Etiket Arşivleri: Milling

Cereal Technology – Grain Cleaning & Milling ( Assoc. Prof. Marie Hrušková )

CEREAL TECHNOLOGY – grain cleaning & milling

Assoc. Prof. Marie Hrušková, PhD

CEREAL TECHNOLOGY – flour processing

Main parts of flour processing:
• grain mass cleaning
• grain milling and sieving
• commercial flours mixing
• quality standardisation

CEREAL TECHNOLOGY – grain cleaning

Main objectives of grain cleaning:
• to separate the grain from organic and mineral impurities, feromagnetic components
• to remove parts of bran from grain endosperm
• to moisturing the grain mass for reduce adhesion between bran and endosperm
• to standardisation of grain moisture before milling

Wheat cleanners:

For organic impurities

For mineral impurities

Bran removing machine

Water content regulation

– basic procedure before milling

Moistening machine Automatic regulation of moisture level before and after moistening

CEREAL TECHNOLOGY – moistening before the milling

Moisture level recommended for different wheat

Wheat type                                          Moisture %
Extremally hard (Manit., dur.)   16,5 – 17,5
Americ. Bakery hard (HRW)       15,5 – 16,5
American (Austral.) soft               15,5 – 16,0
Traditional Soft European            15,0 – 16,0

CEREAL TECHNOLOGY – milling

Two main objectives of wheat milling:
• to separate endosperm of the grain from bran and germ
• to reduce dimensions of endosperm particles for fine flour particles
Fine flour – particles passing through the sieve with the rectangular apertures 140 μm in side

Middle Europe – mainly Czech
Austria – also coarser flours


Source: http://sch.vscht.cz/materialy/erasmus/CCHT2Engl-Hr-2010.pdf

Milling

DISCUSSION

In this experiment, we have learned the working principals of dry milling, and how it effects the wheat particles, also which changes occurs during the milling of wheat. In the other hand, some quality parameters are also was discussed, and how they are changing by which parameters has been considered too. The tampering was also discussed, and the effects of the tempering was learned.

We have done dry milling in our experiment, and we have recorded the sieving results, which gives us the distrubution of particle diameter. We have used two types of sieves; the milling machine’s sieves and, specifically designed sieving machine which screen diameters are known. According to our data, we could not able to obtain 100 % flour at first sieving, but we get fractions instead of this. Also some of these were bran particles which can not ground in to so fine particles. Also this may be caused by the gap between the crushing rolls, which can be not so close to each other. According to other data, we also could not be able to get the all feed that we hav introduced into the machine. There was some losses, they may be due to loss of water by evaporation during the milling, which apply large shear stress on wheat and cause high temperature increase in microregions, and the losses can be occur because of formation of fine particles, and suspending in the milling machine. This problem also, seen in the industry, which can cause explosion due to fine particle formation. These particles can be charged statically, and can be explode soon.

In the experiment, we have looked for the ash content of the flour, which is a quality parameter for the flour. We have looked first three sieves for the ash content. The results show us, the first sieve has highest ash content value, and the third has lowest ash content value. This was because of the accumulation of the bran particles on the first sieve. They contains more minerals than the endosperm. This was the expected result.