Wheat and wheat milling description

1. Wheat & Wheat Milling

3. Plansifter
• Sifting: It is done after each break roll
using plansifters
• Stacked up to 12 sieves
• Sieves consist of wooden frame with a
coarse wire grid bottom
• Apertures of sieve clothing range from
1600 μm – 100 μm
• Coarse : wire mesh; finer : nylon or silk
Contd…
• Suspended from grinders by canes and are driven by a rotating vertical
shaft
• Sifters have a throw from 75 to 100 mm & rotate from 180-225 rpm
• Large pieces of bran are sent to next break rolls
• Particles of other sizes are sent to purifiers/subsequently to reduction
rolls

4. • Purifier: An inclined sieve that becomes coarser from head to tail
• Greater density of endosperm
• Bran-rich or germ-rich particles are removed by the air
• Endosperm chunks are graded and sent to reduction rolls (4-5)
Purifier
Contd…

5. Particles to Purifiers

7. Tour to a Roller Flour Mill
Video
Coarse particles of starchy endosperm
(150-850 μm)
Durum Wheat - Semolina / Suji / Rava
Common Wheat – Farina
Input – Whole Wheat
Output – Bran
Middlings
Fine flour

8. Wheat Flour Grades
• A roller milling operation produces many flours, one from each grinding
step/break roll system
• Yield of flour is expressed as extraction rate (ER)
• ER is the percentage of total product in any desired fraction
• Straight-grade flour : A composite of all flours produced on the mill
(72% extraction flour)
• Patent flour : Flour produced at the head (first grinding steps) of the
reduction system (65-45% extraction)
• Short-patent flour : Flour with lowest ash (about 45% of the total products)
• Long-patent flour : Flour up to 65% of the total products
• Mill feed : It comprises of bran (11%) & shorts (15%)
• Germ : Usually recovered at about 0.5%

10. 0 10 20 30 40 50 60 70 80 90 100
% Extraction
Whole Wheat Flour
Straight Grade Flour
Shorts & Bran
Patent Flour
Low-grade flours

11. Extraction
Rate
Protein Crude Fat Carbohydrate Crude Fiber
100 12.2 2.4 64.1 2.00
85 12.1 1.6 69.8 0.40
80 11.7 1.4 70.2 0.21
70/72 11.3 1.1 72.0 0.10
near 40 10.0 0.8 74.5 trace
Composition of Flours at Various Extraction Rates

12. Change in Composition from Wheat to Flour
Component Wheat 70% Extraction Flour % Change
Ash, % 1.55 0.4 -74
Fiber, % 2.17 Trace > -90
Protein, % 13.9 12.9 -7
Oil, % 2.52 1.17 -54
Starch, % 63.70 70.90 + 11
Thiamine, μg/g 3.73 0.70 -81
Riboflavin, μg/g 1.70 0.70 -59
Niacin, μg/g 55.60 8.50 -85
Iron, mg/g 3.08 1.42 -54
Sodium, mg/g 3.20 2.20 -31
Potassium, mg/g 316.0 83.0 -74
Calcium, mg/g 27.90 12.90 -54
Magnesium, mg/g 143.0 27.20 -81
Copper, mg/g 0.61 0.18 -71
Zinc, mg/g 3.77 1.17 -69
Total Phosphorous, mg/g 350.0 98.0 -72
Phytate Phosphorous, mg/g 345.0 30.4 -91
Chlorine, mg/g 39.0 48.4 + 24

13. BIS (1155: 1968) Requirements for Whole Wheat Flour (Atta)
Characteristic Low Grade High Grade
Moisture (% by wt) (Max) 13.0 13.0
Total Ash (on dry basis), % by wt. (Max) 2.5 2.5
Acid insoluble ash (on dry basis) % by wt.
(Max)
0.10 0.10
Gluten (on dry basis) % by wt. (Min) 7.0 to 9.0 Above 9.0
Crude fiber (on dry basis) % by wt. (Max) 2.5 2.5
Alcoholic acidity (as H2SO4), with 90%
alcohol, % by wt., (Max)
0.1 0.1
Granularity
To satisfy test
(not more than
0.2 % by wt. left
on 600 μ sieve)
To satisfy test
(not more than
0.2 % by wt. left
on 600 μ sieve)

