OldMcDonald
Platinum Member
Sorry for the delay – and it is a long response.
First, Forgeblast, most of the olive varieties in Portugal have an oil content of between 18 and 25 %, with a few lower or higher, but not all of the oil is available under normal crushing conditions. I would assume that other countries’ varieties are similar, otherwise we would all be using the same variety by now. The more it is pressed, and heated after the Extra Virgin and Virgin are taken off the worse the quality of the oil, and the lower grades are not normally used for human consumption. They go into industrial use. The grade immediately next to Virgin is the one my wife uses to make soap – slightly higher acid content than Virgin and known as Lampante, although we have cooked with it and found it satisfactory. My intention is to make biodiesel from the olives that fail to make table quality. I have planted a total of 440 in the last five years and production will increase dramatically in the next couple of years. A general rule of thumb is that you would get about one litre (fairly close to a US quart) of food quality oil from the mill for every 7 or 8 kilos (15 to 18 pounds) of olives you took in. The mill operator will have kept back a percentage, about 15 to 20, so if you were making your own, and assuming you were not as proficient as the professionals, you might get similar results of a pint to 7 or 9 pounds of olives. That is a bit vague, but a fairly reliable expectation. With a good set-up you might do even better.
Psient, Yours is a more complicated question and one that I have not needed to consider before. I have heard of a small mill that was set up in a remote village by a man shortly before he died and it has never been used. I heard he also had a threshing mill for grain. He had intended to do all the locals’ olives and grain. I am trying to make arrangements to see it, but am going through a chain of three people so do not hold your breath.
I think we might have a language problem in describing the action of milling equipment, but are you familiar with grain crushers? These are two cylindrical steel rollers, often grooved or chequered, and almost touching, grain is hoppered into the top and the rollers crush the grain into “flakes”. The gap between them can be adjusted so that the kernels are just slightly squashed, or, put very close together the kernels will be broken into pieces. How small depends on the moisture content of the grain. I have a grape crusher that performs a similar task, but the rollers are held further apart so that the individual grapes are broken without crushing the pips. I also use it as a corn sheller because I cannot find anything better. In this case I run it in reverse (hand cranked) and the corn falls through the gap whilst I have to pick out the cobs. With olives you want to squash the pips, and they are hard. I am using the word pip rather than stone so as not to confuse them with the stone rollers.
The problem I foresee with that set-up is that you would only squash everything and not grind it down to a paste. I have not seen inside a steel roller mill as used by the commercial olive mills, but the old stone version runs two stones in a circular trough. It is possible to have anywhere between one and four in the trough if they are set up properly. There are quite a few good photographs on various webs sites. I have been doing some Googling to try to find a really good site, but most are not and some are downright misleading. I found one that suggested the stone rollers remove the pulp but do not crush the pips!! Some also imply that the pips are removed before crushing begins. A small mill I know put through 4m kilos (say 9m pounds) two years ago. Can you imagine pitting that many olives? No doubt there are machines that are capable of taking the pulp off, but that is not normal – at least in the Old World. Most websites are, of course, aimed at selling something and claiming that the way they do things, or the equipment they sell is the best. A lot of them use information from other sites that have no idea where the source of the original information came from. You can read exactly the same word for word on several sites. Nothing new in that either, the web, and indeed books are full of mis-information.
Come the end of modern civilisation as we know it (whenever that might be) and I have to construct an olive mill, I will make a circular trough and crush the olives. Stone rollers would be extremely expensive and finding someone to make and maintain them for you is probably a non-starter. Steel seems the only way. Hubs from trucks with a flat metal band around? They need to be heavy and kept firmly on the bottom of the trough, so some ingenuity in adding weight is needed. Roll them around with whatever power source is available. Run off the paste, press it. The mill I know best uses hydraulic power (it actually uses water as the fluid) and straw mats. On a small scale I am sure that either a vehicle jack type arrangement or a cider press would give reasonable results. Keep the pomace for stock feed or fuel – there will still be oil in it. Put the liquid into a container and skim off the oil similar to skimming cream from milk – a cream skimmer will probably do the job just as well as anything. If you could arrange it, a really old fashioned idea was to have a series of vats, maybe four, so that the oil floated on top of the water in the first one and spilled into the next and so on.
I have copied some extracts from my book that relate to olive growing, which hopefully those of you interested in growing olives will find useful:-
Soil analyses showed a low pH, adequate to high levels of Potassium, and most of the property having adequate to high Phosphate, with a couple of areas being quite low. The biggest problem I had with that soil was lack of organic material. I gathered that none had been applied for a long time, and with irrigation, much of the property had had adequate quantities of water and warmth – an ideal situation for rapid breakdown of OM.
