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Probe Structure-function Relationships in Foods Using Nuclear Magnetic Resonance
Paul Chen, Ph.D., Senior Research Associate
Department of Bioproducts and Biosystems Engineering
Program Director
Center for Biorefining
UNIVERSITY OF MINNESOTA
Outline
Introduction
Probe structure-function relationships in foods using NMR techniques
Future research and teaching in cereal science and technology
1983 1986 19941990 1997 2002
BS MS PhD
Faculty Post-doc Res. Assoc. Sr. Res. Assoc.
Pomology
Agric-product
Processing Food Science
• Botany• Physiology• Biochemistry• Microbiology• Genetics• Breeding• Pathology• Postharvest handling• Food chemistry• Food nutrition• Food processing• Food storage
Courses
• LM• TEM• Cryo-SEM• X-ray microanalysis• Viscometry• TPA• Color analysis• Mass transfer• Math modeling
Techniques
• Research• Teaching• Papers• Reports• Grants• Services
Responsibilities
• Structure-function • Functional and health-
promoting ingredients• Shelf life of foods• Heat and mass transfer• Non-thermal processes• Biorefining process
development • Modeling
Areas of Interest
Snapshots of Some Projects
Structure-function relationships of highly refined cellulose (HRC) – dietary fiber
Functional and health-promoting ingredients in red corn (anti-oxidant), buckwheat (fagopyritol), and lily (soluble polysaccharides)
Hardening of dehydrated fruits in breakfast cereals
Stickiness of tortilla wraps
Water migration between pizza crust and toppings
Rheological and water properties of flour dough
Fu
nct
ion
al
Fo
od
s/in
gre
die
nts
Cer
eals
/Flo
ur-
bas
ed F
oo
ds
Snapshots of Some Projects (cont’d)
Staling of baked goods and cooked wild rice
Caking of powered foods
Firming of high protein bars, caramel candies
Ozone-aided corn steeping process
Ozone treatment for barley malting
Fusarium scab and mycotoxin in wheat
Non-destructive analysis of sweet corn maturity
Water distribution in corn kernel and soybeans during soaking and drying
Effect of storage on dry bean soaking
Fo
od
po
lym
erS
cien
ceG
rain
Pro
cess
ing
Structure-Function
“Our strength resides in two signature areas:
The structure and function, including sensory and microbial properties, of healthy, safe, and high quality foods; and
The impact of nutrients and bioactive food components on chronic diseases and obesity across diverse populations.”
- Dr. Allen Levine, Prof. and Head, FScN 2004 Annual Report
Structural Elements
Chemical structure (molecular level)
Small chemicals: water, salts, minerals, simple sugars
(e.g., plasticizers in state transition)
Macromolecules: proteins, complex carbohydrates (e.g., starch retrogradation vs staling)
Physical structure
Microscopic level: cellular structure, food matrix
Macroscopic level: dimensions, multi-components (e.g., particulate foods in soup, sandwich)
Functional Elements
Solubility Diffusion Deformation Porosity
Molecular mobility Geletinization Crystallization Melting Phase/state transition Properties of water Emulsification and
foaming
Ph
ysic
alP
hys
ioch
em
ica
l
Rh
eolo
gic
alP
roce
ssin
gB
iolo
gic
al
& H
ealt
h
Enzymatic and non-enzymatic reactions
Digestibility and bioactivities
Microbial deterioration Disease prevention
Texture Viscosity Cohesiveness,
stickiness
Hydration Dehydration Heating/cooling
NMR Relaxometry & MRI
Major relaxation parameters: Signal intensity – proportional to proton density
Relaxation times: spin-lattice relaxation time (T1) and spin-spin-relaxation time (T2) – related to molecular mobility
A function of: Concentration of proton-containing compounds (e.g.,
water & lipids) Chemical and physical structures Temperature
In magnetic resonance imaging (MRI), spatial information is encoded into the signal intensity, T1 and T2
• NMR and MRI• Non-destructive• Non-invasive• Temperature control
