1
Q
Wet milling definition
A
Maceration process in which chemical and physical changes occur in the basic components constituents of the endosperm, in order to bring about the complete separation of the endosperm cell wall contents with the release of starch granules from the protein network
2
Q
Main product of wet milling
A
Starch, secondary are the co-products
3
Q
Wet milling maize process goal - Anatomical separations
A
Germ isolation
Pericarp (fiber) isolation
4
Q
Wet Milling maize process goal - Component separations
A
Starch isolation
Protein isolation
5
Q
Four co-product of wet maize milling and their uses
A
Starch, Fiber (bran), Protein, oil (germ)
-All can be food or feed
6
Q
Main source of starch in the US is from
A
Maize wet milling
7
Q
Wet Milling Maize steps
A
Steep
Germ separations then refining
bran separation
starch and “gluten” protein purifications
8
Q
Why steep maize in wet milling
A
Plasticization of the bran and germ
germ swells and is easily removed
Facilitates protein-starch separation
9
Q
Why can’t we use heat damaged corn in wet milling?
A
The proteins don’t swell and the starch doesn’t separate well.
10
Q
Unique aspects of wet milling maize
A
- Effluent recovery (only water leaves the system as steam)
- Counter-flow movement of the process water
11
Q
Steeping of maize
A
- multiple tanks
- excess water running counter-current (concentrates the solubles for removal for feed or fermentation)
- Sulfur Dioxide modifies the protein bonds and allows starch to be released (this is used up in reactions and none remains at the end.)
- Lactobacillius fermentation (produces lactic acid early which prevents off flavors and odors)
12
Q
Germ recovery maize wet milling
A
Germ released through gentle grinding
Hydroclones separate the germ
13
Q
Fiber, protein, and starch separation (maize wet milling)
A
Fine grinding in attrition mill AFTER the germ has been removed
14
Q
Fiber recovery maize wet milling
A
Overs: to dewatering press then to feed dryer
Thrus; starch and protein
15
Q
Starch and protein recovery maize wet milling
A
Separated with hydroclones
Then starch is purified by washing and hydrocloning repeatedly, then dried
The protein is concentrated and dried
16
Q
Native / Pearl Starch (maize)
A
Virtually pure starch (less than 0.3% protein)
17
Q
Wheat differences from Maize concepts
Wet Milling
A
- Primary product is vital wheat gluten
- secondary product is starch
- starting material is flour
18
Q
Wheat differences from Maize process
Wet Milling
A
- Not bottled or counter flow
- No concentration of the steep (bc of water soluble arbinoxylins)
- No sulfur dioxide
19
Q
Why do we want higher quality flours for starting material in wet milling wheat
A
Low grade flours have more damaged starch
- absorb more water
- interferes with gluten aglomeration
- less prime starch per weight
20
Q
Wheat wet milling steps
A
- Washing
- Screen
- Starch isolation
- Starch drying
- starch grading
21
Q
Washing wheat flour
A
gluten proteins self associate and the starch separates
-water solubles created
22
Q
Starting material wet milling flour
A
High quality flour, turned into a batter
23
Q
Screening of the wheat wash water
A
Through: starch, solubles, water
Retained: crude gluten
24
Q
Starch isolation -how, why
wheat wet milling
A
Centrifuges/hydroclones, or sieves
- remove remaining gluten
- produce varying purity of starch
25
Starch drying danger wheat wet milling
Bimodal starch granules.
| The small ones can be explosive if mishandled
26
Prime starch
Mostly pure, long lenticular granules
| -Most valuable
27
B-Starch (tailings)
Mostly small and/or damaged granules
-cell walls, unextractable arabinoxylans.
(challenged to find a use for this. Feed and fermentation)
28
Vital Gluten
- Retains most of its functional properties - it will form a dough
- Makes wheat starch recovery economically possible
29
___ is a critical step for vitality retention of vital gluten
Dry because heat damage reduces functionality
30
How to dry vital wheat gluten
Flash dry with evaporation
| freeze drying is great but is slow and expensive.
