The relevance of
starch structure and
fermentable sugars The first studies combining:
* starch structure,
* gelatinisation temp
* diastatic power enzymes and
* fermentable sugars
@GlenFox9
Acknowledgements
• The University of Queensland
• QAAFI (Centre for Nutrition & Food Science)
• QDAF
• Prof Bob Gilbert
• Dr Ben Schulz (SCMB)
Past postgrads (barley starch)
• Peter Gous
• Shang Chu
• Sandra Balet (South Africa)
• Oi Wan Mo (Hons)
Current PhDs
• Wenwen Yu
• Sarah Osama (proteomics)
• Rex Quek (Hons)
Outline
Starch properties
Gelatinisation
Starch hydrolysis and fermentable sugars
Starch protein interaction
Starch (substrate) in grains
Starch = energy
Total starch (50-80% db) depending upon cereal type
Starch = Amylose:amylopectin; ratio approx. 25:75
Amylopectin most abundant component in grains (approx 30 to 40%, compared to 8 to 15% protein)
Starch = energy
Total starch (50-80% db) depending upon cereal type
Amylose (AM):amylopectin (AP); ratio approx. 25:75
Amylopectin most abundant component in grains (approx 30 to 40%, compared to 8 to 15% protein)
Granules: size, shape, ratios, AP content
Large granules have more AM
Impacts on gelatinisation temperatures ‒ higher GT - lower AM content and shorter AM chains
1. Know your substrate +
2. Know your enzymes
The mechanics of starch
hydrolysis during mashing?
Biochem 101: Substrate + Enzyme = Products
Virtually no research
A lot of research
Brewing 101: Starch + DP Enzymes = Fermentable sugars
Amylose LD Maltose
Amylopectin BA Maltotriose
AA Glucose
GA
Simple! Everything is under control, right
Raw materials
Malt (barley, wheat, sorghum)
Adjuncts (wheat, barley, rice, corn, ……) Liquid adjunct (sucrose)
All the solid material have variable starch structure
Starch in brewing
Range of starch in different cereals
Normal, high amylose, high amylopectin (waxy)
Major starch synthesis proteins (genes)
X
X
Ratios SS:BE:DBE
More BE to SS then
shorter chains and
increase in gel temp
Hierarchical levels of starch structure in cereal grain
Stationary phase (the columns)
Rubsam, H., M. Krottenthaler, M. Gastl and T. Becker (2012). "An overview of separation methods in starch analysis: The importance of size exclusion
chromatography and field flow fractionation." Starch-Starke 64(9): 683-695.
Size exclusion
chromatography
The separation of molecules a
Fully dissolve the starch in a solvent system which gives molecular dispersion
without degradation - DMSO/LiBr 80˚C
Measuring starch structure
Measuring starch
structure
Chain length – No
of glucose units
Size of the AP and
AM polymers
Environmental impacts on starch structure
-2.00E-01
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
1 10 100 1000 10000 100000
w(l
og
X)
DP X
H Fitzroy Low N
H Fitzroy High N
H Grout Low N
H Grout High N
Y Fitzroy Low N
Y Fitzroy High N
Y Grout Low N
Y Grout High N
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
1 10 100 1000 10000 100000
w(l
og
X)
DP X
Fitzroy Low N
Fitzroy High N
Grout Low N
Grout High N
Variation in amylose chain length (310 barleys and malts)
XAM – number of glucose units
0 1000 2000 3000 4000 5000 6000
A10
A7
A27
A3
A21
A28
A12
A20
A11
A24
B19
B14
A4
A25
B18
B13
B17
A22
B9
B15
B16
B6
B7
B5
B25
B29
B27
B31
B35
B24
B30
B33
S
a
m
p
l
e
s
Range in total starch – 47% to 64%
Range in total amylose – 22% to 32%
(25% published value)
