Making Lye Cured Olives



We harvested our olives this week, and followed the usual tradition of picking the best olives for preserving and the rest for pressing into olive oil. The majority of the olives we grow are Sevillano olives, which are perfect for preserving using a traditional lye cure, or for making Spanish style fermented olives. They can also be cured using a water extraction process, which I explained in another post several years ago.

Curing olives leaches out the bitter compounds that make the raw olives inedible. These bitter phenolic compounds are more concentrated in green olives and decrease as the olives mature. The phenols in olives give the “peppery bite” found in many high quality extra virgin olive oils and are the primary source of the many health benefits attributed to olive oil including reducing the risk of cancer, heart disease, inflammatory disease and Alzheimer’s.

We definitely like some bitterness in our olive oil, and thus prefer to harvest and press our olives green. A touch of bitterness in brined fermented olives is fine too, but all olives require leaching of the majority of bitter compounds prior to consumption, and in green olives treatment with lye is the most rapid and effective way to do this. The traditional black olives most Americans grew up eating are green lye cured olives that are then treated with iron and an oxidation process to create a black olive. Green lye cured olives have the familiar mild olive flavor that most of us grew up with. They are also like a blank slate that can then be jazzed up with a variety of flavorings depending upon your preferences.

The University of California guide to preserving olives is a dependable resource for making a variety of olives. Over the years we have tried many of their recipes, but the lye cured olives are always the most popular. The recipe in their guide along with these visuals will guide you on the steps in the process.

The first step is the olive harvest. For preserved olives, harvest carefully to prevent bruising of the fruit.


olive-harvest w

The 2015 Olive Harvest

Olives for oil are stripped from the trees onto cloths placed on the orchard floor. For preserved olives picking by hand and gently placing into a collection vessel will lessen the risk of bruising. On occasion I have picked through the “oil olives” after harvest looking for the nicest fruit and preserved those but I examine them carefully to avoid bruised olives.

You also should inspect the olive carefully for any spots which might indicate the presence of the olive fly. Do not preserve the fruit with spots.olives-with-flyw


Olives with olive fly damage. Each of these has a spot from the fly and are unacceptable for making preserved olives but can be used for olive oil.

If you have any doubts about whether the spots you see on your olives are from olive fly, cut them open and examine them. Often the damage on the inside is much worse than what might appear on the exterior.

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Olive fly damage inside the olive

If you are harvesting olives from trees that have been neglected it may be difficult to find any olives that are acceptable. We prune yearly and spray our olives several times with an organic kaolin clay compound (brand name Surround) to discourage the moths. Even with all this care, most of our olives have damage on them.

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Basket of carefully selected Sevillano Olives ready to cure

Once you harvest the olives you should treat them soon, preferably within 24 hours. Don’t chill the olives, just store them at cool room temperature until you begin processing.

The lye that is used to cure olives might be sold as a product for making soap, or as a drain cleaner. It sounds scary, as in strong concentrations it is a caustic base which can burn you if splashed on your skin or swallowed. But lye is used in a variety of processed food products that you might routinely eat, including hominy, soft baked pretzels and peeled mandarin oranges. It is even on the list of substances allowed in organic food production. Lye (sodium hydroxide) is a compound that is only harmful when in a very high concentration. Just as the acid you might add to your pool can burn you when taken straight, but can be completely safe to swim in when diluted, so the caustic base of lye can burn you when concentrated but when diluted is not harmful. When your olives are made properly, the residual amount of lye in the final product should be negligible.

Find a source of lye that is 100 percent lye. I found this lye at a local hardware store.


100 percent lye sold as drain cleaner

Read the directions on using lye in the UC guide for making olives carefully prior to beginning the lye curing process. It is very important that you read these precautions as exposure to concentrated lye can cause burns to the skin or blindness if splashed in the eyes. Remember to always protect your hands with gloves and your eyes with goggles before beginning to work with the lye solution. Be gentle during the process so you don’t splash the liquid, and don’t worry. I am uncoordinated but have been doing this for years and have never splashed it on myself.

Fill a food safe plastic bucket or other lye resistant container with enough water to cover your olives completely. I had about 3 gallons of olives, and I used 3 gallons of water. Add 3 Tablespoons of the powdered lye to each gallon of water. For this 3 gallons I used 9 Tablespoons of lye. Do not add water to lye, you should only add lye to water. Stir gently to dissolve the lye.

adding-lye-to-water w

Adding lye gently to the water.  Notice the eye and hand protection. Long sleeved shirts, long pants and shoes are recommended, and goggles are preferred over glasses too so I was somewhat negligent here! mixing-lye-and-waterw

Stir to dissolve lye in the water

Once all the lye has been added the temperature of the liquid might warm up. Check the temperature with a thermometer, and don’t add the olives until it has cooled down to cool room temperature (below 70 degrees).

