In vitro starch digestibility and predicted glycemic
response of extruded pulse products
Sijo Thandapilly Ph.D, Visiting Fellow
Nancy Ames, Ph.D, Research Scientist
Agriculture & Agri-Food Canada
Winnipeg, Manitoba
[email protected]
Pulses and glycemic control
• Pulses are recognized for their superior nutritional profiles
• low in fat
• high in protein
• high in dietary fibre
• rich source of micronutrients and phytochemicals
• It has been well established that whole cooked or canned
pulses have a low glycemic index (GI) and favourable
postprandial glycemic response
• The effects of a variety of whole pulses on short term glycemic
control have been assessed in multiple human studies
Pulses and glycemic control- proposed mechanisms
Fermentation
products
(SCFA)
Pulses and glycemic response- research gaps
• Optimal dose and combination of pulse flours and fractions
that should be incorporated into commercially relevant
products
• Effect of processing and genotype variations on glycemic
response of pulses
• The precise physiological mechanisms by which pulses exert
their health effects
The science driving pulse food innovation
Farming/breeding
Processing
Consumers
In vitro functional analysis –A breeder’s perspective
• The current pulse breeding programs in
western Canada focus on genetic
improvement for a few major traits: yield,
maturity, disease resistance and seed
quality
• Breeding varieties with enhanced health
benefits will help drive the food
innovation and marketability of pulses
• Breeders are interested in improving
nutritional values with human health
benefits however, they are often limited
by the lack of elite screening tools and
rapid methods for effective selection
In vitro functional analysis –A processor’s perspective
• Different processing techniques may alter the digestibility and
physico-chemical properties of pulse components
• Identifying or altering processing techniques will have a
significant impact on its biological effects
• A rapid predicted glucose response assay will aid the processors
to optimize the processing conditions to maximize the health
effects
In vitro functional analysis –A consumer perspective
• Studies confirm that Canadian consumers are looking for foods
with health benefits
• Health claims could be effectively used and help Canadians
achieve their wellness and healthy living goals
• Well designed human trials are needed to substantiate health
effects
• However, human feeding studies are intensive and tedious and
not always feasible for product development and screening a
large number of sample types
According to Health Canada’s draft guidance
document
Specific study objectives:
• To determine the optimal dose and combination of pulse
flours and fractions that should be incorporated into
commercially relevant products for glycemic and satiety
effects
• To determine the effect of pulse processing, such as extrusion,
on predicted glycemic response
• To identify the potential pulse fractions and formulations that
can be used for the upcoming human studies
In vitro glycemic response assayMethod Development
250mg of sample is
weighed into the
bottom of a test tube.
Include mini stir bar.
At 20min, remove 100uL aliquot
and transfer into tube with 5mL
ethanol. Repeat at times 40, 60,
120, 240, 360 min.
Add 2.5mL pepsin guar solution is added
to tube. Incubate at
37°C for 30min.
Vortex and centrifuge.
Transfer 100uL into a test
tube and add 3mL GOPOD.
Incubate at 50°C for 20min.
Add 2.5mL sodium acetate +
1.25mL pancreatin amyloglucosidase - invertase
solution. Incubate at 37°C.
Read absorbances to
determine glucose
content.
