Question

Describe the industrial method of preparation of ethyl alcohol from starch. Give chemical equations of reactions also.

Answer 1

(1) Germinated barely seeds are heated to 60 ${}^{o}C$ to prevent further growth. They are then crushed with water and the solution is filtered.
(2) The filtrate (malt extract) contains diastase is heated with mash (starchy material + steam) at $50{}^{o}C$ to obtain maltose.
(3) Maltose is cooled to 30 ${}^{o}C$ and yeast is added and kept for 2-3 days to obtain wort (10% ethanol).
(4) Wort is then distilled and rectified to obtain rectified spirit.
$\underset{\text{Mash (starch)}}{2(C_6{H}_{10}{O}_5{)}_n}+n{H}_{2}O\underset{{\text{50 -60}}^{o}C}{\overset{\text{Malt extract (diastase)}}{\to }}\underset{\text{Maltose}}{2C_{12}{H}_{22}{O}_{11}}$
$\underset{\text{Maltose}}{C_{12}{H}_{22}{O}_{11}}+H_{2}O\stackrel{\text{Maltase}}{\to }\underset{\text{Glucose}}{2C_6{H}_{12}{O}_6}\stackrel{\text{zymase}}{\to }2C_2{H}_5-OH+2C{O}_2\uparrow$