This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The question with many bottlers is, Which process is the most practical and economical one ? We unhesitatingly decide in favor of the cold process provided the best refined sugar is employed. It has the advantage of greater simplicity in manipulation and is decidedly preferable for the preparation of syrups into which, enter no fruit-acids at all, or for such acidified syrups that are, with the beverage, to be consumed within a limited time. This the reader should always bear in mind. The hot process should be employed in preparing champagnes, champagne-cider, also in preparing any beverage into which, wine or cider enters as a component. Also it should be followed to prepare the syrups for all those acidified beverages that are for storage or export, exposed to heat, for tropical climates, etc., and not likely to be consumed early. In all these cases the syrup should be prepared by boiling, after having added the required quantity of fruit acid to the mixture. This process ensures more stability for acidified beverages, and has been by practical experience found to accomplish what is claimed for it. The admixture of fruit-acid converts the sugar solution, and any precipitate or turbidity caused by this chemical action is clarified by following filtration and clarification. Thus a syrup is obtained which undergoes no mora change within the beverage when ordinary care is taken. It is said that syrup thus prepared by the hot process is directly fermentable. This is a fact; however, when we exclude all ferments by careful preparation and clarification, it will keep indefinitely, but the cautious may even add a preservative to his beverage. Syrup otherwise. prepared and not brought to the modification of invert-sugar, is always exposed to the inverting influence of the fruit-acids, from which a preservative cannot protect it.
We therefore urge, that when the "hot syrup process" is employed, combine the "inversion process" with it,.as heretofore explicitly explained; and to dispense with all other modes of hot syrup making, such as heating the mixture gradually to the "simmering" point or immersing the sugar in water and afterwards heating it, etc.
Either the cold or the hot or inversion syrup process should be adopted for this purpose. When infusions are employed the hot syrup process must be applied in order to coagulate albumen. When inferior or raw-sugar is used, the hot process is likewise necessary. The inversion process, that is, to heat the mixture with the fruit-acids, is combined herewith when the syrup is to be acidified for the purposes explained. Otherwise the fruit-acids should be added to the clarified syrup when entirety cold. When fruit-syrups are to be prepared, the hot process is indispensable and inversion takes place by the fruit-acid contained in the juice.