Unraveling Food Digestion -- Challenges and Opportunities...

Unraveling Food Digestion --

Challenges and Opportunities

for Food Scientists

R. Paul Singh

University of California, Davis

Freezing

Drying

Grilling

Thawing

Time-Temperature Integrators

Shelf life

Air-Impingement Systems

Physical Properties

Energy Accounting

Frying Modified Atmosphere Packaging

Water Use

Food Chain

Farm to Fork

Link between physical and material

properties of foods and nutrient

release from foods in the GI tract?

Role of Food Material Properties and Disintegration Kinetics in Gastric Digestion

USDA NRI 2008-12

Food Matrix and Nutrient

Bioavailability Nutrient Food Matrix state Bio-availability Reference

b-carotene Carrot Raw 19-34% Van het Hof et

al. (2000)

Carrot Carrot Juice 70% higher than raw Castenmiller et

al (1999)




al. (2000)


al (1999)

a- tocopherol Broccoli Different cooking

methods

480%-530% higher

than raw

Bernhardt &

Schlich (2005)




al. (2000)


al (1999)

a- tocopherol Broccoli Different cooking

methods

480%-530% higher

than raw

Bernhardt &

Schlich (2005)

Lutein Tomato Tomato paste 22%-380% greater

plasma response

than fresh tomato

Van het Hof et

al. (2000)

Almonds are one of the richest sources of

dietary vitamin E with benefits to reducing

risk of CHD and certain cancers.

Only about 45% of vitamin E was

bioaccessible from powdered almonds.

Samples obtained via

ileostomy after 3.5 hr of

digestion. Volunteers fed

2 mm cube raw almonds

Mandalari et al. (2008) J Ag Food Chem

Bioaccessibility

Proportion of a nutrient that

can be released from a

complex food matrix and

potentially available for

absorption in GI tract

Food Disintegration in the GI Tract

• Oral processing

• Gastric digestion

Digestion system

• The overall function

– extract nutrients into useable form

– absorb nutrients

– eliminate unneeded materials

• Food takes between 24-36 hours to pass through the gastrointestinal tract

Solid Food Disintegration

in the Stomach

-Stomach emptying

-Satiety, Obesity

-Nutrient release

-Food safety:

- Allergens

-Nanoparticles

digestion.mp4

Stomach

• Volume: 50ml to 4 liters of liquid – Chemical digestion by enzyme activity

– Mechanical digestion by the mixing in the stomach

Stomach

• Volume: 50ml to 4 liters of liquid – Chemical digestion by enzyme activity

– Mechanical digestion by the mixing in the stomach

• Gastric juice: Colorless fluid – 1.5 L secreted/day

– Hydrochloric acid • breaks the food apart and kills most of the

bacteria that you swallow

– Mucus (~1.5 g/L) • forms a gelatinous coating over the

mucosal surface.

– Pepsin (~ 1 g/L) • proteins broken down into smaller

polypeptide chains

– Salt, Gastric Lipase • fat digestion begins here

Antrum

Stomach_Movie.wmv

• Fundus: begins digestion

of proteins and mixes

together stomach

contents. Antrum

Stomach_Movie.wmv



together stomach

contents.

• Body: digests proteins

and blends materials in

stomach and reduced to

a paste

Antrum

Stomach_Movie.wmv



together stomach

contents.




a paste

• Antrum: Breaks down

large food material into

small particles

Antrum

Stomach_Movie.wmv



together stomach

contents.




a paste

• Antrum: Breaks down

large food material into

small particles

• Pyloric sphincter: a specialized valve that selectively empties the small particles and retains the large

Antrum

Stomach_Movie.wmv

Dynamic MRI image series showing propagating antral contraction waves (small

arrows) displayed in time intervals of 10 s. (Schwizer and others 2006)

Antral contraction of stomach

Propulsion, grinding, and retropulsion of solids by peristaltic

contractions of distal stomach (Kelly 1980)

Retropulsive.mpg

• From an engineering perspective, the

human stomach is a receptacle, a grinder, a

mixer and a pump that controls the digestion

process.




process.

