top of page

Frequently Asked Questions

What is Virgin olive oil?


The International Olive Council definition : Virgin olive oils are the oils obtained from the fruit of the olive tree solely by mechanical or other physical means under conditions, particularly thermal conditions, that do not lead to alterations in the oil, and which have NOT undergone any treatment other than washing, decantation, centrifugation and filtration’

What is Extra Virgin olive oil?


The highest grade of olive oil available. It must have a acidity level less than 0.8% measured as free fatty acid, declared as oleic acid; and a peroxide value of less than 20 meq/kg, to comply with the International standard set by the International Olive Oil Council. This is tested and certified by an independent laboratory. No additives can be added to classify the oil as Extra Virgin Olive Oil.

What does the 'Red Sticker' represent on our bottles and cans?
This is the standard set for for compliance of New Zealand olive oil by Olives NZ. It is much more stringent than the International Standard as discussed above.
The olive oil has been certified as Extra Virgin Olive Oil(currently in Australia), NOT just labelled as such. The olive oil is first laboratory tested to ensure that the oleic acid content is less than 0.5% of free fatty acids and the peroxide value is below 15 meq/kg. If the oil is equal or less than those values it is sent for organoleptic sensory testing. Any single defect found -the oil is automatically downgraded to Virgin olive oil, even though its chemical composition may still comply. OlivesNZ will issue a certificate to authenticate all olive oils that pass that test. The certification will lapse 2 years from harvest date. 
What are the other grades of olive oil?


There are internationally two clearly defined grades of olive oil, 'Virgin' and 'Refined'.


In the virgin olive oil range the grades are Extra Virgin, Virgin, Ordinary and Lampante (lamp). These genuine unadulterated olive oils are graded by their free fatty acid content and the appropriate sensory characteristics with extra virgin less than 0.8%, virgin being less than 2%, ordinary virgin not more than 3.3% and lampante more than 3.3%. Lampante (lamp) oil is just that; or to be used in food chain, must be refined, as below.


The 'Refined' olive oils are frequently found in the food chain. These oils are usually from the second pressing or subsequent; and are often heated above 35 deg to extract more oil and thus are not considered cold pressed or virgin. They are then processed through various filtering systems. There is plenty of mislabeling to mislead the consumer as to what grade the actual oil is.The grades are Refined, 'Pure' olive oil, Crude Pomace oil, Refined Pomace oil, and Olive-pomace oil.There has been some impetus to classify pomace oil as a non food chain commodity in Europe, which has no conclusion to date. 

Does colour determine the quality of the oil?

Colour is not is not an indicator of the oil quality and oil is not judged with any consideration to colour.

What is 'cold pressed'?

Cold pressed means that the oil is processed under 35° centigrade. More oil can be extracted at temperatures exceeding 35°, but it is of a lower grade and is usually refined to be used in the food industry.

What is the fat content of olive oil?


Olive oil has 485 kilojoules (115 calories) per tablespoon, the same as any other oil. It is cholesterol free. Monounsaturated fats such as olive oil lower the damaging LDL-cholesterol (low density lipoproteins) which are responsible for depositing cholesterol in the arteries, and leave the beneficial HDL-cholesterol (high density lipoproteins) untouched or even at a higher level. Olive oil has antioxidants in great variety. These are needed to prevent the harmful LDL-cholesterol from becoming oxidised. Olive oil and olives are an essential part of the traditional Mediterranean diet which nutritionists are recommending as one of the most healthy diets. Click here for more about the Mediterranean diet and health benefits of olive oil.


"Total Cholesterol is fairly meaningless as a single indicator of hardening of the arteries, it is the 'good' (HDL) and bad (LDL) which matter. I see many people with heart attacks who have total cholesterol less than the recommended 5.0 , but their bad LDL may be 3.2 -the LDL is what counts and which needs to be LESS THAN 1.7 in a person with known heart disease or under 2 in all diabetics (adults). Olive oil ( as well as grape seed oil and the like) and also the Omega 3 and 6 'fish oil' compounds change how the body metabolizes and makes the triglycerides and which portion is HDL or LDL. These plant oils lower LDL.


The medications which are sometimes so vilified (the statins- lipex-simvastatin) lower LDL but actually reduce heart attack and stroke much more by a whole different biological mechanism- they reduce inflammation and oxidative stress of the cells. Olive oil and Fish oil also have the same- although not so strong, based on the dose as these powerful medicines .


My background on my fathers side is Italian. When I was growing up we ate all the time with his parents and other Italian relatives. There was always olive oil in deep dishes at every meal. I think they used a gallon every few weeks. The amount most Kiwis use is really just for the brief taste, and has not gotten to the daily amounts which change health." - Dr. Dan Tartaglia

Does Olive Oil get better with age?

Olive oil does not mature with age and is at its best soon after processing. The recommended period is 2 to 2 1/2 years from harvesting to consumption. Even the best oil will start to loose some of its characteristics after the first year from harvest.

Why is oil better stored in dark bottles and cans?

River Estate olive oil is bottled in dark glass to help preserve the excellent properties of the oil. Larger quantities are canned to eliminate the light as much as possible.


Olive oil in clear bottles start losing their qualities when exposure to light is prolonged, especially so, when exposed to fluorescent light for extended periods.

What else causes oil quality to deteriorate?

Heat and air are the other two elements that will cause your oil to deteriorate and exposure to both will shorten the life of your oil. The oil should be stored in a cool cupboard with the cap on to retain the high quality of the oil. Once opened, it is recommended that the oil be used within 3-6 months.

Can I use olive oil in my cooking?

