Roller Milling of Wheat

Question 1

roller milling main products

Answer 1

Flour, farina, semolina

Question 2

Semolina

Answer 2

mostly the white flour (endosperm) with some remaining small pieces of bran. coarse, sandy texture. puddings.

Question 3

Flour

Answer 3

flour is the white endosperm, ground up. silky texture. pastries, bread, cakes.

Question 4

Wheatfeed

Answer 4

used for animals; ground up bran

Question 5

Bran utilization

Answer 5

bran is sold as bran or used to make cereals

Question 6

wholemeal/whole wheat flour

Answer 6

mix pure flour with bran that was separated initially in the same ratio it was initially.

Question 7

dry milling

Answer 7

separation of anatomical parts of the grain as cleanly as possible. subsequently, some of the parts are reduced in particle size.

involves recovery of the main tissue (starchy endosperm) and the concomitant removal of the bran (pericarp, seed coat, nucellar epidermis, and aleurone)

germ is usually separated from the endosperm as it is high oil.

Question 8

what does the ‘bran’ consist of

Answer 8

pericarp
seed coat
nucellar epidermis
aleurone layer.

Question 9

benefits of roller milling

Answer 9

consumer preference for white flour.

improved baking performance

enhanced shelf-life of flours and products.

Question 10

Roller Milling objectives

Answer 10

1. separate bran, germ, and starchy endosperm.
2. grind starchy endosperm into flour, farina, or semolina

Question 11

Drawbacks of Milling

Answer 11

1. Cost of milling
2. Nutritional losses – fibre, protein, lysine, oil, vitamin E, phytochemical.

Question 12

How does milling separate particles

Answer 12

by size and composition differences via sifting/sieving. differences in bulk density between flour and bran aid their separation.

Question 13

Roller Milling of Wheat steps:

Answer 13

1. Preparation for Milling (blending, cleaning, tempering)
2. Milling (break roll, sifting, purification, reduction)
3. Flour blending and finishing

Question 14

1. Prep for Milling – Blending

Answer 14

types of wheat are blended to make specific flours. ensures quality requirements are met at the lowest cost. generates the grist for the mill

Question 15

1. Prep for Milling – Cleaning

Answer 15

removes foreign materials. Machines, screens, aspirators, de-stoners, disc separators, indented cylinders, and scouring are all used.

Question 16

1. Prep for Milling – Tempering/Conditioning

Answer 16

Adjusts moisture content with hot water/steam to soften endosperm, toughens bran, and makes germ rubbery. Moisture/time determined by hardness of wheat, desired fineness of flour, and temperature.

Tempering adds water. Conditioning adds steam. Rate of water uptake increases with temperature. Temperatures exceeding 50ºC will damage gluten.

Soft wheat tempered to 15.5% moisture, hard wheat to 16.5%, durum even higher.

Question 17

2. Milling – Break Roll System

Answer 17

Consists of 3 or more pairs of closest set, counter-rotating, differing speed, spirally-corrugated, steel rolls.

Rolls crush and break open kernels and scrape/chop the endosperm from the bran.

Each successive pair of rolls is more finely corrugated and set closer together.

Ground material from each pair is sent to the sifting system.

Question 18

2. Milling - Sifting System

Answer 18

Stacks of sieves in shaker boxes that segregate ground material from the break rolls into a number of fractions according to particle size (composition).

Coarse material is sent back to the break system for further milling.

Intermediate and fine fractions are sent to either purification, reduction roll milling, or flour collection.

The germ is collected after the first break. Bran and shorts collected after the last break.

Question 19

2. Milling – Purification

Answer 19

separates the intermediate and fine fractions from the Sifting System into purified middlings, flour, and branny particles.

Separation based on particle size & bulk density.

Purified middlings & flour sent to reduction rolls or flour collection. Branny particles sent back to break roll system or to the millfeed stream

Question 20

2. Milling – Reduction Roll Milling

Answer 20

Gradual Reduction of purified middlings into flour.

Several pairs of closely set, counter-rotating, different speed, smooth, steel rolls. each successive pair is set closer together.

Material from each pair of reduction rolls is sent to the appropriate stage of the sifting system where flour is sifted from coarser material.

Coarser material is returned to the appropriate set of reduction rolls for further size reduction.

Question 21

3. Flour Blending & Finishing

Answer 21

A mill generally produces several flours and not just straight-grade flour.

Finished flours are combinations of the multiple streams produced during milling.

Streams are combined on the basis of composition and functionality to meet the needs of end-users.

Flour additives- vitamins, minerals, amino acids, protein, bleaching agents, maturing agents, enzymes.

Question 22

Products of Milling

Answer 22

Flour – 70-75% yield

Bran & Shorts – 20-25%

Germ – 5-10%

Middlings – purified or unpurified

Millfeed – consists of bran and germ

Question 23

Milling Yield

Answer 23

extraction rate (%)

Question 24

What is dough?

Answer 24

Dough = flour + water + mechanical energy

Dough is used in the preparation of yeast-leavened products: pasta, noodles, perogies, tortillas, chapattis.

Question 25

What is bran used for

Answer 25

feed, 60%/100% whole wheat bread, graham flour, pasta, baked goods, cereal, snacks.

Question 26

what is the germ used for

Answer 26

feed, baked goods, cereal, snacks, wheat germ oil, germ meal.

Question 27

Semolina

Answer 27

The coarse, purified wheat middlings (intermediate milling stage) of durum wheat mainly used in making pasta, couscous, and pudding. High-gluten flour made from hard durum wheat. It is coarse in texture, yellow in colour, and high in gluten protein.

Question 28

Farina

Answer 28

The coarse, purified middlings of hard common wheat. typically made into a hot breakfast cereal.