Process induced structural features of

solid cereal foams- in relation to oral

processing

PhD thesis

Syed Ariful Alam

VTT Technical Research Centre of Finland

2 22/04/2015

Ariful’s dissertation:

Process induced structural features of solid cereal foams

Work started in 2014

Research at VTT Espoo

Studies at the University of Helsinki, Department of Food and Environmental

Sciences.

Supervisors:

Docent Nesli Sozer (Senior Scientist at VTT)

Assist. Prof. Kati Katina (UH)

Academy Prof. Kaisa Poutanen (VTT)

Funded by: Academy of Finland, VTT & Raisio Plc. Research Foundation

Objective: Understand the main structural and mechanical features of healthy

solid foams. Elucidate mechanism of structural disintegration of healthy solid

foams in mouth and stomach phase.

3 22/04/2015

Overview of the PhD thesis & publications

Influence of particle size reduction on structural & mechanical properties

of extruded rye bran

Published at Food and Bioprocess Technology, 2014

Effects of rye bran particle size reduction on in vitro starch digestibility

and structural & textural properties of high-fibre extrudates

Submitted to Food and Bioprocess Technology, 2015)

Structural and mechanical properties of brittle cereal foams affecting

disintegration in mouth during in vivo mastication

On-going study…….

Disintegration of high fibre solid cereal foams in mouth (in vivo) & in

stomach (in vitro) & their positive impact on physiological responses

Funding: 2016-2017 (to be applied)

http://dx.doi.org/10.1007/s11947-013-1225-2http://dx.doi.org/10.1007/s11947-013-1225-2http://dx.doi.org/10.1007/s11947-013-1225-2http://dx.doi.org/10.1007/s11947-013-1225-2

4 22/04/2015

Why RYE?

90% of world rye production is in Europe

30% is consumed as food

Traditional use as whole grain breads, often

produced by sour dough fermentation

Health effects of rye bread increasingly demonstrated

Development of new types of rye products & ingredients for the modern consumer is important

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Beneficial physiological

effects in humans

RYE BRAN

40-45% dietary fibre

15-20% protein

13-20% starch

4-5% fat

BRAN

5 22/04/2015

Background

Extrusion processing can be used for production of a wide range

of solid cereal foams e.g., puffed snacks, flakes etc.

Addition of DF into extruded product improve the nutritional quality

Bran addition product quality (e.g., expansion, hardness &

crispiness) attributes reduced

Addition of DF into extruded product improve the nutritional

quality

Breakdown in mouth by mastication inversely related to food

hardness and thus affects hydrolysis rate

Prediction of the disintegration pattern of solid cereal foams

Mathematical modelling

Changing the date: View – Slide Master – change the date on the slide master uppermost

6 22/04/2015

Importance of structure and texture formation in food design

Composition & Processing

Texture

Structure

Product design

Increased demand for high

quality healthy food products.

Technological and physical

challenges in high fibre food

matrices.

Adverse affect on sensory

texture and flavor/taste.

Important to understand the

physical basis of texture in order

to be able to design palatable and

healthy foods.

7 22/04/2015

Objectives

Understand the main structural and mechanical features of

healthy solid foams e.g., puffs and flakes

Assessing the effect of structural and mechanical properties

of high fibre extruded puffs & flakes on disintegration in

mouth (in vitro) and in bolus formation

Elucidate mechanism of structural disintegration of healthy

puffs and flakes (in vivo mouth and in vitro stomach phase)

in comparison to regular wheat based foams

8 22/04/2015

Flow chart of 4-year work

Macrostructure

Texture WAI & WSI Starch HI

Microstructure

Open cereal matrices

Open & closed cereal matrices

Extrusion

In vitro stomach

In vivo mastication

Particle size

Viscosity

Hierarchical model

Bolus Psychophysical model

9 22/04/2015

Experimental design paper 1 & 2/4

Publication 1: Publication 2:

Raw material:

RYE BRAN

100 % rye bran

3-particle sizes of rye bran:

Coarse (440 µm)

Medium (143 µm)

Fine (28 µm)

Screw speed: 300/500rpm

Feed Moisture: 17/ 19 %

Barrel T profile: low (110°C) / high (130°C)

