8267 | FarmKnowledge

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Olives: Safe Methods for

Home Pickling

Revised by SYLVIA YADA, Scientist, and LINDA J. HARRIS, Extension Specialist in

Microbial Food Safety, Department of Food Science and Technology, UC Davis, working from

the original publication by GEORGE YORK, Professor Emeritus, and REESE VAUGHN

(deceased), Department of Food Science and Technology, UC Davis.

WHAT ARE OLIVES?

The olive tree, Olea europaea, valued for both its beauty and its fruit, has been a part

of Mediterranean civilization since before recorded history. The olive was cultivated

and its oil traded as early as 3000 B.C.E. Olives and olive oil have been used for food,

cooking, medicine, salve, soap, and lamp fuel.

Today, most of the world’s olives are still grown in the Mediterranean region.

The olive tree is best suited to areas with a Mediterranean climate—a long, hot grow-

ing season and a relatively cool winter. Most commercial olive acreage in the United

States is in California, with growth concentrated in the interior valleys of Central

California.

Five commercially important olive varieties are grown in California: Manzanillo,

the most common variety; Mission, which was originally cultivated by Franciscan

monks; and Sevillano, Ascolano, and Barouni, which have very large fruit. Over 80

percent of California’s olives are used in the production of canned black ripe style or

California black ripe style olives; the remaining crop is crushed for olive oil or pro-

cessed into specialty styles of olives. Many other popular table and oil olive variet-

ies, including Kalamata, Hojiblanca, and Picholine, are grown on a smaller scale in

orchards and home gardens throughout California.

NUTRITION

Olives and olive oil are good sources of monounsaturated fat. Olive oil has the high-

est percentage (over 70%) of monounsaturated fat of any edible oil. Olives and olive

oil also contain other minor components such as pigments, flavonoids, and phenolic

compounds that act as antioxidants and may offer protective health benefits.

SELECTING FRESH OLIVES

Select only freshly harvested, unbruised olives for processing at home. Olives are har-

vested at different stages of ripeness (fig. 1)—green-ripe, turning color, and naturally

black ripe. The first mature green-ripe olives are ready to be picked in California start-

ing in mid-September, when the fruit have reached their full size. Mature green-ripe

olives will release a characteristic creamy white juice when you squeeze them. Most

green-ripe olives are harvested when they are even colored, from yellow-green to a

straw color. As the olives ripen further, their color turns from yellow-green to rose to

red-brown. These turning color olives are still firm and their flesh lacks dark pigment

or is partially pigmented close to the skin. Naturally black ripe olives are allowed to

ripen fully on the tree. They reach the desired dark red to purple or black stage of

color about 3 to 4 months after the green-ripe stage.

PUBLICATION 8267

UNIVERSITY OF

CALIFORNIA

Division of Agriculture

and Natural Resources

http://anrcatalog.ucdavis.edu

Note: Research on food preservation is ongoing—recommendations may change. Make sure your food

preservation information is always current. Always follow up-to-date, tested guidelines and recipes

from reliable sources. 06/2007

http://anrcatalog.ucdavis.edu

ANR Publication 8267 �

Naturally black ripe olives are harvested in California starting in mid-November

and continuing through December, depending on the variety, crop yield, and region,

and on weather conditions. When mature, these olives will release a reddish black liq-

uid when you squeeze them and their flesh will be nearly completely pigmented. Ripe

olives bruise easily and must be handled with care.

The oil content of olives increases during ripening. Naturally black ripe olives

are primarily used for oil extraction. Black olives with pigment through to the stone

are considered overripe and will be softer when processed, but are the preferred

fruit for some types of dried olives. Olives with varying maturity will usually need

to be sorted according to ripeness before you begin any of the processing methods

described in this publication.

Some olive varieties are preferred for specific olive styles, based on their flavor,

texture, size, and processing characteristics. For example, the Manzanillo variety is

ideal for lye-cured olives and Spanish-style green olives, the Mission variety is excel-

lent for dry salt cured ripe olives and dark ripe style or California black ripe style

olives, the Kalamata variety is ideal for Kalamata-style water-cured olives, and the

Sevillano variety is often used for Sicilian-style fermented olives.

