Instruction

How to Harvest Olives

Instruction

How to Harvest Olives

A Guide for Harvesting, Milling, Curing and Canning Olives

Harvesting olives for food and oil has been done for thousands of years. Making harvest decisions about methodology, timing, and more, are based upon a number of factors. Which cultivars are you growing? Each one has unique characteristics, such as fruit (drupe) size, pit-to-pulp ratio, oil content, color and flavor profile, as well as considerations for the type of harvest (hand or mechanical), climate conditions, etc. Use this guide as an aid in making your harvest decisions.

olive trees with ladder for harvesting

Above: Harvesting ladder against olive tree

Olive Harvest Basics

Introduction

The key to the olive flavor, color, and texture is the moment of harvest. Fruit can be harvested when it is green and unripe, fully ripened to black, or any stage in between. Older olive fruit can be salt-cured or dry cured to produce a salty, wrinkled product. Damaged fruit can still be used by pressing it into oil. It is the combination of the harvest, the cure, and any added flavors that yield the characteristics sought by the producer and consumer.

Therefore, the factors to consider in harvesting olives include:

  1. Are you harvesting to make oil or to eat?
  2. If you don’t know, much will depend upon what cultivar(s) you are growing, as some are ideal for producing oil, and others are prized for their flavor profile.
  3. Are you harvesting mechanically or by hand?
  4. Do you have a set harvest date(s), or are you waiting to determine ripeness level?
  5. For producing oil, is this for home or commercial use? (For the latter, will you be targeted EVOO [extra virgin olive oil] standards?)
  6. For food production, do you have preferences in curing methods or recipes?

Here’s a terrific, short video, produced by California Ripe Olives as an introduction:

Harvesting Basics

If you are new to olive growing and harvesting, here’s a primer:

  • Olives are harvested most commonly in mid- to late-fall. In California, in the Northern Hemisphere, that is usually late October and November. But harvest can last into December depending upon the desired flavor profile.
  • All olives are green. Black olives merely indicate a high level of ripeness. Some cultivars are traditionally harvested with only modest ripeness (green); others are ripened completely to achieve optimum flavors (black).
  • Depending upon ripeness, it takes about 80-100 pounds (36-45 kg.) of olives to make 1 gallon (3.8 L.) of olive oil. And 80-100 lbs. of olives is often more than one tree’s worth of olives.
  • Olives are harvested both by-hand and mechanically. Harvested olives may be milled to make oil or cured for food production. Olives cannot be consumed direct from the tree; they are too bitter without curing. The raw fruit is bursting with oleuropein, a bitter compound that must be removed prior to eating.
  • Different cultivars work best for oil or for food production. Cultivar drupes (the fruit), with high oil content and small pit-to-pulp ratio, are often exclusively produced for oil.
  • Olive production for food is similar to winemaking, going through a fermentation process before being edible. Olives picked in October are typically ready to eat in the following May or June. Shelf life may be relatively short (one year or less), with most canned olives having a maximum shelf life of three to four years.

Let’s make sure we’re on the same page with our harvest decisions. Below are olive farming components and methodologies that affect harvest.

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Taste

Your first consideration is the desired flavor profile, whether harvesting for oil or food production. Are you targeting a more mild flavor or strong? Do you seek sweet flavors and aromatics? Herbal? Tropical? Or are you targeting strong and pungent flavors?

Ripeness has a strong effect on flavor. Greener olives (less ripe) generally have an intense grassy flavor and less oil. More mature, purple olives will have a milder buttery flavor and produce more oil that tends to be golden in color.

Timing

Factors affecting harvest timing may include current weather conditions but also available harvest crews (if hand harvesting), volume of trees to harvest, spacing of those trees and more.

Mechanical harvesters reduce the need for hand crews and may reduce bruising of fruit since it doesn’t drop to the ground. But they can’t see if you plan to harvest only the ripest olives early and return to the tree in three weeks to harvest newly ripened olives by hand since ripening is not even across trees.

