Archive for the ‘Creating Olive Oil’ Category
strong>How olive maturity affects flavor profile
The main determinants of olive oil flavor are maturity, variety, cleanliness and time to milling. Olives picked a week apart for the same tree can have strikingly different flavor profiles. Like any tree fruit, more mature olives will have more sweet and fruity notes through the development of alcohols, esters and aldehydes. Oil picked from mature fruit can often be consumed immediately without racking. Some varieties such as Mission can produce bland oil if picked too late.
Greener fruit may produce oil with more antioxidants in the form of polyphenols so can have a longer shelf life. Green fruit tends to make a more bitter, peppery oil which takes several months of storage before it is palatable.
Fruit maturation will depend on temperature, sunlight and irrigation. A hot Fall can cause fruit to ripen quickly, resulting in a narrow window for optimum picking. A cool Fall may result in green fruit hanging on the tree well into winter. Some farmers are forced to pick green fruit to hedge against frost damage.
How olive maturity affects oil yield
Generally, the oil content of olives goes up as the fruit grows then plateaus when the fruit has reached its maximum size. Per ton oil yields may go up as the fruit ripens due to dehydration of the olives.
Using the Olive Maturity Index
The maturity index depends on the color of the skin and flesh to assess maturity. Olives are picked from representative trees in a random manner to fill a large container. 100 olives are picked out at random. An olive is picked from the 100 to represent each of the 8 maturity levels below. The rest of the 100 are now compared to the reference olives and sorted accordingly. The number of olives in each group is counted. The olive Maturity index is the sum of the number of olives in each category multiplied by the score, with the sum then divided by 100. The olives in a grove may reach this maturity index sooner or later in the year depending on weather but olives picked year after year at the same maturity index should produce similarly flavored oil.
“Warm Soil Cool Air” sums up the philosophy of those who believe as I do that fall is the best time for planting olive trees. Planting a tree in early fall after the intense heat of the summer has passed relieves the tree of suffering through a period of high stress that heat can bring on and which often results in setting the tree back and retarding growth. This is also a philosophy shared by my friends in the olive nursery business in Italy.
As the soil is still relatively warm the roots are stimulated to grow while the foliage part of the plant enjoys the mildness provided by short days and nights not yet cold. Good root development first lets the tree get ready for abundant spring growth.
While it is true that a younger tree is more sensitive to extremes of cold, planting in early October gives the tree two months to harden up before the coldest period of the year. Also as much of California is quite mild in winter (more so than much of central and northern Italy) cold is often not the primary consideration of when to plant.
If for whatever reason you wish to plant at another time of year, early spring is a good choice. Again, subjecting the tree to as little stress is the objective. Early spring avoids the hard frosts of December and January as well as the extremes of summer.
Given what seems to have become the real unpredictability of the rainy season in California, drip irrigation is a must no matter when one chooses to plant. By using drip those in the milder areas have had success planting during most of the year. Early fall however remains optimal.
Olive Water Management
Olive (Olea europaea L.) is considered drought tolerant and trees can survive on shallow soils with little supplemental water beyond winter rainfall. However, olive fruit production and the economic survival of the orchard operation does not depend solely on tree survival. In table olive production, maximum fruit size and fruit yield must be maintained, while in olive oil production, oil yield and quality must be maximized if an orchard is to remain economically viable. Adequate water is critical to maintaining orchard productivity since olive is extremely responsive to irrigation in terms of maximizing shoot growth, fruit size, and fruit yield, and oil yield per acre.
Olive Water Use
Before any sort of regulated deficit drought irrigation strategy can be managed the timing and amount of what constitutes full olive irrigation must be understood.
Water is lost from an olive orchard to both evaporation and transpiration (the combination of which is referred to as evapotranspiration, or ET). ET is affected by a myriad of factors, including humidity, temperature, wind, solar radiation (day length), and the percent canopy cover (the percentage of ground shaded by trees). Reference evapotranspiration (ETo) is based on the ET of a reference grass crop. To acquire real time ETo data, visit the Department of Water Resources California Irrigation Management Information System website: www.cimis.water.ca.gov.
Crop water use of mature olives (ETc) is determined by multiplying the reference ETo by the olive crop coefficient (Kc) of 0.75 (Goldhamer, 1994). The resulting average water requirements of olive trees at full ETc can be met by a combination of rainfall and irrigation.
Increasing the amount of water applied beyond full olive ET showed little to no increase in yield (yield components including shoot growth, bloom, fruit size, fruit load, and oil content). Altering the Kc used in irrigation scheduling also did little to increase the value of the fruit, and thus the overall revenues collected. Goldhamer’s study (Goldhamer, 1994) showed that table olives perform best under these optimal conditions, but will survive extremely water-stressed conditions, as they are naturally drought tolerant trees.
Other factors affecting full crop water use
Full ETc is reached once canopy cover exceeds 50% of the orchard surface. In young orchards with less than 50% canopy cover, crop water use will be reduced but not by the amount of the cover reduction. Increased reflection from the soil surface and advective heat from unshaded areas between rows increases young tree water use. If canopy cover is less than 50%, water use is estimated to be twice what the canopy cover percentage would suggest. For example, 10% cover would mean multiplying full ETc by 0.2 (or 20%), 30% cover means multiplying full ETc by 0.6.
How to manage TABLE OLIVE irrigation when water is limited
Maximizing fruit size and fruit yield are key components of table olive production that must be maintained if an orchard is to remain economically viable. After establishing the Kc for olives, Goldhamer went on to research olive trees’ reactions to various levels of water stress imposed as regulated deficit irrigation (Goldhamer, 1999).
