1. 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. 222/04/2015
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. 322/04/2015
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)

4. 422/04/2015
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. 522/04/2015
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

6. 622/04/2015
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. 722/04/2015
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. 822/04/2015
Flow chart of 4-year work
Macrostructure
TextureWAI & 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. 922/04/2015
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. 1022/04/2015
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. 1122/04/2015
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. 1222/04/2015
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. 1322/04/2015
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. 1422/04/2015
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. 1522/04/2015
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
CrispinessIndex(x104)
0
2
4
6
8
10
Coarse
Medium
Fine
CI of extrudates
increased with particle
size reduction
IB= In-barrel water feed; PC= Preconditioning; Screw speed = 300 & 500 rpm

16. 1622/04/2015
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
Hardness(N)
0
100
200
300
400
500
600
Coarse
Medium
Fine
Fmax of extrudates
reduced with particle
size reduction
IB= In-barrel water feed; PC= Preconditioning; Screw speed = 300 & 500 rpm

17. 1722/04/2015
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. 1822/04/2015
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 0,7
CrispinessIndex(10)
0
1
2
3
4
5
6
7
8
Porosity %
60 65 70 75 80 85 90
CrispinessIndex(104)
0
1
2
3
4
5
6
7
8
Coarse + medium
Fine

19. 1922/04/2015
Crispiness increases with increased expansion and decreased
piece density for fine particle sized rye bran extrudates
Fine particle size branR2 = 0.84
Expansion Rate (%)
120 140 160 180 200 220 240
CrispinessIndex(x104)
0
2
4
6
8
R2 = 0.70
Piece Density (kgm3)
200 300 400 500 600 700 800 900
CrispinessIndex(x104)
0
2
4
6
8
 Higher expansion tends to
give crispy puffs
 Higer density reduced
crispiness
Coarse + medium
Fine

20. 2022/04/2015
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 %
CrispinessIndex(x104)
0
5
10
15
20
25
30
a
b
a
ab
b
a
b
IB 15 % IB 30 % PC 15 % PC 30 %
CrushingForce(N)
0
10
20
30
40
50
60 Coarse
Fine
d
cd
bc
d
b
a
bc b
c

21. 2122/04/2015
15 % 30 % 100 % Bread
Hydrolysisindex
0
25
50
75
100
125
Coarse
Fine
Wheat
Rye
abc
be cde
g
h
f
ad
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. 2222/04/2015
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. 2322/04/2015
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 bolusWheat bread Wheat bolus
Starch: purple
Protein: green

24. 2422/04/2015
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. 2522/04/2015
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. 2622/04/2015
THANK YOU!
ariful.alam@vtt.fi

27. 2722/04/2015
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