Report on olive oil production

“ The olive is an evergreen tree growing to 15 m. in height, the tree most be kept to about 4m. ”

REPORT ON OLIVE OIL PRODUCTION

WRITTEN DOCUMENT BY DR. GIOVANNI RIVA

 

CAP.I  THE HARVEST OF OLIVE TREE

 

 

The olive is an evergreen tree growing to 15 m. in height, the tree most be kept to about 4m. with regular pruning. Olives are long-lived with a life expectancy of 500 years. The trees are also tenacious, easily sprouting back even when chopped to the ground. Olives will grow well on almost any well-drained soil up to ph 8.5 and are tolerant of mild saline conditions. The olive is native to the Mediterranean region, tropical and central Asia and various part of Africa, the related species are: Wild Olive (Olea Africana), Oleaster (O. europaea var. oleaster).
Hand harvesting is the more expensive of the harvest options due to labour costs. In the first few years after planting, olives are harvested by hand from the ground. Olives are first harvested by hand at the proper stage or ripeness and maturity , is important to minimaize the time between picking and pressing. In time ladders must be used.
Trunk shakers were the first mechanical harvesters used commercially . The goal is to conduct vibration from where the machine grips the tree to the point  of fruit attachment. The canopy-contact mechanical harvest it consist of a single or multiple, vertical-mounted, cylindrical heads with radiating rods 1,1,m in length. The head is mounted on a mobile unit above a catch frame; the radiating rods engage the tree branches and passively rotate to the head , the hanging olives are removed. Picked fruit begins to lose moisture immediately . When harvested is hot, sunny weather, fruit should be set in the shade while waiting to be hauled away.  Unshaded  fruit becomes sunburned. Ideally olives should be graded and storage or processing begun within 24 hours of  picking. Another device, the oliviera, is an electronic tool that connects to a battery. The oliviera has large tongs that are spun around quickly, removing from the tree. This method is used for olives used for oil. Table olive  varieties are more difficult to harvest. In southern Europe the olive harvest is in winter, continuing for several weeks, but the time varies in each country, and also with the season and the kinds cultivated.

 

CAP II   HOW OLIVES ARE TURNED INTO OIL
MILL AND PRESS FACTS

 

1. CLEANING THE OLIVES

Stems, twigs and leaves are removed and the olives may o may not be cleaned with water to remove pesticides , dirt etc.

2. GRINDING THE OLIVES TO PASTE
• Stone olive mills: stone rollers or wheels roll in circles on a slab of granite to grind the olives into a paste.
• Metal toothed grinder: olives are fed into this grinder , an electric motor attached to a toothed grinder pulverizes the olives .
• Hammer mill: a hammer mill has swinging arms which through centrifugal action push the olives into the sides of a rotating chamber, similar to a home garbage disposer. The mill may have one to several hammers.
• Destoning the olives first: some studies show that destoning lowers olive yields by less than 1,5%. Advantages seem to be more in acidity, peroxide level and phenol content which effects shelf life.
3. MIXING THE OLIVE PASTE – MELAXATION

Mixing for 20 to 40 minutes allows small oil droplets to combine into bigger ones which can be removed in the next step. It is an absolutely necessary step. The paste is often heated to 28 degrees centigrade during this process. The most common mixer is s horizontal trough with spiral mixing blades.

1. SEPARATING THE OIL AND WATER FROM THE OLIVE PASTE (POMACE)

 

• Lever olive press: of historical interest only, the olive paste was put on round mats or in bags, stacked and squeezed with a long lever weighted with stones.
• Screw olive press: of historical interest only. Here being used with the “sacceto” type bags for holding the olive paste, twisting the screw.
• Hydraulic olive press: like hydraulic car jack, the piston squeezes the paste which   has been applied to stacks of filter like discs
• Centrifugal decanter: spins the olive paste in horizontal drum; the heavier flesh and pits goes to the outside and water and oil is tapped of from the center.
• Advanced dual phase, triple phase centrifuge:  same as above but some of the vegetable water is recycled to extract more from the pomace. Water , oil and pomace simultaneously removed in a single step.
• Percolation- sinolea: rows of metal discs or plates are dipped into paste; the oil preferentially wets and sticks to the metal and is removed with scrapers in a continous process.
1. SEPARATING THE OIL FROM THE WATER:

 

• Centrifugal olive separator: like a cream in a dairy, the liquid is span which separates the heavier water from oil.
•  

Gravity olive decanter: the oil and water is put into tanks where they separate by gravity.