When water was cut by 50% from June 1st to August 15th (Moderate Deficit Irrigation – Table 2) up to nearly 21% of the season’s water requirement was saved. Fruit growth slowed during the regulated deficit but accelerated upon return to full irrigation. This irrigation strategy led to no differences in gross fresh fruit yield, fruit size, or gross revenue when this mild to moderate regulated deficit irrigation approach was employed over four years. This olive regulated deficit irrigation strategy can save water while maintaining good yield of high quality fruit, but you must have good control of your water applications and know what you’re doing.
The severe regulated deficit irrigation regime saved nearly 40% of the olive water requirement but resulted in a 10% yield reduction and a 25% reduction in gross revenue due to a substantial increase in smaller fruit sizes. Since olive is extremely responsive to irrigation in terms of maximizing shoot growth, fruit size, and yield, adequate water is critical to maintain orchard productivity and economic sustainability.
If limited water supplies require that olive irrigation be cut back by 40 to 70 percent of ETc, then it is no longer feasible to produce table olives. The only alternative may be to produce olives for oil. The economics of olive oil production in a table olive orchard is difficult at best and it is not likely to be economically sustainable in the long term. See the following section on optimum irrigation for olive oil production.
Optimum OIL OLIVE irrigation
Irrigation management has a profound influence on olive oil production and on olive oil quality but with some flexibility over a rather broad range of water applications below full ETc. Since the price received for olive oil is not related to fruit size, oil olives can be irrigated less than table olives and still produce good olive oil.
A comparative study evaluating the influence of seven different levels of water applied by drip irrigation to ‘Arbequina I-18′ olive trees grown in a super high density orchard (670 trees per acre) in the Sacramento Valley of California was conducted in the early 2000′s (Grattan et al, 2006). Full ETc was met in the Spring by annual rainfall and a fully recharged soil profile until the irrigation season began in late April to early May. The reduced percentages of ETc applied were imposed during the irrigation season from roughly May to October at which time seasonal rainfall once again began to contribute to ETc demands in all treatments prior to harvest.
Similar to table olives, oil olive trees show reduced vegetative growth and have smaller fruit size as the percentage of ETc is reduced. Since oil olives are grown in hedgerows where small tree size must be maintained once the trees are mature (filled their space), discouraging excessively vigorous growth by controlling water is a desirable result. Fruits per branch, fruits per inflorescence, fruit density, and fruit set were all increased as applied water increased up to 71-89% ETc. Fruit retention was unaffected by irrigation treatment. Olive fruit weight increased as water applications increased with fruit yield approaching a maximum at about 71% ETc. Trees with higher irrigation levels were first to show color changes in fruit maturity but once fruits on water stressed trees began to mature they did so at a much faster rate.
The percentage of olive oil extracted from fruit decreased in a linear fashion at three of four harvest dates as the amount of applied water was increased. The reduction in oil extraction with increased applied water was somewhat offset by increased fruit yield. Hence, total oil yield per tree reached a maximum at 70-75% ETc (Fig. 2) but was optimized over a rather broad range.
A companion study on oil quality measured fruitiness, bitterness and pungency of oils produced at various levels of water stress. Results showed that stressing olives to between 33 and 40% ETc produced oils that had a better balance of pungency and bitterness, were pleasantly fruity, held both ripe and green character, had more complexity and depth, and boasted higher polyphenol content. High levels of irrigation lowered oil extractability and produced bland oils with significantly less fruitiness and almost no bitterness or pungency. Trees under the greatest water stress produced oils with excessive bitterness, very high pungency, and woody herbaceous flavors. Although all irrigation treatments produced oils of “extra virgin” quality, oil chemical and sensory characteristics indicate that intermediate irrigation (33-40% ETc) provided the best overall balance in oil quality (Berenguer et al, 2006).
OIL OLIVE irrigation when water is limited
Excellent olive oil yield can still be achieved when in-season deficit irrigation is held at 70% ETc or a 30% reduction compared to full olive ETc. At this level of irrigation, olives for canning experience significant reductions in fruit size and in subsequent grower returns.
If severe drought water shortages are experienced and water is only supplied at 40% of ETc, olive oil quality can still be maintained but oil yield will begin to suffer. This 60% reduction in applied water compared to full ETc can still produce good quality olive oil but the oil yield at this level of irrigation is not economically sustainable for ongoing production.
Irrigation reductions to levels below 30% ETc (a 70% cut back) will result in very low oil yield as well as poorer quality oil. This level of water availability begins to approach dry land farming, a situation in California that is not economically sustainable.
Based on the most recent oil olive irrigation research, optimum irrigation for producing olive oil ranges between the 33-40% ETc that maximizes olive oil quality and the 70-75% ETc that maximizes olive oil production.
(contact author or publication source for copy of the reference)
Hartmann, H.T., Panetsos, C. 1961. Effect of soil moisture deficiency during floral development on fruitfulness in the olive. Proc. Amer. Soc. Hort. Sci., 78: 209-217.
Goldhamer, D.A., J. Dunai, and L. Ferguson. 1993. Water use requirements of Manzanillo olives and responses to sustained deficit irrigation. Acta Horticulturae 335: 365-371.
Goldhamer, D. A. , J. Dunai, and L. Ferguson. 1994. Irrigation requirements of olive trees and responses to sustained deficit irrigation. Acta Horticulturae 356: 172-176.
Metheney, P. D., L. Ferguson, D. A. Goldhamer and J. Dunai. 1994. Effects of irrigation on Manzanillo olive flowering and shoot growth. Acta Horticulturae 356: 168-171.
Beede, R. H. and D. A. Goldhamer. 2005. Olive irrigation management. In: Olive Production Manual, Second Edition, G. S. Sibbett and L. Ferguson, eds. University of California Publication 3353. pp. 61-69.