• Consider stomach to be a flexible wall

reactor, with peristaltic wall motility.




process.

• Food enters the stomach through the oesophagus

as a bolus

• Bolus disintegration ?

• Solid particulate disintegration ?

Develop a realistic computer-

aided model of the human

stomach and study flow

characteristics and solid

disintegration

3D MODEL-AVERAGE SIZED HUMAN

STOMACH

• Average dimensions*

– Greater curvature ≈ 31 cm long.

– 15 cm wide (at its widest point).

– Pylorus’ diameter is ≈ 1 cm.

– Stomach’s capacity is about 0.94 L.

25 Max curvature = 34 cm

Max width = 10 cm

Pylorus

diameter 1.2 cm

Volume = 0.9 L

* Keet, 1993; Schulze, 2006.

geometry-mesh.wmv

GASTRIC MOTILITY • The motility of the stomach wall can be characterized

by three types of muscle contractions.

– Slow and weak contractions that originate

and develop in the upper part of the

stomach.

– A series of regular-peristaltic contraction

waves (ACWs) that originate in the middle

of the stomach, and propagate towards

the pylorus.

– A tonic contraction of the entire gastric wall

that allows the stomach to accommodate

itself to varying volumes.

Fundus

Body

Antrum

Pyloric

canal

GASTRIC MOTILITY • Despite recent advances in imaging technologies, the motility

pattern of the gastric wall is still poorly characterized.

27

Fundus

Body

Antrum

Pyloric

canal

• The dynamics of ACWs is the only motor

activity experimentally characterized.

– By using MRI techniques, the motility of ACWs

was tracked during 20 minutes after the

ingestion of 500ml of a 10% glucose solution

(Pal et al., 2007).

4

32

1

0-30%30-40%40-80%

30%

GASTRIC MOTILITY DURING

DIGESTION

28

ACW dynamics:

• Initiated every 20s at 15cm from the

pylorus.

• Relative occlusion of ACWs: from 0

to 80%.

Grey Stomach.mpg

FLUID MOTIONS IN THE STOMACH

• The strongest fluid motions were predicted within the lower part of the stomach model.

• The rheological properties of gastric contents has a significant effect on the behavior of the antropyloric flow.

29 Contours of Velocity Magnitude (m/s) (Time=4.8001e+01)FLUENT 6.3 (3d, pbns, dynamesh, lam, unsteady)

Jun 19, 2009

2.75e-02

2.61e-02

2.47e-02

2.34e-02

2.20e-02

2.06e-02

1.92e-02

1.79e-02

1.65e-02

1.51e-02

1.37e-02

1.24e-02

1.10e-02

9.62e-03

8.24e-03

6.87e-03

5.50e-03

4.12e-03

2.75e-03

1.37e-03

0.00e+00

Z

Y

XContours of Velocity Magnitude (m/s) (Time=4.8001e+01)

FLUENT 6.3 (3d, pbns, dynamesh, lam, unsteady)Jun 19, 2009

2.75e-02

2.61e-02

2.47e-02

2.34e-02

2.20e-02

2.06e-02

1.92e-02

1.79e-02

1.65e-02

1.51e-02

1.37e-02

1.24e-02

1.10e-02

9.62e-03

8.24e-03

6.87e-03

5.50e-03

4.12e-03

2.75e-03

1.37e-03

0.00e+00

Z

Y

X

Velocity Magnitude (m/s)

Stomach_vel1.wmv

RHEOLOGICAL PROPERTIES OF GASTRIC

CONTENTS

• Fluid-dynamics of three different liquid meals were investigated.

– Newtonian fluid ( = ). • Water: =1 cP.

– Newtonian fluid ( = ). • Honey: =1000 cP.

– Non-Newtonian ( = K n). • Tomato juice (5.8 %): K = 0.223 Pa.sn n = 0.59.

ANTROPYLORIC FLOW MOTION

• Effect of viscosity on the formation of the retropulsive jet-

like structure.

