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J.I. Lombraña
Dept. of Chemical Engineering. Faculty of Science and Technology. Universidad del País Vasco. *P.O Box 644. 48080 Bilbao (Spain). Phone +34 94 601 25
5th Euro-Global Summit and Expo on
Food & Beverages June 16 – 18, Alicante, Spain
QUALITY VALORIZATION OF MICROENCAPSULATED
PROBIOTICS DEHYDRATED BY MICROWAVE DRYING
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Functional foods
FF or nutraceuticalsaid specific bodily functions
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Probiotics
Functional food
• The term functional foods was first introduced in Japan in the mid-1980s and refers to processed foods containing ingredients that aid specific bodily functions in addition to being nutritious.
• In this way, a nutritionally more complete product is obtained, by adding, probiotics, vitamins and proteins, in most cases.
• There has been a rising interest in producing probiotics, the most frequent FF because of their transcendence on health beneficial effects.
• FF and specially probiotics are specially sensible material that requires protection.
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Probiotics
Inmunomodulation
Metabolic effects
Normalised microbiota composition
lactobacillus acidophilusbeneficial strain (DDS-1)
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Encapsulation
• The encapsulation searches to protect the nutritional extra added value during drying and cocking process which suffers the food.
• Capsules are formed mixing the added components with support materials (gelatine, alginate, sugars…) forming spherical particles depending on the technique used.
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Microencapsulation Techniques
… probiotics
Extrusion techniqueEmulsion techniqueRennet-gelled protein encapsulation
Combination of encapsulation and drying
Freeze dryingSpray DryingFluid bed
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Extrusion TechniqueB
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Probiotic elaboration
Mixing(homogenization)
Micro-encapsulation
Jet-cutting+
(droplet jelling)
Drying
Alginate sol.
+Cell culture
Fix-fluidized bed+
Microwaves
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Conventional Drying
The conventional drying process (convective heating), dries the product from out to inside, so the energy is applied from the surface of the product.
There is a significant loss of energy for heating the surroundings where drying occurs.
The high thermal level in conventional drying is the cause of low efficiency in the process and thermal damage.
General drawback - longer drying period and higher drying temperature for sensible products.
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Microwave Drying
In microwave heating, the heat is generated inside the product, favoring heat distribution due to agitation of the polar molecules contained in it.
the inverse temperature gradient, favors the drying of the particles from inside out.
Microwave drying utilizes very fast volumetric heating reducing temperature and operating times.
MW drying offers to shorten the drying time without degradation of final quality of the dried product
Fix-fluidized bed
Fix-fluidized bed and MW heating are specially indicated for drying: fix-fluidized microwave drying (FFMWD).
During the packed bed periods : Allows Better heat distribution by conduction
inter-particles. avoids superheated spots with enough
circulating air.
During the fluidized bed periods: Fluidized bed is used to homogenize and
control temperature. Fluidization favours mass transfer.
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Objectives
The main objective of the our research is to find the optimum operating conditions for FFMWD
Analysis of Drying kinetics.• Drying parameter estimation through fitting
experimental data to the mathematical model.• Moisture content and • Drying rate profiles for each thermal level
applied
Quality of dehydrated product.• Water activity profiles• Results of final water content (KF %)• Post drying cell viability
Selection of the most suitable drying condition under quality and kinetic criteria.
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Methodology
• Suspension preparationo 3% Sodium alginateo 10% of a cell suspension of
Saccharomyces cerevisiae ,
• Microencapsulation Technique: Jet Cutting. p 0,225 cm.
• Drop in 2% Calcium cloride solution.
Encapsulated Probiotic material
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Equipment
Control VariablesF: Inlet air flowTin:Inlet air TemperatureTf: Control product
temperature (MW Power)
FTin
Tf
(1)Dehumidifier , (2) Heater-cooling,(3) Microwave chamber,
(4)Temperature Display
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Drying experiments monitoring
Measuring control variables.• F: Inlet air flow . Vair 1.7 to 1 m/s • Tin: Inlet air Temperature• Tf: Control product temperature (MW Power)
Mass loss along drying. Build-in scale.