Additionally, you may have contractual agreements requiring harvest completion by specific dates.

Whatever your constraints, most producers are racing to get the perfect balance of maturity of their fruit before the first frost of the year, after which the olives might not pass the sensory and chemistry tests necessary in making extra virgin olive oil (EVOO).

Olives mature on the tree and can be harvested for green table olives when the fruit is immature or left on the tree to ripen. The ripe olives are also harvested for processing as food but are left on the trees still longer if they are to be used for oil. Six to eight months after the flowers bloomed, the fruit will reach its greatest weight; and 20-30% of that weight (excluding the pit) is oil. Inside each olive, the pit contains one or two seeds; botanists call this kind of fruit with a seed-bearing stone a drupe; plums and peaches are other drupes.

Harvest Methodologies

There are two basic harvesting methods. For hand-harvesting, crews use ladders to reach the fruit and carefully pick the olives off each branch, tree by tree. There can be up to 1,000 olives on each tree, so each crewmember is only able to harvest 2 or 3 trees in a day. Some farmers, however, utilize mechanical harvesting, which increases the speed in which olives are harvested.

Below are detailed descriptions of hand and mechanical harvesting methods.

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Hand Harvesting

Hand harvesting olives is the most traditional and common method of picking olives. This harvesting method is done with the hands, rakes, and vibrating rakes that shake the fruit into nets, either suspended above the ground or laid down on the ground. This method makes sense for a lot of small farms or farms located on mountainsides. Their trees generally are taller and more spread out, making hand harvesting their only option. Harvesting by hand can be labor intensive and expensive. For California olive growers, harvesting costs are their largest expense each year, forcing them to charge a high price for their olive oil.

When olives are harvested by hand, sheets of netting or plastic are placed on the ground under the trees, and the harvesters climb ladders and comb the fruit from the branches. Long-handled rakes made of wood or plastic are used to pull the olives from the tree. There are other methods of harvesting including striking the branches with long canes or using shaped animal horns as combs to scrape the fruit from the branches. Pickers who use their fingers only employ a milking motion to strip the fruit from the trees. Hand picking is preferred by most growers, but it is also expensive.

Olives Unlimited offers harvesting services if you are in need of a crew and the necessary equipment.

After harvesting of a tree’s crop is completed, the nets filled with olives are emptied into baskets or crates, which are then transported to the processing plant.

olive tree net for olives
Picked olives at harvest in bin

Mechanical Harvesting

Machine harvesting is a recent addition to the olive grower’s arsenal. The machines were borrowed from the nut harvesters and are able to grasp the trunks of the trees and shake them. Each machine has a crew of six to nine men to operate the machine, shepherd the falling olives into the nets, and strike the branches to knock down the stubborn few by hand. The vibrations of the machine shake down about 80% of the tree’s crop, and knocking at the branches with staves yields another 10% percent. About 1,100-1,800 lbs. (500-815 kg) of olives per day can be harvested in this manner. The trees are sensitive to such assaults by machines, however, and many purists prefer hand harvesting.

Harvesting olives with over-the-top harvesters allows olive oil producers to harvest at their perfect ripeness. This method aims to minimize any damage to the fruit by never letting the olives touch the ground, and by turning the olives into extra virgin olive oil as quickly as possible. This method requires particular olive cultivars and tree spacing in order to work with the over-the-top harvesters. This method is now used around the world.

olive tree harvester
olive tree mechanical catcher or net

Harvesting for Oil or Food Production

Whether harvesting to mill for oil or process for food, there are choices to be made depending upon cultivar, ripeness, production for home use or commercial use and more. Some cultivars, such as Sevillano, may be used for both olive oil production and canning. Others, such as Leccino, are advised only for olive oil production and not for canning. Read on for details about each.

Below are detailed descriptions of olive oil and olive food production processes.