MARAN DRX, 21.4 MHz, Resonance Instruments, Oxon, UK
Large Bore MRI
Whole food items Small processing
devices Small animals
Analysis of Structure-function in Foods Using NMR Techniques Dough rheology
Firming of baked and boiled starch-based foods
Firming of food bars
Caking of dry powders
Physiochemical properties of extrudates, breakfast cereals, wraps
Physiology of sweet corn
Freezing of dough
Heat and mass transfer during soaking, drying, cooling, and heating
Examples
Chemical structure changes
Starch retrogradation
Bread staling
Water-solid interactions
State transitionCaking of powdered ingredients
Multi-component
system
Process modeling
Heating of
particulates-in-
liquid system
Chemical structure changes
Starch retrogradation
Bread staling
Native crystalline starch
Amorphous starch
Crystalline starch
Gelatinization
Retrogradation
Starch Retrogradation and Bread Staling
0
30
60
90
120
150
180
0 2 4 6 8 10
Storage days
Firm
ness
(gra
ms)
Change in Firmness of Crumb During Storage
0
10
20
30
40
50
60
0 2 4 6 8 10
Storage days
T2
(ms)
T21 T22/10 T23/50
600
800
1000
1200
1400
1600
1800
0 2 4 6 8 10
Storage days
Pro
ton i
nte
nsi
ty (
arbit
ary u
nit
)
Fraction 1
Fraction 2
Fraction 3
NMR Relaxation Properties of Bread Crumb
Low mobility water Medium mobility water High mobility water
Mobility Intensity
To Analyze change in the properties of water in bread-with-crust with normal packaging
Structure transformation and properties of water
Fraction 3Hi mobility
Fraction 2Me mobility
Fraction 1Lo mobility
Mobility Amount
Change during Staling
Crust & Surroundings
Gluten transformationreleasing water
Plasticization
Water incorporated into crystalline amylopectin
Water-solid interactions
State transitionCaking of powdered ingredients
State Transition
Glass-rubber transition and glass transition temperature
Texture, physiochemical changes, chemical and biological reactions
Measurement: DSC, DMA, DMTA, ……
Water - plasticizer and probe
NMR based techniques
2
2.5
3
3.5
4
4.5
5
0.0026 0.0027 0.0028 0.0029 0.003 0.0031 0.0032 0.0033
1/T (°K-1)
ln [
T2]
(m
s)
T21
T22
2.23
2.33
2.43
2.53
2.63
2.73
2.83
2.93
3.03
3.13
0.0028 0.0033 0.0038 0.0043 0.0048
1/T (°K-1)ln
[T2 (m s
)]
91g/kg
120g/kg
147g/kg
183g/kg
Spin-spin relaxation time (T2) as a function of temperature (T) in maltodextrins (DE15). The legends indicate the grams of water in 1kg maltodextrins.
Relationship between spin-spin relaxation time (T2) and temperature in PLA
NMR State Diagram
Temperature increasing
Implications
NMR-determined transition temperatures are
generally lower than DSC-determined Tg
Mobility is detected below DSC-determined Tg
This may be an explanation for reported chemical
and biological activities below DSC-determined Tg
It is possible that NMR is more temperature sensitive.
NMR state diagrams for powdered ingredients
Evaluating Caking Tendency of Dry Powered Ingredients
A B
C D
Temperature (°C)
T2
Schematic demonstration of four different temperature-T2 curve patterns for the dry soup powders.
Caking was found to be a function of curve pattern characterized by transition temperature (TTran), slope before transition (KBT), and slope post transition (KPT). This technique is being used by a company for caking prediction and development of caking resistant formula.
KBT
KPT
TTran
MRI & Process Modeling
Analysis of:
Moisture, fat, and mobility distribution in foods
Water movement during storage, soaking, drying
Temperature mapping/heat transfer
Model verification
Mathematical modeling – numerical simulation
Verification by experiment data from MRI
Raw Cooked
Hard Soft Bruised
Kiwifruit: Conversion of starch and pectin to soluble compounds during maturity of the fruit has an effect on the structure and mobility of water in the tissue.
Egg: Cooking caused egg protein to denature, which reduced the mobility of water.
