In most parts of olive country the olive trees are just about ready to bloom. This is the time to prepare for making your own olive oil if you decide you want to try this most rewarding process. It’s similar to sitting in the dead of winter reading seed catalogs. Eventually the weather will be right and you’ll be ready to go.
Making olive oil is for the patient person. If you’re a person who needs things to happen “now,” I would recommend having a picking party and then ship your olives to a public mill for processing. Check out this website: www.oliveoilsource.com. It’s a really good place to get an overview, and, if you do decide that you just can’t wrap your mind around all the things you need to do and the time it takes to do them, they have a list of public mills where you can have an expert with the right equipment press your olives. If you’re thinking "well I’ll just cut to the chase and buy my own press," remember that presses are not cheap. The most basic ones are generally in the neighborhood of $2,500 purchased new.
When making oil you generally use a mixture of the green and black or purple olives. You want at least 50 percent color when you start production. Check the color of your fruit. It should be about 1/3 solid green, 1/3 solid black or purple and 1/3 in between. That is to say, a mix of the two colors. You can harvest the olives by spreading a tarp and knocking the fruit off the tree, but the best method is to hand pick them. Handpicking ensures that the fruit is not bruised or broken. Bruised or broken fruit degrades faster and the oil will not taste as good. Any damage to the olives can trigger oxidation, which creates an "off" flavor. So invite all your friends and family for a barbecue and have a picking party! You’re going to have your own “olio nuovo.”
Before you embark upon this it will be good practice to familiarize yourself with olive oil pests such as the olive fruit fly. If your fruit is invested with fly maggots you can still press but them your oil will be “grubby” and to me this has too much of the “yuck” factor. There are establishments that can help you with controlling the fruit fly. Places like Ernie’s Pest Control in Orland, California, can be helpful. Again, oliveoilsource.com online can put you in touch with the suppliers you need.
It takes about 1 ton of fruit to make 35 gallons of oil. Do the math and you get a calculation of about 500 pounds of fruit to yield 8 gallons of oil or 10 pounds to produce about 32 ounces. Another way to look at it is your yield of oil will be about 5 to 25 percent of your volume of olives. It is all depending on the oil content of your olives.
A tree will be about 3 years old when you start seeing pick-able fruit. If you don’t have mature trees, see if you can find a neighbor who will let you glean fruit from his trees. Olive trees are messy, and the neighbor will probably be happy to let you pick to help clean up what will eventually be a mess when the fruit falls off the tree. Remember, either handpick the fruit or knock it off on to tarps. Don’t use the fruit that has fallen off the tree. It will be rotten and bruised.
After olives are picked get rid of any leaves, twigs and stems. Then rinse them. In pressing you’re going to use the whole olive. Pitting is not necessary. The pits themselves have oil in them and depart flavor as well.
Back in the old days, people used stone wheels or mortar and pestle to crush the olives. Today, at big manufacturers, stainless steel rollers crush the olives and pits and grind them into paste. You’re going to crush the olives into as fine a paste as you can using a food processor. I’ve heard that you can modify an under-sink disposal to do this, too. Then you put the paste through a process called malaxation. This means slowly stirring the paste. Malaxation allows the tiny oil molecules to clump together and concentrate. You can do it in a stand mixer. Stir it for about 45 minutes or until you see little pools of oil forming. The paste is ready to press.
Wrap up the mash in cheesecloth, top it with a block of wood and put it under the press. Stacking thin layers of mash works better than adding it all to one bag. Press very slowly. You can press and rest, press and rest.
Use a catch bin with a hole in the side of the bin to let the oil drain out into your jar. It will be a mixture of oil, water and bits of pulp that will quickly separate leaving the oil on top. Let it sit for an hour to make sure it separates completely.
Use a turkey baster to suction off the oil and filter it through a thick fold of cheesecloth a couple times twice. You can also use paper coffee filters.
Here’s a tip: Get everything set up and ready to go a month before you plan to harvest. This is one time when advance planning can save you a world of headache. Then when it’s time, do it on a day where you can go from start to finish without stopping. To have the best-tasting oil, you really need to go from picking to washing to grinding to pressing. If you stop in between steps, oxidation begins and the taste of the oil will degrade or the olives will begin to rot.
Buckets to gather the olives in
A sink (stainless steel would be great)
Work surface like kitchen countertop
Grinder (try a food processor or an under-the-sink garbage disposal)
Power source and cord for the grinder
Press (try Harbor Freight or make one yourself)
Cheesecloth to wrap the mash in
Large blocks of smooth unfinished wood to set the press on and to press the olives with
Filters (paper coffee filters or more cheesecloth)
Some kind of a bin to catch the oil as it is pressed out
Bottles to decant the oil into (mason jars work fine but if you can find opaque bottles they are the best)