Goldhamer, D. A. 1999. Regulated deficit irrigation for California canning olives. Acta Horticulturae 474(1): 369-372.
Grattan, S.R., M.J. Berenguer, J.H. Connell, V.S. Polito and P.M. Vossen. 2006. Olive oil production as influenced by different quantities of applied water. Agric. Water Mang. 85 (1-2): 133-140.
Berenguer, M.J., P.M. Vossen, S.R. Grattan, J.H. Connell, and V. S. Polito. 2006. Tree irrigation levels for optimum chemical and sensory properties of olive oil. HortScience 41 (2): 427-432.
Vossen, P.M., Berenguer, M.J., Grattan, S.R., Connell, J.H. and Polito, V.S. 2008. The influence of different levels of irrigation on the chemical and sensory properties of olive oil. Acta Horticulturae 791: 439-444.
Rebecca Wheeler, UCCE Farm Advisor Intern and
Joseph Connell, UCCE Farm Advisor
phone (530) 538-7201
Steve Grattan, UCCE Plant-water Specialist
phone: (530) 752-4618
Dave Goldhamer, UCCE Water Management Specialist
phone: (559) 646-6500
Larry Schwankl, UCCE Irrigation Specialist
phone: (559) 646-6569
Paul Vossen, UCCE Farm Advisor
phone: (707) 565-2621
From Wikipedia, the free encyclopedia
Olive oil extraction is the process of extracting the oil present in the olive drupes for food use. The oil is produced in the mesocarp cells, and stored in a particular type of vacuole called a lipovacuole, i.e. every cell contains a tiny olive oil droplet. Olive oil extraction is the process of separating the oil from the other fruit contents (vegetative extract liquid and solid material). It is possible to attain this separation by physical means alone, i.e. oil and water do not mix, so they are relatively easy to separate. This contrasts with other oils that are extracted with chemical solvents (generally hexane). The first operation when extracting olive oil is washing the olives, to reduce the presence of contaminants, especially soil which can create a particular flavour defect called “soil taste”.
Traditional method: olive press
People have used olive presses since Greeks first began pressing olives over 5000 years ago. Extant Roman era olive presses survive to the present time, with a notable collection present at Volubilis in Morocco. An olive press works by applying pressure to olive paste to separate the liquid oil and vegetation water from the solid material. The oil and vegetation water are then separated by standard decantation.
This basic method is still widely used today, and it’s still a valid way of producing high quality olive oil if adequate precautions are taken.
First the olives are ground into an olive paste using large millstones. The olive paste generally stays under the stones for 30 to 40 minutes. This has three objectives:
• to guarantee that the olives are well ground
• to allow enough time for the olive drops to join to form the largest droplets of oil
• to allow the fruit enzymes to produce some of the oil aromas and taste
Rarely, olive oil mills use a modern crushing method with a traditional press.
After grinding, the olive paste is spread on fiber disks, which are stacked on top of each other, then placed into the press. Traditionally the disks were made of hemp or coconut fiber, but in modern times they’re made of synthetic fibers which are easier to clean and maintain.
These disks are then put on a hydraulic piston, forming a pile. Pressure is applied on the disks, thus compacting the solid phase of the olive paste and percolating the liquid phases (oil and vegetation water). The applied hydraulic pressure can go to 400 atm. To facilitate separation of the liquid phases, water is run down the sides of the disks to increase the speed of percolation. The liquids are then separated either by a standard process of decantation or by means of a faster vertical centrifuge.
The traditional method is a valid form of producing high quality olive oil, if after each extraction the disks are properly cleaned from the remains of paste; if not the leftover paste will begin to ferment, thereby producing inconsistencies of flavors (called defects) that will contaminate the subsequently produced olive oil. A similar problem can affect the grindstones that, in order to assure perfect quality, also require cleaning after each usage.
Advantages and disadvantages
Proper cleaning produces higher quality oil. Grindstones, while ancient in design, are a suitable way to grind olives, because this method breaks up the drupe’s pulp while only slightly touching the nut and the skin. This reduces the release of the oil oxidation enzymes present in these organs. In addition, in this extraction method, the introduction of water is minimal when compared to the modern one, thus reducing the washing-off of the polyphenols. The exhausted paste, called pomace, has a low content of water making it an easier residue to manage.
• Better grinding of the olives, reducing the release of oil oxidation enzymes
• Reduced added water, minimizing the washing of polyphenols
• Pomace with a low content of water easier to manage
• Difficult cleaning
• Non-continuous process with waiting periods thus exposing the olive paste to the action of oxygen and light.
• Requires more manual labour
• Longer time period from harvest to pressing
Modern method: decanter centrifugation
The modern method of olive oil extraction uses an industrial decanter to separate all the phases by centrifugation. In this method the olives are crushed to a fine paste. This can be done by a hammer crusher, disc crusher, depitting machine or knife crusher. This paste is then malaxed for 30 to 60 minutes in order to allow the small olive droplets to agglomerate. The aromas are created in these two steps through the action of fruit enzymes.
Afterwards the paste is pumped in to an industrial decanter where the phases will be separated. Water is added to facilitate the extraction process with the paste.
The decanter is a large capacity horizontal centrifuge rotating approximately 3000 rpm, the high centrifugal force created allows the phases to be readily separated according to their different densities (solids > vegetation water > oil). Inside the decanter’s rotating conical drum there is a coil that rotates a few rpm slower, pushing the solid materials out of the system.
The separated oil and vegetation water are then rerun through a vertical centrifuge, working around 6000 rpm that will separate the small quantity of vegetation water still contained in oil and vice versa.
Three, two, and two and a half phases decanters
With the three phases oil decanter, a portion of the oil polyphenols is washed out due to the higher quantity of added water (when compared to the traditional method), producing a larger quantity of vegetation water that needs to be processed.