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Oil

The basic procedure for making olive oil has remained the same for thousands of years: harvest the olives at the right time, crush them into paste, separate the solids from the liquid, and further separate the water from the oil. The method of extraction has a distinct effect on the flavor and ultimate quality of the olive oil. The mechanical process has undergone numerous changes and refinements that have increased both productivity and quality.

Note: You may find olives infested with the olive fruit fly at harvest time. Depending upon larvae development, you may be able to salvage your olive-curing plan by converting it to an olive-milling operation. Check with all local, state and federal requirements for infestation tolerance levels permitted to continue with harvesting olive for oil production. Learn more in How to Manage Olive Fruit Fly Infestations.

Food

There are two parts to olive food production for both home and commercial use. First, olives are cured via a number of different methods and recipes. Then, they are canned or bottled in jars. Some methods are relatively quick and others, resulting in highly complex flavor profiles, may take many months.

Here’s a terrific video by California Ripe Olives on how commercial olives are processed in two of their family-owned plants:

Olive Curing Methods

Various methods of curing include oil-cured, water-cured, brine-cured, (salt) dry-cured, and lye-cured. The simplest for the novice are water-curing and brine-curing (which is essentially the same process as pickling). After the olives are cured they are placed in a pickling brine.

Below are detailed curing descriptions and processes.

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Water

Green olives, which are young, immature olives, can be cured in water, which removes the bitter taste of the raw fruit. They will have a fresh, nutty flavor and firm texture. After a week or so of water curing, they are stored in a pickling brine, which adds a salty flavor. Brine curing is a similar process, but instead of simple water, the olives sit for a week in a salt and water solution. This method can be used with green olives as well as ripe (purple or black) ones. No matter which kind of cure you select, the brining process is similar.

The longer the olive is permitted to ferment in its own brine, the less bitter and more intricate its flavor will become.

If using a water-cure process, place the prepared olives in a pan and cover with cold water; let sit for about a week, changing the water twice a day. Once the bitterness is gone, you are ready to place the olives in a brine.

For a brine-cure, place the prepared olives in a mixture of 1 part salt to 10 parts water, making sure they’re submerged, and leave for 3 to 6 weeks, changing the brine every week and shaking the pan once a day. Weigh them down with a plate and let sit for 1 week. Drain the olives and repeat the brining process for another week. Do this two more times so they brine for about a month or so.

NOTE: Water-only cured olives are not stable and should be stored in an air-tight container in the refrigerator.

NOTE: Some recommend not changing the water or washing the olives during the above steps. Read on in Brining to understand alternate methodologies.

Here’s a recipe we found that has since been taken off the internet, so we’ll share it here:

Water Cured Green Olives

Ingredients:
5 pounds fresh green olives
1-1/2 quarts water
3 Tbsp salt
2 lemons, sliced into 1/2 inch thick pieces
2 Tbsp dried oregano
2 cups white wine vinegar
1 – 3 dried chile peppers (optional)
6 cloves garlic, peeled and sliced in half lengthwise
Olive oil as needed

Directions:
Make a long, deep incision along the side of each olive with a sharp paring knife. Place each cut olive immediately into a large container of cold water to prevent browning from oxidation. When all of the olives have been cut, place them in a non-reactive container (stoneware, glass, or porcelain) sufficient to hold them all and cover with cold water. Keep the olives submerged by weighing them down with a plate or a plastic bag filled with water. Place the container in a cool, dark place for at least ten days, draining the water and replacing it with fresh every day.

After the olives have been soaking for 10 days, boil 1-1/2 quarts of water and dissolve the salt in it. Remove from the heat and set aside. Drain and rinse the olives with cold water and return to the container. Cover the olives with the warm salt brine mixture. Mix in the lemon slices, dried oregano, vinegar, garlic, and chiles, if using. Pour in just enough olive oil to form a thin layer on the surface. Store in a cool place for at least two weeks before eating. The olives will keep for at least two months. Refrigerate to extend shelf life.