Olive oil is excellent for stir frying, sautéing, deep frying, roasting and braising, and brushing on food before and during grilling and barbecuing. Olive oil can be heated to a much higher temperature in cooking that most other oils without damaging any of the fatty acids. It also forms a seal around food so that less fat is absorbed into the food. It can be filtered after frying, because olive oil is stable at high temperatures. Olive oil can also be used to make delicious moist cakes and bread.

How is Olive Oil Produced?


  • The trees are now shaken by mechanical means and the olives are caught in a net extended around the tree.

  • At the mill the olives are weighed, washed and the leaves removed.

  • The olives then enter the crusher where they are broken down to a paste, which then drops into a mixing chamber.

  • After a short time in the mixing chamber to allow the oil to come together after crushing, the paste is transferred into the second chamber.

  • The paste is then transferred to a modern centrifuge system, which floats the oil off the paste, thus separating the olive oil.

  • The oil is then settled in small vats before transferring to storage vats.

  • The oil is bottled after approx 5-6 weeks of further settling.

Heated cooking oils and cancer


Web based sites see a deluge of mail from persons concerned about developing cancer from frying with olive oil. It is unknown where this common food myth comes from but this sort of misinformation seems to spread like a computer virus. Perhaps it was the finding of contaminants in Spanish refined olive oil (fraudulent oil) in early 2001 which prompted the concerns. Or perhaps it is based on the production of certain chemicals in oils either in the natural state or when they are severely heat abused. If we review the chemical basis for these myths we often see a kernel of rationality but the facts get blown out of all proportion by people who cannot apply logic or scientific inspection to chemical analyses.



Polycyclic aromatic hydrocarbons are a group of chemicals which are formed when petroleum, petroleum products, coal, wood, cellulose, corn, or oil are burned. There are over 100 PAHs which have been studied. During oxidation and detoxification in the liver they are thought to form substances which damage DNA, starting a chain of events which could lead to cancer. A few of them have been classified by the EPA and The Department of Health and Human Services as carcinogenic to animals in studies and probably carcinogenic to humans.

A person's exposure at home to PAHs would likely be through tobacco smoke, wood smoke, vehicle exhausts, asphalt roads, coal, coal tar, wildfires, agricultural burning, waste incineration, creosote-treated wood products, cereals, grains, flour, bread, vegetables, fruits, meat, processed or pickled foods.


Twenty years ago there was a food scare when PAHs were first being researched. They were found in meat and other foods which had been cooked at high temperatures, such as grilling and charring. The American Institute for Cancer Research recommends avoiding charring meat when grilling, pre-marinade, which somehow minimizes PAH formation, and minimizing the amount of grilled meats consumed. (Grilled vegetables or fruit do not form PAHs).


Many foods naturally contain small quantities of PAHs. Olive oil, like other vegetable cooking oils, has been found to contain minute amounts of up to 17 PAHs such as benzanthracene and chrysene. Unripe olives tended to have more than ripe olives.


Burning any cooking oil can increase the amounts of PAHs. Oil of any kind which has been repeatedly heated to its smoking point will lose its natural antioxidants and begin to accumulate free radicals and other cancer causing substances. Whether this has actually caused cancer in humans has never been proven. Commercial industrial kitchens which fry foods repeatedly would be where this sort of thing might happen. It is unlikely that you would repeatedly fry at continuous high temperatures with the same oil at home. In commercial operations the oil is examined regularly with a rancidity test and discarded before it gets to a dangerous stage. Olive oil is typically not used in commercial kitchens as it is much too expensive. Cheaper oils like canola, corn or peanut oil are used instead. Extra virgin olive oil has more natural antioxidants which soak up free radicals. So heating it would produce fewer free radicals than a lower grade olive oil. It is most unlikely that in home use olive oil or other cooking oils would be a significant source of PAHs.

Other compounds implicated in health effects of heated oils


Sometimes when people hear cancer, they panic and forget that we are surrounded by possible carcinogens, ranging from nearly every food we eat to sunlight. Although a substance we are exposed to is capable of causing cancer, the probability that this actually happens may be extremely small. Exposure to second hand cigarette smoke or going outside without sun block is probably thousands of times more likely to cause cancer than burning your cooking oil.


Deep fat frying is becoming encountered these days in commercial outlets rather than the home. A lot of research work has been carried out over the years on the nutritional and toxicological significance of heat abused frying fats. The compounds implicated were cyclic monomers and dimmers. Despite many hours of high temperatures, the fats and oils showed very few deleterious effects in animal models.

The major exceptions were from oils with high levels of polyunsaturated fatty acids such as soybean oil and sunflower oil. Olive oil was noted for its stability (because it is monounsaturated) and the presence of natural antioxidants.


Research has repeatedly shown extra virgin olive oil contains significantly more natural antioxidants than refined virgin olive oil and pomace oil. Because in vitro studies have shown the antioxidant activity of hydroxytyrosol and oleuropein is dose dependent, the amount of olive oil consumed is likely to affect its chemo protective and cardio protective effects.Many years ago in Abels’ laboratories, trial experiments were carried out collecting the volatiles from various oils and fats at typical frying conditions.There were huge differences between stable frying oils and unsaturated oils such as sunflower and soybean oil. Linolenic acid should be less than 3.0% in frying oil and preferably less than 1.0%.Conclusions and recommendationsThe urban myth that heating Extra Virgin olive oil when cooking, can cause cancer is not founded on scientific fact. It is highly unlikely that domestic cooking oils cause any nutritional or toxicological problems. Olive oil is considered a very stable oil due to its high monounsaturated fatty acid content and composition of natural antioxidants. Deep frying is not nutritionally advisable due to the high calorific content of deep fried foods.


For further reading see a recent article in Consumer Magazine (August 2009, p15) or for an in-depth review see; Deep Frying mediums in New Zealand, Drummond, L., Handbook of Australasian Edible oils p271 (2008).

bottom of page