Hydration regimen: In-barrel/

Preconditioning

Rye endosperm fllour + 15/30% rye bran

2-particle size (Coarse vs. Fine)

Screw speed: 500 rpm

Feed moisture: 17%

Barrel T profile: low (110°C)

Hydration regimen: In-barrel/

Preconditioning

10 22/04/2015

Partile size reduction and effect on rye bran quality and on

extrudates

Rye bran

extrudates

Starch: black

Lignified cells: yellowish brown

Protein: red/brown

ß-glucan: light blue

11 22/04/2015

Structural & textural parameters

Macro-structural vs. Textural parameters

Expansion

Piece density

Crispiness

Microstructure

Effect of particle size and extrusion on microstructure (LM)

X-ray microtomography (XMT)

Texture Analysis: Uni-axial compression test for puffs & crammer

shear compression for flakes

Micro-structural vs. Textural parameters

Porosity, air cell diameter

Cell wall thickness, crispiness

12 22/04/2015

Crispiness index

Mechanical properties of the extrudates were

analysed using a texture analyzer (TAXT2i) and the

Texture Exponent software (v5.1.2.0) (both from

Stable Micro Systems, UK).

A 36 mm Al cylindrical compression plate was

used to compress the samples to 70% of their

original diameter (test speed of 1 mm/s).

𝐶𝑟𝑖𝑠𝑝𝑖𝑛𝑒𝑠𝑠 𝑖𝑛𝑑𝑒𝑥 𝐶𝐼 =𝐶𝑢𝑟𝑣𝑒 𝑙𝑒𝑛𝑔𝑡ℎ (𝑁)

𝐴∗𝐹𝑚𝑒𝑎𝑛

𝐶𝑢𝑟𝑣𝑒 𝑙𝑒𝑛𝑔𝑡ℎ

= ∆𝐹𝑜𝑟𝑐𝑒

A = Area under the f-d curve

Fmean = Average force of the

# peaks from the F-d curve

13 22/04/2015

Particle size reduction gives lower thickness to radius ratio; less thick

and more expanded cells

In barrel

Pre-conditioned

Representative XMT images of

a) Coarse

b) Medium

c) Fine particle-sized

extruded rye bran samples

b

c

a

c

b

a

14 22/04/2015

Macro-structural vs. Textural parameters

High screw speed and small particle size

good expansion

low density

High expansion and low density

More crispy

less hard textrure

15 22/04/2015

Particle size reduction to 28 μm gave extrudates with crispy texture.

Pre-conditioning had an adverse affect on crispiness

Fine particle increased the

crispiness for both in-barrel

and preconditioned

extrudates

In-barrel water feed in

combination with high

screw gave crispiest puffs

IB 300 IB 500 PC 300 PC 500

Crispin

ess In

de

x (

x104)

0

2

4

6

8

10Coarse

Medium

Fine

CI of extrudates

increased with particle

size reduction

IB= In-barrel water feed; PC= Preconditioning; Screw speed = 300 & 500 rpm

16 22/04/2015

In general particle size reduction reduced Fmax. Pre-conditioning

before extrusion reduced hardness (Fmax) values

Higher screw speed

reduced the hardness

Preconditioning reduced

the hardness for all

particle size

IB 300 IB 500 PC 300 PC 500

Ha

rdn

ess (

N)

0

100

200

300

400

500

600Coarse

Medium

Fine

Fmax of extrudates

reduced with particle

size reduction

IB= In-barrel water feed; PC= Preconditioning; Screw speed = 300 & 500 rpm

17 22/04/2015

Fibre modification

Coarse rye bran

No significant effect

Medium and fine rye bran:

Increase in IDF and TDF

SDF increased only in few samples

Extrusion had only limited effect on DF composition

The effect was more pronounced with medium and fine rye bran

18 22/04/2015

Micro-structural vs. Textural parameters

Particle size reduction to 28

µm

Porosity ↑

Air cell diameter ↑

t/D ratio ↓

more expanded air cells in

relation to cell wall thickness

Energy required to fracture big air

cells with thin cell walls is lower

than that required for small air

cells with thick cell walls

Less hard, more crispy extrudates

t/D

0,1 0,2 0,3 0,4 0,5 0,6 0,7C

rispin

ess Index (

10)