Brine

Flavorings can be added to a brine. Red pepper or a variety of Mediterranean herbs for black olives, and lemon or hot green peppers or chilies for green olives, make unique flavor profiles. Fennel, wine vinegar, or garlic can be used to add interest to any olive, but the time required for the olives to take on these flavors can range from a week (for whole chilies) to several months (for a more subtle taste like the herb fennel).

To create a home brine, use 1/4 cup kosher salt to 4 cups water, plus 1/2 cup of white wine, cider or simple white vinegar. Submerge the olives in this brine and top with cheesecloth or something else to keep them underwater. Do not cut them.

Cover the top of the container loosely and put the jar in a dark, cool place. Check it from time to time — meaning every week or so at first. The brine should darken, and you might get a scum on the top. That’s okay. Your olives are fermenting; it is the fermentation that breaks down the oleuropein over time. (If you wash olives before curing, you may be removing the natural yeasts that accumulate on the outside of the olive, eliminating their magic.

You may wish change the brine every month or two when it begins to look nasty. It’s your choice to re-rinse the olives (or not), during changes, because the residue can act as a “starter” to get the next batch of brine going. Remember the timeline: Olives picked in October are typically ready to eat in May or June. It’s a lot like making wine.

Add seasonings after the New Year, otherwise you risk too much spice and not enough olive flavor; this is especially true of chiles. If you find you’ve gone too far, change the brine and don’t add new seasonings, and let it steep for a few weeks. That should calm things down a bit.

Commercial brine curing: For green olives, add a 12-14% salt and water solution to the barrels filled with olives. One cup of live active brine is added to each barrel; the live active solution is previously used brine that contains airborne yeasts and sugars from the olives that fermented in the brine. The active ingredient transfers enough yeast to begin the curing process in the new batch of brine. If salt and water alone were added to the olives, fermentation (curing) would not begin on its own, so the live active brine is a starter. A salometer—a salinity meter or specific gravity meter—is used to measure different types of olives.

The salometer measures the percentage of salt in solution in the barrels. For green olives, the salinity is increased by 2% every two to three weeks from the initial salinity of 12-14%. Black olives begin their curing at 8-9% salinity; this is increased by 1-2% every 2 weeks until a maximum solution of 22-24% is reached.

Lye

Freda Ehmann’s curing method is a seven-day process that is initiated by soaking olives in a lye curing solution to leach out bitterness. (This method is most commonly used for commercial processing.) Next is a series of cold-water rinses designed to remove all traces of the curing solution. During the multi-day curing process, pure air is constantly bubbled through the olives. This air is what creates their rich, dark color. Olives that do not have exposure to oxygen in their tanks will remain green in color. Small amounts of organic iron salt (ferrous gluconate) are occasionally added to the mixture for black olives only, to maintain the historically rich black color of Manzanillo and Sevillano olives even after the cans are stored.

According to the purists, lye-cured olives are bland, either spongy or hard (but not crunchy), with most of the flavor gone. Lye-cured olives are also almost always pitted, and the most naturally flavorful part of the olive is adjacent to the pit. Curing with lye softens the olive so it can be picked when it is still hard, but olives to be naturally cured must be more ripe, handled carefully, and processed quickly. Lye curing also changes the color and texture of the olive and removes many of its nutrients.

Dry (Salt)

Dry (or Greek-style) curing is a method in which plump black olives are layered in barrels with dry rock salt (no liquid is added). The salt breaks down the bitterness and leaches it out. The olives are stirred daily, and purplish liquid leached from them is drained from the bottoms of the barrels. After four to six weeks, the olives are rinsed to remove the salt and glycoside and lightly coated in oil; they are wrinkled and purple in color, and these qualities are unpleasant to some despite the excellent flavor and nutritional value of dry-cured olives.

Salt-cured (dry-cured) olives will keep in crocks almost indefinitely.

