syed ariful alam
TRANSCRIPT
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)
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
27 22/04/2015
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