31

Pathlines Colored by Velocity Magnitude (m/s) (Time=4.8001e+01)

FLUENT 6.3 (3d, pbns, dynamesh, lam, unsteady)

Jun 19, 2009

2.76e-02

2.62e-02

2.48e-02

2.34e-02

2.21e-02

2.07e-02

1.93e-02

1.79e-02

1.66e-02

1.52e-02

1.38e-02

1.24e-02

1.10e-02

9.65e-03

8.28e-03

6.90e-03

5.52e-03

4.14e-03

2.76e-03

1.38e-03

0.00e+00

Z

Y

X

Newtonian

(1 cP)Pathlines Colored by Velocity Magnitude (m/s) (Time=4.8252e+01)


Jan 15, 2010

3.97e-02

3.77e-02

3.57e-02

3.38e-02

3.18e-02

2.98e-02

2.78e-02

2.58e-02

2.38e-02

2.18e-02

1.99e-02

1.79e-02

1.59e-02

1.39e-02

1.19e-02

9.93e-03

7.94e-03

5.96e-03

3.97e-03

1.99e-03

0.00e+00

Z

Y

X

Newtonian

(1000 cP)

Pathlines Colored by Velocity Magnitude (m/s)ANSYS FLUENT 12.1 (3d, pbns, lam)

May 18, 2010

3.54e-02

3.37e-02

3.19e-02

3.01e-02

2.84e-02

2.66e-02

2.48e-02

2.30e-02

2.13e-02

1.95e-02

1.77e-02

1.60e-02

1.42e-02

1.24e-02

1.06e-02

8.86e-03

7.09e-03

5.32e-03

3.54e-03

1.77e-03

9.37e-09

X

Y

Z

Non-Newtonian-shear thinning

(40-570 cP)

vmax = 2.8 cm/s vmax = 4.0 cm/s

vmax = 3.6 cm/s • No retropulsive jet-like

structure developed.

• Higher and more localized

retropulsive velocities were

predicted at the peak of the

ACW.

• Effect of viscosity on the formation of eddy

structures.

32

Pathlines Colored by Velocity Magnitude (m/s) (Time=4.8001e+01)


Jun 19, 2009

2.76e-02

2.62e-02

2.48e-02

2.34e-02

2.21e-02

2.07e-02

1.93e-02

1.79e-02

1.66e-02

1.52e-02

1.38e-02

1.24e-02

1.10e-02

9.65e-03

8.28e-03

6.90e-03

5.52e-03

4.14e-03

2.76e-03

1.38e-03

0.00e+00

Z

Y

X

Newtonian

(1 cP)Pathlines Colored by Velocity Magnitude (m/s) (Time=4.8252e+01)


Jan 15, 2010

3.97e-02

3.77e-02

3.57e-02

3.38e-02

3.18e-02

2.98e-02

2.78e-02

2.58e-02

2.38e-02

2.18e-02

1.99e-02

1.79e-02

1.59e-02

1.39e-02

1.19e-02

9.93e-03

7.94e-03

5.96e-03

3.97e-03

1.99e-03

0.00e+00

Z

Y

X

Newtonian

(1000 cP)

Pathlines Colored by Velocity Magnitude (m/s)ANSYS FLUENT 12.1 (3d, pbns, lam)

May 18, 2010

3.54e-02

3.37e-02

3.19e-02

3.01e-02

2.84e-02

2.66e-02

2.48e-02

2.30e-02

2.13e-02

1.95e-02

1.77e-02

1.60e-02

1.42e-02

1.24e-02

1.06e-02

8.86e-03

7.09e-03

5.32e-03

3.54e-03

1.77e-03

9.37e-09

X

Y

Z


(40-570 cP)

• Eddy structures are confined

to smaller regions closer to

the gastric walls.

RESULTS: VISCOSITY AND

LUMINAL PRESSURE

• Effect of viscosity on the pressure

gradients within the stomach.

