How to preserve olives
In this brief guide, we are going to answer the question “how to preserve olives” and discuss the different methods of preserving olives.
How to preserve olives
World consumption of table olives continues to increase, passing from 957 to 2,480 thousand tones in the period from 1990/91–2014/15, which represents a growth of more than 250% (1).
Olives can be preserved by :
- Curing and packaging in brine or olive oil
How to preserve olives by refrigerating
Studies show that cold storage of olives delays in the progress of the decay incidence due to weight loss and discoloration of the fruit, which are noticed on the first day of storage in ambient temperature. The handpicked olives stored at 3°C showed 6% decay incidence after 21 days, whereas the machine-harvested fruits already surpassed this value after 4 storage days (2).
Both fresh and marinated olives can be preserved by refrigeration. To refrigerate fresh olives, store them in a clean container. A container is preferred because olives bruise easily and storing in a bag may not be enough.
Marinated, store-bought olives can also be refrigerated.
Refrigerated olives will stay good for about 2 weeks.
How to preserve olives by freezing
Fresh olives can be preserved by freezing. Place the olives in an airtight container, moisture-resistant plastic containers, freezer-safe glass jars, or plastic freezer bags to prevent the olives from drying out during storage, label and freeze. Frozen olives must be consumed within 6 months up to 1 year (3).
How to preserve olives by curing
Fresh olives are not edible because of the presence of oleuropein, a bitter glucoside. Processing of fresh olives reduces bitterness and makes them edible. Processing involves soaking in water, brine, or diluted alkali or drying by heating or salting. . When the olives are first placed in the brine, a robust fermentation by a heterogeneous group of microflora occurs. When the brine pH falls from 7 to 5, a mild fermentation occurs that is supported predominantly by yeasts and, to a lesser extent, by the lactic acid bacteria. Processing takes between 3 and 12 months, depending on the variety, maturation level of the fruit, temperature, salt, and pH levels of the brine (4).
Curing is the most popular method to store olives. Curing enhances the flavor of the olives and enables a longer storage time. There are several techniques used to cure olives. Different techniques result in a different flavor and texture of the cured olives.
The flavor and texture of each style of olive depends partly on the curing process used. Lye-curing is the most rapid and efficient process for de-bittering, but many people think that lye-cured olives are less flavorful than other styles of olives. Brined olives undergo a natural fermentation not unlike that used for traditional dill pickles and sauerkraut. Acids produced in the fermentation process by lactic acid bacteria that are naturally present on the fruit give these olives a distinctive flavor and aroma. Brined olives tend to be saltier than lye-cured olives. Water curing does not change the flavor of the olives as much as other curing methods (3).
In this article, we will look at the three most common methods for curing olives (3).
Olives can be cured by :
- Curing in brine
- Curing in vinegar and oil
- Curing in caustic soda (lye)
- Dry curing in salt
For all the above methods, whenever salt is used, it must be non-iodized. Kosher salt or pickling salt must be used instead of iodized table salt. Using iodized salt will alter the taste of the final product.
How to preserve olives by curing in brine
Brine is a solution made from salt and water. The typical ratio of a brine solution is 1 kg of water and 100 g of salt for every 1 kg of olives. Acid is also added to the brine solution. The acid can be either vinegar or lemon juice.
To brine olives :
- Remove the stems and wash the olives.
- Discard any bruised and damaged olives. Also, look out for holes and insects and discard any pest-infested olives.
- Score the olives using a knife. Olives contain a chemical called oleuropein which is responsible for their bitter taste. Breaking open the olives with a knife will allow this chemical to leach into the water, thereby reducing the bitter flavor of the olives.
- Add the olive into a clean, glass jar.
- Add brine solution to cover the olives. The brine solution must cover all the olives. Any olives left uncovered with brine will not be cured and may rot.
- Seal the jar and place it in a cool dry place.
- After about a week, open the jars and discard the brine.
- Taste one olive to check for bitterness. Olives must be repeatedly immersed in brine, stored for a few days and drained until they are no longer bitter.
- Next, add acid in the form of lemon juice or vinegar.
- Seal and store the jars in a cool shelf or a refrigerator for up to a year.
A detailed recipe for curing olives in brine can be found here.
How to preserve olives by curing in vinegar and oil
Olives can be preserved by curing in vinegar and oil. The same method as for curing in brine solution is used and vinegar is added as the acid. After the curing process is complete, the brine solution is drained and the olives are covered in extra-virgin olive oil. Spices can also be added at this point to enhance the flavor.
How to preserve olives by curing in caustic soda (lye)
Olives can be cured in a caustic soda solution and then preserved in brine. Caustic soda is corrosive and can cause burns so gloves must be worn at all times.
The concentration of caustic soda must be carefully controlled so that the olives do not rupture. A typical ratio is 20 to 40 g of caustic soda per Kg of olives.
How to preserve olives by dry curing in salt
Olives can also be preserved by dry curing. During dry curing, the olives are mixed with salt with no added water. It is important to use only ripe olives for dry curing. If the olives are unripe, dry curing will not remove the bitterness completely.
To dry-cure olives, clean and scored olives are mixed in a crate with the correct quantity of salt as per the weight of olives. The crate is then placed outside or in a well-ventilated place and curing is allowed to take place. The air drying must take place for at least a month. More details on dry-curing olives can be found here.
After the olives are cured they are immersed in olive oil and stored until needed.
Other FAQs about Olives that you may be interested in.
In this brief guide, we answered the question “how to preserve olives” and discussed the different methods used to preserve olives.
- Lombardi, S. J., et al. Effect of different storage conditions on the shelf life of natural green table olives. It J Food Sci, 2018, 30.
- Yousfi, K., et al. Responses of fruit physiology and virgin oil quality to cold storage of mechanically harvested ‘Arbequina’olives cultivated in hedgerow. Grasas y Aceites, 2013, 64, 5.
- Yada, Sylvia, et al. Olives: Safe Methods for Home Pickling. 2007.
- Boskou, Dimitrios, Salvatore Camposeo, and Maria Lisa Clodoveo. Table olives as sources of bioactive compounds. Olive and olive oil bioactive constituents. AOCS press, 2015. 217-259.