If you too buy a property with olive trees then this situation is likely. It is common practice in some areas to keep the land clear of growth amongst the trees by cultivating several times a year. Your predecessor might have applied mulches of manure around the trees, but not on the remainder of the land, so expect a very low level of OM in the soil, and be prepared to feed it if you wish to crop any of the open areas. Good husbandry in the locality is said to be that every third year the trees should be mulched with farmyard manure (abbreviated to FYM in the rest of the book, or referred to as muck) if following the system of bare ground, and heavily pruned every third year too. If the land between the trees is cropped then the whole area should be mucked every year. Producing that much FYM is at best extremely difficult and impossible on most properties.
…………………………….
The main disease problem for olives is known as Gafa in Portugal and sometimes, I think incorrectly, referred to as Anthracnose in English speaking parts of the world, the responsible organism being Colletotricum gloesosporioides and apparently also being know by some other equally long name which I cannot pronounce either. The only treatment is to use copper based sprays, similar to Bordeaux Mixture which is used against potato and tomato blight in other parts, but a sunny break in the weather is needed after the autumn rains start. Another problem is the fact that most of the older trees across the whole country are of cultivars that are extremely susceptible to the disease and spraying these is not 100% effective.
The wet weather also encourages the olive fly and prevents adequate control of this pest. In turn its damage to the fruit increases the Gafa problem by giving the disease access to the internal part of the fruit through the fly’s egg depositing entry in the olive. The problem with doing nothing is that the olives are a basic income source. I never liked spraying food crops, even if it means losing a wee bit of cash and I have only done it in the past as a last resort. Subsequent October and November weather each year has been very similar to our first year and an almost total lack of table quality fruit in the following two years had me rethinking my strategy. If I do not spray I lose the crop, and there arose the added problem that a severe infestation of the susceptible trees made the level of risk of infecting the new grove too high to be acceptable.
……………………….
As an example of misinformation you will find books giving production of olives as tens of kilograms per tree, I have seen as much as 70kgs mentioned, yet the European average is a little over 3000kgs per hectare. Tree spacing varies but at say, 250 trees per hectare this gives about 12 or 13kgs per tree. Individual tree output is extremely variable, in mature trees increasing yearly from a low figure in the year after heavy pruning until it is pruned again, which is often three but sometimes four year intervals. There is no doubt that production can be considerably more than this European average, and indeed is if the trees are properly managed, but it would be dangerous to budget for an average of more until you were sure you could harvest more on a regular basis year after year. The same applies to all crops. I know an ageing Portuguese farmer with several hundred olive trees and whom I expect has done his best over the years. His wife had great pleasure in telling me that they had averaged over 10kgs per tree for the first time.
……………………………..
If anybody thinks I can help further please do not hesitate to ask. I do not profess to be an expert but am commencing my 9th harvest so have a little practical experience to back up the theoretical knowledge.
First, Forgeblast, most of the olive varieties in Portugal have an oil content of between 18 and 25 %, with a few lower or higher, but not all of the oil is available under normal crushing conditions. I would assume that other countries’ varieties are similar, otherwise we would all be using the same variety by now. The more it is pressed, and heated after the Extra Virgin and Virgin are taken off the worse the quality of the oil, and the lower grades are not normally used for human consumption. They go into industrial use. The grade immediately next to Virgin is the one my wife uses to make soap – slightly higher acid content than Virgin and known as Lampante, although we have cooked with it and found it satisfactory. My intention is to make biodiesel from the olives that fail to make table quality. I have planted a total of 440 in the last five years and production will increase dramatically in the next couple of years. A general rule of thumb is that you would get about one litre (fairly close to a US quart) of food quality oil from the mill for every 7 or 8 kilos (15 to 18 pounds) of olives you took in. The mill operator will have kept back a percentage, about 15 to 20, so if you were making your own, and assuming you were not as proficient as the professionals, you might get similar results of a pint to 7 or 9 pounds of olives. That is a bit vague, but a fairly reliable expectation. With a good set-up you might do even better.
Psient, Yours is a more complicated question and one that I have not needed to consider before. I have heard of a small mill that was set up in a remote village by a man shortly before he died and it has never been used. I heard he also had a threshing mill for grain. He had intended to do all the locals’ olives and grain. I am trying to make arrangements to see it, but am going through a chain of three people so do not hold your breath.
I think we might have a language problem in describing the action of milling equipment, but are you familiar with grain crushers? These are two cylindrical steel rollers, often grooved or chequered, and almost touching, grain is hoppered into the top and the rollers crush the grain into “flakes”. The gap between them can be adjusted so that the kernels are just slightly squashed, or, put very close together the kernels will be broken into pieces. How small depends on the moisture content of the grain. I have a grape crusher that performs a similar task, but the rollers are held further apart so that the individual grapes are broken without crushing the pips. I also use it as a corn sheller because I cannot find anything better. In this case I run it in reverse (hand cranked) and the corn falls through the gap whilst I have to pick out the cobs. With olives you want to squash the pips, and they are hard. I am using the word pip rather than stone so as not to confuse them with the stone rollers.