14. FSSR (2011) Requirements for Milled Wheat Products
Characteristic Atta Maida #
Protein-rich *
(Paushtik )
Atta
Protein-rich *
(Paushtik )
Maida
Semolina /
Suji / Rava
Moisture (% by wt) (Max)
(when determined by heating to 130-135°C for 2 hr)
14.0 14.0 14.0 14.0 14.5
Total Ash (on dry basis), % by wt. (Max) 2.0 1.0 2.75 1.4 1.0
Acid insoluble ash (on dry basis) % by
wt. (Max)
0.15 0.10 0.10 0.10 0.10
Gluten (on dry basis) % by wt. (Min) 6.0 7.5 -- 7.0 6.0
Total Protein (N x 6.25) (Min) -- -- 12.5 12.5 --
Crude fiber (on dry basis) % by wt.
(Max)
-- -- 2.50 0.53 --
Alcoholic acidity (as H2SO4), with 90%
alcohol, % by wt., (Max)
0.18 0.12 0.12 0.12 0.18
# When used for bakery purposes may contain flour improvers: Benzoyl peroxide (40 ppm Max.), Potassium
bromate (20 ppm Max.) & Ascorbic acid (200 ppm Max.)
* By mixing whole/refined wheat flour with groundnut flour or soy flour or a combination of both up to 10%

15. BIS (10898: 1984) Requirements for Fortified Wheat Flour
Characteristic Requirement
Moisture (% by wt) (Max) 13.0
Total Ash (on dry basis), % by wt. (Max) 2.75
Acid insoluble ash (on dry basis) % by wt. (Max) 0.20
Gluten (on dry basis) % by wt. (Min) 7.0
Total Protein (N x 6.25) (on dry basis) % by wt. (Min) 10.0
Crude fiber (on dry basis) % by wt. (Max) 2.5
Alcoholic acidity (as H2SO4), with 90% alcohol, % by wt., (Max) 0.1
*Calcium, mg/ 100 g, (Min) 120
Iron, mg/ 100 g, (Min) 5
Thiamine (as hydrochloride), mg/ 100 g, (Min) 0.25
Riboflavin, mg/ 100 g, Min 0.5
Niacin, mg/ 100 g, Min 2.5
* PFA Act requirement for atta / maida:
Calcium carbonate powder (chalk), if added for fortification, shall not contain less than 0.30
parts and not more than 0.35 parts out of 100 parts of fortified atta / maida

17.  Wheat endosperm upon grinding is
fragmented
 Flour contains mixture of particles
Whole endosperm cells (singly or in
lumps), segments of endosperm cells,
& clusters of starch granules and
protein (>35 μm in dia)
Large and medium sized starch
granules, some with protein attached
(15-35 μm in dia)
Small chips (wedges) of protein and
detached starch granules (< 15 μm in dia)
Air Classification of Flour
Endosperm cells
(before & after milling)
Prismatic
Polyhedral

18. • Soft wheat contains about 50% of medium-sized and small particles
(below 35 μm) in flour
• Hard wheat contains only 10%
• Further fine grinding separates the components with increasing
proportions of starch & protein (pinned disc grinder)
• Particles below about 80 μm are considered as sub-sieve range
• Separations at 15 μm and 35 μm is fractionated by air classification
• Air classification process involves elutriation in which particles are
subjected to the opposing effects of centrifugal force and air drag
• Small particles are influenced by air drag
• Air classification results in protein-rich (< 15 μm) fraction, starch-
rich (15-35 μm) fraction and other fractions (> 35 μm) of cells or
parts of cells
Contd…

