Addressing consumer needs: potential
for developing wheat products with lower
glycemic response
Dr. Nancy Ames & Dr. Sijo Joseph
Agriculture and Agri-Food Canada
Richardson Centre for Functional Foods and Nutraceuticals
Winnipeg, MB
November 24, 2016
How can we develop wheat
products with lower glycemic
response?
Consumers:
Breeding:
• Awareness
of consumer needsBreeding
- E.g. results from recent Manitoba
Processing
Consumer
MonitorMethods
(MCM)
show:
• Higher
fibre, surveys
including
resistant starch
- • Toast/bread
was one of the foods most often consumed for breakfast by almost
Composition
protein
70%• of Higher
respondents
• Milling
– particle
size
- 77%• of Altered
respondents
indicated
that increasing fibre is a main reason for choosing to
starch composition
Processing
wholegrains
• purchase
Sourdough
fermentation
• (higher amylose; slowly
• Collaboration
with food industry partners E.g. Warburtons
• Freezing
digestible
• Interactions
with healthstarch)
professionals
Consumers
• Bread Structure
and clinical researchers
• Starch
bioaccessibility
• Provide
consumers
with substantiated benefits (health claims)
- Only 11% of respondents considered health claims to be a trustworthy source of info
when purchasing wholegrain products (MCM); shows more consumer education is
needed surrounding health claims
Glycemic Response and Diabetes
• Glycemic Response: The elevation of blood glucose concentrations
after consumption of a food and/or meal (ie. post-prandial)
• Glycemic Index (GI): A scale that ranks foods based on how much
they raise blood glucose compared to glucose or white bread
• Type 2 Diabetes: The body no longer uses insulin properly and is
unable to control blood sugar, leading to high levels of sugar
(glucose) in the blood
• One in three Canadians are
already living with diabetes or
prediabetes, including an
estimated 1.5 million with
undiagnosed diabetes
(Canadian Diabetes
Association, 2016)
Consumer Perspective
• Wheat based food products have
varying ranges of glycemic
indices.
• Choosing low glycemic foods is
especially important for those
who live with diabetes.
• Access to low-GI wheat products
is an important priority for
consumer health and presents
market opportunities for the
wheat industry.
Starch Digestibility and Glycemic Response
• Rate of starch digestibility is related to glycemic response
• Rapidly digestible starch (RDS): broken down in 20 minutes
• Slowly digested starch (SDS): broken down in 100 minutes
- Raw cereal starches naturally have high SDS
- Offers the possibility of moderated glucose delivery to the body
• Resistant starch (RS): not digested in the small intestine but
fermented in the large intestine
− Higher RS content for high amylose products
↑ Resistant starch
Formed during processing
(retrograded amylose)
Not hydrolysed in the small
intestine
(undergoes colonic
fermentation and forms
bioactive SCFA)
Lower
glucose
response
Opportunities for Wheat Breeders
• Breeding for lower glycemic wheats
- Slowly digestible starch
- Resistant starch (high amylose)
- Starch/ protein matrix
- Digestive enzyme inhibitors
E.g. AAFC potato breeders have
successfully developed a low GI potato using
traditional breeding methods and natural
genetic diversity
Starch Synthesis Enzymes
• Starch consists of amylose and amylopectin;
granule bound starch synthase I (GBSSI) is
responsible for amylose synthesis and soluble
starch synthase IIa (SSIIa) plays a major role in
amylopectin synthesis.
• Combining wild type and null A,B and D genes for
GBSSI and SSIIa allows production of genotypes
with a range of starch characteristics.
• A recent study (Regina et al, 2015) showed
suppression of both SBEIIa and SBEIIb resulted in
wheat with up to 85% amylose and >35% RS.
Two dimensional array of homozygous genotypes developed from GBSSI and
SSIIa wild-type mutant alleles. For each of the six genes, the homozygous wild type
allele is indicated by “+” and the homozygous mutant allele “-”. Homoeologous
genes are indicated as A1, B1 or D1
Nakamura et al, 2015.
