Corn Flour Production: Dry Method of Germ Separation and Milling Technology
libre
The challenge of separating the germ and producing a defatted, storage-stable flour was largely solved by V. T. Lyubushkin, an associate professor at the Moscow Technological Institute of the Food Industry.
This stage is an integral part of the process of producing corn flour. Unlike the so-called "wet method" of germ separation — which is used in the starch and syrup industry and is wholly unsuitable for milling — V. T. Lyubushkin proposed a "dry method" of germ separation and developed a new technological scheme for grinding corn.
How does the dry method of germ separation work?
The production of corn flour begins with cleaning the grain. After cleaning, the corn kernel is moistened and conditioned for roughly two hours. During this time the moisture does not have time to penetrate deep into the kernel and remains mostly on the surface — that is, in the husks.
This surface moisture makes it easier to separate the husks from the endosperm. The grain is then crushed and ground, during which the germ is partly or entirely chipped off the endosperm and subsequently sifted out. When the grain is ground on roller mills, the endosperm is easily reduced to a fine particle, while the tougher germ and husks merely deform and flatten.
Sifting frees the flour from most of the flattened germ and husks. Lyubushkin's scheme was tested under production conditions over several years at milling enterprises in Moldova, Ukraine, and the Stavropol region, and it is now adopted at a number of flour-milling plants.
A different dry method was proposed by researchers P. Demidov and S. Zolotarev of the Odessa Technological Institute named after M. V. Lomonosov, separating the corn germ from the kernel on a scouring machine fitted with an abrasive cylinder.
According to the authors, this method is more effective, but it requires specialized equipment. In milling practice it has not yet found application.
What are the properties of corn flour?
Corn flour produced today contains no more than 1.9–2.1% fat — roughly the same as wheat flour. 
It is worth briefly explaining how these grades and the milling methods themselves differ. In milling, two main types of grinding are distinguished: single-pass and repeated (multi-pass).
In single-pass grinding, the grain passes through the milling machine only once, whereas in repeated grinding the grain and the products of grinding are passed in sequence through a series of grinding and sifting machines, with intermediate milling products being drawn off along the way.
Simple repeated grinding yields wholemeal flour with an extraction of 96–97% of the weight of the grain delivered for milling. Complex repeated grinding uses winnowing machines to sort the intermediate products.
The purpose of this kind of grinding is to separate the ground endosperm of the grain from the germ and husks as completely as possible. It is this grinding, in its various forms, that produces corn flour at 85% and 75% extraction.