31
Wheat germ oil storage
Highly unsaturated so goes rancid quickly
32
Wheat germ oil vitamin E
High in Vitamin E
| -used as a nutritional supplement
33
Saturated fatty acid stability
More stable against oxygen induced rancidity
34
Higher unsaturation the ___ the melting point
lower the melting point
35
Rice bran oil is
by-product of solvent extracted bran production
36
Maize germ oil -characteristics
Light in color, bland flavor - used for cooking and frying
| -major cereal source
37
Expeller
Using mechanical pressure, high temps, and a solvent to extract oil from maize germ.
38
Over heating maize oil may result in
Off flavor, off color
39
Expeller yields
Crude oil out
| -Foots
40
Expeller foots
Residue
- foots solvent extracted and sent to feed
- Hexane is stripped to recover residual oil
41
Solvent only extraction of maize germ oil
- Large volumes of hexane
- Sealed system, could be recovered
- High quality oil
- BUT possibility of explosion
42
Maize oil processing after expeller
- Filter press to remove particulates
- Alkali (base) treatment to convert free fatty acids and polar lipids into water soluble salts (prevents saponification)
43
Maize oil treatments after Alkali treatment
Bleaching
-pigment absorbed by activated clay
Winterization
-remove waxes that would cause cloudiness in the fridge
44
Deodorizing maize oil
```
Vacuum distillation (high temp, no oxygen)
Volatile compounds removed (flavors, aromas, some color compounds)
```
45
Maize oil packaging importance
Must be UV- blocking material
- UV initiates fatty acid break down and oxidation
- UV creates free radical scavengers that keep the rancidity reaction going.
46
Why study starch
- Most abundant food carbohydrate polymer
- Properties affect all cereal foods
- Functional component in many non-cereal foods
47
Ancient uses of starch
-Medicinal applications, textiles, cosmetics by ancient romans and Egypytians.
48
Complex carbohydated (CHO) definition
Large, polymeric polysaccharide (many gluclose molecules)
| -exist in nature as granules (water insoluable, highly organized structure) main source of energy for plants
49
Which crops have compound starch granules
rice and oats (makes them very tiny)
50
Unique characteristics of starch CHOs (digestibility)
-Digestible by enzymes in monogastic (human) gut. Other polymers its not until the end of the gut
51
Starch granule the branched polymers are ___ and the linear is ____
- crystalline
| - amorphous
52
Unique characteristics of starch
- inexpensive biopolymer
| - Extreme uniformity in granule size (difficult to duplicate non-biologically)
53
Non-Food uses for starch
Textiles
| Pharmaceuticals, paper, and misc.
