Saccharification of starch and alcoholic fermentation

The saccharification, which should be carried out at about 40°, is accelerated by stirring and is complete in about an hour. Its course is followed by removing 5 c.c. of the solution a quarter of an hour after the malt extract has been added and determining in this sample, by the method of Willstatter and Schudel,2 the amount of maltose formed (see below). After thirty minutes more the determination is repeated. 

The Sugar Determination.—Dilute the 5 c.c. sample in a measuring flask to 25 c.c. and pour 10 c.c. of this diluted solution into 25 c.c. of 01 N-iodine solution. Then add 40 c.c. of 0-1 N-sodium hydroxide solution (free from alcohol) and leave for twenty minutes. Make faintly acid with dilute sulphuric acid and titrate back with 0-1 N-sodium thiosulphate solution. One equivalent of iodine corresponds to 0-5 mole of reducing biose, or 1 c.c. of 0-1 N-iodine solution to 17-1 mg. of maltose. What is the course of the reaction  

When the consumption of iodine is the same in two successive tests and a sample of the mixture is no longer coloured by iodine the saccharification is complete. Usually 75-80 per cent of the starch taken is converted into sugar. The rest of the starch is only broken down into dextrins, which are, however, also saccharified in the course of the subsequent fermentation. The volume of the mash is measured in a cylinder, and from the result of the final maltose titration the sugar content is calculated. For the C02-determination 10 c.c. are retained (cf. p. 402). 

Fermentation.—The solution is next transferred to a round-bottomed flask (capacity 31.) for fermentation. To set this going 10 g. 

1 If it is desired to start from potatoes (500 g.), they must be heated in a digester under 2-3 atmospheres pressure, since simple boiling till soft does not produce a breakdown sufficient for complete saccharification. 

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