Ingredients and utensils for curing olives with lye:
- A few pounds of fresh-picked green olives.
- A small bottle of 100% pure lye (sodium hydroxide).
- A quart of white vinegar.
- Two containers of plain non-iodized salt.
- Herbs and spices. (optional)
- A couple of 2-gallon-sized plastic food containers with lids.
- A plastic gallon-sized pitcher for measuring water.
- Plastic measuring spoons and plastic stirring utensil. (Never use metal containers or spoons when dealing with lye. Lye reacts to metal, especially aluminum, and is dangerous and potentially poisonous!)
- A few small squares (12”) of clean cloth.
For years I have lived in the vicinity of olive trees and yet have never cured olives. It seemed to be a complex, time-consuming affair and I didn’t personally know anyone who cured them. But this year, in early November, I noticed that here at the Boyce Thompson Arboretum, our olive trees were loaded with fruit. Some cultivars had small olives, some had large. Most were green, although some were black. Why let them go to waste? I started calling around for recipes and scanning the Internet for further information. Native food-expert Jean Groen even came out to Boyce Thompson Arboretum to give me a few tips.
Unlike most fruit which you can easily make into jam or jelly, the fruit from the olive tree is incredibly bitter and must have unpalatable compounds, such as oleuropein, removed. (I can’t help but be curious as to what the evolutionary advantage is in having such a profusion of extremely bitter fruit. Are there any animals that eat these straight off the tree?) To remove these compounds you can use the tried and true way of soaking or covering the olives for weeks in salt or you can be fairly quick about it and use lye. (Dark olives are usually cured with salt and I’ll get into that in the next feature.)
The word “lye” should strike a note of concern among the literate, especially if one considers that there is a lye-based product called “Draino”, which should never be considered a kitchen condiment. Yet, 100% pure lye (sodium hydroxide) is precisely what is used in curing olives. My search for 100% lye took me away from the comfort of a grocery store, which had no lye (no lie!), to the well-lit aisles of an Ace Hardware store, which had what I needed. There is something disconcerting about finding a substance you are going to use in food preparation in the plumbing section of a hardware store. And what made it all the more worrisome is that the small bottle of granulated lye had a bold warning of “poison!” emblazoned with skull and crossbones. I made sure that the ingredients said only “sodium hydroxide”. The skull seemed to be smiling at me. Should I smile back? Yes, yes I should.
At the Arboretum, I carted a ladder out to the olive trees and started picking. I kept three olive varieties separated in three different baskets – large green, small green, and small black. After about an hour or so, I had easily collected around 3 or 4 pounds of large green olives, and a couple pounds each of the small green and black olives. I did not collect any olives that seemed too soft, wrinkled, or damaged in any way. You will note that in the photographs, the small green olives have just a little darkening…a blush if you will…while some of the small black olives have a little green on them. (Except with lye, I’m not much of a purist.)
So the segregated small and large green olives were rinsed. I had two large (two-gallon size) clean plastic storage containers (with lids!) and a one gallon pitcher to measure the water. Also, nearby I had a cup of white vinegar just in case I splashed myself with some of the concentrated lye solution. Apparently the vinegar helps render the lye less caustic. I will point out here that various publications suggest you wear some safety glasses and a long-sleeved shirt while preparing the lye. Do keep a sample raw olive of each kind OUT of the lye bath as you will want to compare the color of a treated olive with that of a raw one.
The recipe called for one gallon of cold water (not warm!) in a plastic container. Never use metal pots to hold the lye water, especially aluminum, which would basically poison you. So, use food grade plastic which means any plastic container you can store food in. Use a measuring spoon, again PLASTIC not metal, and measure out 3 tablespoons of lye granules to the water. This is the potentially most dangerous part of the operation so don’t be splashing the water when you add the lye. When the lye has been added to the water, use a plastic or wooden spoon to slowly and carefully stir the lye until it’s completely dissolved in the water. The lye will warm up the water a bit, so wait a few minutes before putting the olives in. Once the lye has been thoroughly mixed, the solution is not nearly as deadly because the lye has been diluted. You still shouldn’t splash the water on yourself, but you should also not freak out if it gets on your hands. Simply pour a little of that vinegar on your hands and rinse it off.