Now carefull add the olives to the lye bath, again gently to avoid splashing. I put them in a glass measuring cup, then gradually tipped the cup to pour them into the solution.adding-olives-to-the-lye-bucketw

 Gently add olives to the lye bath

The olives must be protected from contact with air as this will cause discoloration. Cover the top of the olives in the bucket with a wet dish cloth. Then place a plate, a bowl or something else (I used a strainer) on top of the cloth to hold them under the liquid.

cover-lye-with-a-moist-towel-to-limit-air-exposure (1w)

A wet towel is used to hold the olives under the lye solution while curing. Put a plate or bowl or strainer on the cloth to hold the olives under.

The UC guide says to stir the olives every few hours while curing, but I only stirred them once and they seemed to cure well.

The olives are finished curing when one of the larger olives is removed from the water, rinsed and cut and the cure has softened the olive and turned the flesh green all the way to the pit. testing-lye-penetrationwThis olive is not fully cured. Note the white ring close to the pit. Cure the batch longer if your test olive looks like this.

Usually after about 12 hours my Sevillano olives are ready. Sometimes theoretically the olives may require a separate new lye cure but that has never been my experience. You can read more about that in the UC Guide.

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When the olives have been cured, you will note the lye bath has become very dark from all the compounds leached from the olives.

Once the test olive has been adequately penetrated by the lye, your lye cure is finished. You must now remove the lye from the olives. First drain the liquid from the olives by pouring them into a large strainer or colander. It is safe to pour the lye solution down the drain at this time. Return the olives to the bucket, cover the olives well with cool water, then drain them and rinse them in the strainer several times to rinse off the surface lye. During this whole process you should still be careful about avoiding any contact of the lye with your skin or eyes. Once they are rinsed the residual lye is no longer concentrated enough to be caustic.

You now will begin the process of soaking and rinsing several times per day to gradually remove the lye from the olives. Put the olives back in the bucket, cover them with water, put a clean wet cloth over the top, and let them soak for a few hours. Rinse off the water in the strainer or colander and repeat this process several times per day for at least 3 days. This process leaches the lye from the olives. The water should be completely free of any color when the olives have been adequately cleaned of the lye. The olives will no longer feel soapy or slippery. At this point you can taste an olive and should not note any soapiness or lye residue. 

Congratulations, you have successfully lye cured your olives!  Your olives are now a blank slate for flavoring. There are so many ways to flavor these plain olives. To eat some in the next few days, flavor them with a simple marinade. A good starting marinade can be made with 1 quart of water, 2 teaspoons of salt, 2 Tablespoons of vinegar, several sliced cloves of garlic, and some hot pepper slices or flakes to taste. For some variety, rosemary, thyme or bay leaves can be added to the brine or 1/4 cup of lemon juice can replace the vinegar, and sliced lemon rind can be added. The olives are usually ready to eat after 24 hours of soaking in the marinade.


 Marinated olives with lemon, garlic and hot peppers

Olives you are not planning to eat in the next few days must be preserved for long-term storage. Preservation requires either salt or vinegar brine and refrigeration. I prefer salt as it is easier to remove with soaking and leaves me with a bland olive to flavor later.

Salt brining for storage is a multiple step process. First make a lighter brine using 3/4 cup salt per gallon of water. Soak the drained olives in this brine for about 1 week. Then drain the olives and soak them in a stronger brine of 1 1/2 cups of salt per gallon of water for 10-12 days, Now drain them again and store them in the final freshly made brine of 1 1/2 cups salt per gallon of water. Store the olives in the refrigerator int he brine and use them within 2 months. I consider the olives a seasonal treat to enjoy over the holiday season and usually finish them by New Years Day.

Home cured olives in strong salt brine ready for the holidays! 

Don’t forget to plan ahead when you want to eat these olives because they are salty! A day or two before you want to eat some olives, soak them in water in the refrigerator to remove the salt.  You can then eat them plain or flavor them by soaking in the marinade discussed previously.


© 2015. Dayna Green-Burgeson RD, CDE. All Rights Reserved.

Reproduction of any content in the article without the written persmission of the author is prohibited.