The two phases oil decanter was created as an attempt to solve these problems. Sacrificing part of its extraction capability, it uses less added water thus reducing the phenol washing. The olive paste is separated into two phases: oil and wet pomace. This type of decanter, instead of having three exits (oil, water and solids), has only two. The water is expelled by the decanter coil together with the pomace, resulting in a wetter pomace that is much harder to process industrially. Many pomace oil extraction facilities refuse to work with these materials because the energy costs of drying the pomace for the hexane oil extraction often make the extraction process sub-economical. In practice, then, the two phases decanter solves the phenol washing problem but increases the residue management problem. This residue management problem has been reduced by the collection of this wetter pomace and being transported to specialized facilities called extractors which heat the pomace between 45ºc and 50ºc and can extract up to a further 2 litres per 100 kilos of pomace using adapted two phase decanters.
The two and a half phases oil decanter is a compromise between the two previous types of decanters. It separates the olive paste into the standard three phases, but has a smaller need for added water and also a smaller vegetation water output. Therefore the water content of the obtained pomace comes very close to that of the standard three phases decanter, and the vegetation water output is relatively small, minimizing the residue management issues.
Advantages and disadvantages
• Compact machinery – one decanter can take the place of several presses
• Continuous and automated
• Limited labor required
• Highest percent of oil extraction
• Vegetable water disposal less of a problem
• Olive oil from two-phase centrifugation systems contains more phenols, tocopherols, trans-2-hexenal and total aroma compounds and is more resistant to oxidation than oil from three-phase ones and from hydraulic presses
• More technical labor required
• High energy consumption
• Pomace may end up moist
• Greater amount of vegetable water to be disposed of
• Reduced antioxidants due to added water
• Subject to wear from rocks, grit
The Sinolea method to extract oil from the olives was introduced in 1972; in this process, rows of metal discs or plates are dipped into the paste; the oil preferentially wets and sticks to the metal and is removed with scrapers in a continuous process. It’s based on the different surface tension of the vegetation water and the oil, these different physical behaviors allow the olive oil to adhere to a steel plaque while the other two phases stay behind.
Sinolea works by continuously introducing several hundreds of steel plaques in to the paste thus extracting the olive oil. This process is not completely efficient leaving a large quantity of oil still in the paste, so the remaining paste has to be processed by the standard modern method (industrial decanter).
Advantages and disadvantages
• Higher polyphenol content of oil
• Low temperature method
• Low labor
• Oil/water separation step is not needed
• Low energy requirement
• Often must be combined with one of the above methods in order to maximize oil extraction which requires more space and labor.
• Large surface areas can lead to rapid oxidation of the olive product
• Sale of future machines currently outlawed in the European Union due to difficulty in cleaning large surface areas.
First cold pressed – cold extraction
Many oils are marketed as first cold pressed or cold extraction, this is a denomination describing the temperature at which the oil was obtained.
In the EU these designations are regulated by article 5 of Commission Regulation (EC) No 1019/2002 of 13 June 2002 on marketing standards for olive oil. This article states that in order to use these designations the olive oil bottler must prove that the temperature of malaxation and extraction was under 27°C (80°F).
For olive oil bottled outside EU countries this regulation does not apply, and thus the consumer has no assurance that these statements are true.
The temperature of malaxation and extraction is crucial due to its effect on olive oil quality. When high temperatures are applied the more volatile aromas are lost and the rate of oil oxidation is increased, producing therefore lower quality oils. In addition, the chemical content of the polyphenols, antioxidants, and vitamins present in the oil is reduced by higher temperatures. The temperature is adjusted basically by controlling the temperature of the water added during these two steps. High temperatures are used to increase the yield of olive oil obtained from the paste.
Some producers, in order to maximise product quality, choose to combine the traditional grinding method, the stone mill, with a modern decanter. This technique produces more selective grinding of the olives, reduces the malaxation time olive paste, and avoids the complicated cleaning of the olive press fibre disks. Because the use of the stone mill requires a loading and unloading phase, this extraction method is discontinuous, i.e. there are times when all the machinery is stopped, therefore it is generally not used on a large commercial scale, being applied only by small scale olive mills producing high quality olive oil.
Consumer point of view
High quality olive oil can be obtained by all the methods if proper measures are taken. Olive oil quality is equally dependent on the quality of the olives themselves and on the time they have to wait from harvesting to extraction, in addition to the extraction method itself.
The 2 worst “enemies” of olive oil are oxygen and light. Once an olive is harvested, it should be pressed within 24 hours. Oxidation begins immediately upon harvesting. In the period between harvest and grinding, the fruits’ enzymes are very active and increasingly degrade the endogenous oil, and therefore oil obtained after a longer wait is of lower quality, presenting higher acidity (oleic acid percentage).
In addition, if additional oxygen is allowed to interact with the olive paste during the extraction process, the acidity level will increase further. Sealed extraction methods are best to prevent the continued introduction of oxygen, as well as light to the oil.
After extraction is complete, in most cases the oil has a cloudy form, mainly due to the presence of minute amounts of water. This type of oil is called cloudy olive oil, or veiled olive oil.
It is common practice that olive oil, or more specifically cloudy olive oil, is stored in cool stainless steel silos with a conical bottom that are pumped free of oxygen. This will ensure the complete precipitation and separation of the two phases and additionally facilate the final stage in olive production, filtration; It will also contribute in the integrity and stability of the oil.
The future of olive extraction points to reducing the negative aspects of the present methods, decreasing the degradation oil produced by the extraction process in itself.
