Characterization of a Low Glycemic Index Potato Cultivar Kai Lin Ek Jennie Brand-Miller, Shujun Wang Glycemic Index Foundation Agrico Holland Mitolo Group (Australia) Les Copeland University of Sydney, Australia Faculty of Agriculture and Environment Research Symposium 15 July 2014
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Characterization of a Low Glycemic Index Potato Cultivar Kai Lin Ek Jennie Brand-Miller, Shujun Wang Glycemic Index Foundation Agrico Holland Mitolo Group.
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Characterization of a Low Glycemic
Index Potato Cultivar
Kai Lin Ek
Jennie Brand-Miller, Shujun Wang
Glycemic Index Foundation
Agrico Holland
Mitolo Group (Australia)
Les Copeland
University of Sydney, Australia
Faculty of Agriculture and Environment Research Symposium 15 July 2014
Grand challenges
Increase food supply
- 70% more food by 2050
Foods that deliver health benefits
- about one third of disease burden in Australians is related to poor diet
- over 30% of adults are obese, 25% have diabetes or pre-diabetes
Managing disease risks through diet
• Preventative• Small effects on many targets
• Changing the types of foods consumers eat will be difficult • Need to produce acceptable foods with health-promoting ingredients- carbohydrates with better glycemic control, prebiotic effects - oils to reduce saturated and trans fats, improved omega oils- increased bioavailability of micronutrients- reduced allergens
• Moderate glucose release• Increase satiety• Promote healthy gut microbiota
Dietary carbohydrates
• Source of energy, prebiotics, fibre for monogastric digestion
• Starch - 50-70% of dietary energy- source of essential pre-formed glucose
• The type of starch we eat has health implications
• Selected for firm cooking quality, size, agronomy
• Noticed by chef/potato grower with knowledge of nutrition (Graham Liney)
• Carisma was not differentiated from high GI cultivars by
- dry matter, total starch, reducing sugar and fibre content of the potato
Why is Carisma low GI?
Differences in potato tissue?
10
Carisma
Russet Burbank
Thickness of cell walls?
Why is Carisma low GI?
Differences in potato starch?
•Good correlation between GI value and in vitro starch hydrolysis•Carisma starch has higher melting temperature than the other starches
•Carisma was not differentiated by- starch granule size distribution- amylose content of starch- relative crystallinity of starch- phosphate content of starch- amylopectin chain length distribution
•Differences likely to be at level of starch fine structure
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CA
NI
DE
RB
VR
BJ
MF
-9
-8.5
-8
-7.5
-7
-6.5
-6
-5.5
-5
-4.5
-4
50 60 70 80 90
End
oth
erm
ic h
eat
flow
(W
/g)
Temperature ( C)⁰
Carisma
Starch is made up of two glucose polymers
Amylose •20-35% of most starcheslow degree of branching low solubility in water
Amylopectin65-80% of most starcheshighly-branched with complex architecturesemi-crystallinesoluble in water
• Functional properties of starch are determined by the structure of amylose and amylopectin, and how these molecules are arranged inside granules
• Starches vary greatly in amylose content, length of amylopectin branches, spacing between clusters, stability of clusters
Organization of AM and AP in starch granules
• Starch granules have concentric growth rings made up of amylose and amylopectin arranged into amorphous and crystalline lamellae
- crystalline lamellae contain organized clusters of amylopectin chains in double helices
- amorphous lamellae contain inter-cluster amylopectin chains and branch points, and interspersed amylose
Kozlov, Krivandin et al. 2007
Digestibility of starch
• Digestibility of native granules is low• Digestibility of cooked starch is high ... 5-20 x faster than raw starch• Digestibility decreases on cooling• Affected by source and type of starch, amylose content, extent of
gelatinization and retrogradation due to hydrothermal processing, lipids, ...
CoolingHeating
Goesaert et al. 2005
Gelatinization Retrogradation
Digestibility
Conclusions
• Carisma potatoes are low GI
• Carisma potatoes were not differentiated from high GI potatoes by simple analyses
• Higher temperatures are required to melt crystallites in Carisma starch compared to other potato starches
- Carisma starch does not gelatinize to the same extent as starch in other potatoes that are cooked similarly
• Fine structural differences in the starch are likely to be sources of variation in digestibility