Titulo Mas Descriptivo

APTEFF, 40, 1-220 (2009) DOI: 10.2298/APT0940025F

UDC:664.71-11:664.762:66.012 BIBLID: 1450-7188 (2009) 40, 25-34 Original scientific paper

REDUCTION OF WHEAT MIDDLINGS USING A CONVENTIONAL AND EIGHT-ROLLER MILLING SYSTEMS Aleksandar Z. Fišteš and Đuro M. Vukmirović1 Possibilities for the rationalization of the wheat flour milling process using the eightroller mill on the 1M and 2M passagesof the reduction system have been investigated. At the same roll gaps and under the same sieving conditions, the lower flour yield has been obtained using an eight-roller mill compared to the conventional milling system (5-8 %) followed by a higher energy requirements for grinding. By decreasing the roll gap setting and increasing the upper size limit of flour in the process with the eight-rollermill it is possible to increase flour yield and therefore decrease milling energy consumption per unit mass of flour produced without deterioration of flour quality as determined by ash content. With appropriate adjustments of the processing parameters in the eight-roller milling system it is possible to achieve similar milling results to those in the conventional system, while the overallinvestment, energy and maintenance costs are significantly lower.

KEY WORDS: Wheat flour milling, process rationalization, eight-roller mill
INTRODUCTION

The objective of the wheat flour milling process is to separate the branny cover and germ of the wheat kernel from the endosperm and achieve as high as possible flour extraction with the lowest contamination of bran and germ that increase theash content. Breaking the wheat kernel is affected by corrugated cast steel rolls that gradually separate the endosperm, bran and germ. Reduction of relatively pure endosperm to flour is achieved by using smooth rolls. Segregation between the kernel parts occurs in plansifters, where sieves separate particles of different size, and in purifires, where sieves and airflow separate particles ofdifferent size, specific gravity and shape (1). Ever since the grinding of grain has been known to the mankind, possibilities and solutions have been sought out in order to simplify the grinding process and make it more efficient. New concepts and ideas only have chance of being successful if the yield as well as the quality of the finished products are not affected and requirements such as reduction ofinvestment, operating and maintenance cost are met (2). The traditional
Aleksandar Z. Fišteš, M.Sc., fistes@uns.ac.rs, Faculty of Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia; Đuro M. Vukmirović, B.Sc., djuro.vukmirovic@gmail.com, Institute for Food Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Serbia

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APTEFF, 40, 1-220 (2009) DOI: 10.2298/APT0940025FUDC:664.71-11:664.762:66.012 BIBLID: 1450-7188 (2009) 40, 25-34 Original scientific paper

wisdom in flour milling is that after every grinding step the ground material should be sieved and the undersize material removed before regrinding (3). Over the years the main equipment used in the grinding system has been redesigned to such an extent that it has been possible to multiply the throughputs of thesemachines but flour process technology has not changed fundamentally since the introduction of the roller mill, the purifier and the plansifter (4). This is the reason why the double grinding of intermediate streams before sieving has been one of the most notable process developments in flour milling (3). Eight-roller mill (a total of 8 rolls in one housing) provides two grinding passages without anyintermediate sifting. Compared to a conventional process with the four-roller mill, the introduction of the eight-roller mill into the milling flowsheet offers the following advantages (2, 4, 5-8): • fewer pneumatic suction lifts (conveying the stock from the roll to the sifter) – resulting in lower material and installation costs • lower pneumatic system air requirements – resulting in lower...