TUVP+HHP

IAFP's European Symposium on Food Safety - Budapest
Combined effects of TiO2-UVC photocatalytic reaction
and high hydrostatic pressure on inactivation of
E. coli O157:H7 on orange surface and juice
May 09, 2014
Sungyul Yoo*, Sanghun Kim, Sunghyun Lee,
Jinho Cho, Jiyong Park
Department of Biotechnology
Introduction
2
Comparison of surface decontamination methods
Thermal
processing
Fresh
produce
Sodium
hypochlorite
(Chlorine)
TiO2-UVC
Photocatalytic
reaction
• Effective bacterial
inactivation
• Degradation of quality
• Off-flavor, discoloration
undesirable texture
• Short bactericidal
inactivation effect
• Need water rinse to
eliminate residual chlorine
• Effective bacterial
inactivation
• No residual material and
simple process
• No deterioration in quality
of food
3
Titanium dioxide (TiO2)
• TiO2 provides whiteness (pigment) and opacity to products such as
paints, coatings, plastics, papers, inks, foods (e.g., white chocolate),
medicines (e.g., pills and tablets), toothpastes as well as cosmetics (UV
protection sunscreen).
• TiO2 is widely used as a photocatalyst due to its nontoxicity, chemical
stability, capability for repeated use without the loss of catalytic activity,
and absence of waste.
• The TiO2 photocatalytic reaction generates hydroxyl radicals, and the
hydroxyl radicals have far more oxidizing power (2.80 V) than ozone (2.07
V), hydrogen peroxide (1.78 V), hypochlorous acid (1.49 V), and chlorine
(1.36 V) (Srinivasan and Somasundaram Curr. Sci. 85:1431–1438, 2003)
• TiO2 under UV lights exhibits a strong bactericidal activity; two killing
modes were proposed:
1. The oxidation of coenzyme A inhibiting cell respiration
2. The significant disorder in cell membrane permeability
4
TiO2–UV photocatalysis (TUVP)
• Electron-hole pairs, an electron in a conduction band (e-cb) and a hole
in a valence band (h+vb), are generated on the TiO2 photocatalyst
surface by UV radiation
• The e-cb changes oxygen to a hydroxyl radical via the reductive
pathway, and h+vb changes hydroxyl ions or water to hydroxyl radicals
via the oxidative pathway.
H2O
H2O2
O3
O2·
TiO2
e-cb
·OH
Hydroxyl radicals
Conduction Band
O2
Electron
Excitation
Photon
(hν < 387.5 nm)
3.2eV Recombination
Valence Band
·OH
CO2
h+vb
OHH2O
C2H4
5
TUVP reactor
1st generation
2nd generation
6
TUVP reactor
3rd generation
4th generation
7
Previous TUVP researches
Cho et al. (2007) Journal of Food Protection 70(1): 97-101
8
Previous TUVP researches
Kim et al. (2009) Journal of Food Protection 72(9): 1916-1922
9
Previous TUVP researches
Effects of different nonthermal disinfection methods on counts of
total aerobic bacteria on fresh produce
Treatment
NaOCl
Electrolyzed water
Ozonated water
Citrate + ascorbate
Citric acid
Lactic acid
TiO2-UV
UV
TiO2-UV
UV
NaOCl
Fresh produce
Romaine lettuce
Spinach
Cucumber
Strawberry
Iceberg lettuce
Cucumber
Strawberry
Cucumber
Strawberry
Iceberg lettuce
Iceberg lettuce
Iceberg lettuce
Iceberg lettuce
Carrot
Carrot
Iceberg lettuce
Iceberg lettuce
Iceberg lettuce
Condition
600 ppm
600 ppm
151 ppm
151 ppm
100 ppm
32 ppm
32 ppm
5 ppm
5 ppm
4 ppm
0.25% citrate + 0.5% ascorbate
5,000 ppm
5,000 ppm
254-nm UV, 16 mW/cm2
254-nm UV, 16 mW/cm2
254-nm UV, 35 mW/cm2
254-nm UV, 35 mW/cm2
150 ppm
Maximum log reduction
0.5
0.3
1.2
0.8
1.6
1.4
0.8
0.7
0.4
1.6
1.0
1.7
1.6
1.8
1.1
2.5
1.1
1.0
Kim et al. (2009) Journal of Food Protection 72(9): 1916-1922
10
High hydrostatic pressure (HHP)
 High hydrostatic pressure (HHP) is a promising non-thermal
technology that has gained an increasing application over the last
15 years due to an ability to preserve nutritional and sensory
characteristics and to improve the overall quality of foods.
