0.162% f EU supermarket 0.5-0.6% |
Quality
Culinary |
|
Polyphenol level | n/a | 260 ppm a#
195 ppm b# 240 ppm g# |
Style
Culinary Shelf life Health |
|
Peroxide Value | 20 mEq /Kg | 9 meq/kg d
6 meq/kg f |
Shelf life |
|
!
Analysis |
IOOC limit for EV |
Average |
Effect |
Comments |
Fatty Acid Profile | ||||
Major Monounsaturated Fatty Acids | ||||
Oleic acid (C18:1) | 55-83% | 73.6% d | Health
Shelf life |
|
Major Saturated fatty acids | ||||
Stearic acid (C18:0) | 0.5-5.0% | 1.9% d | Health
Shelf life |
|
Palmitic acid (C16:0) | 7.5-20% | 12.7% d | Health
Shelf life Other |
|
Major Polyunsaturated Fatty Acids | ||||
Linoleic acid (C18:2) | 3.5-21% | 9.2% d | Health
Shelf life Adulteration* |
|
Linolenic acid (C18:3) | <1.0% | 0.7% d | Shelf life
Health Adulteration* |
|
!
Analysis |
IOOC limit for EV |
Average |
Effect |
Comments |
Other Analysis | ||||
Iodine Value | Typical value
80 b |
Health
Shelf life |
|
|
Saponification value | Typical value
190 b |
Health
Shelf life |
|
|
Induction Time | None | 5.3 hours b | Shelf life |
|
Moisture content | Shelf life |
|
||
UV absorption at 232nm and 270nm | <2.5 (232nm) <0.22 (270nm) |
Quality
Shelf life |
|
|
UV absorbance at 255nm | n/a | Style |
|
|
Diacylglyceride(DAG) ratio | n/a | Good EVOO 79%+e
90%+ typical of high quality |
Quality
Shelf life |
|
!
Analysis
|
IOOC limit for EV | Average in EVOO | Effect | Comments |
Adulteration Analysis | High Levels are suggestive of* adulteration with: | |||
Waxes | < 250 mg/kg | 45mg/kg (cold climate) to 115mg/kg (hot) d | Adulteration* | Olive pomace oil, solvent extracted oil or high leaf content. |
UV-absorption 270nm | <0.22 | Adulteration* | Refined oil | |
Pyropheophytins | Adulteration | Refined oil and soft deodorized oil. Also can suggest that the oil was stored in a hot place. | ||
Trans fatty acids | 0.05% | Adulteration*Health | Refined oils, soft deodorised oils. Trans-fats are significant contributors to cardiovascular disease. | |
2-position palmitic acid | Adulteration* | Palm oil and re-esterified oils. | ||
R1 value | Adulteration* | The ratio of campestadiene to stigmastadiene. A high level is indicative of* adulteration with refined seed oils. | ||
Eicosenoic acid (C20:1) | <0.4% | Adulteration | Vegetable (soybean) oil and canola oil.. | |
ECN42 | <0.2 | Adulteration* | Indicates oils with a high proportion of triacylglycerides containing three linoleic fatty acids i.e. sunflower oil. | |
Total aliphatic alcohols | Adulteration* | Pomace oil | ||
Fatty acid alkyl esters | Adulteration Quality |
High levels indicate that olives were not processed quickly into oil after harvesting. High levels of ethyl esters indicative of soft deodorization. |
||
Stigmastadiene | <0.1 mg/kg | Adulteration* | Refined oils. | |
Sterols | (% of total) | |||
Cholesterol | <0.5% | Adulteration* | Animal based fats | |
Brassicasterol | <0.1% | Adulteration* | Canola oil | |
Campesterol | <4.0% | 2.1-4.5% variety dependent e | Adulteration* | High oleic sunflower oil or other seed oils. |
Stigmasterol | <campesterol | |||
d-7-stigmasterol | <0.5% | |||
Other sterols^^ | >93% | |||
Erythrodiol and uvaol | < 4.5% | Adulteration | Solvent extracted oils. | |
Total sterols | >1000 mg/kg |
Sources: All data with the exception of e- ‘fresh’ samples are from commercially produced extra virgin olive oils.
a- 2005-2010 Australian National, Royal Perth, Royal Canberra Extra Virgin Olive Oil Shows (n=2,356). Compiled by R. Gawel –unpublished.
b- 2005 data, New South Wales Department of Agriculture – unpublished (n>200).
c- Australian Olive Oil Association National Olive Oil Survey – unpublished (n>200).
d- Mailer (2007) (n=1800)
e- Mailer and Ayrton (2008) (n=21 fresh, n=6 EU supermarket)
f- Anon (2010) Oli Extravirgini di Oliva di Firenze Selezione 2010 (n=33)
g- Gawel and Rogers (2008) (n=327)
#- Measured as caffeic acid equivalents
^- ‘unsaturated’ refers to fats that contain more than one double bond somewhere in their chemical structure. Monounsaturated fats have health benefits over saturated fats (ones with no double bonds). However polyunsaturated fats (i.e. those with two or three double bonds) such as linoleic and linolenic acid are more prone to oxidation and therefore degrade (go rancid) more quickly.
^^ – b-sitosterol, d-5-avenasterol, d-5-23-stigmastadienol, Clerosterol, Sitostanol, d-5-24- stigmastadienol
*- olive oil is a complex natural product. As such the amount of individual components in olive oil varies. As a result, unadulterated oils may be high in one or more components normally associated with adulteration practices. For example the varieties Barnea and Koroneiki often produce oils that contain naturally high levels of campesterol.
Disclaimer: This table should be used only as a guide. While every care was taken in the compilation of this table, the author takes no responsibility for any inaccuracies.