Eight fold difference in average chain length
Over 8oC difference in gelatinisation temp
30% amylose
30% amylose
60% starch
60% starch
Starch and gelatinisation temperature in mashing
Factors influence gelatinisation temperature ‒ AP content (AM content)
‒ AP:AM
‒ AP and AM CLD
‒ Proteins
‒ Granule architecture| crystalline:amphorus
‒ Processing (malting and milling)
More AM increase GT
Shorter AM chains increases GT
Lower protein (higher KI) increases GT
14
Starch
Gelatinization
Fermentable sugars
Leached out starch chains
Starch structural effects on gelatinisation
Substrate + enzyme/s
=
products
Sweet (wort) spot
Gel temp
Enzyme activity (and life)
Starch to be solubilized prior to full enzyme activity
Longer to gel then less Enzyme, impact on FS profile
DP enzymes
Gelatinisation temperatures of different malts (low to high protein)
59.5a
64.5 fg
63.2 d
63.9e
61.5b
61.6b
62.6c
64.1ef
64.8 g
64.9 g
DSC curves
Changes to structure during mashing
unmalted (Black),
Malted (Red),
BSG (Blue) and
Wort (yellow)
• Coarse grist
• 1:4 G:L
• 65oC mash 60 min, ramp to
75 for 10 min
• Low protein (8.5% - top)
• High protein (12.0% - left)
(non-fermentable) Dextrins in wort
• Variation in residual
AP linkages and AM
chains
• Top - molecular size
• Bottom - oP
Brewers spent grains
• Coarse grist
• 1:4 G:L
• 65oC mash 60 min, ramp to
75 for 10 min
• Low protein (8.5% - left)
• High protein 12.0% - right)
What happens when we add an adjunct?
Brewing 101: Starch + DP Enzymes = Fermentable sugars
Amylose LD Maltose
Amylopectin BA Maltotriose
AA Glucose
GA
Brewing 101: Malt +adjunct + DP Enzymes = FS
Amylose LD Maltose
Amylopectin BA Maltotriose
AA Glucose
GA
Starch
Adjunct
LD
+ BA = FS
AA
GA
What happens when we add an adjunct?
Adjunct G:L ratio Gravity
(oPlato)
Maltose
(mg/kg)
Liquid 1:3 15.4 9.1
Liquid 1:4 12.6 7.9
Solid 1:3 17.7 8.3
Solid 1:4 13.3 6.9
Starch protein interactions
More than just starch
Protein matrix
Protein negatively correlated to starch
Large grain, more starch, less protein
Protein specs (9% to 12%)
Protein content and composition of fermentable sugars
Protein Glucose Maltose Maltotriose Total
Sugar
Total protein -0.3 -0.6 -0.73 -0.64
Malt protein -0.45 -0.79 -0.83 -0.79
Water- insoluble -0.33 -0.7 -0.77 -0.71
GLT0 -0.041 -0.353 -0.651 -0.401
GLT5 -0.445 -0.468 -0.697 -0.562
Hordein B -0.082 -0.144 -0.164 -0.147
Hordein D 0.026 0.066 -0.395 -0.071
Hordein C -0.558 -0.852 -0.754 -0.824
Hordein A -0.244 -0.572 -0.672 -0.575
• Coarse grist (12 different malts)
• 1:4 G:L
• 65oC mash 60 min, ramp to 75oC, hold for 10 min
• Proteomics on malt
• FS – sweet wort
Significantly negative correlations
Protein content and composition and fermentable sugars
Summary starch structure and quality
• Variation in starch structure (degree of branching and
length of AM and AP chains) from all cereals
• Shorter starch chains increase gelatinization temp
• Longer chains lower GT and increases maltose content
• Survival of DP enzymes temperature dependent
• Protein content negatively related to get temp.
• Knowing gel temp of malt may be helpful
• Can’t pre-program starch structure in barley (cereal) grain
• Currently investigating barley variety effects and flavour
• Sorghum for gluten-free beer
• Next step – fermentation tests (various yeast)
• What does the brewer want to know? GT; FS profile;?
Questions