• Reducing the oxidation by performing part of the process of malaxation and the extraction under a controlled nitrogen atmosphere
• Extracting the nut of the olive before grinding, this will reduce the release of oxidative enzymes present in this organ, and yield a pomace that is free from wood residues, making it possible to be used in animal feeding
• Reducing the addition of water to minimize the washing of polyphenols
• Improving the sinolea method, through an increase in the efficiency of the adsorption of the oil to the plates, thus reducing the need for the use of standard methods of extraction
Developing an orchard is a long term investment and should be regarded it with extra caution. The waiting period sometimes takes one, for several years to wait before the plant bears fruit.
You should understand that whatever profitable fruit variety you are going to plant you should always choose for the right planting materials although it’s quite expensive compared to the ordinary kind but it’s worth it in the long run.
To shorten the waiting period for fruit harvest, one should opt for grafted or marcoted fruit trees instead of the traditional seed propagation where the waiting period is much longer.
Fruit trees are just like any other crops need care and attention. You need to adequately nourish them with organic fertilizer and protect them from pesky vines that usually choked the trees resulting in mortality.
Getting the right planting materials is just one of the recommendations for successful production of fruit trees. Equally important is the sustained care by the grower to his plants after planting them.
You need to observe the components of taking care in growing of your fruit trees. The chosen variety should be adaptable to the climate where your farm is located. If the place is rainy and humid, avoid planting a fruit variety that does not suit to this kind of climate because it will not perform very well.
It will probably grow big but then it will not bear fruit as compared to the place with well defined wet and dry season. Proper distancing should always be adhered to in the planting of fruit trees to avoid overlapping of its branches which will not bear as much fruits as those with adequate space.
If the trees are too close to each other they tend to grow tall where harvesting can be difficult due to reach and accessibility aside that air circulation is obstructed and the crowded condition are favorite breeding grounds of destructive pests. Organic fertilizer or a handful of ammonium phosphate (16-20-0) maybe applied in each hole during its planting.
Provisions of adequate moisture should be observed at all times. They should be provided with enough drainage to avoid water logging or ponding on the area. Accordingly, drainage canals is to be provided when the growing area is flat.
If the planting area is sloping, one should see to it that moisture is retained around the root zone. A flattened portion around the base of the tree is recommended with organic matter or compost be added to the planting hole to help retain the moisture.
As an orchard owner, one should closely monitor the young planted trees and should visit them regularly at least once in a week. If there’s mortality, they should be replaced immediately and find out the cause of mortality and try to avoid it.
The taking care of fruit trees includes judicious pruning, remove the weak and unnecessary branches, especially those inside and below the crown. Those weak and crowded branches will only make the trees unproductive.
Many fruit trees are sensitive to too much as well as too little water, especially during summer. They should be given enough moisture and fertilizer throughout the year. Installing a drip irrigation is one good alternative, it requires a big investment though it can be recoverable in due time.
Sustained fertilizer is necessary to keep the plants healthy and be more resistant to disease.You can fertilize your fruit trees through the soil as well as through the leaves. Applying vermicompost or processed animal manure and spraying with vermitea is now becoming popular and the cheap way of fertilizing your orchard.
Hence, if you intend to set up an orchard,make sure that you don’t leave everything to mother nature. Foremost, fruit trees need your care and attention all throughout the years so that in return they will reward you with bountiful and luscious fruits from your orchard.
Where you live (your “climate zone”) will determine which varieties of temperate tree fruit and nut crops will perform best in your home garden, when fruits and nuts are harvested, and which pest and disease problems are more common. This table describes selected varieties that are suitable for home gardeners in California. The number of varieties could easily be doubled or tripled if all heirloom varieties and newer varieties available at nurseries or through mail order were included.
Certain varieties are superb eaten fresh. Other varieties tend to be used more often for cooking, canning, and freezing. Experts do not always agree about which varieties are best suited for various uses because individual tastes differ. Thus, the comments in the table regarding these issues are offered as points of interest only, not as official advice endorsed by the UC.
(Olea europaea L.)
The olive tree is an evergreen tree that performs best in hot, dry areas of California; it does not tolerate wet winter soils. It is an attractive ornamental, produces table fruit, and oil. Crop production is irregular under cool coastal conditions. Rooted cuttings are used without specific rootstocks. Space trees 16-20 ft apart. Olives for canning and pickling are usually harvested in September and October in California.
Commercially, heavy crops of small fruit unsuited for canning are left on the trees until January or February and harvested for their oil. Some new varieties grow specifically for oil have recently been imported into California from the Mediterranean countries.
– Ascolano – Large fruited variety, the most cold hardy of all table varieties in California. Large fruit. Oil is very aromatic.
– Manzanillo – The main variety used for the black “California”-style olive. Low spreading, medium-sized tree, early-maturing fruit with a medium oil content. Trees are susceptible to cold injury, peacock spot, and olive knot.
– Sevillano – Largest fruit. Many minor problems.
– Arbequina – A variety from northern Spain that produces a very high quality fruity oil. Fruit is small. Very fruitful.
– Frantoio – Italian variety used as one of the main ingredients in gourmet olive oil production. Very high oil content and excellent flavor.
– Leccino – Italian variety used in olive oil blends with ‘Frantoio’. Ripens a little earlier than other varieties.
– Maurino – Italian variety used in olive oil blends. Very flavorful, spicy oil.
– Mission – Medium-sized fruit. High oil content. Late maturing. Trees are very cold tolerant and grow quite tall. Can be used for table fruit or oil.
– Pendolino – Italian variety used in olive oil blends. Also used as a pollenizer.
by Gayle A. Alleman
The craft of turning olives into oil has been honed in the Mediterranean region over thousands of years, and techniques have been passed down from generation to generation. The process is truly a regional art. The method used in Greece is different from the one used in Spain, and each individual grower might have a unique way of tending the trees and producing the tasty liquid gold.