Starch – Protein Matrix
• Gluten proteins may form matrices with starch, offering
protection from gelatinization and digestive enzymes (↓ starch
digestibility )
• Jenkins et al. (1987) and Hallstrom (2011) showed that natural
starch-protein interactions played an important role in reducing
rate of starch digestion and subsequent glycemic response
• Excessive kneading/mixing can lead to poor matrix structure
(disulfide bond breakage and glutenin particles dissociated into
smaller fragments) (↑ starch digestibility)
• Breeding for stronger protein may lower glycemic response
Processing Effects on Glycemic Response
• Shorter proof time resulted in decreased bread loaf volume
and significant reduction in glycemic response (Burton &
Lightowler, 2006)
• Steam bread process showed trend towards lower IAUC, GI
and max peak rise in glucose compared to baked bread,
regardless of ingredients (Lau et al., 2015)
• Sourdough bread showed significantly lower post-prandial
glucose and insulin responses compared to a standard white
wheat bread control (Lappi et al., 2010)
• Products with low porosity but with similar composition to
bread resulted in lower peak glucose and insulin response
(Eelderink et al., 2015)
Source: Eelderink et
al., Food Funct.,
2015, 6, p. 3236
Control Bread
Flat Bread
Pasta
Processing Effects on Glycemic Response
• Freezing and toasting of bread resulted in lower glycemic response
compared to fresh bread (Burton & Lightowler, 2007)
• Incorporation of intact kernels into bread elicited changes in insulin
response and GLP-1 hormones (Eelderink et al., 2016)
• Coarse particle size (2 mm) wheat
porridge resulted in significantly lower
blood glucose, insulin and other
metabolic outcomes compared to
smooth porridge (<0.2 mm). These
results were consistent with in vitro
starch digestibility rates. (Edwards et
al., 2015)
Source: Edwards et al., 2015. Am J Clin Nutr
102; 791-800.
Combining Breeding and Processing Strategies
• Using a wheat genotype with high amylose combined with a
baking process to promote amylose retrogradation
significantly increased RS (Hallstrom et al., 2011).
• Pumpernickel baking (slow temp increase and acid) alone
also resulted in increased SDS.
White
Wheat
Bread (Ref)
Whole
Grain
Wheat
Bread
Elevated
Amylose
Content
Elevated
Amylose
with Lactic
Acid
Resistant
Starch
(g/portion)
1.5
5
8
11
Glycemic
Index
100
89
82
70
Hallstrom et al., 2011
Food & Nutrition Research
55:7074
Slowly Digestible Starch
Opportunities for Breeding and Processing
• Chemical structure leading to SDS formation (E.g. –physical
modification of starch using heat-moisture treatments)
• Food factors that decrease digestion rate (E.g. – breed for natural αamylase and α-glucodisase inhibitors (phenolics); delay gastric
emptying with organic acids (sourdough fermentation)
• Processing techniques that form food matrix structures that decrease
enzyme accessibility (E.g. – dense protein matrix of pasta)
Rapid screening tools to
effectively evaluate the
physiological outcomes
How do we effectively
translate the research?
How do we evaluate whether
these products really exhibit
significant physiological effects
in human?
Research exists on how to
develop low glycemic wheat
products through
breeding/processing strategies
New Predictive Tools: In vitro models of digestion
• There are various factors relevant to glycemic response (E.g.
bioavailability of starch, processing, storage time, botanical
origin and genotype) which can be measured using in vitro
methods.
• We have developed a static in
vitro starch digestibility assay to
predict glucose response
• Dynamic stomach model (TIM 2TNO) to assess the glycemic
response to cereal food products
and formulations
New AAFC Collaborative Project: “Developing a platform comprising
novel experimental tools for improving the health benefits of wheat”
Summary - Breeding
• Opportunities exist for breeding wheat with increased amylose content
and slowly digested starch.
• New methodologies such as in vitro digestion assays and model
stomach systems offer new opportunities for rapid screening of bioactive
components and predicating physiological outcomes of wheat
consumption
Summary - Processing
• Several studies show how processing impacts food macrostructure,
particle size, degree of starch gelatinization and resistant starch content,
which in turn affects starch digestibility (amount of slowly digestible starch)
and glycemic response.
• Overall, processing steps that limit starch accessibility to enzymes are
beneficial (Fardet et al., 2006). E.g. a more compact structure, due to
reduced porosity and/or air cell diameter
• Milling can cause physical damage to starch granules :
- particle size is an important predictor of starch bioaccessibility
(fractured particles = increase access to enzymes)
THANK YOU
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