19. Results of Air-Classification of Wheat Flour

20. Commercial applications of air-classified wheat flour
 Fine fraction:
 Increasing protein content of bread flours
 Usage in the manufacture of gluten-enriched bread & starch
products
 Medium fraction:
 Use in sponge cakes & pre-mix flours
 Coarse fraction:
 For biscuit manufacture, where the uniform particle size and granular
nature are advantageous
Contd…

21.  Additives and treatments are added or applied to flour e.g.
bleaching agents, maturing agents, etc.
 Together all these are referred to as Flour Improvers
 When added to improve final bread quality they are called as
bread improvers
 Alternative names : dough conditioners, processing aids, oxidizing
agents, additives, concentrates, etc.
 The principal flour treatment agents / improvers: Nitrogen peroxide,
Chlorine, Ascorbic Acid, L-Cysteine, Potassium bromate, potassium iodate,
Nitrogen trichloride, Chlorine dioxide, Benzoyl peroxide, Acetone peroxide,
enzymes, other grain flours, etc.
 Aids to - dough processing (malt flour), - gas production (ammonium
chloride), - gas retention (oxidizing agents), - bread softness (GMS), -
improving crumb colour (soy flour)
Flour Treatment Agents

22. Permitted Flour Treatment Agents / Improvers in India (as per PFA Act)
Calcium iodate Potassium bromate (50 ppm Max)*
Potassium iodate Potassium iodate (50 ppm Max)*
Nitrogen oxide Calcium bromate
Nitrosyl chloride Chlorine
L-Cysteine and its hydrochlorides-sodium
& potassium salts (90 ppm Max)*
Chlorine dioxide
Potassium perchlorate Azodicarbonamide
Ammonium perchlorate Carbamide (urea)
Ammonium chloride (500 ppm Max)* Benzoyl peroxide (40 ppm Max)#
Acetone peroxide Calcium peroxide
Amylases (fungal 100 ppm Max)* Ficin
Proteases Magnesium lactate
Papain Monocalcium orthophosphate
Bromelain Ammonium phosphate (2500 ppm Max)*
Ammonium persulphate (2500 ppm Max)* Calcium phosphate (2500 ppm Max)*
Calcium carbonate (5000 ppm Max)* * For Bread; # for Biscuit and Bread

23.  Bleaching Agents
 Flour contains a yellowish pigment consisting mainly xanthophylls
or its esters (95%) & has no nutritional significance
 With bleached flour, a white coloured flour and hence a white
coloured loaf can be obtained
 Bleaching of the natural pigment by oxidation occurs rapidly when
flour is exposed to atmosphere; more slowly when it is stored in
bulk
 However, this can be accelerated by chemical treatments
 Advantage to miller: A whiter flour can be obtained at a higher
extraction rate (profitability)
 Optimum level of treatment can be determined by treating flour
at various levels of the bleaching agent and extracting the treated
flours with an appropriate solvent

24.  Benzoyl peroxide ((C6H5CO)2O2) is a solid bleaching agent,
supplied as mixture with inert, inorganic fillers such as CaHPO4,
Ca3(PO4)2, sodium aluminum phosphate, chalk, etc.
 Advantage over gaseous agents; non-hazardous
 It has only bleaching action and no improving action
 Bleaching action occurs in 48 hrs
 Dosage rate : 45-50 mg/kg (In India: 40 ppm Max)
 Treated flour contains traces of benzoic acid
Contd…

25.  Maturing Agents
 Performance of a flour improves with age
 Aged flour handles better, with more tolerance in the dough,
giving larger loaves with a finer crumb structure
 Natural aging process requires considerable time, which may vary
with storage temperature and wheat type
 Relying on natural process places heavy economic demands
 Maturing process is one of oxidation processes and, as it relates to
flour performance, is specifically modification of protein
 Modification involves sulfhydryl and disulfide groups of the
protein molecule, resulting in cross-linking of the protein chains
 Application of a maturing compound decreases extensibility of the
dough and increases dough resistance to extension
Contd…

