The Olive Its Culture in Theory and Practice/Chapter 11
Harvest and Product.
CHAPTER XI.
"L'uliva quanto piu pende piu rende."[1]
THE FORMATION OF THE OLIVE AND ITS FATTY SUBSTANCE.
Dr. A. Funaro, of Pisa, from some very interesting experiments conducted by him at that place in 1878, has been able to prove that the nut is the first part of the fruit to form. The olives experimented upon were gathered from a farm near Pisa, at intervals from July 10th to February 25th, and carefully analyzed, with the object of studying the formation of the fatty material. This fact had already been stated by Prof. A. Roussille.
On the 25th of July the nut itself was not perfectly formed, but on the 10th of August it was quite perfect, though tender, and could not be detached from the fleshy part.
On the 25th of September it had reached its full development. Then commenced the increase of size and weight of the pulp, and the rapid increase of the fatty matter, while the quantity of water diminished slowly, oscillating according to the atmospheric conditions of the days when the olives were gathered. These, after the 10th of August, increased gradually until the 10th of September. Between the 10th and 25th of September they almost doubled in weight. One hundred olives which on September 10th weighed 75.94 grams, on the 25th of that month weighed 144.22 grams. After this period the increase of weight was gradual, but only slight, up to the 25th of October; after that date a progressive and slow decrease set in.
In fact the same one hundred olives
GRAMS.
On the tenth of October weighed |
161.73 |
"twenty fifth of October |
163.93 |
"tenth of November |
117.53 |
"twenty fifth of November |
128.88 |
"tenth of December |
136.50 |
"twenty fifth of December |
136.40 |
"tenth of January |
163.85 |
"twenty fifth of January |
109.85 |
"tenth of February |
132.50 |
"twenty fifth of February |
131.65 |
The variations are due to the quantity of water contained in the pulp according to the hygromic condition, the winds, the rain and the hoar frost which coincided with the gathering.
On the twenty fifth of November the olives were empurpled, and had a reddish pulp, on the tenth of December they had turned black and the pulp was still more highly colored, and on the tenth of February the pulp was entirely of a winey red.
In one hundred parts of these olives the following proportion was found in weight of water, of dry material and of fatty material.
| Date When Gathered. | Fresh Pulp | Fresh Nut. |
By the investigations of Signor Harz, of Vienna, confirmed by those of Roussille, it has been shown that the fatness of the olive is formed in little special cells of secretion precisely as the chlorophyl or green coloring matter is evolved and these are distributed through the berry side by side. When the fruit is still young these cells contain a material which is not fatty, nor is it starch, or any of the hydrates of carbon similar to these substances but instead is charged with nitrogen and contains a substance which in the process of ripening, takes on the character of a tough gum, wax, and fat. Finally this compound material, as maturity approaches, liquifies becomes oil and working from the inside, outwards, the membranes of the little cells themselves are gradually dissolved and the berry is filled with oil.
Messrs. Roussille and Funaro have also discovered that while the fatty material of the pulp is always on the increase up to maturity, that of the leaves on the other hand, is almost constant and always in such quantity as to overthrow the belief that there may be any connection whatever between them. The former undoubtedly is formed in the berry as Harz discovered by microscopical observation.
Funaro has further proved that the sugar of the leaves only appears when the oily substance is perfected, that is to say when the plant is near the term of its vegetative period and the fruit is well developed. In truth it is not found before November, the season when the oily material is formed in notable quantity, and on the other hand it is met with in December, January and even in February an epoch in which the vital functions are at the minimum of activity.
The conclusion from this is, that the sugar existing in the leaves has no part in the formation of the fatty material, and it is not to be considered other than as a product of metamorphosis of other hydrates of carbon of secondary importance for oily plants.
WHEN TO GATHER THE OLIVE.
The time in which to harvest the olive varies according to climate and the product desired. It may depend absolutely on climate, as the maturity of the olive is hastened and more oil is obtained where the temperature is high and vegetation has the advantage of a vivid light.
So the olive matures earlier and carries more oil at the extreme south of its zone, but the oil is fatty, high-colored and only useful in manufactures or as an illuminant, being utterly useless for food. For the latter purpose it should carry little fat or color.
Hence it follows that the northern part of the olive zone produces the finest oils at full maturity, whilst towards the south to secure the same result it is necessary to anticipate and to harvest while the berries are still yellowish or just turning purple.
So in northern Italy and southern France a fine table oil is obtained from olives that are black and fully matured, and the famous white oil is made by allowing the berries to become over-ripe and deferring the harvest till March, April and even May.
On the other hand, in southern Italy and Sicily a fine oil is obtained by early harvesting, mature berries giving an oil that is exceedingly gross, dense, highly colored and of a disgusting taste. So when seeking to produce an oil for table use, the effect of the climate may be modified to a certain degree.
The so-called white oil is preferred simply because some markets demand it, but it is undesirable from every point of view. As it is made from over-ripe fruit it soon becomes rancid, and lacks the delicate flavor of oil made at just the proper time. But worse than all this it is made at the expense of the tree, for it is evident that the sooner the tree can be relieved of the burden of its crop, the better it will recuperate for the following season.