2 thoughts on “Making Lye Cured Olives

  1. I often find that folks describing the lye curing process stress the safety of consuming properly cured olives that have undergone treatment with lye (which is absolutely true when done right)but they usually fail to express just how important it is to prevent splashing as well as dry contact or any type of contact with lye…especially in your eyes, LYE IS AMONG THE MOST CAUSTIC SUBSTANCES USED IN FOOD AND MEDICINE PRODUCTION AND A SMALL AMOUNT EVEN IN DILUTE CONCENTRATION CAN CAUSE PERMANENT BLINDNESS..WEAR SWIM GOGGLES OR BETTER YET A SWIM/DIVING MASK WHEN FIRST MIXING AND POURING YOUR LYE SOLUTION.. NEVER USE STANDARD SAFETY GLASSES AROUND CAUSTIC SODA (LYE/NaOh/sodium hydroxide) ONE SLOSH OR SLIP WHEN MIXING DRY LYE AND WATER COULD CAUSE A DROP OR TWO OF FAIRLY CONCENTRATED CAUSTICFLUID TO LAND ON YOUR FOREHEAD AND RUN DOWN NEAR ONES EYES WHERE THE INTENSE CAUSTIC BURNING SENSATION (AS IT RUNS DOWN ALONG ONES NOSE)COULD CAUSE A PERSON TO PANIC AND ACCIDENTALLY WIPE CAUSTIC FLUID INTO HIS/HER EYES AND THIS COULD POTENTIALLY BE THE BEGINNING OF A DARK NEW CHAPTER IN A PERSONS LIFE! FURTHERMORE BEFORE TAKING THE MASK OFF ITS NOT BEING TOO CAREFULL TO WIPE YOUR FOREHEAD AND THE TOP OF THE MASK WITH A WET OR DRY CLOTH…ONE CAN NEVER BE TOO CAREFULL WHEN WORKING WITH CONCENTRATED ALKALINE OR ACIDIC SUBSTANCES (IF YOU’VE EVER NOTICED CHEMISTS IN THEIR LABS ALWAYS WEAR GOGGLES THAT SEAL AROUND THEIR EYES AND NEVER WEAR REGULAR SAFETY GLASSES..THEY ARENT DOING THIS AS A NERD FASHION STATEMENT!) AND YOU ONLY HAVE 2 EYES. TAKE THIS ONLY AS A MANDATORY PRECAUTION AND LOOK INTO HOW LYE WORKS AND ITS MANY USES. LEARN WHAT TO DO IF YOU SPILL IT ON YOURSELF OR CLOTHING OR PETS..ETC.. SODIUM HYDROXIDE ISNT ANY MORE DANGEROUS THAN CAMPFIRE MARSHMALLOWS…we know not to swing a flaming marshmallow and not to get too close to the flames/coals…etc..we understand how it works and when the marshmallow is safe to eat..we make sure our children understand the danger & how to react when it ignites without making them afraid of the marshmallow,the stick or the fire… Make yourself the child and the MSDS and the research studies that are available your guardians. Flushing skin that has been exposed to dilute lye sollutions must be immediate and it is usually necessary to continue flushing for at least 10 strait minutes regardless of the presence of pain in order to assure that deep tissue alkali burns do not develope. Its a fact that sodium hydroxide when warmed to approximately 95degrees farenheit can create burns through muscle tissue to the bone in 13 minutes and the noted case of such unusual heated contact proved to be fatal. (*source:Lee-1995) Under normal conditions (not heated) a 2mol/l solution of lye can penetrate the cornea causing irreversable damage and possibly blindness in under 40 seconds!(source: gerard-1997)…my point is just do your research and understand your substance and how to react if contact occurs. Alkali burns can really do some damage. Laboratory splash goggles (rinsed after use) stored far away from granulated lye storage areas are a must. Rinse goggles inside and out after each use…i made the mistake of placing my goggles face down on the table in front of me while i screwed the cap back on the lye container and failed to notice several tiny beads of lye had fallen into the inside lense of my goggles and the hygroscopic nature of the lye caused the beads to react with the slight moisture in the air causing them to adhere temporarily to the inside edge of my lenses and their release occurred suddenly and without warning two weeks later as i geared up to give my olives one more short lye treatment. This really bummed me out and frightened the hell out of me as one of the tiny pearls of caustic insanity found the moisture content of my lower left eyelid to be a suitable location to park its water lovin self. Trust me..even with your bases seemingly covered to the letter there is always the potential for accidental exposure and as much as it hurts when that happens A thorough understanding may be the difference between an hour of agony and permanent blindness.

    • My post does stress the importance of limiting lye exposure, but thank you for your extra precautionary statement. In your case it appears that the dry lye powder ended up on the goggle which is incredibly unfortunate and scary because that would be the pure lye solution contacting your eye. The most important thing to remember in the lye curing of olives is to add the lye to the water, not the water to the lye, to not splash, and to make sure the dry lye powder does not get on anything. In this manner the product is very diluted by the time it is used to treat the olves. And once you have completed the first draining and rinsing of the olives int the soaking of subsequent batches the solution is very diluted. The risk is all about the concentration of the product. Again, I do not want to discourage using lye in treating olives as thousands of people use lye in making olives or soap every year, but it is a good reminder that it is no joke and should be treated with respect. I have never splashed one bit of the lye solution, but next year I will use googles in the process just for another measure of protection.

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