33

Pmax = 6.5x10-3 mmHg

Newtonian

(1 cP)

Newtonian

(1000 cP)


(40-570 cP)

Pmax = 1.2 mmHg

Pmax = 0.1 mmHg

VISCOSITY AND LUMINAL

PRESSURE

• The higher pressures that develop within the

stomach, may improve the mechanical

digestion of solid meals by:

34

– Improving the mechanical breakdown of food particles.

– Increasing the distension of the antral wall (i.e. by modifying the motility pattern of the stomach wall).

Particle Strength Threshold

Maximum force supported by the particle

Fparticle-particle

Fpressure

Fparticle-wall

PARTICLE MOTION - NEWTONIAN 1cP • These results are in good agreement with experimental

data obtained using real-time ultrasonography.

35

– Brown et al. (1993) tracked the

motion of solid particles associated

with the ingestion of 500 mL of clear

chicken broth with five 5 garbanzo

beans cut in half. Shuttling of particles by antral

contractions (Review article)-

Schulze, 2006.

“…immediately after ingestion of the test meal, the beans, which

were heavier than the surrounding liquid, were retained in the

dependent portion of the stomach.”

“…liquid passed over the beans which, for the most part, were

retained along the gastric greater curve in the gastric sinus.”

Brown et al., 1993.

pea_trajectory_slow.mpg




In vitro Systems

• To study food disintegration and digestion

Canard Digerateur

Jacques de Vaucanson, 1739

Voltaire wrote that "without...the duck of Vaucanson, you will have nothing to remind

you of the glory of France."

("Sans...le canard de Vaucanson vous n'auriez rien qui fit ressouvenir de la gloire

de la France.")

The Digesting Duck

http://en.wikipedia.org/wiki/Voltaire

TNO intestinal model (TIM)

Stomach

Intestine

pH electrode

Hollow fiber membranes

simulating the absorption

TNO Nutrition and Food

Research (Zeist, The

Netherlands)

The model gut

Institute of Food Research,

Norwich Research Park, Colney,

Norwich NR4 7UA, UK

Needs in Pharmaceutical research

• “... mechanical functions of stomach and

duodenum are well defined in terms of

viscoelastic properties, movement patterns of

their walls….flow phenomenon to digestion

remains to be established…contribution of

pressure forces, shear stresses, flow reversals

and vortical flow remains to be quantified.”

Schulze (2006)

In Vitro Dissolution Testing of Oral

Dosage Forms: USP apparatus

• Apparatus 1 - Basket (37º)

• Apparatus 2 - Paddle (37º)

• Apparatus 3 - Reciprocating Cylinder (37º)

• Apparatus 4 - Flow-Through Cell (37º)

• 500 ml –1000 ml (900 ml)

• Agitation speed: 50-100 rpm for basket method, and 25-75 rpm for paddle method.

• Aqueous dissolution medium composed of 0.1 N HCl (or pH 1.2)

Food Disintegration System

• Food Disintegration system

-Custom-built turntable

-Glass chamber

-Stainless steel annular container

-Force measuring apparatus

• Useful in studying dissolution and

disintegration kinetics of

individual food particulates

MSS.avi

Food Disintegration System

• Custom-built turntable

• Jacketed glass chamber

• On-line Force measuring apparatus

GP-22 ABS plastic

beads (~3 mm dia)

Sample holder

Kong and Singh (2008) J Food Sci

MSS.avi

Profile of periodic force

0

0.07

0.14

0.21

0.28

0.35

0 5 10

Time (min)

Fo

rce

(N

)

Vassallo MJ, et al. 1992.

In vitro

In vivo

Typical disintegration profiles

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20

Disintegration time (min)

Wt/W

0

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30


Wt/W

0

• Exponential: canned kidney beans, ham, Gummy

bear candy, apple bar

• Sigmoidal: fruits such as raw carrots

• Delayed sigmoidal: dry foods such as peanuts,

almonds, fried dough products

In vivo stomach emptying curves from

scintigraphy data

(Camilleri et al. Am J Physiol 249: G580–G585.)

Ham Raw carrot

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50


Wt/W

0

Roasted

almond

Carrot disintegration

0

10

20

30

40

50

0 10 20 30 40 50

Soaking time (min)H

ard

ne

ss (

N)

.