Mediterranean olive trees must mature for several years before they produce olives. Careful pruning optimizes the number of olives a single tree will bear. A meticulous hand is necessary because it takes at least ten pounds of olives to produce one liter (about four cups) of olive oil.
Hundreds of olive varieties exist, but only several dozen are grown commercially around the world. Some varieties are bursting with health-promoting polyphenols, while others contain few. The type of olive used to make any particular bottle of oil is rarely listed on the label. However, for those labels that do have the information, the following table, which shows which olives are richest in beneficial polyphenols, will be helpful.
The time at which olives are harvested also plays a major role in flavor and polyphenol content. The peak time is a short period right as the olives ripen. Olives are at their prime for only about two or three weeks. Healthy compounds then rapidly diminish over the next two to five weeks.
It takes quite a bit of work to coax oil out of olives. Traditionally, trees were shaken or beaten with sticks to make the olives drop to the ground. Such tough treatment is not good for olives, however. Tumbling out of a tree and plopping onto the ground causes bruising.
What Color Says About Olive Oil
Olive oils made from unripe, green olives have a light- to deep-green color. Oils made from ripe olives tend to be a golden- or light-yellow color. The color of olive oil is not an indicator of quality in relationship to culinary uses; however, if you’re looking to get the most polyphenols from your olive oil, choose one with golden or yellow tints because they come from ripe olives and may contain more healing compounds.
Soft fruits, such as peaches and plums, wouldn’t take kindly to this type of treatment; they would bruise, too, and we would never think of harvesting them this way. Olives are also soft fruits that should be treated delicately because once they bruise, the beneficial oils within start to degrade.
Some olive oil labels declare that their bottles’ contents are made from handpicked olives. This typically denotes a better-quality oil. Some growers separate their olives into “ground” olives (those collected from the ground) and “tree” olives (those picked from the tree) and use them for different grades of oil. Many large-scale growers use a tree-shaking device and set up nets beneath the trees that catch the olives before they hit the ground.
Growers must be careful when transporting olives from the trees to the processing plant. Olives are best carried in shallow containers so they don’t pile up too deeply and crush one another. Any damage to the olives can trigger oxidation and fermentation, which create an “off” flavor. Olives should be processed soon after harvest because storing them also diminishes their quality.
After olives are picked, any leaves, twigs, and stems are removed, and the olives are washed. Then it’s time for pressing. Back in the old days, processors used stone or granite wheels to crush the olives.
Today, stainless steel rollers crush the olives and pits and grind them into paste. The paste then undergoes malaxation, a process in which water is slowly stirred into the paste. Malaxation allows the tiny oil molecules to clump together and concentrate.
The mixture is stirred for 20 to 40 minutes. Longer mixing times increase oil production and give the oil a chance to pick up additional flavors from the olive paste. However, the mixing also exposes the oil to air, producing free radicals that poorly affect its quality.
Modern systems use closed mixing chambers filled with a harmless gas to prevent oxidation. This method increases yield and flavor and preserves quality. The mixture may be heated to about 82 degrees Fahrenheit, which further increases yield but does allow some oxidation. This temperature is low enough to be considered “cold pressed.”
Next, the paste is put on mats and further pressed or sent through a centrifuge (a compartment that is rotated on a central axis at extreme speed to separate materials). When the centrifuge spins, the olive paste remnants are pushed to the sides of the compartment cylinder while water and oil are extracted from the center of the centrifuge. The oil and water are later separated.
The solid material that remains after the extraction of the oil is called pomace, and it contains residual oil. Some manufacturers will use steam, hexane, or other solvents to squeeze more oil out of the pomace. This low-quality oil must be labeled as pomace oil.
Oil may then be refined, bleached, and/or deodorized. Refining reduces acidity and any bitter taste. Bleaching removes chlorophyll and carotenoids (naturally occurring pigments that give plants their colors) and possibly pesticides, resulting in a light-colored oil with fewer nutrients. Deodorizing removes the fragrant aroma of the olive oil.
In the manufacturing plant, oil is stored in stainless steel containers at about 65 degrees Fahrenheit to prevent breakdown before it is bottled and shipped.
Lots of different types of olive oil come out of the presses. On the next page you’ll learn what all the label terms mean and what’s inside each of the bottles.
Understanding Olive Oil Labels
Here are some terms you might see on olive oil labels that describe extraction methods. The first two are cold-extraction processes. Olive oils processed by these methods retain the vitamins, health-boosting phytochemicals, color, flavor, and aroma of the olives. The second two are heat-extraction processes. The heat used in these techniques takes a toll on olive oil. Excessive heat destroys many of the fragile nutrients and phytochemicals and just about all of the color, flavor, and aroma.
Cold pressed. This method removes the oil from olives through pressing and grinding. For the oil to be labeled “cold pressed,” the heat generated by friction from the grinding must not exceed 86 degrees Fahrenheit. (Other oils, such as safflower and canola, are sometimes cold pressed, but for those oils, friction temperatures of up to 120 degrees Fahrenheit are allowed.)
Vacuum extraction. This is a cold-extraction method done in the absence of air and light at temperatures as low as 70 degrees Fahrenheit. Olives are crushed and ground, then mixed with water and churned in a device that uses a vacuum. The process ensures no air is introduced into the system and preserves the antioxidants and nutrients.
Expeller pressed. This method also uses grinding and pressing, but with extreme amounts of pressure, sometimes up to 15 tons per square inch. This intense amount of pressure creates a lot of heat and friction that takes the oil to temperatures of up to 300 degrees Fahrenheit.
