Kosterina Olive Oil: An Honest Review and How It Compares
If you have come across Kosterina olive oil, you have probably seen the same things we have: a tall dark bottle, a clean Greek story, and a polyphenol number that sits well above what most supermarket bottles can claim. Kosterina has built its name on early-harvest, single-origin Greek extra virgin olive oil with independently tested polyphenol levels — and on the honest observation that a great deal of what is sold as "extra virgin" in shops is nothing of the sort. This article looks at what Kosterina actually offers, what is genuinely strong about it, and where a different oil — our own — sits alongside it. We will be fair, and we will be specific.
For our own oil, see our cold-pressed organic Marrakech olive oil.
The Short Answer
- Kosterina is a Greek extra virgin olive oil brand, founded in 2016, built around early-harvest, single-origin Koroneiki olives from southern Greece.
- Its headline strength is genuinely high polyphenol content — the Original EVOO is stated at over 500 mg/kg, with independent third-party testing after each harvest. That is a real, creditable claim, not a slogan.
- Kosterina's Organic Everyday line is USDA Certified Organic; the Original line is made with organic farming practices but is not itself sold as certified organic.
- The olives are pressed the same day they are picked, which is exactly what you want for flavour and polyphenol retention.
- Sidr & Stone's olive oil is single-estate, rain-fed, organically grown, and cold-pressed within hours of harvest — from a family grove near Marrakech, Morocco, rather than Greece.
- We do not yet publish a polyphenol figure for our first harvest; we would rather show you a tested number than claim one. Where Kosterina has a verified figure, we credit it honestly.
Who Kosterina Is, and What They Actually Sell
Kosterina was founded in 2016 by Katerina Mountanos, whose family comes from Koroni — a fishing village in the south of Greece that happens to sit in the heart of Koroneiki olive country. The brand name is a blend of her name and her husband Kostas's. The founding story is a common and honest one: she found that the "Greek extra virgin" oil on American shelves tasted nothing like the oil her family pressed back home, and set out to import the real thing.
That origin matters, because it shapes what Kosterina is good at. The company started with one product — a single-origin, early-harvest extra virgin olive oil — and has since grown into a broader Mediterranean range: a USDA-certified organic "Everyday" oil for cooking, flavoured oils, vinegars, olives, and even olive-oil skincare. For our purposes, the part that matters is the extra virgin olive oil, and on that the brand has a clear, defensible position.
Polyphenols: Kosterina's Real Strength
Polyphenols are the antioxidant compounds in olive oil that the research community has spent the most time on — oleocanthal, oleuropein, hydroxytyrosol, and tyrosol among them. The EU has a registered health claim (Regulation 432/2012) for olive oil polyphenols protecting blood lipids from oxidative stress, set at 5 mg of hydroxytyrosol and its derivatives per 20 g of oil. Higher-polyphenol oils tend to taste more peppery and bitter, and they hold up better to time and heat. This is genuinely the most evidence-grounded thing you can say about why a fresh, well-made olive oil is worth choosing.
Kosterina's Original EVOO is stated at more than 500 mg/kg of polyphenols, which the brand describes as several times the level of a typical supermarket oil, with independent third-party testing carried out after each harvest. That is a strong, specific, verifiable claim — and we will not pretend otherwise. A brand that publishes a number and has it independently tested is doing the right thing by its customers.
One fair, category-wide point worth knowing: polyphenol figures depend on the testing method used. Different laboratory methods can return different numbers for the same oil, so the most useful comparison is always like-for-like — the same method, ideally the same accredited approach, across the oils you are weighing up. This is not a criticism of Kosterina, which tests independently; it is simply how to read any polyphenol claim sensibly, theirs or anyone else's.
Early Harvest and Same-Day Pressing: What Kosterina Gets Right
Two things drive polyphenol content and flavour more than almost anything else: when the olives are picked, and how quickly they are pressed. Kosterina picks early, while the olives are still unripe, which yields a smaller amount of more concentrated, more bitter, more antioxidant-rich juice. It then presses the same day the fruit is picked, which limits the oxidation that begins as soon as an olive leaves the tree.
This is exactly the right approach, and it is the same logic our own oil is built on. Cold-pressing — mechanical extraction below 27°C under the international standard for "first cold pressing" — protects the heat-sensitive compounds that refining destroys. Speed from grove to press protects them further. On process, Kosterina and Sidr & Stone are far more alike than different: both early-attentive, both cold-pressed, both unrefined. The honest differences lie elsewhere — in origin, in certification, and in what each brand has so far chosen to publish.
How to Judge Any Olive Oil You're Considering
If you are comparing Kosterina with anything else, including us, the same handful of questions cuts through most marketing. Is it genuinely extra virgin, cold-pressed, and unrefined? Is the origin specific and traceable, or vague? Is it early-harvest? Is it sold in dark glass or tin that protects it from light? And is there a polyphenol figure — ideally tested independently — rather than a bare adjective like "premium"?
Kosterina answers most of these well: specific origin, early harvest, dark bottle, a tested polyphenol number. Those are the markers of a serious oil. For a fuller walkthrough of how to read a label and what each term actually means, see our guide to choosing a quality olive oil. The point here is simply that the questions are the same whichever bottle you are holding — and that a good brand will have plain answers to all of them.