Strawberry: Softening (high maturity) and physical damages increased the mobility of water in the tissue.
2D MR Images
Raw Mature
2D MR Images of Dough
Low resolution
High resolution
Calculation of volume and distribution of air bubbles
3D MR Images of Bagel with Raisins
Low S/N High S/N
13 raisins countedBagel with raisins
3D MR Images of ExtrudatesUnuniform distribution of water and mobility – responsible for irregular shapes of baked products?
Raw 0h 1.5h 3h 6h 9h 12h
Slice 1
Slice 2
MR images showing that moisture distribution in puffed rice kernels during temperingbecame more uniform with increasing tempering time.
Low High
Multi-component
system
Process modeling
Ohmic heating
of particulates-
in-liquid system
Modeling of Ohmic Heating and MRI Verification
Ohmic heating is efficient because it does not rely on heat transfer
Suitable for cooking/sterilization of solid particles in liquid (e.g., mixture of meats, carrots, potatoes and soup)
Difficult to demonstrate actual sterilization value in multi-component systems such as particulates-in-liquid
Modeling provides insight into the heating behaviors of ohmic process
Instrumental verification is important
Cross-section of sampleAt MRI slice
Transformer
AC power
Sample
Electrode
RF Probe
Main magnet
Cylindrical potato particulate
Liquid 0.2% NaCl + 0.7% CMC
MRI slice
Ohimic Heater inside MRI Probe
Modeling Theory: Coupled Nonlinear Partial Differential Equations (PDE)
0])([ VTi
iiii
Pi uTkt
TC
i
)(
)(2
TVu ii
sfpsfpspp TThnTk )(
w)T
fsU(Twnf
Tfk
Electric field:
Thermal field:
Heat generation:
Boundary conditions:
Between liquid & particulate:
System boundary condition:
Mesh statistics:
Number of nodes: 5643
Number of edges: 6139
Number of elements: 26599
-0.02 0 0.02
-0.02
0.02
0
m
Cross-section at vessel center
Model Scheme Generated by FemLab based on Finite Element Method (FEM)
Model MRI10 Min
50 Min
40 Min
Model Prediction vs. MRI Map (Case #1, 120 V)
Model MRI2.5 Min
12.5 Min
7.5 Min
Model Prediction vs. MRI Map (Case #2, 240 V)
0 500 1000 1500 2000 2500 3000 350010
20
30
40
50
60
70
80
90
Model:potato
MRI:potato
Model:liquid
MRI:liquid
Heating time (s)
Tem
pera
ture
( °C)
0 500 1000 1500 2000 2500 3000 350010
20
30
40
50
60
70
80
90
Model:potato
MRI:potato
Model:liquid
MRI:liquid
0 500 1000 1500 2000 2500 3000 350010
20
30
40
50
60
70
80
90
Model:potato
MRI:potato
Model:liquid
MRI:liquid
Heating time (s)
Tem
pera
ture
( °C)
Model Prediction vs. MRI Map: Hot and Cold Spot (Case #1, 120 V)
0
20
40
60
80
100
0 200 400 600 800
Heating Time (s)
Tem
pera
ture
( o C
)
Model: liquid
MRI: liquid
Model: potato
MRI: potato
Model Prediction vs. MRI Map: Hot and Cold Spot (Case #2, 240 V)
Summary
We can understand the stability, properties, and processes of foods through the analysis of structure-function relationships.
Future research should also look into structure-function relationships in biological activities and bioavailability of nutrients.
There exist many opportunities for collaborative research with faculty in FScN and the food industry in this signature area.
Acknowledgements
Dr. Roger RuanDr. Ted LabuzaDr. Gary FulcherDr. Paul AddisDr. Eric BastienDr. Joe Warthesen
Dr. Zata VickersDr. Susan RaatzDr. Bernhard van LengerichDr. Victor HuangDr. Peter PesheckDr. Phil Perkins
Dr. Kehua ChangDr. Lun YiMr. Zhenzhong LongMr. Li XuDr. Cheng ZouDr. Brock LundbergDr. Xiaofei YeDr. Myonsoo ChungDr. Hanwu LeiMr. Jun HanMr. Lide ChenMs. Qin LiuDr. Su NingDr. Jinning QiMs. Hong Li
Mr. Ray MillerMr. Fred RigelhofMs. Regina de BarrosMs. Michele FrenchMr. Shaobo DengMr. Fei YuMs. Yun Li Thank You!