Solvent extraction. This technique uses chemicals, such as hexane, to remove oil from olives. The oil is then boiled to get rid of the chemicals. The oil may then undergo additional heat processing, bleaching, or deodorizing, which leads to a bland oil, but one with a high smoke point and long shelf life.
This article is designed to assist growers in the pruning of their olive trees during the first two years after planting. The information given is for trees between approximately 1 ft and 5 ft in height. During this fast growth period the trees require specific pruning to maximize their growth, keep them in good health, and very importantly, prepare them for mechanical harvesting. The briefness of this sheet cannot give all the answers and options but it does give a basic guide to pruning and staking during the first couple of years.
Whenever you are pruning a young olive tree there are four main points to keep in mind:
1. Too much pruning at a young age will stunt the tree’s growth.
2. You ultimate goal is to prune for mechanically harvesting the crop
3. A central leader trunk will assist growth in the early stages.
4. Practice makes perfect!
Let’s take a closer look at these points.
1. BODY TALK – Olive trees are like human beings in many ways and in no way are they so similar as in the pruning. It’s as simple as this:
A human can afford to lose an arm or even a leg and still live reasonably well BUT if you lose both arms and both legs at the same time, you’re in trouble! – SO IS AN OLIVE TREE.
If your young tree is 3 ft tall and has side branches growing all the way up its trunk DO NOT take them ALL off just because you’ve read that you need a clean straight trunk for 40-48 inches.
At first, only take off any that are growing below 1 ft and then in several months time when the tree has grown considerably more on top, and has ‘recovered’ from the first pruning, you can take off any branches between 1-2 ft. Repeat this process until finally after about two years, you have your clean straight trunk for 40-48 inches. Don’t make the mistake of pruning ‘too much too soon’. This can send the young tree into ‘shock’ and set it back by up to a full year. Always leave large amounts of leaf on the tree for photosynthesis to take place so that maximum root growth etc will occur.
2. Mechanical harvesting is the most efficient method of removing fruit from olive trees. Whereas oil olives have been the only mechanically harvested olives for many years, table fruit are now sometimes dropping into catching umbrellas in countries around the world, including California. Unless you have made a clear decision to hand harvest your fruit, to neglect pruning for future mechanical harvesting in the modern orchard may be a serious error from a long term economic viewpoint.
So what shape of tree do we need for mechanical harvesting? The most important requirement is a straight trunk for 3’4″-4 ft from the ground. This section of trunk must finally be free from all branches to allow the harvester’s head to securely grip the trunk without any obstruction. This will allow the harvester to work more quickly and will also avoid damage to the tree.
Achieving this straight clean trunk occurs over about 18 months to two years. Initially, when the tree is only 1-2 ft tall you simply need to remove any branches which want to grow off the trunk below 1 ft from the ground. Other branches above 1 ft can be left to grow or, if they try to grow larger and faster than your main leader, they can have their tips removed to slow down their growth – thus allowing more nutrients to be focussed into the leader. This clearing will make it easier for weed spraying and will also allow the tree to focus all of its growth into the main ‘leader’ trunk and some higher lateral branches. At no stage should any growth touch the ground. In the early years, it is important to leave as much growth as possible on the tree because foliage promotes root growth which in turn promotes the production of more foliage.
Some trees will develop with a ‘leader’ (trunk) going straight up the center with small side branches. Others will head straight for the sky as a single trunk with no side branches. Both cases are fine, but with single trunks you will need to nip off the growing tip at about 48-50 inches to encourage side or lateral branches to grow at this place. It is these lateral branches that will form the main structure of your mature tree. (For notes on another pruning method see our page on Monoconical Pruning)
Mature olive trees need to be kept reasonably open in the center to allow light penetration for better tree health and fruit production. This is best achieved through a vase shaped, sturdy growth habit which also facilitates mechanical harvesting. Your trees will probably have quite a number of lateral branches at about 40 inches or so from the ground when the tree is 18 months of age. Thoughtfully choose out four evenly spaced lateral branches. These need not all come from exactly the same height but should not be any lower than 30 inches from the ground. As these will form the vase framework for your tree, if possible choose branches that are growing at least 30 degrees up from horizontal. This will give a vase rather than a flat plate shaped tree structure. Remove the other growth as outlined below.
If your main leader is damaged or slow growing for some reason then you may choose to allow a faster growing side branch to become the new leader. Simply remove the old leader from the stake and tie the new leader to it. (A bit like politics!)
When the tree is between 3-4 ft tall, and if it has plenty of leafy branches towards its top, you can remove the branches which are growing from the trunk between 1-2 ft from the ground. You should now have a tree with a straight clean trunk to 2 ft and a nice number of branches above 2 ft. If your tree is over 4 ft high then you can remove the tips of any branches that leave the trunk between 2-3 ft. (Don’t forget BODY TALK’s advice – if there aren’t many branches between 3-4 ft then don’t cut too heavily at this stage).
Several months after you have done the last step of pruning above, you can remove any of the final branches up to about 40 inches. Your trunk is now clean to the desired height for machine harvesting and yet you still have about four evenly spaced solid branches at the top of the tree to keep root growth to a maximum. Depending on variety, land preparation and climate this whole pruning cycle from a 1 ft tall tree to a solidly trunked tree which is branching well on top should take about eighteen months to two years.
3. A central leader trunk will help to speed up your tree’s growth during the early years. Because this trunk will be fast growing and always growing upwards in the center of your tree, it will be drawing nutrients up through the tree to sustain its growth. As it draws these nutrients up the tree, the nutrients will be carried to lower branches and thereby increase their speed of growth as well. The central leader acts as a type of ‘nutrient pump’ within the tree. (If your tree decides to grow straight up without any lateral (side) branches, nip the growing tip out when it reaches about 4 ft. This will force it to start lateral branching into your vase shape.) Don’t get this central leader method confused with monoconical pruning.