1. PROCESSING THE OLIVE  OIL:

 

Refining: steam, alkali , purpose is to reduce acidity and improve flavour.
Bleaching: diatomaceous earths, activates carbon or synthetic silicas, reduces chlorophyll, carotenoids, residual fatty and pesticides by using.
Deodorization: activates carbon, reduces odors.
Materials added to increase yield, extract additional oil from pomace: enzymes, talc, steam, hexane, other solvents, alkali.

CAP. III  TECHNIQUE TO PRUNE OLIVE TREES

 

 

Pruning olives trees is very important, both regulates production and shapes the tree for easier harvest. The trees can with stand radical  pruning, so it is relatively easy to keep them at a desired height; right after planting a new tree it is necessary to cut any side shoots remaining below, this encourages low branching and balances the top and root system.
I suggest painting the tree with with a latex paint to protect it from sunburn and borer attack. Young trees should be pruned fairly heavily and encouraged to grow rapidly for the first 3 years without much fruit. Generally upright branches are vegetative and vigorous, horizontal branches are more fruitful, a good combination of the two is necessary for fruiting in future years.
Topping a vertical branch encourages vegetative growth but it is necessary a good balance thinning the vertical branches opening the tree to more light, topping horizontal branches is done to renew fruiting wood, naturally it is necessary to remove diseased or broken branches and suckers and most competing branches growing straight up into the tree.
Technically I suggest making clean cuts and remember that sun exposed wood remains fruitful and produces the largest fruit. Shaded branches eventually stop fruiting and will never produce again without drastic topping.
The olive requires a long , hot growing season to properly ripen the fruit, no late spring frost to kill the blossoms and sufficient winter chill to insure fruit set, winter temperatures most do not drop below 12°, normally green fruit is damaged at about 28°. Hot , dry winds may be harmful during the period when the flowers are open and the young fruits are setting.  

 

 

CAP IV THE IMPORTANCE OF FERTILAZATION

 

The fertilization is one of the most important agricultural techniques involved in the cultivation of olives as it must guarantee the necessary nutritive elements necessary for the correct development of the plant.
An  insufficient vigour in the olive plant – it there is an insufficient nutrition of the plant ( due also to insufficient irrigation) it can induce a precocious fall of the fruit before complete ripening , a well balanced feed would favour resistance against cold or drought.
The fundamental nutritive elements for the olives are nitrogen (N) , phosphate (P), potassium(K), calcium and microelements such a boron.
On the basis of the effective production of the olive grove it must be determined the necessary dose of fertilization (N.P.K.).
Nitrogen it must be calculated a basic dose for maintenance and one for production necessity. For a grove of 1,000 mq. A basic dose of 4 kg. An added dose of around 4 to 6 kg, if production requires, would mean in all from 8 to 10 kg of nitrogen every  year . Phosphate end potassium : it is important to consider the natural quantity already present of which a good measure would be of 4 – 6 units phosphate  and 10 – 12 units of potassium for every 1,000 square metres of olive grove.
If analysis shows either high or low levels of the above ingredients , the added quantities needed , will vary.
The fertilization with nitrogen should be done before the spring rainfalls. The quantities of N,  P, K should be given during the winter and must be mixed into the soil in a circle which reflects the foliage and not at the base of the tree trunk.