26.  Chlorine dioxide (ClO2) is widely used as improving and bleaching
agent
 The ClO2 gas is released (in situ) by passing Cl gas through an
aqueous solution of sodium chlorite
 Air is then passed through the solution to obtain a gas mixture
with 4% ClO2 and is applied to flour at 12-24 mg/kg
 Being a gas, control of feed rates is not easy
 Unfortunately it also destroys the tocopherols
 Permitted in the UK, the USA, Australia, Canada and Japan
 Chlorine gas is usually used for treatment of mainly cake flour
(1000-1800 mg/kg)
Contd…

27.  Ascorbic acid
 It has been used for many years in bread making
 Commonly used oxidant (additive / improver)
 In bread making it is used to improve gas retention through its
effect on gluten structure
 It is a reducing agent but during dough mixing AA is readily
converted to dehydroascorbic acid in the presence of oxygen and
ascorbic oxidase
Contd…

28.  It involves oxidation of sulfhydryl groups (-S-H-) of gluten-forming
proteins and the formation of disulfide bonds (-S-S-)
 Results in improved ability to retain gas and yields bread with a
finer crumb cell
 The quantities of air incorporated during dough mixing play a
significant role in promoting oxidation
 The oxidizing effect of AA is mainly limited to dough mixing period
because yeast will remove oxygen in the air bubbles by the end of
mixing
 The action of AA during mixing also bring about changes in the
rheology of the dough making it more resistant to deformation
Contd…

29. Baking & Baked Products

30.  Baking is a millennia old process
 Baking: Food products in which flour is the basic material and to
which heat is applied directly by radiation from the walls and/or
top and bottom of an oven or heating appliance
 Bakery products range in complexity from ingredients of a plain
pastry to the numerous components of a cake
 Bread, cake, pastry, biscuits, crackers, cookies, muffins, etc.
where flour is the essential and principal ingredient
 Also includes the toppings, frostings, fillings, etc. that finish the
baked product
 Although differences exist between products, they share two
important issues: baking ingredients and baking techniques
Baking & Baked Products

31.  The function of baking is to present cereal flours in an attractive,
palatable and digestible form
 Wheat is the principal cereal used for breadmaking
 Bread is made by baking dough which has four main ingredients:
wheat flour, water, yeast and salt
 Optional ingredients include: flours from other cereals, fat, malt
flour, soya flour, yeast foods, emulsifiers, milk and milk products,
fruits, vital gluten, etc.
 Composite Flour is made by blending varying amounts of non-
wheat flour with wheat flour and used for production of baked
goods that are traditionally made from wheat flour
Contd…

32. When ingredients (F, W, Y & S) are mixed in correct proportions, three
processes commences:
1. The protein in the flour begins to hydrate to form gluten
 Flour consists of discrete and separate particles, but the gluten
is cohesive, forming a continuous 3-D structure which binds
the flour particles together in a ‘dough’
 Gluten has peculiar extensible properties
Contd…
2. Air bubbles are folded into the dough
 During subsequent handling these
bubbles divide or coalesce
 Eventually dough resembles a foam with
bubbles trapped in gluten network

33. 3. Enzymes in the yeast start to ferment the sugars
 Sugars present in the flour & those released by the diastatic
action of the amylases on damaged starch
 Breakdown of sugars into alcohol & CO2
 CO2 gas mixes with the air bubbles and brings about expansion
 Corresponding with these requirements, there are three stages in
the manufacture of bread:
 Mixing and dough development
 Dough aeration, and
 Oven baking
Contd…

35.  Flour
 Water
 Leavening agents
 Salt
 Yeast food
 Sugar
 Shortening
 Dairy products
 Nutritive fortificants
 Vital gluten
 Fungal enzymes
List of Ingredients used in Bakery Products Preparation
 Diastatic & non-diastatic malt
 Other cereal flours
 Soy flour
 Flour improvers
 Sweeteners
 Cocoa powder
 Egg and egg solids
 Fruits & Nuts
 Spices & flavourings
 Emulsifiers
 Mold Inhibitors