Moisture content• water activity (aw) along the process.• Water content. Karl Fischer
Cell viability after drying. • Units forming colony (ufc/d.s.)
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Control Variables
Air velocity
Air Temperature
P. surfaceTemperatureTs* / Ts
ExternalT. Gradient
P. surface temperature Ts*Controlled by the MW power Measured through Tf film or inter-particle temperature. Levels:
L 15ºCM 35 ºCH 55ºC
Air temperature Tin
Controlled by the heating device at the entrance
External gradient: Ts*- Tin. Levels: L 15ºC
M 30ºCH 50ºC
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Experiments planification
Phase I Phase II Phase IIICode
Exp. Tin Tf TS* Tin Tf TS
*
Decre.Temp.
1 5 20 35 5 20 35 MM/MM
2 5 20 35 20 27.5 35 MM/ML
3 5 30 55 40 47.5 55 HH/HL
4 20 27.5 35 5 20 35 ML/MM
5 20 27.5 35 20 27.5 35 ML/ML
6 20 37.5 55 40 47.5 55 HM/HL
7 20 37.5 55 20 27.5 35 HM/ML
8 40 47.5 55 40 47.5 55 HL/HL
9 40 47.5 55 20 37.5 55 HL/HM
Air flowPhase I: 5 Nm3/h (1.7 m/s) Phase II: 3 Nm3/h (1 m/s)
Letter T (ºC)
M 35
H 55
1st letter Thermal level Ts
*Letter T (ºC)
L 15
M 30
H 50
Second letter Gradient
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Drying selection
Best dryin
g strate
gy
Water activity
(aw)
Drying kinetics
Cell viabilit
y
Energy valorisat
ion
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Drying Kinetics
0 20 40 60 80 1000
1
2
3
4
5
6
Modelled
time (min)
M (
g H
2O
/g d
.s)
0 20 40 60 80 1000
0.04
0.08
0.12
0.16
time(min)
-dM
/dt
0 20 40 60 80 1000
1
2
3
4
5
6Modelled
time (min)
M (
g H
2O
/g s
s)0 20 40 60 80 100
0.00
0.10
0.20
0.30
time (min)
-dM
/dt
Exp 1
Exp 1
Exp 9
Exp 9
Phase I
Ph
ase
II Phase III
Phase I Phase IIIPh
ase
II
Ph
ase
I
Ph
ase
II
Phase III
Phase III
Ph
ase
I
Ph
ase
II
Exp 1. Excessive low temperature (Exp1-Tin=5ºC ) can cause cell damage so as the high temperature (Exp9-Tin=55ºC). Extreme drying kinetics are unfavourable
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Water activity
01234560
0.2
0.4
0.6
0.8
1
Exp.2
Exp.9
M [g H2O/g ss]
aw
Phase I Phase II
Phas
e II
I
0 50 100 150 200 250 3000
0.2
0.4
0.6
0.8
1
Exp.2
Exp.9
time (min)
aw
Phase III is decisive for the cell viability. A fast lowering of aw of Exp 2 is recommended
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Energy efficiency
0 10 20 30 40 50 600
10
20
30
40
Ts
Tair
Tf
t(min)
T(º
C)
CodePhase I Phase II
Taire Tf Ts* Taire Tf Ts
*
HH/HL 5 30 55 40 47,5 55
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In the experiment 3 (HH/HL)Convective losses are low. Onlyin Phase I, Ts>Tair
Quality and kinetic valorization
Exp. rI-II Mfin II rglobal
time (min)
(%)KFfin
Viablility (%)
Code
10,11
40,783 0,017 275 6,726 0,0 MM/MM
20,12
60,946 0,024 184 7,522 96.3 MM/ML
30,21
91,245 0,021 231 7,706 93.9 HH/HL
40,18
40,945 0,023 240 7,577 88.6 ML/MM
50,16
31,309 0,023 228 7,458 91.8 ML/ML
60,19
80,646 0,022 210 7,599 87.7 HM/HL
70,15
90,907 0,019 243 8,414 77.7 HM/ML
80,34
91,184 0,026 251 8,830 78.0 HL/HL
90,25
40,992 0,025 224 7,726 0,0 HL/HM
Lyoph.