Raw carrots

2-min-cooked carrots

6-min-cooked carrots

• The different profiles are a result of competition among surface erosion,

texture softening and absorption of gastric juice

Hardness of carrot in gastric juice

(n=8)

Disintegration profiles of carrot

(n=6)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

0 20 40 60 80 100

Time (min)

Wt/W

0

Raw carrot, 0.015 N

2-min-cooked

carrot, 0.017N

6-min-cooked

carrot, 0.017N

Food particulate

during digestion

Tenderization front Soft layer

a)

b)

c)

Absorbed water

Tenderization front

Soft layer

Simultaneous surface erosion, absorption of gastric juice and texture softening

0

0.2

0.4

0.6

0.8

1

1.2


Wt/W

0

0

0.2

0.4

0.6

0.8

1

1.2


Wt/W

0

0

0.2

0.4

0.6

0.8

1

1.2

Disintegration time (min)W

t/W0

Erosion front

Penetration front

Carrot (Methylene blue)

Penetration front of gastric juice in carrot

Carrot

Pectin

Cell wall

Penetration front

of gastric juice

Categorize foods based on their structural breakdown in gastric environment?

Candy, apple bar, Canned kidney

beans

<5 min

Ham, breakfast pretzels, fried

dough (no yeast)

5-10 min

Apple, raw carrots 10-20 min

Raw almond and peanut >10 hours

• Linear-exponential equation:

– k: increase in weight with time t

(min)

– β: the concavity of the time-weight

retention relationship (β >0)

• Half time( t1/2) - Can be derived by regression

- Express as disintegration rates

tetkty - bb1)(

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50


Wt/W

0

Delayed sigmoidal

Sigmoidal

Exponential

y = 52.378e68.286x

R2 = 0.9956

20

40

60

80

100

120

0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2%

Gum concentration (%)

Half t

ime (

min

)

Effect of viscosity

• Increase in the viscosity of gastric content delays food disintegration

Effect of gastric viscosity on carrot disintegration

)

Peanut digestion

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 50 100 150 200 250 300 350


We

igh

t re

ten

tio

n r

atio

.

Raw

Boiled

Roasted

Fried

tetkty - bb1)(

0

2

4

6

8

10

12

Raw boiled roasted fried

Half t

ime (

hrs

) .

Almond digestion

• Slow disintegration and swelling in the

stomach contribute to satiety feeling

• Satiety properties of almonds?

0

2

4

6

8

10

12

Raw Roasted

t1/2

(hrs

)

Human Gastric Simulator (HGS) • Create peristaltic movement of walls

• Simulate gastric secretion (enzyme and acid) and stomach emptying

• Study size distribution of food particulates in digesta, nutrient release, and rheological properties

• Study physiological effects (pH, emptying, contraction) on digestion

HGS_1.wmv

Comparison of stomach forces

between in vitro and in vivo

0

0.5

1

1.5

2

2.5

3

3.5

0 2 4 6

Time (min)

Fo

rce

(N

)

Profile of contraction force. Left: in vitro force created in the bottom of

HGS simulating antral force in human stomach; right: in vivo force profile

obtained from stomach proximate to antrum (Vassallo et al. 1992. Am J

Physiol Gastrointest Liver Physiol 263: G230–9.)

Comparison of gastric pH between

in vitro/in vivo

0

1

2

3

4

5

6

0 1 2 3 4

Hours

pH

Profiles of pH. Left: pH of the emptied fluid of HGS; right: in vivo gastric

pH; red rectangle area indicates the pH after food intake (Malagelada et

al. 1976. Gastroenterol 70: 203-10)

Comparison of disintegration efficiency

between HGS and shaking bath

0

10

20

30

40

50

60

70

80

d>6.3 4<d<6.3 2.8<d<4 d<2.8

Particle size (mm)

Dry

solid

s p

erc

enta

ge (

%)

.