Test products
• Pulse flours (pea, lentil, bean, chickpea) incorporated into extruded
snack products at a rate of 40% (replacing corn ingredients)
• Pea fractions added to extruded breakfast cereals both as individual
ingredients (fibre vs. protein vs. starch) and in different
combinations (e.g. fibre + protein; protein + starch; starch + fibre)
Ingredient
Corn
Whole Yellow Pea Flour 1
Split Yellow Pea Flour #1
Split Yellow Pea Flour #2
Split Yellow Pea Flour #3
Split Green Pea Flour
Green Lentil Flour #1
Green Lentil Flour #2
Red Lentil Flour
Chickpea Flour
Navy Bean Flour
Pinto Bean Flour
Sample Type
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
extruded snack
Ingredient
80% oat
65% oat, 18% pea hull
39% oat, 50% pea starch
47% oat, 40% pea protein
24% oat, 18% pea hull, 50% pea starch
32% oat, 18% pea hull, 40% pea protein
6% oat, 50% pea starch, 40% pea protein
16% pea hull, 45% pea starch, 36% pea protein
Sample Type
breakfast cereal
breakfast cereal
breakfast cereal
breakfast cereal
breakfast cereal
breakfast cereal
breakfast cereal
breakfast cereal
Results
E30814-1 Corn
E30814-2 Whole Yellow Pea Flour 1
E30814-3 Split Yellow Pea Flour #1
E30814-4 Split Yellow Pea Flour #2
E30814-5 Split Yellow Pea Flour #3
E30814-6 Split Green Pea Flour
E30814-7 Green Lentil Flour #1
E30814-8 Green Lentil Flour #2
E30814-9 Red Lentil Flour
E30814-10 Chickpea Flour
E30814-11 Navy Bean Flour
E30814-12 Pinto Bean Flour
E31114-9 80% oat
E31114-10 65% oat, 18% pea hull
E31114-11 39% oat, 50% pea starch
E31114-12 47% oat, 40% pea protein
E31114-13 24% oat, 18% pea hull, 50% pea starch
E31114-14 32% oat, 18% pea hull, 40% pea protein
E31114-15 6% oat, 50% pea starch, 40% pea protein
E31114-16 16% pea hull, 45% pea starch, 36% pea protein
Available Carbohydrate (%, db) Protein (%, db)
Average
Average
94.66
5.15
78.02
12.14
83.62
11.49
80.28
12.02
82.65
12.57
81.61
11.44
77.53
13.21
79.12
12.57
78.75
14.69
77.15
12.67
75.87
12.69
77.29
12.61
79.02
64.50
80.80
53.50
66.95
39.78
57.85
46.78
9.58
8.63
8.22
24.29
7.53
23.20
22.60
20.75
Results
Extruded Snacks - Glucose Release Over Time
90.00
80.00
Corn
Whole Yellow Pea Flour 1
g glucose / 100 g sample, as is
70.00
Split Yellow Pea Flour #1
60.00
Split Yellow Pea Flour #2
Split Yellow Pea Flour #3
50.00
Split Green Pea Flour
Green Lentil Flour #1
40.00
Green Lentil Flour #2
30.00
Red Lentil Flour
Chickpea Flour
20.00
Navy Bean Flour
10.00
Pinto Bean Flour
0.00
0
50
100
150
200
Time, min
250
300
350
400
Results
Results
Breakfast Cereals - Glucose Release Over Time
80.00
80% oat
70.00
65% oat, 18% pea hull
g glucose / 100 g sample as is
60.00
39% oat, 50% pea starch
50.00
47% oat, 40% pea protein
40.00
24% oat, 18% pea hull, 50% pea starch
32% oat, 18% pea hull, 40% pea protein
30.00
6% oat, 50% pea starch, 40% pea
protein
20.00
16% pea hull, 45% pea starch, 36% pea
protein
10.00
0.00
0
30
60
90
120
150
180
210
Time, min
240
270
300
330
360
Summary
• Incorporation of pulse flours into extruded corn snacks resulted in
lower in vitro glucose release over 360 min compared to an all-corn
extruded snack
• Combinations of fractions (fibre + protein and fibre + protein +
starch) incorporated into extruded oat cereal had lower in vitro
glucose release over 360 min compared to all-oat cereal
• The current study outcomes will aid in selecting the pulse products
for the upcoming human clinical trial based on their in vitro
response
• It will provide breeders and processors with knowledge of the
factors affecting variation in glycemic response, and result in a new
method that could be implemented to screen pulse germplasm and
food products
Investigators
• Dr. Nancy Ames, AAFC, Winnipeg
• Dr. Rebecca Mollard, RCFFN, Winnipeg
• Dr. Danielle Bouchard*, University of Manitoba
• Dr. Julianne Curran, Pulse Canada
• Dr. Peter Jones*, RCFFN, Winnipeg
* Principal Investigators
Technical Support
Camille Rhymer, Tracy Exley and
Joanne Storsley, Sijo Thandapilly AAFC Winnipeg
Funding
Saskatchewan Pulse Growers
Alberta Pulse Growers