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