The problem I foresee with that set-up is that you would only squash everything and not grind it down to a paste. I have not seen inside a steel roller mill as used by the commercial olive mills, but the old stone version runs two stones in a circular trough. It is possible to have anywhere between one and four in the trough if they are set up properly. There are quite a few good photographs on various webs sites. I have been doing some Googling to try to find a really good site, but most are not and some are downright misleading. I found one that suggested the stone rollers remove the pulp but do not crush the pips!! Some also imply that the pips are removed before crushing begins. A small mill I know put through 4m kilos (say 9m pounds) two years ago. Can you imagine pitting that many olives? No doubt there are machines that are capable of taking the pulp off, but that is not normal – at least in the Old World. Most websites are, of course, aimed at selling something and claiming that the way they do things, or the equipment they sell is the best. A lot of them use information from other sites that have no idea where the source of the original information came from. You can read exactly the same word for word on several sites. Nothing new in that either, the web, and indeed books are full of mis-information.
Come the end of modern civilisation as we know it (whenever that might be) and I have to construct an olive mill, I will make a circular trough and crush the olives. Stone rollers would be extremely expensive and finding someone to make and maintain them for you is probably a non-starter. Steel seems the only way. Hubs from trucks with a flat metal band around? They need to be heavy and kept firmly on the bottom of the trough, so some ingenuity in adding weight is needed. Roll them around with whatever power source is available. Run off the paste, press it. The mill I know best uses hydraulic power (it actually uses water as the fluid) and straw mats. On a small scale I am sure that either a vehicle jack type arrangement or a cider press would give reasonable results. Keep the pomace for stock feed or fuel – there will still be oil in it. Put the liquid into a container and skim off the oil similar to skimming cream from milk – a cream skimmer will probably do the job just as well as anything. If you could arrange it, a really old fashioned idea was to have a series of vats, maybe four, so that the oil floated on top of the water in the first one and spilled into the next and so on.
I have copied some extracts from my book that relate to olive growing, which hopefully those of you interested in growing olives will find useful:-
Soil analyses showed a low pH, adequate to high levels of Potassium, and most of the property having adequate to high Phosphate, with a couple of areas being quite low. The biggest problem I had with that soil was lack of organic material. I gathered that none had been applied for a long time, and with irrigation, much of the property had had adequate quantities of water and warmth – an ideal situation for rapid breakdown of OM.
If you too buy a property with olive trees then this situation is likely. It is common practice in some areas to keep the land clear of growth amongst the trees by cultivating several times a year. Your predecessor might have applied mulches of manure around the trees, but not on the remainder of the land, so expect a very low level of OM in the soil, and be prepared to feed it if you wish to crop any of the open areas. Good husbandry in the locality is said to be that every third year the trees should be mulched with farmyard manure (abbreviated to FYM in the rest of the book, or referred to as muck) if following the system of bare ground, and heavily pruned every third year too. If the land between the trees is cropped then the whole area should be mucked every year. Producing that much FYM is at best extremely difficult and impossible on most properties.
…………………………….
The main disease problem for olives is known as Gafa in Portugal and sometimes, I think incorrectly, referred to as Anthracnose in English speaking parts of the world, the responsible organism being Colletotricum gloesosporioides and apparently also being know by some other equally long name which I cannot pronounce either. The only treatment is to use copper based sprays, similar to Bordeaux Mixture which is used against potato and tomato blight in other parts, but a sunny break in the weather is needed after the autumn rains start. Another problem is the fact that most of the older trees across the whole country are of cultivars that are extremely susceptible to the disease and spraying these is not 100% effective.
The wet weather also encourages the olive fly and prevents adequate control of this pest. In turn its damage to the fruit increases the Gafa problem by giving the disease access to the internal part of the fruit through the fly’s egg depositing entry in the olive. The problem with doing nothing is that the olives are a basic income source. I never liked spraying food crops, even if it means losing a wee bit of cash and I have only done it in the past as a last resort. Subsequent October and November weather each year has been very similar to our first year and an almost total lack of table quality fruit in the following two years had me rethinking my strategy. If I do not spray I lose the crop, and there arose the added problem that a severe infestation of the susceptible trees made the level of risk of infecting the new grove too high to be acceptable.
……………………….
As an example of misinformation you will find books giving production of olives as tens of kilograms per tree, I have seen as much as 70kgs mentioned, yet the European average is a little over 3000kgs per hectare. Tree spacing varies but at say, 250 trees per hectare this gives about 12 or 13kgs per tree. Individual tree output is extremely variable, in mature trees increasing yearly from a low figure in the year after heavy pruning until it is pruned again, which is often three but sometimes four year intervals. There is no doubt that production can be considerably more than this European average, and indeed is if the trees are properly managed, but it would be dangerous to budget for an average of more until you were sure you could harvest more on a regular basis year after year. The same applies to all crops. I know an ageing Portuguese farmer with several hundred olive trees and whom I expect has done his best over the years. His wife had great pleasure in telling me that they had averaged over 10kgs per tree for the first time.
……………………………..
If anybody thinks I can help further please do not hesitate to ask. I do not profess to be an expert but am commencing my 9th harvest so have a little practical experience to back up the theoretical knowledge.