Air

Black olives can also be cured by air curing. The olives are stored in burlap bags that allow air to pass through and around the olives. Over a period of weeks, the olives will cure, although they tend to be stronger in flavor than olives cured by other methods.

NOTE: Air cured olives are not stable and should be stored in an air-tight container in the refrigerator.

Finishing and Canning

Once cured (pun intended), olives can be flavored with a finishing brine, stuffed and canned (for home or commercial use). Here are a few ideas and storage information:

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Stuffing

Green olives are usually pitted, and often stuffed with various fillings to provide color, flavor and texture, including pimentos, almonds, anchovies, jalapenos, onions, mushrooms, anchovies, or capers. If you would like to have pitted and/or stuffed olives, remove the pits and add the fillings at this point after curing. Then, mix up a similar brine, adding vinegar and herbs if desired. Store the olives in the brine in a jar and refrigerate. The olives will last up to a year this way.

Canning

After curing is completed, the barrels of olives are emptied onto a shaker table and rinsed with clean water. The shaker table sorts the olives by size while inspectors watch and remove damaged fruit. The olives are moved to another station where they are pitted then stuffed. At filling stations, they are put in jars that are filled with an 8-11% saline solution. If the saline is flavored, herbs or other flavorings are also added to the brine. The jars are then capped and sealed for safety.

Olives are canned in a mild salt-brine solution, and because they are a low-acid product, they are also heat sterilized under strict California State health rules. They are inspected by the U.S. Department of Agriculture to ensure consistent quality, color, flavor, and texture. Canned olives are offered to consumers in a variety of convenient forms including: whole, pitted, sliced, chopped, or wedged.

In the San Francisco Bay Area, find canning services at:

Bell-Carter Foods, Inc. / Lindsay Olives
590 Ygnacio Valley Road, Suite 300
Walnut Creek, CA 94596
Contact: Tom Rickard
Phone: (925) 284-5933
www.ilovelindsay.com

Musco Family Olive Co.
17950 Via Nicolo
Tracy, CA 95377-9767
Contact: Dan Kelly
Phone: 866-965-4837
www.olives.com
https://calolive.org/our-story/from-the-farm-to-the-table/

Storage

In many households, an open can of olives goes fast, but what if you have leftovers? Here are some tips from the California Olive Committee (www.calolive.org) on how to store them:

  • Once opened, store unused olives in their original brine in the open can and cover with plastic wrap to allow oxygen to permeate.
  • Partially used cans may be stored in the refrigerator for up to 10 days.
  • If the original brine has been discarded, replace with a solution of one cup water and one-half teaspoon salt.
  • The shelf life for unopened cans is 36 to 48 months, stored at room temperature.

Cultivar Chart and Harvest Details

Harvest Guide by Olive Cultivar

Use the chart below as a reference on ripening speed, harvest time, type of harvest (hand or mechanical), oil and/or food profile and recommended curing method.

Cultivar Harvest Type Oil Food Curing Type
Arbequina Small fruit but oil sweet and aromatic, shorter shelf life
Ascolana Terena Hand Harvesting Only Large fruit with tropical aromatics, including peaches
Cerignola Small fruit but oil sweet and aromatic, shorter shelf life
Coratina Small fruit but oil sweet and aromatic, shorter shelf life
Frantoio High yielding, gourmet oil, with strong, pungent flavor
Kalamata Not ideal for oil production Big flavor Brine or dry (salt) curing
Koroneiki Mechanical Very green oil, very fruity, slightly herbal, medium pungent flavor
Leccino Ripens earlier than others High yielding oil Not used for food
Manzanillo #1 Olive oil producing cultivar Brine or dry (salt) curing
Maurino Mild oil flavor
Pendolino Sweet oil and aromatic, shorter shelf life
Sevillano Low yielding, mild oil flavor Ideal for canning due to large size and fruit flavor Lye curing

Resources

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