0,007 720 8,855 90.7 -
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Global valorization
Exp.Phase I Phase II
Tair Tf Ts* Taire Tf Ts
*
2 5 20 35 2027,5
35
3 5 30 55 4047,5
55
5 20 27,5 35 2027,5
35
Convective lossesViabilit
yPhase I Phase II Total- - -- 97,9
- +++ ++ 93,7
++ ++ ++++ 90,9
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Experiments 2 and 3, spite of their favourable drying rate and good viability results, are discarded because the significant convective losses
Medium thermal levels and low gradients, such as of Exp. 5, are recommended because of its good quality and process efficiency
Conclusions
• Microwave drying has proved to be a good technology for microencapsulated probiotics with high percentage of survival.
• The mathematical model show in the first phase that the diffusivities values are not as high as for the second phase in which a combination of liquid and gas diffusion mechanism take place.
• Considering the viability the best drying conditions would be a medium thermal level and gradient with good results under quality and kinetic criteria.
• In further studies is thought to use a lactobacillus strain applying medium thermal strategies here found as the most adequete.
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AcknowledgementsGroup at UPV/EHU
Janire MardarasDr. Monika OrtuetaDr. J. Ignacio Lombraña
e-mail: [email protected]
Group at Tecnalia
Dr. Noelia HidalgoDr. M. Carmen Villarán
e-mail: [email protected]
UPV/EHU
The authors are grateful to the Basque Government for the financial support of the study through the Aid (IT801-13) within the program to consolidate Groups (Basque University System) and to the University of the Basque Country (UFI 11/39 UPV/EHU).
Dept. of Chemical Engineering. Faculty of Science and Technology. Universidad del País Vasco. *P.O Box 644. 48080 Bilbao (Spain). Phone +34 94 601 25
5th Euro-Global Summit and Expo on
Food & Beverages June 16 – 18, Alicante, Spain
QUALITY VALORIZATION OF MICROENCAPSULATED PROBIOTICS DEHYDRATED BY MICROWAVE DRYING
THANK YOU FOR YOUR ATTENTION!!
Dr. J. Ignacio Lombrañae-mail: [email protected]
Mass transfer model
z
M
zy
M
yx
M
xD
t
MD1,D2,D3
Boundary conditions:
)exp()( 0 tMMMM eeS (Shivhare 1994)
sph
sphav V
dxdydzzyxM
M
),,(
Diffusion coefficients and Surface drying coefficient (β)
Exp. βD1(x 10-
8)D2(x 10-
8)D3(x 10-8) Code
1 0.054 3.2 4.8 7.0 MM/MM
2 0.050 4.2 6.0 3.2 MM/ML
3 0.074 6.0 8.0 1.0 HH/HL
4 0.066 2.2 4.2 1.0 ML/MM
5 0.055 5.0 7.2 0.7 ML/ML
6 0.090 6.1 9.1 0.8 HM/HL
7 0.069 3.4 5.6 1.0 HM/ML
8 0.110 3.6 3.4 0.1 HL/HL
9 0.090 5.2 5.0 0.9 HL/HM*Units: β (min -1), D ( m2/min).
0
1
2
3
4
0 25 50 75 100 125 150
M (g H2O/g d.s.)
time(min)
Exp 1Exp 2Exp 3
I II III
01234560
0.2
0.4
0.6
0.8
1
Exp.2
Exp.9
M [g H2O/g ss]
aw
Phase I Phase II
Phas
e II
I
0
0.2
0.4
0.6
0.8
1
0246
aw
M [g H2O/g ss]
Exp.2
Exp.9
Phase I Phase II
Phase
III