0

1

2

3

4

5

6

7

8

Porosity %

60 65 70 75 80 85 90

Crispin

ess Index (

104)

0

1

2

3

4

5

6

7

8

Coarse + medium

Fine

19 22/04/2015

Crispiness increases with increased expansion and decreased

piece density for fine particle sized rye bran extrudates

Fine particle size bran R2 = 0.84

Expansion Rate (%)

120 140 160 180 200 220 240

Crisp

ine

ss I

nd

ex (

x1

04)

0

2

4

6

8R2 = 0.70

Piece Density (kgm3)

200 300 400 500 600 700 800 900

Crisp

ine

ss I

nd

ex (

x1

04)

0

2

4

6

8

Higher expansion tends to

give crispy puffs

Higer density reduced

crispiness

Coarse + medium

Fine

20 22/04/2015

2nd paper: Effects of rye bran particle size reduction on in vitro starch

digestibility and structural and textural properties of starch-based

high-fibre extrudates (submitted)

Fine IB 30:

High cell wall thickness

&

Large cell wall area

IB 15 % IB 30 % PC 15 % PC 30 %

Crispin

ess Index (

x104)

0

5

10

15

20

25

30

a

b

a

ab

b

a

b

IB 15 % IB 30 % PC 15 % PC 30 %

Cru

shin

g F

orc

e (

N)

0

10

20

30

40

50

60 Coarse

Fined

cdbc

d

b

a

bc b

c

21 22/04/2015

15 % 30 % 100 % Bread

Hydro

lysis

ind

ex

0

25

50

75

100

125

Coarse

Fine

Wheat

Rye

abcbe cde

g

h

fad

f

In-barrel water feed extrudates

15% bran addition

Fibre: 12.6%

Fibre: 8.2%

30% bran addition

Effect of particle size on in vitro starch digestibility

22 22/04/2015

Publication 3:

Experimental design 3/4

Interidividual variance due to

chewing pattern

Effect of fibre: 7 vs. 9%

Structure/texture effect on

masticaation: puffs vs. flakes

100% Rye flour & Rye flour + 10% rye bran Screw speed : 250 (F) & 345 (P)

Feed moisture 4.5 (P) & 12 (F) In-barrel

Barrel T profile: low (80-95-110-120°C)

EMG: EMG activity time -> Chewing time -> Number of bites -> Duty cycle ->Total work-> Work/bite

23 22/04/2015

3rd paper outline

Extruded puffs and flakes

Mastication & EMG

100% Rye flour

Bolus Image analysis

Starch digestibility

Microscopy

Saliva impregnation

90% Rye flour + 10% Rye bran &

Fibre: 7 & 9% 15 female volunteer

Starch HI

X-ray Microtomography

Microscopy Texture

Viscosity

Microscopy & particle area distribution of masticated bread sample

Wheat bolus Rye bolus Wheat bread Wheat bolus

Starch: purple

Protein: green

24 22/04/2015

Mastication trial/Electromyography

• 15 participants

• Bipolar electrodes on the masseter and temporal

muscles on both sides of the face

• 3 portions

• control bread: (2x2x2) cm cube

• Puffs: (2x3.5) cm ribbon

• Flakes: 1 table spoon

• Masticated until subjective swallowing point and the

bolus was then expectorated

• EMG activity measured continuously

• Onset, duration and amplitude of each bite event were

extracted from EMG time series

Masseter

Temporalis

25 22/04/2015

Raw materials Food structure & texture

Sensory responses, Bolus formation

Digestibility

HIGH FIBRE (RYE) FOODS ARE HAVE GOOD POTENTIAL TO ASSIST IN REDUCTION OF RISK OF CHRONIC DISEASES. UNDERSTANDING THEIR STRUCTURE FORMATION AND ORAL DISINTEGRATION - THE CONNECTION BETWEEN FOOD PROCESSING AND EATING – HELPS TO DEVELOP BETTER FOODS.

Oral processing- structure disintegration

Digestion- Structure disintegration

Food processing- structure formation

Conclusions

26 22/04/2015

THANK YOU!

ariful.alam@vtt.fi

27 22/04/2015

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