HGS

Shaking bath

Comparison between particle size distribution of apple after digestion

in HGS and shaking bath (mean of three trials)

In vivo trials Human trials

Experiments and

observations on the

gastric juice and

the physiology of

digestion

By

William Beaumont,

June 6, 1822

Mackinac Island

Michigan

Alexis St. Martin

Experiments and

observations on

the gastric juice

and the physiology

of digestion

By

William Beaumont,

In vivo methods to assess gastric

disintegration and emptying rate • Feeding study

– acquiring the digesta samples using naso-gastric tube

• Intubation techniques: gastric barostat and intraluminal manometry

– “gold standard” for assessing motility of the stomach

In vivo methods to assess gastric

disintegration and emptying rate • Feeding study

– acquiring the digesta samples using naso-gastric tube

• Intubation techniques: gastric barostat and intraluminal manometry

– “gold standard” for assessing motility of the stomach

• Scintigraphic imaging: liquid barium sulphate, radioopaque spheres

– standard method to measure gastric emptying

• Ultrasonography measures gastric volume or antral cross-section. The information is used to estimate the rate of emptying and evaluate antral motility.

• Magnetic resonance imaging (MRI)

• Indirect methods such as blood test and breath test

Scintigraphic

images shows

capsule

disintegration and

gastric emptying of

its contents)

Gamma

scintigraphy

www.bio-images.co.uk/AAPS2002.pdf

MRI images showing disintegration and

gastric emptying of drug tablet

www.pharmprofiles.co.uk/UserFiles/File/pdf/DepomedPresentation.pdf

MRI

In vivo trials Animal trials

Rats

Pigs

Canulated

Euthanized

Canulated Cow

http://t1.gstatic.com/

In vivo trials

Pigs Arrive at Housing Facility

Massey University New Zealand

Meal Preparation

Obtain in vivo data examining impact of various conditions on food digestion -- 96 pigs

Processing

White rice (cooked)

Brown rice (cooked)

Digestion time

20 min

60 min

120 min, 180 min, 300 min

Location in stomach

Fundus/body

Antrum

Feeding Trials using Pigs

*Approved by the Massey University Ethics

Committee*

69

Sampling

Distal Region

Proximal Region

Food Reservoir?

Main location for breakdown?

Mixing between regions??

Pigs euthanized at 0, 60, 120, 180, or 300 min after eating brown or white rice meal

Samples taken from body/fundus & antral

regions

Key Measurements

Texture

Rheological properties

pH

Moisture content

Particle size distribution

Methods

esophagus

Pyloric sphincter

Results:

20 min white rice

More “liquid-like”

portion in antrum

Results: 20 min brown rice

Evidence of “antral grinding” outer bran layer broken off of

inner endosperm layer

Brown Rice White Rice

Rice Gastric Digestion: 20 mins

300 min digestion

White rice -- antrum Brown rice -- antrum

20 min digestion

0

100

200

300

400

500

600

700

800

900

1000

0 0.5 1

shear

stre

ss (

Pa)

shear rate (1/sec)

white proximalwhite distalbrown proximalbrown distal

Data points are experimentally measured values. Lines represent Hershel-Bulkely model predictions.

20 min digestion

0

100

200

300

400

500

600

700

800

900

1000

0 0.5 1

shear

stre

ss (

Pa)

shear rate (1/sec)


Difference between proximal & distal regions


120 min digestion

0

100

200

300

400

500

600

700

800

900

1000

0 0.5 1

shear

stre

ss (

Pa)

shear rate (1/sec)



120 min digestion

0

100

200

300

400

500

600

700

800

900

1000

0 0.5 1

shear

stre

ss (

Pa)

shear rate (1/sec)



Less difference between proximal &

distal regions

120 min digestion

0

100

200

300

400

500

600

700

800

900

1000

0 0.5 1

shear

stre

ss (

Pa)

shear rate (1/sec)



Less difference between proximal &

distal regions

BUT… Greater difference between

brown & white rice

Rice Grain Compression

0

10

20

30

40

50

60

20 60 120 180 300 480

pe

ak

fo

rce

(N

)

digestion time (min)