 

CAP V  GROWTH AND PROPAGATION

 

Olive trees show a market preference for calcareous soils, they tolerate drought well, thanks to their sturdy and extensive root system. Olive trees can be exceptionally long-lived and can remain productive for long, provided they are pruned correctly and regularly. The olive produces two kinds of flower: a perfect flower containing both male and female parts   and a staminate  flower with stames only. The flowers are largely wind pollinated with most olives varieties being self-pollinating, although fruit set is usually improved by cross pollination with other varieties.
There are self-incompatible varieties that are incompatible with certain others. Incompatibility can also occur for environmental reasons such as high temperatures. None of the cultivated varieties can be propagated by seed. Seed propagated trees revert to the original small-fruited wild variety. The olive is propagated in various ways, but cuttings or layers are generally preferred; the tree roots easily in favourable soil and throws up suckers from the stump when cut down. However, yields from trees grown from suckers or seeds are poor; it must be budded or grafted onto other specimens to do well. The seedlings can, of course, be grafted or chip budded with material from desired cultivars. The variety of an olive tree can also be changed by bark grafting or top working. Another method of propagation is transplanting suckers that grow at the base of mature trees. However, these would have to be grafted if the suckers grew from the seedling rootstock. A commonly practiced method is propagation from cuttings. From the two year old wood of a mature tree, the cutting is treated with a rooting hormone, planted in a light rooting medium and kept moist. Trees grown from such cuttings can be further grafted with wood from another cultivar. Cutting grown trees bear fruit in about four years.
Where the olive is carefully cultivated, as in Liguria (Italy),the trees are regularly pruned. The pruning preserves the flower-bearing shoots of the preceding year, while keeping the tree low enough to allow the easy gathering of the fruit. The spaces between the trees are regularly fertilized. The crop from old trees is sometimes enormous, but they seldom bear well two years in succession, and in many instances a large harvest can only be reckoned upon every sixth or seventh season.

CAP VI  QUALITY PROCEDURES AND SPECIFICATIONS

When olive oil is too old and as oxidized, it is usually rancid. Rancidity is most commonly detected by taste but a a chemical test can also check for rancidity. Oil doesn’t suddenly go rancid, it slowly becomes more oxidized and as it does, the flavour suffers.. Different oils age at different rates Some olive varieties make oil with more natural antioxidants which resist ageing. These oils may be good for up to 3 – 4 years if properly stored in unopened containers. Other oils, particularly unfiltered oils, may be unpalatable in a year even if stored well.
The most important factors which effect oil oxidation  and rancidity are  : Heat, Exposure to light and Exposure to air , Time.
Before the oil ever goes into the bottle, different factors will affect final shelf life:

• Olive Variety: Polyphenols and other natural antioxidants in the oil will help keep the oil from going rancid. Some varieties have more antioxidants than others. The Italian varieties : Frantoio , Taggiasca, Coratina, Pendolino, Leccino, Tonda Iblea    tend to be higth in polyphenols.
• Time of year picked: Olives picked earlier in the year may have more polyphenol and longer life.
• Picking method: fast process between picking and pressing.
• Time to Milling: Live olives start to die when picked. The longer it takes to get to the mill, the more oxidized the oil.
• Milling method: Modern melaxation tanks make sure the paste is always enclosed with minimal contact with air.

Olive oil can be stored in containers as plastic , glass, or as indestructible as stainless steel. Glass is an excellent storage container if it is tinted to exclude light but is not practical for bulk storage. Stainless steel is much better and is considered one of the best storage methods, but has been considered expensive.
Bottling equipment is now available which  will put a charge of inert gas into the airspace above the oil in the bottle which delays oxidisation and rancidity.

 

CAP VII ANALYSIS OF OLIVE OIL

The organic valutation of extravirgin olive oil:

The present methods described are only used to determine or classify eventual defects found in various selections of extravirgin olive oils by a panel of expert tasters.
Negative attributes:
Warming: the characteristic flavour due to amassment of  olives thus causing fermentation.
Mustiness: the characteristic flavour whereby yeast and musty developed due the storage of olives in damp places for many days.
Acidity: characteristic flavour of certain oils similar to that of wines or vinegars. This is due to the formation of the acids acetic, ethyl during the process of fermentation.
Metallic: a metallic flavour which is characteristic of oils maintained in contact at length with metal during the pressing mixing and storage.
Rancid: characteristic flavour due to oxidation.
Positive attributes:
Fruity: the characteristic fruity odour perceived from certain varieties of olives which are fresh, green and mature, inhaled.
Bitter: characteristic taste of green olives , astringent .
Piquant: the typical  pungent taste characteristic of the newly collect olives just beginning to mature.
Each region has its own particular cultivar with distinct characteristics . West Liguria cultivar “Taggiasca” is known for its   characteristic dolcezza (sweet) with refrains of almond and artichokes.