Carefully add the olives without splashing too much. Remember that you want to keep the olives segregated by size. You don’t mix little olives with big olives because they cure at slightly different rates. In my case, the small olives went into one container, the big olives into another. The olives will tend to float at first so take a scrap of clean cloth and place it on top of the water. It will keep the olives submerged. Once the olives and covering cloth are in the lye bath, put the lid on the container and ignore it for a few hours. After, say, 5 hours, take a plastic (not metal!) mixing spoon and slide it under the cloth to stir the olives a little. You just want to be sure that all sides of all the olives are well-exposed to the lye bath. After this, cover the olives again. Let them soak in the lye bath for a total of 12 hours or so. After twelve hours you will want to remove an olive and slice a wedge out of it to see if the lye has penetrated down to the pit. Compare it to a wedge you cut out of the “sample” raw olive that you left out of the bath. It’s a bit difficult to tell because, no matter what, the olive “meat” next to the pit is always a bit lighter in color than the outer flesh. But you can see that all of the inner flesh is not white/green in color like a raw olive. Don’t stress too much about exact coloration next to the pit. The main thing is that you want to see some color differentiation compared to a raw olive. The idea here is to give the lye bath time to work its way down to the pit.
Okay, in the case of my olives, 12 hours just didn’t seem quite long enough. The inner olive that I sampled out of the batch still looked too light. That meant I had to create a whole new lye bath for both batches. And that meant I had to first mix another gallon of cold water with 3 tablespoons of lye. Once that was mixed, I drained the old lye bath off of the olives and quickly covered them with the new. One thing you don’t want to do is leave the olives uncovered by liquid for any length of time. By exposing the olives to air, they begin to turn dark. I don’t know if this affects the taste of the olives, but they tend to look bruised. So, allow very little exposure to air while you prepare a new lye bath.
Once the olives have been covered with the new lye bath, check them once every 4 hours. Again, by “checking on them”, I mean you remove a sample olive and slice a wedge out it to check on the inner flesh. Then toss that sliced olive in the garbage. Oh, and don’t even think about tasting it straight out of the lye bath! With my olives, I waited another 8 hours (for a total of 20 hours) before emptying the lye bath of the small olives and then covering them with plain cold tap water for soaking. The larger green olives stayed in the lye bath for a total of 24 hours. After I was satisfied that the olives had been lye-cured through and through, I poured the lye down the sink drain and covered the olives with cold tap water. Then, three or four times a day for the next 5 days, I poured off the “old” tap water and replaced it with fresh tap water. The water draws off the lye. You will see that for the first couple of days, the water will quickly grow cloudy and brown. But by the fourth or fifth day, the water will remain clear. You want to keep changing the water until it no longer gets cloudy and stays clear. Am I clear about that?
After approximately 5 days, when the water stays clear, prepare a gallon of brine. This is where the salt comes in. Combine one gallon of cold water with ¾ cup of non-iodized salt. Mix it thoroughly and then pour it over the freshly strained olives. Again, you might want to put a clean cloth scrap on top of the water to hold down any floating olives. Let the olives soak in that salt solution for one full week.
There are a couple of things to note here. First of all, allow the olives to soak in this brine solution somewhere cool and out of direct sunlight. Second of all, after two or three days, open the lid and peer in. Do you see any mold? If you see a little mold, spoon it off the surface. If you start seeing a lot of mold, the batch of olives may be contaminated and you will have to discard it. In my olives, there was no mold whatsoever.
After a week of the first brine solution, prepare a new gallon of brine, but this time you are using a full cup of non-iodized salt. Mix it well. You can even throw in some dry herbs or pepper or mustard seeds. When this new heavier brine is made, pour off the old brine and pour in the new. You can also go ahead and taste your first beautifully cured olive. Deeelish! With the new salt bath, let the olives soak for one more week. Do keep your eye out for any weird moldy growth. If you’ve been clean in your preparations and have not exposed the olives to too much air, you shouldn’t have much of a problem with mold. Like I said, I had no problem at all and you probably won’t.
After that second week of brining the olives, they are ready to keep refrigerated in smaller jars of brine for a couple of months. They are perishable now and should be eaten over the next few weeks. Give any excess amount to friends who will, undoubtedly remember you in their wills.
Finally, if the olives are too salty for your taste straight out of the brine, you can soak a few for an hour to remove much of the salt. But if you do that, those olives need to be eaten within a couple of days. Without the salt, they won’t stay preserved for any length of time. What I do is soak the olives in water for an hour, drain the water, and then stir in a little olive oil and Balsamic vinegar. Tasty!