Brown Rice Proximal Brown Rice Distal

White Rice Proximal White Rice Distal


0

10

20

30

40

50

60

20 60 120 180 300 480

pe

ak

fo

rce

(N

)




Firmness decreases with time Increased breakdown


0

10

20

30

40

50

60

20 60 120 180 300 480

pe

ak

fo

rce

(N

)




Distal < Proximal More breakdown in Antrum

In Vivo Trial with Raw and Roasted

Almonds Animal Housing

72 male pigs (23 ± 1.5 kg)

Housed in metabolic cages

7 day acclimation period

Diet Preparation

Raw & roasted, medium diced almonds

Individual meals prepared 2x daily

Final meal

Prior to final meal 18 hr fast

2 hr without water

Meal of only almonds

Gastric Emptying: Processed Foods

White Rice Linear Model

y = -0.0017x + 0.9398

R² = 0.9992

Roasted Almonds Linear Model

y = -0.0005x + 1.0304

R² = 0.9901

0%

20%

40%

60%

80%

100%

120%

0 100 200 300 400 500 600 700 800

% d

ry m

att

er

rem

ain

ing


Roasted Almonds & White Rice Gastric Emptying

White Rice

Roasted Almonds

Unpublished Data

0%

20%

40%

60%

80%

100%

120%

0 100 200 300 400 500 600 700 800

% d

ry m

att

er

rem

ain

ing


Raw Almonds & Brown Rice Gastric Emptying

Raw Almonds

Brown Rice

Unpublished Data

Gastric Emptying: Less Processed

Brown Rice Linear Exponential Model

y = (1+ 0.844*0.006x)*e(-0.006x)

R2 = 0.996

Raw Almonds Power Model

y = 1.6199x-0.13

R² = 0.9091

Mixing of Digesta in Stomach

50% of daily dry matter requirement of almonds

25% water

0.3% indigestible marker evenly mixed with sample Titanium dioxide (TiO2)

Chromium oxide (Cr2O3)

Particle Mixing using Markers Each meal divided into 2 portions

Proximal Region

Distal Region

Esophagus


Portion 1: Titanium Dioxide (TiO2)

Proximal Region

Distal Region

Esophagus


Portion 1: Titanium Dioxide (TiO2)

Portion 2: Chromium Oxide (Cr2O3)

Raw Almond Digestion

20 min

Chromic oxide “portion”

Titanium dioxide “portion”

Raw Almond Digestion

20 min 1 hour

1

2

3

4 5

6

7

8

9 10

1

2

3

4 5

6

7

8

9 10

Mixing Index Calculation Difference between variance (s2

t) and equilibrium variance (s2

∞) drives mixing

Mixing index:

s2t = variance at time t

s20 = long time variance

s20 = initial variance

Evolution of mixing indices over time to determine rate of mixing:

t = time elapsed

kmix = mixing rate constant

220

22

-

-

ss

ss tM

tkM mix *)ln( -

References: Smith, 2003; Schofield, 1976 ;

Mixing Index Calculation: Cr

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 100 200 300 400 500

-ln

(M)


White Rice

Brown Rice

Brown Rice -ln(M) = 0.0064t

R2 = 0.96

White Rice -ln(M) = 0.0078t

R2 = 0.95

White Rice: kmix,Cr = 7.8 * 10-3

1/min

Brown Rice: kmix,Cr = 6.4 * 10-3

1/min

Food Structure, textural properties and digestion

Gastric digestion of foods remains a poorly

understood process

A quantitative understanding is required to

develop next generation of foods for health

Strong collaborations among food scientists

and engineers and researchers from medical,

nutrition, and pharmacology fields are

necessary to advance science in this area.

Summary

Gail Bornhorst

Maxine Roman

David Phinney

Jessica Widjaja

Ryan Mayfield

Dr. Samrendra Singh

Dr. Maria Ferrua

Dr. Fanbin Kong

Dr. Jerry Xue

Research Staff at

Riddet Institute

Massey University

New Zealand UC

Davis

Unraveling Food Digestion -- Challenges and Opportunities...

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