It is doubtful whether the olive produces more oil when picked barely ripe, or at full maturity, or when it commences to fall from the tree. The usual belief is in favor of a deferred harvest, and the country people express it in the couplet that heads this chapter.
The longer the olive hangs
The more it renders.
This is an illusion. The longer the berries hang on the trees the greater is their exposure to a variety of perils; the birds devour many, more are beaten off by storms, and unless they are taken off the ground immediately, acquire an earthy flavor which renders them unfit for oil making. Another serious danger is that of being touched by frost which diminishes the yield of oil. But even supposing all olives to remain on the tree up to the point of full maturity, they are not making any more oil but are losing water. They become softer inasmuch as they lose in bulk, thus increasing the relative but not the actual quantity of oil.
We may therefore draw the following conclusions;
First: That the greatest absolute quantity of oil is to be obtained when the olives are ripe.
Second: That in a late harvest there is no gain in quantity but an actual loss in quality.
Third: That in anticipating maturity in southern countries, it is possible to reduce the tendency to grossness, high color and bad taste and so produce a finer oil.
HOW TO HARVEST THE OLIVE.
From very ancient times the olive has been gathered by beating the trees with poles and so knocking the berries to the ground. The temptation to do this is great. It is evident that it is the cheapest way to get in the crop. But it is penny wise and pound foolish, If the crop of that year was the only one to deal with, well and good, there would be nothing to say against it, but the beating makes it impossible for the tree to bear the following year.
Hence it is plain that instead of being the cheapest mode of dealing with a crop, it is the most expensive as it is one of the direct causes of the olive bearing only every other year.
Each leaf shelters a bud which in time will be a twig or a blossom, if the leaf is knocked off the bud is killed, for its life depends upon the preservation of the leaf, and these leaves are more plentiful on the fruit branches than any other part of the tree. No matter how carefully the fruit be poled off, damage is sure to be done. Olives should be picked by hand from ladders.
If the berries are to be immediately crushed they may be thrown upon a canvas cover placed about the tree to receive them; but if they have to be carried any distance or kept for any length of time it will be best to handle them more carefully, as the bruises received on being thrown to the ground cause an early decay of the berry to the great detriment of the oil.
Different kinds of olives ripen at different periods and in order to make the best oil the berry should be gathered at the exact period of its maturity and at no other. So a very large olive orchard should be made up of different varieties coming in at successive periods, but a small one should consist of only one variety.
Soil and locality also affect the quality of the oil. The same olive on different soils or on a hill and on a plain will give a very different oil; and these should not be mixed, but made separately, or the quality of the whole may suffer.
The olive takes on four changes of color, although all the varieties do not strictly follow this rule: Green is followed by yellow, then a reddish purple which is succeeded by a wine red and lastly a black red or glossy black. If the berry is left upon the tree the skin finally wrinkles and the color becomes a dull black. This is the state in which it is popularly supposed to give the most oil, which we have already shown to be a fallacy but even granting it to be true, the quality is inferior, the flavor gross and the oil soon becomes rancid. An olive is fully ripe when on being squeezed between the thumb and finger the soft pulp shows no white, but for many reasons, as we have seen, it may be desirable to forestall this period.
No time can be set when an olive crop should be harvested. It may vary by weeks from one season to another, and it is far better on every account to anticipate, than to defer the harvest. The berries should be carefully gone over and all leaves and dirt picked out; the former giving a bitter taste to the oil and the latter lessening the quantity as well as lowering the quality.
What will an olive orchard produce? As we have seen, it is customary in Spain in estimating the annual oil product of an orchard to calculate that every six trees will give four gallons of oil. This at first glance appears to be a very small yield, but it must be remembered that it is an estimate applied to the whole face of the country, that olive trees are very numerous in Spain and many orchards are very old and in a poor state of cultivation. Also that it is a general annual estimate independent of fluctuations from year to year.
A careful observation of the olive districts in Italy by Professor Caruso, extending over many years, shows that the greatest production is found in Sicily, but not the finest quality. The Sicilian product runs as high as ninety gallons of oil to the acre, falling to fifty in Liguria and the Neapolitan States, which would give a mean of seventy gallons to the acre for the whole of Italy.
Mr. Cooper makes the statement that on a piece of two acres of ground seven year old trees averaged one hundred and twenty-two pounds of olives per tree.
On the Quito Farm, Mission olive trees which were grown from cuttings put into the ground in the spring of 1883, and transplanted to position, have now, July, 1888, a fair showing of fruit, one-half the total number of trees carrying berries on them in varying quantities; and those trees grown from cuttings put in at the same time, and which from their position it was unnecessary to transplant, have attained a much greater size, and carry a correspondingly increased crop. Hence we may conclude:
First—That the olive in California will give a remunerative crop in seven years from cutting.
Second—That we may reasonably expect to secure from seventy-five to one hundred gallons of oil per acre from our olive orchards. The newness of the soil, coupled with the youth and vigor of the trees, assure us that we make no mistake in such an estimate.
- ↑ The longer the olive hangs, the more it renders.