54
Starch Food Uses (types)
```
-Adhesion
Binding -pellets
Clouding - drinks
Gel formation - pudding
glazing
-Dusting- candies
Flow- keeps lumps from forming
Thickening - salad dressings
```
55
Starch sources- world wide
```
Cereals (maize leader x10)
Roots and tubers
fruits
stems
beans
```
56
Principal component of starch
```
Glucose (same thing as dextrose)
-Alpha-D
-As polymers
Minor components
-lipids, minerals (phosphorus & nitrogen)
```
57
Lipid component in starches
- From what
- effect in the starch
- minor
| - inhibits water uptake and swelling --> cooking effects
58
Mineral Phosphorus in starches
- From what
- linkage
- minor
- NOT contently linked to starch (only potatoes do naturally)
- from phospholipids (cereals only)
59
Mineral Nitrogen in starches
- From what
- effect in the starch
- minor
- partly from lipids, partly from protein
- may make up the coating that interferes with the protein matrix around granules in soft wheat
60
Glucose
| -structure
Simple 6 carbon monosaccharide that are very specifically oriented
-open chain (linear rope) and ring form (in solution)
D-Glucose= right handed rotation in water /polarized
61
Beta Glucose structure
Hydroxyl (OH) group is cis (same side) as C6 group
62
Open chain glucose
- name
- function
Aldehyde
- can reduce Cu2+ in assays (turns potato blue)
- BC it is a reducing sugar
63
Ring form glucose
- name
- function
Heiacetal
- can't reduce Cu2+
- not a reducing sugar
- functions as a fiber when digested
64
Alpha form of glucose
OH (hydroxyl) is opposite
| -C1 linked to C4 using an alpha bond
65
As we break down polymers we increase the number of ____
reducing groups, which increases the reducing capacity
66
Amylose
- what/location
- structure
- minor polymer of starch
| - linear (only tiny branches) but flexible
67
Amylose behaviors
- linear structure
- forms a double helix in water
- strong interactions with self and others
- results in strong gels and films
68
Four classifications of protein
Albumins - water soluable
Globulins- soluable in salt
Prolamins- soluable in 70% ethyl alcohol (large storage)
Glutelins- soluable in dilute acids or base (large storage)
69
What proteins does whole wheat flour have that refined doesn't
Albumins and Globulins which are found in the Alueron, germ, and pericarps. Are high in limiting amino acids
70
wheat protein content controlled by
Genetics and environment will affect end-use
71
Good conditions late in seed development of wheat affects protein starch by
- more starch synthesis
- Higher yields
- Lower protein
72
Drought or frost damage to wheat plant affects protein and starch by
-Higher protein content
73
Good moisture and climate increases yield and ____ protein
decreases
74
wheat with a low percent protein content will have large amounts of ___ and ___
albumins and globulins
75
As the percent protein in wheat increases, the total amount of ___ and ___ increases, but the relative proportion _____ because___
albumins and globulins... decreases because you are getting more storage proteins.
76
In wet millingwheat ___ and ___ come off as soluables
albumins and globulins
77
In wet milling wheat ___ and ___ are insoluables
prolamines and glutelins
78
Glutelins are further fractionated into
Glutenins
79
Prolamines are further fractionated into
Gliadins
80
Gliadins (prolamines) and Glutenins (glutelins)
- FOrm what
- amounts present relative to eachother
- controlled by
- Gluten forming proteins (form strong doughs that will retain gas)
- present in equal amounts
- Under genetic control
81
Gliadins
- gives gluten which characteristics
- present in varieties
- Allows gluten to be stretchy and extensible
- Not all wheat cultivars have these proteins, it is under genetic control. Bred for selectively
- Single chains with no inter-chain linking
- puts a kink in the chain influencing functionality
82
Glutenins
| -gives gluten which characteristics
- Rubbery, snap back, wants to stay together
| - Become very large cross-linked molecules
83
Glutenin polymerization
- starts when
- gives what to doughs
- starts at flowering in early seed development
- results in huge polymers
- Gives dough strength and elasticity
84
Cereal with the highest percent protein
oats
- good amino acid balance
- mostly globulins
85
Cereal with the lowest percent protein
Rice
- relatively good amino acid balance
- difficult to solubilize
- protein is in protein bodies
86
Proteases
| -function
break peptide bonds of amino acids
87
Endoproteases
| -work where
Work on the interior structure of proteins to produce chunks of amino acids
88
Exo-proteases
Work on the ends of proteins, won't change gluten elasticity
89
Rye proteins
| -kind and amounts
Double in albumins and globulins
| Has more prolamine than glutelin (wheat has equal amounts)
90
Proteases have a ___ variety of specificity and function
wide
91
Unique characteristics of gluten
35% glutamine
very hydrophobic
has a kink/bend which makes it very different in shape
very low charge density makes it dense
92
viscous
resistance to flow - thick
93
Elastic
will return to its size and shape instantaneously when stretched and released.