STORING FRESH OLIVES

Fresh olives, especially naturally black ripe olives, should be processed within a few

days after harvest if possible. Green-ripe olives generally store better than naturally

black ripe olives. For best quality, store olives at temperatures between 41° and 50°F,

preferably in shallow, ventilated crates. Storage of fresh olives at colder temperatures

(from 32° to 36°F) for 2 weeks or more can cause chill injury that will lead to inter-

nal browning and skin browning. Chill injury shouldn’t be a problem if the olives are

exposed to these colder temperatures for only short periods of time. Sevillano olives

are most susceptible to chill injury, followed by Ascolano, Manzanillo, and Mission

(least susceptible). Prolonged (6 weeks or more) storage of fresh olives at 50°F can

cause surface pitting and spotting.

Figure 1. Freshly harvested olives at different stages of ripeness: green-ripe (1 and 2); yellow-

green to straw (3); rose to red-brown (4 and 5); and red-brown (6) (may be too soft for some

types of olive curing). Not shown are naturally black ripe olives (also described as dark red to

purplish black).

ANR Publication 8267 �

METHODS FOR CURING OLIVES

Olives picked off the tree contain a very bitter compound called oleuropein. Harvested

olives must be “cured” to remove the bitterness in order to make them palatable. The

most common curing processes use brine, dry salt, water, or lye treatments. During

these curing processes the water-soluble oleuropein compound is leached out of the

olive flesh.

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. This publication includes

directions for making water-cured, brine-cured, dry salt cured, and lye-cured olives.

The storage life of the olives that you prepare at home varies depending on

the olive style, and is indicated in the instructions. For a longer storage life you can

preserve some olives using additional methods (e.g., freezing, drying, pressure can-

ning)—see table 1 for suitable preservation methods for the olive styles included in

this publication.

WATER-CURED OLIVES

To prepare olives for water curing, you must first individually cut or crack each olive

so that the bitter oleuropein can more easily leach out. The prepared olives are soaked

in water and the water is changed daily over a week or more, depending on the olive

style and the desired level of bitterness. After curing, the olives are placed in a finish

brine, which is a vinegar-salt solution that adds the characteristic flavors. The advan-

tage of this method is that the olives are ready to eat within a few weeks. These olives

will still be slightly bitter because water curing removes less oleuropein than other

methods.

CAUTION: If at any time

the olives become moldy or

soft or bad smelling, do not

eat them or taste them. (See

precautions under “Disposal

of Spoiled and Questionable

Olives.”)

Table 1. Suitable preservation methods for home-prepared olives

Olive style

Suitable preservation methods

Brine Refrigeration Freezing* Drying Pressure canning

Water-cured

Kalamata-style olives √ √

Mediterranean-style cracked olives √ √

Brine-cured

Greek-style black olives in brine √ √

Sicilian-style green olives in brine √ √

Dry salt cured √ √

Lye-cured

Green olives √ √ √ √ √

Dark ripe style olives √ √ √ √ √

Lye-cured fermented

Spanish-style green olives √ √ √

* Freezing is most suitable for smaller olive varieties with higher oil content (e.g., Mission, Kalamata, and Picholine); larger

varieties (e.g., Sevillano, Ascolano, and Barouni) will soften during freezing.

ANR Publication 8267 4

Instructions for two styles of water-cured olives are included here. Kalamata-

style olives are made with naturally black ripe olives that are cut before they are

soaked in water. Mediterranean-style cracked olives are made with green-ripe olives

that are cracked before soaking.

Kalamata-style olives

Use ripe, fully colored (dark-red to purplish black) fruit to prepare this style of olive.

Make sure the olives are firm and were harvested before the first frost. Use an oil-

rich olive variety such as Kalamata or Mission. Do not use Sevillano olives: they will

become too soft.