ACCESSORYES:

In every cabin for the use of the tastes there must be:

• Beakers containing the regulated samples covered by glass lids and maintained at a temperature of 28° c.
• Instruction sheet
• Pen (biro) and pencil
• Plate containing a slice of apple
• A glass of water at normal temperature
•  

OBSERVATIONS FOR TASTING:

The best hours for tasting are indicated as the first hours in the morning, after a night rest, after meals is not the best time but in observance of a light diet and a rapid digestion we can obtain a valid results.

• Tasting should be done in closed area with a moderate temperature with no existing odours.
• If there are numerous samples to be tasted it is necessary to odour and select those samples which present defect for tasting lastly
• Complete calm is necessary, every single ample must be tasted and savoured with care; often the immediate taste( especially with fresh, fruity oils) may be secondary detects ( slight warming, dryness…) or special attributes (pine nuts, apple almond…). It is necessary therefore to savour fully before expelling.
• Between tasting it is normal to “clean” the mouth by chewing a slice of apple.
• The samples to be tasted should be few, an the time between  tasting must be sufficient. It is suggested by the C.O.I. (INTERNATIONAL ORGANIZATION) to give at least 15 minutes between the tastings and to reduce the samples to no more than 3.
• To abstain from smoking for least 30 min. before tasting.
• No strong perfume, cosmetic or soap should be used at the moment of the tasting. Hand washing should be done using only bland soap with plentiful rising to eliminate any persistant odours.

THE TASTE PARTICELLES OF THE TONGUE:

• Sweet: just below the front border of the tongue

• Salt: at the side borders
• Acid: at the side borders in the middle
• Bitter: at the end of the tongue

 

THE CHEMICAL ANALYSIS:

Olive oil is a triacylgylceride : three fatty acids attached to a glycerol backbone , technically it is a type of glycerolipid . Triacyglycerols are the major energy reserve for plants and animals, olive oil is a complex compound made of fatty acids, vitamins, volatile components , water soluble components and microscopic bits of olive. Primary fatty acids are Oleic and Linoleic acid with a small amount of linolenic acid.
Olive oil is about 10% linoleic acid (an omega 6 – oil) and about 1% linolenic acid ( an omega 3 – oil) therefore the ratio is 10:1 .
Other components are: phenols, free fatty acids, peroxide, triacyglycerols (TAG) , diacyglycerols (DAG) and monoacyglycerols (MAG), thiobarbituric acid , reactive substances, chlorophyll and many other substances.
The higher the free fatty FFA ( PARTICULARLY when > 0,5%) the higher the probability that the oil will have a taste defect. In general, the higher the polyphenol level the more bitter and /or pungent (robust) the oil, high polyphenol levels improve shelf life of the oil and a high peroxide level in young oil suggest a short shelf life. High level of oleic acid (C18:1) , linoleic acid (C18:2) and linolenic acid (C18:3) is considered good for health.

The classification of oils:  Low (Cee) N° 1513/2001

• Exrtavirgin olive oil : an acidity below 0,8 g. for 100g.
• Virgin olive oil : acidity below 2,0 g. for 100g.
• “Lampante”olive oil: an acidity above 2,0g. for 100g

 

CAP VII EXTRA VIRGIN OLIVE OIL IS HEALTY

Olive oil presents an acidic composition that low insaturation and contains numerous antioxidant substances that allow it to maintain a particular stability.
The theory is that foods high in antioxidants, such as vitamins C and E and beta-carotene, delay ageing by mopping up free radicals.
Olive oil opposes with a very important action the absorption of cholesterol in the intestine moreover favour a better digestive activity.