36. Role of Ingredients
 Good breadmaking flour is characterized by adequate protein
content (11-13%), satisfactory moisture content (< 14%) &
adequate damaged starch
 Strong wheats meet these requirements
 Protein & water form viscoelastic material (gluten)
 Gluten retains gas formed by sugar fermentation and contributes
to structure of dough and bread
 Starch + water + heat forms a viscous paste that sets to a gel after
baking.
 During bread storage the starch crystallizes (retrogrades) and
contributes to firming (major part of staling) of breads
Wheat Flour

37.  Main purpose is to combine (hydrate) wheat proteins to form
gluten
 Hydrates flour gums (pentosans) and mill-damaged starch
granules
 It is as a solvent and acts as a dispersing agent and medium for
chemical and biochemical reactions
 It aids in dough mobility
Water
Contd…

38. Contd…
 Added to develop and enhance flavour
 It toughens gluten and gives a less sticky dough
 It retards fermentation and its addition is sometimes delayed until
dough has been partly fermented
 It is either added as an aqueous solution (brine) or in dry form
 Usually added in the range of 1.8-2.1% on flour basis (giving a
concentration of about 1.1-1.4% of salt in bread)
Salt

39. Contd…
 Leavening is the production or incorporation of
gases in a baked product to increase volume
and to produce shape and crumb texture
Leavening Agents
 Leavening agent is a term used to indicate a source of gas that
causes a dough or batter to rise or spring
 Gases must be retained in the product until the structure is set
(by the coagulation proteins & gelatinzation of starch) to hold its
shape
 Unleavened medium- to high-moisture baked products are dense
and heavy
 Water, yeast and chemicals are the three types of leavening
agents used in bakery products

40. Contd…
 Water, which when heated, forms steam and expands. However,
it does not contribute significantly to leavening
 Chemical leavening is a faster, more convenient and often
consistent method than yeast
 Hard wheat flour is usually leavened with yeast because of the
protein and gluten formation
 Soft wheat flour is usually leavened with chemical agents

41. Leavening
Gas
Source Characteristics Examples
Air
Mechanical mixing
process
N2 solubility in water is low
Forms nucleation sites during
mixing
Whipped egg &
creaming
incorporates air
H2O Water as an ingredient
High boiling point has a limited
effect
Puff pastry
NH3
Ammonium bicarbonate
Ammonium carbonate
Decomposes completely at 60°C
No residual salts
Used in products that are baked to
near dryness
Cookies and
crackers
CO2
Sodium bicarbonate
Potassium bicarbonate
Sodium carbonate
Yeast fermentation
Needs acids for appropriate
leavening activity
CO2 is production is faster
Products may be baked soon after
dough or batter making
CO2 is produced slowly during
fermentation
Most cakes and
cookies
Cake
doughnuts
Breads
Major Leavening Gases in Bakery Products

42. Contd…
 Baker’s yeast is Saccharomyces cerevisae (top fermenter)
 It produces CO2 and ethanol by fermentation of fermentable
sugars
 Conditions dough biochemically
 Forms flavour precursors (by-products of alcoholic fermentation)
 Rate of fermentation is controlled by temperature, nutrient
supply, water level, pH, sugar concentration, salt and level and
type of yeast
 Yeast is used in several forms: compressed, cream (liquid), dried
into pellets, and instant active powders
 Usually, 1% of yeast is used on flour weight basis
Yeast