Supplies needed

• Mature, fully colored (dark red to purplish black) olives

• Pickling salt

• Red wine vinegar

• Olive oil

• Airtight, food-grade plastic, or glass containers (for olives)

• 1-gallon container (for mixing brine)

Preparation

1. Sort the olives according to size, if desired, and discard any bruised or defective

fruit.

2. Rinse olives in water, and drain.

3. With a clean, sharp knife make 2 lengthwise cuts on each olive, slicing about 1⁄8

inch into the olive flesh.

4. Place the cut olives into a food-grade plastic pail (or other container as listed

above) and cover olives with fresh, cool water. Keep the olives submerged by

placing a heavy plate or a sealed plastic food-storage bag filled with water over the

fruit. Close the container lid loosely and leave the olives to soak.

5. After 24 hours, drain the olives and cover again with fresh, cool water. Repeat the

water change daily for 8 to 10 days to reach the desired level of de-bittering. If you

want less-bitter olives, continue to soak for up to 20 days and change water daily.

Monitor carefully: over-soaking will lead to soft olives with a washed-out taste.

6. Prepare the finish brine: add 1 pound (11⁄2 cups) of pickling salt to 1 gallon of cool

water, stir to dissolve, and add 1 quart (4 cups) of red wine vinegar. This amount

of solution is enough to treat about 10 pounds of fresh olives.

7. Drain the de-bittered olives, cover with the finish brine, and pour 1⁄4 to 3⁄8 inch of

olive oil on top. Close the container lid firmly and store at about 60° to 80°F.

8. Allow the olives to marinate in this vinegar-salt solution for about 1 month to

develop the desired flavor.

9. These Kalamata-style water-cured olives can be stored in the finish brine in a cool,

dark place or refrigerated for about 1 year if the container remains airtight.

Use pickling salt. We

recommend that you use

pickling salt (also known

as canning salt, pure

salt with no additives,

or sodium chloride) for

making brines and for salting

olives. The anti-caking agents

added to regular table salt

will turn the brine cloudy. The

quantities of salt used in the

following recipes are based

on fine-grained pickling salt

that is commonly available in

the United States. Quantities

are given in weight (ounces

or pounds) and also in vol-

ume (cups)—an equivalent

quantity of table salt can be

substituted if pickling salt is

not available. If you use other

types of salt, such as coarse

salt or kosher salt (which

can vary greatly in density),

measure it by weight to make

sure you have the equivalent

quantity. Do NOT use sodium-

reduced “salt substitutes.”

ANR Publication 8267 �

Mediterranean-style cracked olives

Use green-ripe fruit of any variety to prepare this style of olive. After these olives are

cured and placed in the finish brine, you can also add a variety of seasonings, such as

oregano, garlic, and lemon slices, to provide additional flavor.

Supplies needed

• Green-ripe olives

• Pickling salt

• White wine vinegar

• Herbs, garlic, lemon, or other seasonings (optional)

• Airtight, food-grade plastic, or glass containers (for olives)

• 1-gallon container (for mixing brine)

Preparation

1. Sort the olives according to size, if desired, and discard any bruised or defective

fruit.

2. Rinse the olives in water, and drain.

3. Place olives one or two at a time on a clean cutting board and strike with the flat

side of a mallet or with a rolling pin. Crush each olive just to crack the flesh—do

not break the pits or remove them.

4. Place the cracked olives into a food-grade plastic pail (or other container as listed

above) and cover olives with fresh, cool water. Keep the olives submerged by

placing a heavy plate or a sealed plastic food-storage bag filled with water over the

fruit. Close the container lid loosely and leave the olives to soak.

5. After 24 hours, drain the olives and cover again with fresh, cool water. Repeat the

water change daily for 6 to 7 days to reach the desired level of de-bittering. If you

want less-bitter olives, continue to soak for a few more days and change water

daily.

6. Prepare the finish brine—add 1 pound (11⁄2 cups) of pickling salt to 1 gallon of

cool water, stir to dissolve, and add 2 cups of white wine vinegar. This amount of

solution is enough to treat about 10 pounds of fresh olives.

