Olive Oil Packaging: Glass Is Clean Until You Need a Cap

Written by Nicolas Netien, Chief Scientist at Oleaphen. Nicolas holds the world record for the highest polyphenol concentration ever measured in olive oil (4,943 mg/kg, 2018 harvest) and is a Knight of the French Order of Agricultural Merit. He has spent most of his career in olive science, from dryland soil biology field to the mill to the laboratory analysis of phenolic compounds. Full bio at the end of this article.

Quick answer: 

Olive oil packaging is usually judged by the bottle, but the bottle is rarely the weak point. Glass is chemically inert, yet it still needs a cap, and plasticizers leach out of the cap lining into the oil, something I have measured in my own testing. Microplastics are a separate problem, and they enter mostly during milling, not in the container, which is why a 2024 study found no real difference between glass and plastic. PFAS, despite the headlines, is largely a container issue rather than something in the oil itself. What actually keeps an oil clean is controlling the mill, removing plastic from contact with the oil, holding a cold chain, and testing the finished product.

Why I trust the process, not the bottle

In more than fifteen years working with olive oil, I have visited a lot of mills, and the gap between how people imagine olive oil is made and how it is actually made is wide. The picture in most heads is stone and clean tanks. The reality is often plastic hoses, plastic valves, and plastic storage, all in contact with an oil that is one of the best solvents for plastic additives you could design.

That shaped how I read the packaging debate. Most advice tells you to choose glass, and glass is a fine bottle wall. But a bottle wall is not the whole story, and I learned that from our own oil. We produce with a plastic-free process, so I expected clean results, and to check the container side we stored that oil in glass bottles. When we tested it, we found plasticizer in the oil. It had migrated out of the lining of the cap. The glass was innocent. The closure was not. That is the sentence I keep coming back to: glass is clean until you need a cap.

Three different problems that get mixed together

Most articles on this topic blur three separate things that have different sources and different implications. It helps to keep them apart.

Microplastics are physical plastic particles, typically polyethylene and polypropylene, that shed from equipment, packaging, and the wider environment.

Plasticizers are chemical additives such as phthalates, adipates, bisphenols, and epoxidised soybean oil (ESBO) that are added to soft plastics to make them flexible. Some, particularly certain phthalates, are studied as endocrine disruptors.

PFAS, the so-called forever chemicals, are a third category that is often attached to olive oil headlines with far weaker evidence than the other two.

They travel by different routes, they are measured by different laboratory methods, and conflating them is how a lot of the confusion online begins.

Microplastics: universal, and not a glass-versus-plastic story

The most cited recent work is a 2024 analysis of commercial vegetable oils from Italy and Spain, including extra virgin olive oil, published in Food Chemistry. It found a mean of 1,140 microplastic particles per litre, most of them fragments smaller than 100 micrometres, dominated by polyethylene and polypropylene.

The finding that matters for packaging is the one people skip: there was no statistically significant difference in microplastic abundance between oil types or between glass and plastic packaging. That points upstream, to production and processing, not to the bottle on the shelf.

A separate 2023 study of oils in PET bottles reported far higher counts, between roughly 134,000 and 580,000 particles per litre, with over 80 percent of the particles smaller than 10 micrometres.

The practical conclusion is uncomfortable for anyone selling a bottle as the answer. Choosing glass does not remove microplastics, because a large share of them are already in the oil before it is ever packaged. The only real lever is controlling the equipment the oil passes through during extraction and storage, and then testing the finished oil rather than assuming.

Plasticizers: this is where the closure earns its reputation

Here the packaging genuinely matters, and here glass stops being a free pass. It is also where my own finding fits into a much larger body of evidence.

Plasticizers are lipophilic, which is a technical way of saying they dissolve into fat. Olive oil is an almost ideal solvent for them, so a fatty food extracts these compounds from a plastic surface at a much higher rate than water would. The most exposed plastic surface in a glass bottle is the one people forget: the cap liner or gasket, sitting in direct contact with the oil, often for months.

This is not a hypothesis. A Swiss market survey of oily foods in glass jars with metal closures found that the gaskets themselves were built from plasticizers, 64 percent using ESBO and 22 percent using a phthalate, and that these compounds migrated into the food. Follow-up work quantified how much gasket material sits against the food, roughly 17 milligrams per centimetre of jar rim, containing 25 to 45 percent plasticizer. A Danish enforcement study found the highest ESBO levels, around 91 to 100 mg/kg, precisely in the oily products such as olives packed in oil. And a more recent Swiss campaign that stored 109 glass-jarred foods containing free edible oil for six months found that 27 of them exceeded the plasticizer migration limits set by EU Regulation 10/2011.

So when I found plasticizer in our own glass-bottled oil, it was not a fluke. It was the same well-documented mechanism, and it is the reason I stopped thinking about packaging as a choice of bottle and started thinking about it as a choice of every surface the oil touches.

PFAS: mostly a container story, not an olive oil story

PFAS deserves a straight answer because it is the most misrepresented of the three. There is little evidence that PFAS contamination is widespread in olive oil itself. Where the concern is real, it usually traces to fluorinated HDPE containers, a specific type of treated plastic drum that can generate PFAS-like compounds able to migrate into oils and solvents under certain conditions, with migration rising as temperature rises. That is a genuine issue for how bulk oil is sometimes stored and shipped, and it is worth asking suppliers about. It is not the same claim as "olive oil contains PFAS," and the evidence for that broader statement is weak.