Questions?
Cereal Chemistry & Technology:
Bridging Health & Consumer Preferences
through
Future Research & Teaching
in the Department of Food Science and Nutrition
UNIVERSITY OF MINNESOTA
President’s Initiative on Healthy Foods, Healthy Lives
The four priority areas:
To utilize and advance knowledge about the integration of agriculture, food science, nutrition, and medicine to promote healthy lives;
To emphasize prevention of diet-related chronic diseases and obesity through diet, exercise, and human behavior;
To enhance food safety at all stages, from farm to table; &
To inform public policy.
My Vision
Develop nationally and internationally recognized cereal research and education programs at the University of Minnesota
Develop specialized expertise in whole grains and phytochemicals from cereals
Serve the local cereal industry by meeting their R&D needs and providing first class graduates
Research Areas
Cereals& Health
Structure& Functions
ProcessDev & Model
Half of the Grains Whole Grains
New USDA Food Pyramid
Challenge:Offer healthy foods without sacrificing sensory quality
Whole Grain Issues & Opportunities
Unaware of the health benefits
Poorly publicized definition
Poor sensory quality: “Nothing is better than good old white bread”
Limited varieties and expensive
Short shelf stability
Process modification required
June 6, 2005, Star Tribune
Aleurone
“Whole Grain Additives”
Identification of ingredients and their health benefits
Extraction, purification, characterization
Incorporation into grain products
Testing/trials
Rationale
Add whole grain benefits to white flour products
Potential Projects
Extraction and characterization of functional ingredients (“whole grain additives”) from cereals
Generation and evaluation of resistant starch using extrusion cooking
Evaluation of incorporation of whole grains and “whole grain additives” into cereal-based products in terms of sensory quality and health benefits preservation
Safety issues in cereal foods (mycotoxin, acrylamide)
In vivo study and modeling of fluid-mechanics and physiochemical properties of cereal foods in the digestive system in small animals using MRI
Process modeling and improvement
Funding
Fed
Non-profit State & UMN
Industry
FScN 2005 Annual Report
Publications
Food and cereal science and chemistry, food Engineering
Nutrition, biological and health science
Interinstitutional co-authorships
Teaching Experience
1) Food TechnologySCAU, China, 1986-1990
2) Preservation & Processing of Fruits & Vegetables SCAU, China, 1986-1990
3) Cereal BeveragesAACC short course "Asian Food Technology," Baltimore, 1996
4) Managing Water in Food and Biological SystemsBAE 8703, UMN, 2003 - present
5) Biological Processing EngineeringBAE 4713, UMN, 2006
Teaching in FScN
FSCN 5531 - Grains: Introduction to Cereal Chemistry and Technology
Teach other courses related to structure-function and preparation of functional ingredients and foods
New course development
Extension and Outreach
Public education
Serve the industry
Process and product development
Problem solving
Seminars/workshops
Collaborate as a “Whole”
Future of Whole Grains
Nutrition – discover new benefits, verify current claims, provide better definition
Consumer research – understand consumers’ expectation, hurdles to acceptance
Process and product development – develop/modify processing technology, better quality and more varieties
Agronomy and breeding – screen existing grains, develop new grains with better quality through genomics
Multidisciplinary Collaboration/Interaction
UMN, AACC
State/Fed Gov
IndustriesTrade & Health
Multi-Institutes
NationalCenter
Summary
The breadth and depth of my research experience and expertise allow me to establish strong research programs in the field of cereal chemistry and technology
My research will promote the consumption of cereal products that offer health benefits with high sensory quality
I have the desire, capability and necessary interface to collaborate with researchers in different fields
I am committed to enhance the teaching, extension and outreach programs in this department
I have a good track record of research, grants, and publication
I work hard and will do my best to make a significant contribution to this great department.
www.umn.edu/~chenx088