SUGAR BEET CULTURE.

Globe, Volume XXIII, Issue 2210, 26 March 1881, Page 3

SUGAR BEET CULTURE.

fOompiled for the “ Weekly Press.”]

Wo make no apology for calling the attention of the agriculturists of New Zealand in general, and of Canterbury in particular, to what must eventually become one of the industries and manufactures ”{ New Zealand. We refer to sugar beet. The manufacture of sugar from beetroot is practised on a large scale in France, Belgium, and other countries on the Continent of Europe, and also in Ireland, and looking forward to its inevitable introduction as a profitable branch of agriculture in this colony, it may be advisable to give a short account of its culture and the most approved processes of manufacturing sugar from the beetroot. The presence of crystallisable sugar in beetroot was discovered many years since by the celebrated chemist 'Margraif, and Aobard, of Berlin, was the first who suggested the cultivation of beetroot as a crop from which sugar might be economically prepared, and applied to the same purposes for which cane sugar is used. His suggestion, howevar, was received with little consideration until the arbitrary decree of the first Napoleon, prohibiting virtually, to a great extent at least, the importation of cane sugar into France, and other continental countries in that Emperor’s dominions, gave a strong impetus to the manufacture of beetroot sugar. Like most industrial pursuits this newly - created industry had to contend at first with many difficulties, but soon improvement followed upon improvement, and so rapid was the progress, that at present, not only the mechanical means of extracting sugar from beetroot are more perfect than those generally employed in the manufacture of cane sugar, but also the preparation of beat sugar is carried out in stricter accordance with scientific principles than that of cane sugar. There are two principal varieties of sugar beet, the red long beet, and the white or Silesian te.d,many different varieties occupying an intermediate position between the two kinds already noticed have been distinguished, but they are all far less o instant in their characters than the two principal kinds of beet, the seed of which always produces cither the red or white Silesian beet, A variety with which many agriculturists are well acquainted —the common mangold-wurtzel, or field beet, has been supposed to be the result of a cross between these two, and certainly possesses several physical characters of both. Formerly the field beet, with rose colored skin, and presenting on being cut alternate layers or zones of a white and red colour, was much more extensively grown in Germany and France for the purposes of sugar making than it is at present. Preference is now given to the white Silesian beet, introduced into France by Mathieu do Dombasle. The latter gives a larger percentage of sugar, and contains less water, saline matter and nitrogenieed substance than the former. It is also less liable to mechanical injuries, a-’d is not so easily affected by frost and wet, and thus possesses a combination of qualities which render it more valuable to the manufacturer than the common field beet, which generally 'produces a larger crop per acre. Some time ago another variety of beet, the Siberian beet, has been strongly praised in continental agricultural papers, as being richer in sugar and better adapted for sugar-making than any other variety. Hermann, however, observes that the so-oalled Siberian beet, a round, yellow variety, is not used at all in Russia for sugar-making, but that it is grown extensively for feeding purposes. The Siberian beet can be cultivated on a less deep and rich soil than the white Silesian variety, and os it is, nevertheless, highly nutritious, it is grown in Russia with advantage for the feeding of stock. For the manufacture of eugar it is not so well adapted as the white Silesian beet, as it contains less sugar. The percentage of the white Silesian beet has been determined as 11.4 from six' ounces of root, against 5.86 from sixteen ounces roots of the yellow Siberian beet, thus proving that large sized roots give leas sugar than smaller roots. The proportion of water generally varies in different varieties and according to the circumstances under which they have been grown, from 83 to 87 per cent, and that of sugar from 5 to 12 per cant. Similar differences are also observable in the relative proportion of other constituents.