94
Glass transition
transition from vicious state to glassy state
| *most important physical property of amphorous polymers
95
Modulus definition
Resistance to deformation (stiffness)
| ie. stiff doesn't move much when you push on it
96
glass definition
rigid, fragile, brittle
97
rubbery definition
flexible. Higher molecular weight, higher the rubbery platue .
Stretch and snap back
98
Plasticizer definition
Small molecule added to soften a polymer. Water is the universal plasticizer in foods
Lower the Tg temp by reducing friction between molecules and make them more flowable
99
Glass transition temperatue
Midpoint of temp range between glassy and rubbery state
-varies with temperature (energy) an moisture - ie. larger molecules need more energy to get moving so have a higher Tg temp
100
Below Tg the state is
glass-like
| no segmental motion or interaction
101
Above Tg the state is
Leathery into rubbery
-chain motion increases
-inter-chain interaction increases
Modulus of elasticity- change of how it feels
102
Modulus of elsaticity
change of how it feels, the bite
103
Cross linked polyers and glass transition
They don't have a glass transition, they will go right into decomposition
104
Tg in dry milling tempering when
Toughening the bran
Mellowing endosperm
-cellulose undergoes glass transition as water diffused into the kernel
105
Wheat gluten glass transition occurs
At room temp with excess water
106
What happens at Tg
Polymers make dramatic changes in their modulous
107
Why we can't get dough from maize proteins
Dense protein bodies and very high Tg means water can't penetrate at room temp
108
Why is wheat dough so unique in its glass transition
it will occur at room temp with excess water
109
Cellulose linkage, crystalinity and digestability
Beta 1,4
partially crystalline
-non digestable by monogastrics -its fiber
110
Minor consitituents, low in __ high in___
low in percentage, high in importance likely to the plant
111
Hemicellulose
- structure
- includes
Vary widely in sugars and size
| include beta glucans, arabinoxylans
112
Lignin
| function
Cell wall strength
| -complex and diverse structure lacking a primary structure
113
Wheat hemicellulose exsist as __ and __
Water Extractable and water Unextractable in a 2:1 ratio
114
WE_AX
| -role in dough
Increase water absorption and viscosity
| stabilize gas in cells in the oven
115
WU_AX
| -role in dough
destabilize dough, forms physical barriers in gluten network. Interferes with starch extraction in wet milling (requires enzymes to break down)
116
Wheat hemicellulose arabinogalatan peptides
Involved in coating on soft wheat that prevent the protein matrix from bonding tightly with starch granules.
117
Barely hemicellulose beta-glucans characteristics
highly viscous, potentially gel-forming
118
Non-starch degrading enzymes
Wide variety in function and therefore enduse.
| break down betaglucans, cellulose, etc
119
Germ has the ____ sugar content
highest, for germination
120
Phytic acid
- made of
- function
Major form of phosphorus in cereals
| -Chelates cations such as Ca, Mg, Fe, Zn. Decrease absorption of these minerals so not good nutritionally
121
Most minerals are in the
Aluerone
122
Most vitamins are in the
aleurone or scutellum (especially b-vitamins)
123
Fatty Acid definition
Caryboxylic acids with long hydrocarbon chains
124
Highest lipid concentration is in the
germ
125
Lipid in cereals are predominately
nonpolar and unsaturated
126
Tocopherols function
antioxidants (vitamin E wheat) that slow rancidity by interrupting free radicals that feed the oxidation reactions
127
Wax definition lipids
High melting point fat
128
Rice lipids are mostly in the ___ which is unique
bran
129
Free fatty acids will go __ faster when seperated
rancid
130
LIpases
breakdown fatty acids, highest in oats and barely. Will cause more rapid rancidity
131
cellulose is easily removed in milling bc
it is primarily in the hull and bran
132
Barley has the highest ___ content of the cereals
sugar - important for malting and brewing
133
Oats have lipid in the ___ which is unique
endosperm, why it requires stabilization
Cereal Science
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