Olive oil packaging formats, compared honestly

The table below separates what each format does well from where it introduces a contamination route. It is written for the oil, not for a marketing deck, so it names the weak points of every option including the good ones.

Packaging format	Light and oxygen barrier	Closure in contact with oil	Documented contamination pathway
Clear glass bottle	Poor, lets light through	Plastic-lined cap or gasket	Plasticizer migration from the cap gasket into the oil; bottle wall inert
Dark glass bottle	Good	Plastic-lined cap or gasket	Same closure pathway as clear glass; the tint helps light, not the cap
PET plastic bottle	Poor	Plastic closure	Microplastic shedding plus plasticizer migration into fat over months of storage
Soft squeeze bottle	Good, usually opaque	Integral soft plastic	High plasticizer content by design to achieve flexibility, and a large plastic contact surface
Bag-in-box	Good	Plastic tap and liner	Plastic liner and dispensing tap in continuous contact with the oil
Sealed monodose, no separate cap	Good	None resting in the oil	Removes the closure gasket entirely; contamination risk shifts back to mill control and testing

The pattern is clear once it is laid out. Every conventional format still needs a closure, and the closure is usually where the plastic meets the oil for the longest time.

Why olive oil is the worst case for migration

Three conditions decide how much a plasticizer moves from a plastic surface into a food: fat content, time, and temperature. Olive oil maximises the first, shelf life stretches the second, and a warm warehouse or a sunny kitchen shelf pushes the third. A high-fat food sitting for months at ambient temperature against a plasticized gasket is close to the ideal case for migration.

This is also the honest, unproven frontier: keeping oil under a continuous cold chain should slow migration kinetics on first principles, but a controlled study measuring the same oil at 4 degrees against 25 degrees for phthalate migration has not, to my knowledge, been published. I treat cold chain as a plausible mechanism supported by the underlying chemistry, not as a proven claim.

What actually keeps an oil clean

Clean oil is a supply-chain property, not a bottle. Four things do the real work.

• Control the mill, so that extraction and storage happen without plastic in contact with the oil. Since most microplastic contamination is upstream, this is the single highest-leverage step.

• Remove the closure problem, either by eliminating the plastic gasket that sits in the oil or by using a format that does not need one.

• Hold a cold chain, which slows the chemistry of migration and, separately, protects the polyphenols and oleocanthal that make high-phenolic oil worth buying in the first place.

• Test the finished oil rather than trusting the packaging. If a producer tells you their oil is clean, the fair question is whether they have measured it.

How we approach this at Oleaphen

I built our process around those four points rather than around a bottle. Our mill is plastic-free, so nothing leaches into the oil upstream during extraction and storage. Our oil is held under a continuous cold chain from harvest through dispatch. For the harvest ahead we are moving to a monodose format made from 100 percent recycled aluminium, lined with a food-grade coating so the oil never touches the metal, sealed with a snap-off tip and no plastic anywhere. And we test the finished oil for contaminants rather than asking you to take purity on trust.

That last point is the one that matters most to me. The bottle is a decision about one surface. A clean oil is a decision about every surface, from the grove to your hand.

If you want to be notified when the new format is available, you can join the waitlist here.

Frequently asked questions

Is glass the safest packaging for olive oil?

Glass itself is inert and does not leach into the oil, but glass cannot seal or dose itself. It needs a cap, and most caps use a plastic-lined gasket that sits in direct contact with the oil. European enforcement laboratories have documented plasticizers migrating from these gaskets into oily foods in glass jars, sometimes above legal limits. So glass is a good bottle wall paired with a weak point at the closure.

Do microplastics come from the bottle?

Mostly not. A 2024 study of oils from Italy and Spain found no significant difference in microplastic content between glass and plastic packaging, which indicates that most contamination happens during production and processing rather than in the final container.

Does olive oil absorb chemicals from plastic?

Yes, more than water-based foods do. Plasticizers are lipophilic, so olive oil draws them out of plastic surfaces at a higher rate. The effect increases with storage time and temperature.

Is there PFAS in olive oil?

There is little evidence that PFAS is widespread in olive oil itself. The genuine concern is fluorinated HDPE containers used in some bulk storage, which can release PFAS-like compounds under certain conditions. That is a container question, not a property of the oil.

What is the cleanest way to package olive oil?

Clean oil depends on the whole chain, not one material: a plastic-free mill, no plastic closure in contact with the oil, a cold chain to slow migration, and testing of the finished product to confirm it.

About the author

Nicolas Netien is the Chief Scientific Officer and co-founder of Oleaphen. He has worked with olive oil for over fifteen years, visiting mills across the Mediterranean and building a production process designed to protect the polyphenols that give high-phenolic olive oil its value. He oversees cultivation, extraction and preservation and interprets the laboratory analysis behind every harvest. He holds the world record for the highest polyphenol concentration ever measured in olive oil, at 4,943 mg/kg, set with the 2018 harvest.