In the preparation of syrup it is of great importance to employ as little heat as possible, as a solution of sugar, even when kept at a temperature of boiling water, undergoes slow decomposition. The best plan is to pour the water (cold) over the sugar, and to allow the two to lie together for a few hours in a covered vessel, occasionally stirring, and to apply a gentle heat, preferably that of steam or of a water-bath, to finish the solution. Syrups are sufficiently boiled when some taken up in a spoon pours out like oil, or a drop cooled on the thumb nail gives a proper thread when touched. When a thin skin appears on blowing the syrup, it is judged to be completely saturated. These rude tests, however, often lead to errors, which might be easily prevented by employing the proper proportions, or determining the specific gravity by immersing in the syrup one of Baumé’s saccharometers or syrup gauges, as indicated in the following table:—
| Sugar in 100 parts. | Sp. Gr. | Deg. Baumé. |
| 0 | 1·000 | 0 |
| 5 | 1·020 | 3 |
| 10 | 1·040 | 6 |
| 15 | 1·062 | 8 |
| 20 | 1·081 | 11 |
| 25 | 1·104 | 13·5 |
| 30 | 1·128 | 16·3 |
| 35 | 1·152 | 19 |
| 40 | 1·177 | 21·6 |
| 45 | 1·204 | 24·5 |
| 50 | 1·230 | 27 |
| 55 | 1·257 | 29·5 |
| 60 | 1·284 | 32 |
| 67 | 1·321 | 35 |
A fluid ounce of saturated syrup weighs 577½ gr.; a gallon weighs 13½ lb.; its specific gravity is 1·319 to 1·321 or 35° Baumé; its boiling point is 221° F., and its density at the temperature of 212° is 1·260 to 1·261, or 30° Baumé. The syrups prepared with the juices of fruits mark about 2° or 3° more on Baumé’s scale than the other syrups. According to Ure, the decimal part of the number denoting the specific gravity of a syrup multiplied by 26 gives very nearly the number of pounds of sugar it contains per gallon.
The preservation of syrups, as well as of all saccharine solutions, is best promoted by keeping them in a moderately cool, but not a very cold place. Let syrups be kept in vessels well closed, and in a situation where the temperature never rises above 55° F. They are kept better in small than in large vessels, as the longer the bottle lasts the more frequently will it be opened, and the syrup consequently exposed to the air. By bottling syrups while boiling hot, and immediately corking down and tying the bottles over with a bladder, perfectly air-tight, they may be preserved even at a summer heat for years, without fermenting or losing their transparency.
The candying of syrups may be prevented (unless the syrup be over-saturated with sugar) by the addition of acetic or citric acid, 2 or 3 dr. per gallon. Confectioners add a little cream of tartar to prevent granulation. Syrups may be effectually prevented from fermenting by the addition of a little sulphite of potash or lime; also by the use of salicylic acid in small quantities. Fermenting syrups may be immediately restored by exposing the vessel containing them to the temperature of boiling water. The addition of a little spirit is also good, say about 10 per cent.
A solution of sugar prepared by dissolving 2 parts of double refined sugar in one of water, and boiling this a little, affords a syrup which neither ferments nor crystallises.
The basis of most mineral water syrups is simple syrup, which is prepared by adding 16 lb. of finest white sugar and the whites of 4 eggs to 1 gal. water; stir until all the sugar is dissolved; simmer over a gentle heat for 2 or 3 minutes; skim well and strain through a fine flannel bag.
The best way to keep fruit syrups from fermenting is by bottling while hot, into suitable bottles or larger vessels, and to prevent access of air. This is the principle, and it may be carried out in various ways. For instance, fill the syrup while hot in quart bottles, previously warmed, and fill them almost full. Cover or cork the bottles temporarily until the syrup cools a little and contracts in volume; then, having heated a small quantity of the syrup, refill the bottles, cork them securely and wax them.
A great variety of syrups are made by the addition of proper flavouring ingredients to simple syrup; but in other cases, especially when the juices of fruits are employed, the syrup is not first prepared and then flavoured, but the processes go hand-in-hand. In such instances specific instructions will be given. It is always advisable, when fresh fruit can be obtained, to use it in preference to the essence. One general recipe, which answers for nearly all fresh fruit, is as follows: Use nothing but the very best fresh fruit, which must be freed from stocks, &c., and crushed with a wooden instrument (not metal); when well mashed, let it stand in a room of even temperature (about 68° F.) for 4 days, which will give sufficient time for fermentation to take place; press out the juice from the fruit and let it settle in a cool cellar for 2 days, after which 5 lb. of the clear juice is to be simmered with 9 lb. loaf sugar; while warm, strain through flannel. The colour may be improved by a solution of some colouring agent.
It is advisable to add to the fresh fruit before setting it for fermentation, about 2 lb. powdered loaf sugar for every 100 lb. fruit. When cold, it is ready for bottling. Cleanliness should be strictly observed in all the utensils used. When bottling for storing, skim the top off any floating matter from the syrups in the large pan, and see that no residue at the bottom goes into the bottles. Most of the syrups not made of fruit, may have a little mucilage of gum arabic added, in order to produce a rich froth. The following recipes comprise syrups made from the fruit, and also from essences. These may be varied to suit taste and requirements. A variety of syrups have been brought into use by adding the various wines, such as claret, hock, sherry, &c., to simple syrup; others, by the addition of spirits, as milk punch, by adding to vanilla cream Jamaica rum and nutmeg. Almost any syrup may be made by the addition of a sufficient quantity of flavouring essence to simple syrup; but these artificially prepared syrups are inferior to those made from fresh fruits.