Extract of malt represents the matter dissolved from malted cereals, generally malted barley, by water. It is met with in trade in three forms; the first, as a more or less viscid extract, containing 20 to 35 per cent, of water. The colour varies much - in accordance with the temperature at which it has been evaporated and the colour of the malt used - from a golden yellow to a deep brown. The second form is that of a thin solution, containing 60 to 80 per cent, of water. The third form diners from the second in containing 3 to 4 per cent, of alcohol, apparently the result of fermentation. Amongst the various brands, the first form is the most commonly met with. The matter dissolved from malted barley by water consists of albumenoids, phosphates, maltose, dextrine, and a peculiar principle termed diastase. Extract of malt may be considered both as a remedy and as a food. In disease, where artificial digestion is desired, it appears to have a very important application, quite analogous to the application of pepsine to the artificial digestion of albumenoids.
Extract of malt is commended as a sort of elixir vita, but probably its value depends almost entirely upon the amount of diastase which it contains.
Without going fully into the question of the manufacture of malt extract, a few remarks upon it may not be out of place. Diastase is said, when heated in aqueous solution to a temperature of 155° to 158° F. (68° to 70° C), to lose its power of converting starch. This temperature, then, ought not to be exceeded in manufacturing the extract; indeed, a lower temperature than this should be observed, to prevent the coagulation of albumenoids, thereby rendering them insoluble. It is, however, almost impossible to evaporate at so low a temperature without the use of costly vacuum apparatus, and hence it might be expected that malt extract made by pharmacists without such apparatus would contain little, if any, diastase. The method of the German pharmacopoeia, which is largely followed, directs digestion of the malt with water - first, in the cold, then at -150° F. (65 1/2° C) and the solution thus obtained filtered and evaporated at 212° F. (100° C). Of course no diastase survives this evaporation.
Another method is to heat the malt with water at 150° F. (65$° C), until no starch remains, filter and evaporate at 212° F. (100° C). This method differs from that of the German pharmacopoeia, inasmuch as part of the diastase is used up in converting the starch of the malt, and the remainder only is destroyed by the evaporation. From malt extract made by both these methods no diastase resulted in either case. Extract made by macerating the malt in cold water, straining, and evaporating under a low atmospheric pressure at a temperature not exceeding 155° F. (68° C), was found to be rich in diastase. Such a process as this is recommended by the Pharmaceutical Society of Paris.
The following-table includes the results of the examination of a number of trade samples of extract of malt. The albumenoids were calculated from the results of nitrogen combustions in the usual manner. Phosphates were determined in the ash as pyrophosphate of magnesium. The maltose was estimated by a standard solution of cupro-potassium tartrate. The dextrine was estimated by boiling a solution of the malt extract with dilute sulphuric acid, and estimating the sugar present by the cupro-potassium solution as glucose - for maltose and dextrine are both convertible into glucose by ebullition with dilute sulphuric acid - calculating the glucose into maltose, then subtracting from the whole the amount of maltose found before boiling with dilute acid, and calculating the remainder into dextrine. Large quantities of diastase, and therefore large quantities of malt extract, are necessary to effect the entire conversion of every trace of starch, whereas, as is well known, very small quantities of diastase, and therefore very small quantities of malt extract, will convert relatively large quantities of starch into a liquid condition; that is, will practically digest large quantities of starchy foods.
Such a result, useful enough for purposes of digestion, but not sufficiently sharp for analytical purposes, is obtained by using the " pudding " process.
Water at 212° F. (100 C.)
Phosphates as phosphoric pentoxide.............
Grammes of extract required to convert one gramme starch .. .
There are great difficulties in the way of manufacturing a good malt extract, and when it is attempted to overcome one difficulty another is introduced. What is required is a malt extract which shall not only be rich in diastase, but also contain a fair proportion of albumenoids in a coagulable condition, or one which is readily assimilable by the system. It ought also to contain a fair amount of maltose, and a relatively small amount of dextrine, and thus the matter becomes one of very great difficulty as regards the best mode of operating. A malt extract rich' in diastase may be obtained by using a larger proportion of water with an initial temperature of 143° F. (60° C), and then raising the temperature to a little over 150° F. (66° C.) towards the end of the mashing process. But this method, in which a relatively large amount of water is used, is very likely to effect an alteration in the albumenoids. At all events, acetification will readily set in, and there is great danger of effecting a change during the evaporation process.
Again, with reference to the use of water, it is preferable to begin with a low temperature rather than a high one, because the malt partly agglomerates and cannot be so readily mixed with the water at the higher temperature. (Naylor.)
The following recipes are published: -
(1) An infusion of malt is made in water at 160° to 170° F. (71° to 77° C), drained off without pressure, and evaporated to a honey-like consistence. The quantities are - 1 pint crushed malt in 3 pints hot water, and the infusion occupies about 4 hours.
(2) 47} oz. extract of malt, mixed with 1 oz. iron pyrophosphate and ammonia citrate dissolved in 1 1/2 oz. water.
(3) 6 oz. coltsfoot leaves, 6 oz. spotted lungwort, 8 oz. liquorice, 2 lb. stoned raisins, 6 gal. old strong ale, not "hopped"; boil down to 4 gal., express strongly, and evaporate to honeylike consistence.