What we have finally achieved is a young tree with approximately four main scaffold branches. The shape is commonly known as an Inverted Conical Vase.
As mentioned in the introduction, this is not a conclusive pruning guide. It only touches on the basics of pruning young trees with what are considered the most commercially viable methods.
4. Practice Makes Perfect! Olive trees have a mind of their own and as such they will sometimes fight against many of your efforts to prune them into shape. Don’t give up. Perseverance wins the race. Remember that time is on your side. A tree that won’t grow correctly this season can often be restaked and then pruned into shape next season.
STAKING YOUR TREE
The staking of young olive trees is very important. Stakes need to be strong enough to support the tree while the anchor roots are developing, and yet flexible enough to allow the tree to move in the wind. If the stake is too rigid or the tree tied too tightly to it, then the tree will be over protected and not feel the need to develop strong roots. The small bamboo stakes supplied with the trees from the nursery will only support them for a short period.
Santa Cruz Olive Tree Nursery has been recommending the use of bamboo stakes for sometime. The most common size to use was the 5 ft high, 1/2 inch thick stake which is a very suitable stake. However in windy areas, about 10% of the stakes may need to be replaced in the first two years due to breakage. We have now found a thicker bamboo stake that will reduce this problem. This new stake is 5 ft high, 5/8 to 3/4 inch thick and considerably cheaper than hardwood stakes.
The bamboo stakes have some advantages over hardwood stakes as they have a smooth surface and do not damage the bark or rub out newly forming buds, which are going to be the scaffolding branches of the tree. They also allow the tree to flex in the wind thereby encouraging the tree to develop a thick trunk and also to develop its anchor roots quickly. A tree rigidly tied to an unbending hardwood stake will not realize the need to develop its anchor roots strongly. The bamboo stakes are also easy to handle, eliminating splinters and the lifting of heavy bundles.
These thicker stakes will last up to two years at which point the tree will no longer need staking. It is rare for a tree to need any support after it has outgrown such a stake. Place the stake about 2 inches from the base of the tree and push it into the soil at least 1 ft vertically until it feels quite stable. Another good option is to use the stakes to mark your tree sites prior to planting and then simply plant the trees beside them. You can then tie both the young tree and its small nursery stake to the main stake with a tool such as the taper described below. (There is no need to cut off the tapes between the young tree and its nursery stake as they will break away naturally as the tree trunk thickens.)
After planting and staking the tree, the stake will prove to be a good solid anchor point to attach protective guards or netting to if you have severe animal problems and do not have a full netting fence around the boundary of your orchard.
TYING THE TREE
From our experience with tying methods over many years, we have found that the tape tying tools available from McCalif Growers Supply are an excellent investment. The tape tool is very fast and efficient and if you have a number of trees to tie, you will get the cost of your tool back very quickly in saved time. When you order your tool, generally the “Max Tapener” is the most popular choice. You will also need to ask for a packet of staples, a packet of spare cutter blades, and unless you have very thick trunks, the 100 ft rolls of tape will be what you’ll use.
After testing many brands of tape, we recommend the high quality, green, Italian tape which we now stock as standard. As the tree trunk grows thicker it will be better able to support itself without so much need for the stake. As the trunk thickens, the tape will stretch and naturally tear out at the staple point so it will not strangle the tree as some ties do.
1. Does your property have well drained soil?
Too much water is the olive tree’s worst enemy. If your soils are too heavy and/or tend to hold excessive water during extended rainy periods, then you will have to improve the drainage or even change the site of your grove to allow for extra drainage. Do not plant olives in areas that collect water, seep water after rain or hold soil moisture to the point of becoming boggy. Some soils won’t drain sufficiently no matter what you do.
A sloping site does not necessarily mean that the area is well drained. For example, heavy clay soils, even on quite steep sites, are generally not suitable for olives due to their poor internal drainage. Soil pits up to six feet deep will assist in your understanding of the drainage. Agricultural departments and soil analysts are able to assess soil drainage.
The preferred soil types for olives are sandy loams, loams and clay loams as they usually have suitable internal drainage combined with adequate water holding and nutrient storage capacity. Soil must be reasonably well drained for commercial olive production.
2. Does the property have an average daily temperature during Jan of 54 deg F or less?
A theoretical example of this would be a property where every day in Jan went from 32 deg F overnight to 75 deg F at noon. The average between the minimum of 32 deg F and the maximum 75 deg F is 54 deg F. This property would be at what is currently considered the warmest end of the suitable temperature scale. Another example would be a property with average Jan temperatures ranging from 27 deg F to 66 deg F thereby giving a suitable Jan average of 46 deg F . If your property has regular cold periods lower than 23 deg F each year, then you will need see our page on Olive Variety Suitability which outlines the suitable cold tolerant varieties.
Olive trees will grow vigorously in areas with warm winters. However, in lay terms, the problem occurs that due to the warmth, the tree doesn’t realize that it is winter and it continues to grow well. When spring arrives, the tree has not rested and doesn’t realize that it is time to flower, nor does it have enough reserve nutrients available. No flowers equals no fruit and this makes it nonviable for commercial production.
Even though good crops have been observed on some varieties of trees where the Jan average is above 54 deg F (12 deg C), there is not enough data available to recommend planting commercial olive groves at these temperatures.
If you are not sure about the figures for your property, ask the local farmers who have land at similar altitudes in the area. Climatic data from the US Weather Service will also give you a general idea for your total region but may not be 100% correct for your specific property. There are often areas within weather map regions that differ significantly from the map data thereby making your property either suitable or unsuitable for commercial olive production.