manner, a high starch transformation produced by restricted diastase is readily hydrolysed to the low starch transformation (No. 8 equation), containing maltose and stable dextrin only, by the further action of active diastase.

The following example explains the general character of the action during a restricted conversion :—

+20) C12H22O1
+20{C12H20010

+ 20(C12H20010).

On the further addition of unrestricted diastase to the restricted conversion the malto-dextrin only is acted on :—

20(C12H22O11 + 20H2O = 40C12H22O11.
(C12H20010

As a final result, therefore, the original restricted conversion is brought down to the low starch transformation, [a] 150·3°, represented by:

80C12H22O11 + 20(C12H20O10)
Maltose.

Stable Dextrin.

To 200 c.c. of the fermented conversion, add 10 c.c. of malt extract and digest the mixture in a water-bath at 55° (131° F.) for one hour. The malto-dextrins present will thus be converted into free maltose.

Make a check solution by adding 5 c.c. of malt extract to 100 c.c. of water, and treat in a similar manner to the conversion.

Boil, cool, and make up the two solutions to 200 c.c. and 100 c.c. respectively with water.

Filter and determine the reducing power of both solutions. The reducing power of the degraded solution corrected for the malt extract used, less the reducing power of the solution previous to degrading (not corrected for malt extract), is due to maltose derived from the "apparent" dextrin which existed as malto-dextrin.

Calculate the amount per 100 c.c., first as maltose, and afterwards as the equivalent amount of dextrin, according to the equation:

Constitution of the Malto-Dextrin Found.-As the amounts of "apparent" maltose and dextrin existing as malto-dextrin in 100 c.c. of the starch conversion have now been determined, it is now possible to express in a simple form the proportion in which they appear to be combined (e.g., 15 maltose, 1 dextrin). The proportion is sometimes regarded as indicating the type of malto-dextrin found.

ap

Note that the proportion of "apparent maltose to " parent" dextrin found by the above method of experiment may only express the proportion of a mixture of malto-dextrins of varying reducing power.

Determine the Amount of Stable Dextrin present in the Conversion.-Measure 150 c.c. of the degraded conversion (see above) into a flask, add about 1.5 grms. of washed pressed yeast, and allow the solution to ferment at a temperature of 26° (79° F.), until the whole of the maltose present is decomposed. Boil

the solution to expel the alcohol formed, cool and make up to the original volume of 150 c.c. Filter and determine the rotatory power of the solution.

Measure 100 c.c. of the fermented solution into a small flask, add 5 c.c. of malt extract and about 1 grm. of pressed yeast, and keep the flask at a temperature of 26° (79° F.) until all signs of fermentation have disappeared. Also make a check solution of 100 c.c. water, 5 c.c. malt extract and 1 grm. pressed yeast, and ferment as above.

Note that in this experiment stable dextrin, which is not fermented by yeast under ordinary conditions, has been submitted to the joint action of diastase and yeast. Neither of these agents alone is able to hydrolyse stable dextrin, the resisting power of which is however overcome by the joint action of the two, with the result that the dextrin is fermented.

Boil the fermented conversion and the check solution to expel the alcohol formed, cool and make both up to the original volume of 100 c.c. Filter, determine the rotatory power of both solutions, and correct the starch conversion result for the malt extract used. The stable dextrin may now be calculated from the loss in rotatory power of the conversion during fermentation in the presence of malt extract.

When the analysis of the high starch transformation is completed, express the results as amounts of maltose, malto-dextrin, and stable dextrin in 100 c.c. of the conversion.

PART III.

Studies Bearing Directly on the Technology of Brewing.

A Study of the Influence of the Mashing Temperature on the Optical Activity of Malt Worts.Take two beakers, each containing 250 c.c. of water heated to 148° F. and 161° F. respectively, and mash into each beaker 50 grms. of ground pale malt (from the same sample). The mashes should then have "initial" heats of 144° F. and 157° F., and they must be kept at these temperatures for one hour by being placed in separate water baths heated to the required temperatures. Cool, filter, and determine the specific gravities and rotatory powers of the two worts. Use the 3.86 factor to determine the weight of solids present, and calculate the [a]p of the two worts.

Note that the specific rotation of the wort from the high temperature mash is higher than that from the low, indicating the presence of more dextrin in the former than in the latter. The reason for this will be found on considering the results of the experiments already made with high and low starch transformations.

Measure 100 c.c. of each of the two worts into separate flasks, boil for twenty minutes to destroy the diastase present, cool, and make up the volumes again to 100 c.c. Add about 0.5 grm. of pressed

yeast to each solution and ferment in a warm place. When fermentation is complete, filter, and determine the specific gravity or "attenuation" of the fermented worts. Note that the specific gravity increases with the mashing temperature and [a]D of the original wort, indicating that the high temperature mash contains a larger amount of unfermentable matter than the low temperature

one.

Consider this in the light of the experiment

made with a high starch conversion.

The divisor 3.86 is employed in the above experiments as it is customary to use it in determinations of the [a] of brewery worts. The divisor (3·86) was originally obtained from experiments with cane sugar and the divisor 4.00 is more accurate for malt wort solids, but custom at present decides in favour of 3.86, and it is employed here for this reason. As the chief value of determinations of the [a] of worts lies in their use for purposes of comparison, the employment of the incorrect 3.86 factor is of little moment so long as its use is indicated in the proper manner, e.g., [a]D3.86.

The student is often surprised to find, on first determining the [a] of a malt wort, that it is much lower than the [a]» of a low starch transformation (150.3°), although it represents a conversion restricted by heat. The low [a], is occasioned by the presence in malt wort of bodies other than starch transformation products which, as a whole, possess little or no rotatory power.

Experiments on the Fermentation of Boiled and Unboiled Worts, Illustrating the Different Methods of the Brewer and the Distiller or Vinegar Maker. -Mash 100 grms. of ground pale malt in a beaker with 500 c.c. of water at a temperature of 154° F. and keep the mash at a temperature of 150° F. for