7. Drain the de-bittered olives and cover with the finish brine. At this point you can

add herbs or other seasonings if desired, such as chopped oregano, lemon slices,

and garlic cloves. Close the container lid firmly and refrigerate. Note: These olives

must be kept refrigerated. The olives are ready to eat after 4 days in the finish brine

or you can allow the flavors to develop more fully during longer refrigerated

storage.

8. These Mediterranean-style cracked olives can be stored in the refrigerator for up to

1 year in the finish brine.

BRINE-CURED OLIVES

Olives can be cured by placing them directly into brine (a concentrated salt solution)

where they undergo a natural fermentation. The olives develop a unique flavor during

ANR Publication 8267 �

the fermentation when sugars in the fruit are converted to lactic and acetic acids. The

fermentation also breaks down the chemical bond between oleuropein and sugars in the

olive, allowing this bitter compound to be leached into the brine. Brine curing is simple

and requires only water and salt for the initial washing and fermentation. However, the

process takes at least 3 months and may take 6 months or longer, depending on the

fruit variety and maturity as well as the temperature, salt concentration, and acidity (pH

level) of the brine.

Green-ripe olives take longer to cure in brine than naturally black ripe olives.

Instructions for two styles of brine-cured olives are included here. Greek-style black

olives in brine are made with mature olives cured in strong brine over several months

to reduce the bitterness. Sicilian-style green olives in brine are made with green-

ripe olives that are cured in a batch of seasoned brine for 4 to 6 months. The salt is

one of the preservatives for these olives, helping to reduce chances of spoilage and to

ensure a consistent fermentation, so do not alter the brine concentrations given in the

instructions below. You can safely store both styles of olive in brine for 1 year.

Greek-style black olives in brine

Always use mature, fully colored (dark red to purplish black) fruit to prepare this

style of olive. Make sure the fruit is firm and was harvested before the first frost. You

can use any olive variety, but Manzanillo, Mission, or Kalamata are most common

for this method. Some of the olives’ coloring may fade during curing but they tend

to darken again when exposed to air. The cured olives may become slightly shriveled

because of the high salt concentration of the brine used to preserve them. The fin-

ished product will have some fruity and bitter flavors.

Supplies needed

• Mature, fully colored (dark red to purplish black) olives

• Pickling salt

• Airtight, food-grade plastic or glass containers (for olives)

• 1-gallon container (for mixing brine)

Preparation

1. Sort the olives according to size, if desired—a batch of olives will cure more

evenly if the fruit are similar in size. Discard any bruised or defective fruit.

2. Pack the sorted olives into containers that can be made airtight—a 1-quart glass

jar is the smallest size recommended.

3. Prepare medium brine with 8 ounces (3⁄4 cup) of pickling salt per gallon of

cool water.

4. Cover the olives with brine and close lids loosely. Store the filled containers at

about 60° to 80°F.

5. After 7 days, replace brine with a fresh batch of strong brine made with 1 pound

(11⁄2 cups) of pickling salt per gallon of water. Close the lids firmly. Store the

olives in brine for at least 2 months. If you prefer less-bitter olives, replace the

brine with a fresh batch of strong brine at 1-month intervals for 2 or 3 months.

Changing the brine more often will leach out more of the bitter oleuropein.

ANR Publication 8267 �

6. Check the containers at regular intervals. If gas pressure builds up during

fermentation and causes the lids to bulge, carefully loosen the bulging lids to

release the gas, and then firmly close them again. The gas is naturally produced by

the bacteria that are responsible for the fermentation. If brine leaks out, replace it

with fresh strong brine made with 1 pound (11⁄2 cups) of pickling salt per 1 gallon

of water.

7. If you like fairly bitter olives you can eat these olives (or use them for cooking)

after 2 months of storage. If you prefer less-bitter olives, store the olives for at

least 3 months before eating.

8. These Greek-style black olives can be stored in the strong brine in a cool, dark

place for at least 1 year if the jars remain airtight (to minimize surface yeast and

mold growth) and the lids do not corrode.

9. To avoid mold growth on the surface after opening an olive conta