On an average the proportion of sugar contained in the various kinds of beet cultivated for sugar-making is about 10 per cent. This sugar is the same in kind, and when properly prepared also in quality, as that extracted from sugr.r-oane. Eminent analysts have certified that the whole of the sugar in beetroot is cryatolisable, and othc-r chemists have also confirmed the fact in a decisive manner. In the manufacture of beetroot sugar, however, a large quantity is changed into ur.crystalisable sugar, or gluoo-ie, which constitutes the principal part of molasses or brown syrups. In Prance the average percentage of sugar which is actually obtained in beetroot eugar factories amounts to about 5 per cent, A production of 6 per cent, io considered a satisfactory result, and 7 per cent, is seldom obtained even in favorable seasons. Wo thus see that under ordinary circumstances nearly one-half of the amount of crystalisablo sugar which is contained in

the root is converted during its preparation into molasses ; and it it therefore by do means impossible increase the percentage at present obtained in the manufactories’ by a elhil more improved process of preparation. The proportion of sugar in beetroot is dependent on a variety of circumstances, which all influence, more or leas, the percentage of sugar in the root. The relative bulk of tho roots, the variety cultivated, the season of the year, the time when the crop is harvested, and the quantity and quality of the manure employed in the cultivation of the beetroot, together with the condition of tho soil on which the crop is grown, all exercise a marked influence on the composition of beetroot, and more especially on the proportion of sugar which occurs in it. Thus Silesian beet, as already mentioned, is richer in sugar than the common field beet. Again, small roots, it appears, contain more sugar than large ones, which are generally more watery. The different quantities of sugar in large and small roots of sugar-beet is very marked, it having been found that roots weighing 4oz yield 13 per cent., whilst roots of Boz. show 11.12 per cent., and those weighing 21b and 31b produce but 8.10 and 6 7 per cent, of sugar respectively. These results have been confirmed by Hookstetter, who also verified the presence of water in greater quantities in proportion to the increased size of the roots, A great influence is also exerted by various kinds of manures, and this is a matter of great importance to the cultivation of beet root for sugar making. Saline manures, though beneficial when applied in moderate quantities, act prejudicially when used in too largo proportions. Common salt applied above has been found to greatly favor the growth of the root, but is apt to lessen the percentage of sugar. Ammonioal manure will increase the crop, and can be used with advantage on lands not in the best condition, but when applied to rich land in a good state of cultivation is found to increase the bulk but to diminish the percentage of sugar, adding also largely to the proportion of water, and rendering the subsequent operations more difficult and expensive. An excess of decomposed animal manuring substances will also tend to promote the formation of alkaline nitrates instead of sugar. The yield of sugar is also affected by the length of time the root is kept. For instanoo, the fresh root used in the latter part of March or early in April will yield 7 per cent, of sugar, but if kept till July will only yield 5 per cent., end in August less than 4 per cent. The greater part of tho saline constituents of beetroot are soluble in water: they pass, consequently into the juice, and their presence in the inspissated juice presents a great obstacle to the ready crystallisation of the sugar. Especially it has been found that alkaline chlorides greatly oppose tue process of crystallisation without, however, exercising a decomposing action on the sugar, and as beetroot grown with the employment of much salt or saline matter always contains more soluble saline constituents than roots in the cultivation of which the abundant use of such manures have been avoided, the yield of crystallized sugar will be the more considerably diminished the more freely the land has been manured with saline substances. Besides sugar, water, and salts, the nitrogenised organic matters occurring in beet require special notice, because they present, like the salts, a great obstacle to the process of manufacturing. The exact chemical composition of these substances has not yet been accurately determined, but we know that they exist in several different conditions, and that they are liable to rapid changes. In the absence of air they remain unaltered, but in its presence they are readily decomposed, and then act as ferments on tho sugar. Hence the necessity of carefully harvesting beet root, so as to prevent their getting injured. The juice, freshly expressed, and heated immediately, does not coagulate, but when it is allowed to stand for twenty-four hours a small quantity of grey flakes is separated on boiling. These flakes have been assumed to be albumen, and we find consequently this substance mentioned in. most analyses. But the result of recent trials has been to disprove its presence. A recent improvement, to counteract tho formation of sugar into molasses, and to cheek fermentation as much as possible, is to use bisulphate of lime. For the double purpose of checking fermentation by the presence of sulphurous acid in this salt, and of neutralising the sul-. phurio acid as quick as it is formed, this process is followed in several continental factories, and is said to answer well the purpose for which it is employed. ■ In the manufacture of sugar from beetroot, the first operation to which the roots are to be submitted is to* cleanse them thoroughly from any adhering soil or foreign matters. When thoroughly cleansed the roots are rasped, grated, or sliced, in order to facilitate the extraction of the juice by pressure. In most continental factories the process of rasping is now used in preference to slicing, because the cells containing the sugary juice are more thoroughly broken open, and tho root is reduced to a fine pulp. The form of the rasping machine is generally cylindrical, and an arrangement is attached to it which presses the roots regularly and gently against the rasp, turned by steam or water power at the rate of from 800 to 1000 revolutions per minute. - In order to prevent the teeth of the rasp becoming blocked up by small particles of the root, a jet of water is allowed to trickle over the cylinder, which thoroughly removes any impediments into the receiving vessel underneath.