43. Effect of
Temperature on
Yeast Activity

44. Characters
Fresh Compressed
Yeast
Fresh Cream Yeast Dry Active Yeast
Dry Instant Active
Yeast
Form Cake crumbled Liquid Granule Granule
Storage
temperature
2-7 °C 1-4 °C
Room
temperature
Room
temperature
Shelf life 3-4 weeks 10-14 days 2-12 months
More than 1
year
Moisture
Content
67-72 % 80-82 % 6-8 % 4-6 %
Gas power*
Straight dough
Lean dough
Sweet dough
2.2 – 2.3
2.4 – 2.6
1.0 – 1.1
--
--
--
1.4 – 1.5
1.2 – 1.3
0.8 – 0.9
1.6 – 1.8
1.8 – 2.0
0.8 – 0.9
Conversion
factor
1 1.5 – 1.8 0.4 – 0.5 0.33 – 0.40
Handling
requirements
Dispense in water
before mixing
Add with other
ingredients
Must hydrate at
40-43 °C for 10-15
min before use
Blend dry with
other dry
ingredients
Types of Baker’s Yeast
* g glucose fermented / g yeast solid / hr

45.  Chemical leavening systems produce CO2 by one of two means:
 Chemical decomposition through the application of heat
 A reaction of an acid with a base
 NaHCO3 and (NH4)CO3 are two major gas carriers
 For low-sodium applications, potassium bicarbonate may be used
 Sodium bicarbonate can be heat decomposed into CO2, water and
washing soda
 Excess washing soda will react with shortening, giving dark colour
and an undesirable taste to the cake
 Various acids are combined with NaHCO3 to accelerate the
reaction for gas production at a low temperature
Chemical Leavening Agents
Contd…

46. Contd…
 Heat decomposition of baker’s ammonia
 Heat decomposition of baker’s soda
(NH4)2CO3 2 NH3 + 2CO2 + H2O

2 NaHCO3 CO2 + H2O + Na2CO3

 Reaction of baking soda and baking acids
NaHCO3 + C4H5O6K CO2 + H2O + C4H5O6NaK
Cream of tartar
8 NaHCO3 + 3 CaH4(PO4)2 . H2O 8 CO2 + 11 H2O + 3 Ca(PO4)2 + 4 Na2HPO4
MCP

48. Wheat Proteins
Classification of Proteins (Osborne)
• Albumins: Soluble in water
• Globulins: Soluble in dilute salt solutions
• Prolamins: Soluble in 70% ethyl alcohol
• Glutelins: Soluble in dilute acids or bases
 Albumins & globulins are concentrated in aleurone cells, bran & germ
 Prolamines & glutelins are storage proteins in cereals

51. Wheat Flour & Micronutrients

57. Total Food Grains Production in India (2007-09)

59. Fig. 1.4. Cross section (A) and longitudinal section (B)
through the pericarp and adjacent tissues of a wheat
kernel. Epidermis (Ep), hypodermis (Hp), cross cell (CC),
tube cell (TC), seed coat (SC), nucellar epidermis (NE),
aleurone layer (Al), and starchy endosperm (E).
(Reprinted from MacMasters et al 1971)

60. Fig. 1.17. Longitudinal section of a rice kernel. From
top: awn (A), lemma (L), palea (P), pericarp (Pe), seed
coat (SC), nucellus (N), aleurone (Al), bran (B),
subaleurone (Su), starchy endosperm (SE), and
endosperm (E). From bottom: lower glume (LG), upper
glume (UG), rachilla (Rac), radicle (Rad), plumule (Pl),
epiblast (Ep), scutellum (Sc), and germ (G). (Courtesy
L. Lamberts and L. Van den Ende; adapted from
Juliano 1984)

61. %Proteininwheat
Particle size index

64. Item-wise Share of Expenditure to Total Food Expenditure
Source: Economic Survey of India (2011-12)

65. Total Food Grains Production in India

67. Grain Protein Carbohydrate Fat
Crude
fibre
Minerals Ca (mg) P (mg)
Rice 6.8 78.2 0.5 0.2 0.6 10 160
Wheat 11.8 71.2 1.5 1.2 1.5 41 306
Maize
Sorghum
Rye
Oats
Wheat
Barley
Pearl millet
Proximate Composition of Selected Food Grains