Why Sidr & Stone
Sidr & Stone's approach is the same honest, evidence-led posture you would want from any oil you are comparing with Kosterina — applied to a different origin and a different set of choices.
- Single-estate — one family-owned grove on the plains near Marrakech, Morocco, with no blending across origins.
- Rain-fed — no irrigation; the trees take what the season gives them.
- Organically grown — no synthetic fertilisers, pesticides, or herbicides.
- Single, patience-driven harvest — a small batch, picked only when the season says the fruit is ready, sometimes weeks later than neighbouring farms.
- Cold-pressed within hours of harvest — flavour, aroma, and polyphenols preserved.
- Unfiltered extra virgin — minimally processed, and it may show a little natural sediment, which is normal for a genuine unfiltered oil.
- 100% natural — a single ingredient, nothing added.
- Dark glass with a gold label — protective packaging against light.
- Halal certified, with 10% of profits given to charity.
- Fulfilment in the UK, EU, and US.
Here is the honest part, and it is the kind of thing this whole article is about. Kosterina publishes an independently tested polyphenol figure; we do not yet, because our oil is a first-harvest pre-order and we would rather publish a tested number than estimate one. Olive oil made this way — single-estate, rain-fed, cold-pressed within hours of an unhurried harvest — is well placed to be high in polyphenols, but until we have a lab figure to show you, we will say "well placed", not "verified". That is the distinction we hold ourselves to.
We will not tell you Sidr & Stone is the best olive oil — that would be the very claim this article warns against. What we will say is that our oil is single-estate Moroccan, rain-fed, organically grown, and cold-pressed within hours of harvest, and that the evidence of that care is in the colour, the taste, and the season's small limited batch.
Frequently Asked Questions
What is Kosterina olive oil?
Kosterina is a Greek extra virgin olive oil brand, founded in 2016, built around early-harvest, single-origin Koroneiki olives from southern Greece. Its Original EVOO is known for a high, independently tested polyphenol content.
Is Kosterina olive oil high in polyphenols?
Yes. Kosterina states its Original EVOO at over 500 mg/kg of polyphenols, with independent third-party testing after each harvest — well above a typical supermarket oil. Polyphenol figures do vary by testing method, so compare like-for-like where you can.
Is Kosterina olive oil organic?
Kosterina's Organic Everyday EVOO is USDA Certified Organic. The Original EVOO is made using organic farming practices but is not itself sold as certified organic, so check the specific bottle if certification matters to you.
Where is Kosterina olive oil from?
From southern Greece — the Peloponnese region, around Koroni — using single-origin Koroneiki olives. The olives are picked early and cold-pressed the same day.
How is Sidr & Stone olive oil different from Kosterina?
The biggest difference is origin: Sidr & Stone is a single-estate, rain-fed, organically grown oil from a family grove near Marrakech, Morocco, rather than Greece. On process — early attention, cold-pressing, unrefined — the two are closely aligned. Kosterina publishes a tested polyphenol figure; we do not yet.
Is Kosterina olive oil worth it?
If you want a genuinely fresh, early-harvest EVOO with a verified high-polyphenol claim and a traceable origin, Kosterina is a credible choice that does the important things well. Whether it is right for you depends on the origin, style, and certification you are looking for.
Where can I buy a comparable olive oil?
Sidr & Stone's cold-pressed organic Marrakech olive oil is available to pre-order now as a limited first harvest, with fulfilment in the UK, EU, and US. You can find it on our product page.
Is olive oil a medicine?
No. Olive oil is a food, not a medicine. It has a long traditional history — including being honoured in the Prophetic Sunnah — and a substantial body of modern research, particularly around polyphenols, cardiovascular health, and the Mediterranean diet pattern. It can be a worthwhile part of a healthy routine, but it does not cure diseases and is not a substitute for medical care. Be cautious of any olive oil marketed with specific disease-cure claims.
Final Thoughts
Kosterina has earned its reputation honestly. Early-harvest Koroneiki olives, same-day pressing, a specific Greek origin, and an independently tested polyphenol figure are the markers of a serious extra virgin olive oil, and the brand should be credited for publishing a number rather than hiding behind adjectives. If you are choosing between supermarket "extra virgin" and a bottle like this, the bottle like this is the better-made product.
What we offer is a different origin and the same discipline. Sidr & Stone's oil comes from a single family-owned grove near Marrakech — rain-fed, organically grown, harvested only when the season is ready, and cold-pressed within hours. We hold ourselves to the same honesty we have asked of every brand in this article: where we have a tested figure, we will publish it; until then, we will describe what the oil is and how it is made, and let that speak.
Our cold-pressed organic Marrakech olive oil is available to pre-order now as a limited first harvest, with fulfilment in the UK, EU, and US.
Pre-Order Sidr & Stone Organic Marrakech Olive Oil — Limited First Harvest →
Disclaimer: This article describes and compares olive oil brands at the time of writing; specifications, certifications, and brand practices may change, and readers should check current sources. Comparisons are made in good faith and in fair terms. Olive oil is a food, not a medicine, and is not a substitute for medical treatment of any condition. For any health concern, consult a qualified medical professional.