The next stage of the process is the separation of the juice from the pulp. This is done by submitting the pulp, inclosed in circular bags, to hydraulic pressure. At first a very gentle pressure is applied, and when all the juice removable by a slight pressure has drained off, gradually increased pressure is employed _ to squeeze out as much as possible of the juice. Generally a number of bags are piled on each other in the press, each being separated from the other by a perforated metallic plate, and after remaining in the press about twenty minutes the position of the bags is reversed, so that their points of contact may be changed, or, better still, the cake in the bags is broken in pieces before it is again enclosed in the bags, and submitted to a second and greatly increased pressure. Between each part of the operation the bags should be dipped in a weak solution of tannic acid (two to three ports per 1000), which, by combining with the nitrogenised substances of the external surface of the pulp in contact with air, prevents the formation of ferment,* which would change the orystallizable sugar into molasses. In some manufactories, the process of pressing is repeated twice, in others three or four times, and some times a little water is added to the cake of the first pressing, before it is placed in the press a second time. The juice obtained in this manner is turbid, and more or less yellow or dark colored. It has to be clarified and decolorised before it can be evaporated to the paint of crystallization. To effect this the juice is placed in a large pan, heated by steam, and evaporated down to a certain specific gravity ; when it is sufficiently concentrated, a certain quantity of hydrate of lime is added, and the boiling continued for about an hour. According to the quantity of impurities present in the juice, from four to eight parts of lime are required to render the juice perfectly clear. The effects of the lime consist, not merely in the separation of the nitrogenised matters in the juice, but also in the removal of a portion of the fatty and colouring matters, as well as several salts, such as malates and phosphates. _ The various compounds resulting from the mixture of lime with the juice at an elevated temperature partly rise to the surface, and are removed in the shape of a scum ; partly settle at the bottom of the pan. The clarified juice is poured off from the dregs, and filtered as hot as possible through animal charcoal. After having passed through a series of filtering vessels the juice has lost all colour. It is then evaporated by means of steam to a thickish syrup, and as it always becomes browner during evaporation, the concentrated syrup has to be passed once or twice again through animal charcoal.

When perfectly decolorised, the syrup has only to bo concentrated as usual, and is then run into moulds to crystallize. The larger portion hero assumes a solid crystalline form, and the uncrystallizable sugar, together with alkaline salts, and some other impurities, is allowed to drain through the pointed ends of the conical moulds. The mechanical contrivances to assist the crystallization and to effect the separation of the molasses from the loaves are the same as those employed in the refineries of cane sugar. The refuse grated root serves as cattle food, and as it possesses considerable nutritive properties, is used with much advantage for that purpose. The molasses usually aontains about half its weight of sugar, and when mixed with water, slightly acidulated with sulphuric acid and submitted to fermentation, will yield from 24 to 30 per oent. of pure spirit.