 Fruit juices, such as orange juice, are normally treated at 400 MPa
to 600 MPa for few minutes at low temperatures to reduce the
numbers of spoilage microorganisms and to prolong the products
shelf-life.
 Foods subjected to HHP treatment will not undergo significant
chemical transformations.
11
Previous TUVP-HHP research
TUVP
+
HHP
Chai et al. LWT-Food Science and Technology 55: 104-109 (2014)
12
Previous TUVP-HHP research
yeasts and molds
Control
TUVP
HHP TUVP+HHP
coliform bacteria
Control
TUVP
Pseudomonas
Control
TUVP
HHP TUVP+HHP
HHP TUVP+HHP
Bacillus cereus
Control
TUVP
HHP TUVP+HHP
The effects of TiO2-UV photocatalysis (TUVP), HHP, and a combination of TUVP
and HHP (TUVP+HHP) on microbial inactivation in Angelica keiskei juice.
Chai et al. LWT-Food Science and Technology 55: 104-109 (2014)
13
E. coli O157:H7
 Escherichia coli O157:H7 is an enterohemorrhagic serotype of the
bacterium Escherichia coli and a cause of illness, typically through
consumption of contaminated food.
 Pressure resistant pathogen.
 It can survive in juice with a low pH, especially at low temperature
conditions.
14
Pesticide residues
Carbaryl
 Carbamate family.
 The third most used
insecticide in United
States.
Picture: What’s on my food (http://www.whatsonmyfood.org/food.jsp?food=OG)
United Stated Department of Agriculture (USDA) Pesticide Data Program (PDP)
15
Current HHP orange juice production process
Brushing/Air-drying
Air cleaning
Chlorine disinfection
Water Rinsing
Half slicing
Air bubble
Air bubble
Squeeze
HHP
treatment
Orange
juice
HHP orange juice
16
Suggested TUVP & HHP orange juice production process
Brushing/Air-drying
Air cleaning
TiO2-UVC photocatalysis/
Water rinsing
Half slicing
Air bubble
Squeeze
HHP
treatment
Orange
juice
TUVP & HHP orange juice
17
Advantages of TUVP & HHP process
in orange juice production
 Simpler process
 No residual chemicals
 No cross-contamination of chemicals (e.g.
chlorine) and microorganisms
 Environment-friendly process
 Prolonged shelf-life than HHP orange juice
18
Objectives
 Determinate the effect of TiO2-UVC photocatalysis (TUVP) as a
surface decontamination method on E. coli O157:H7 inoculated
orange surface
 Evaluate the optimum pressure to totally inactivate crosscontaminated E. coli O157:H7 in freshly squeezed orange juice
after the surface decontamination treatments
 Determine the applicability of non-linear models by subjecting the
survival curves after the combined treatments
 To evaluated the effect of the optimized treatments on the quality
of the juice
19
Materials & Methods
20
TiO2-UVC Photocatalysis (TUVP) reactor
 Working volume: 28 L
 Wavelength of UV: 254 nm
 Six UVC lamps (30 W),
 Actual dose:
 Air pump
- UVC : 23.7 mW/cm2
 Each lamp is surrounded by TiO2
coated quartz tube
- TUVP : 17.2 mW/cm2
21
High hydrostatic pressure (HHP)
 Working pressure: 50 MPa to 600 MPa
 Working temperature: 25 °C
 Holding time: 1 min
HHP 600 MPa/5L, BaoTou, Kefa, China
22
Mathematical models and assessment
• Biphasic model
𝑙𝑙𝑙10 𝑁 = 𝑙𝑙𝑙10 𝑁0 + 𝑙𝑙𝑙10 (𝑓𝑒 −𝑘𝑚𝑚𝑚𝑚 𝑡 + (1 − 𝑓)𝑒 −𝑘𝑚𝑚𝑚𝑚 𝑡 )
𝒇 : fraction of the sensitive population
(𝟏 − 𝒇) : fraction of the resistant population
𝒌𝒎𝒎𝒎𝒎 : Inactivation rates of the sensitive population
𝒌𝒎𝒎𝒎𝒎 : Inactivation rates of the resistant population
𝒕 : treatment time (min)
Sensitive population
𝒌𝒎𝒎𝒎𝒎
Resistant population
𝒌𝒎𝒎𝒎𝒎
• Weibull model
𝑙𝑙𝑙10 𝑁 = 𝑙𝑙𝑙10 𝑁0 − 𝑏𝑡 𝑛
𝒃 : scale factor
n : shape factor
t : treatment time
23
Microbial analysis of surface decontaminated oranges
Orange
Washing/drying
Initial count of E. coli O157:H7
Spot inoculation: 7.0 log CFU/cm2
Spot inoculation
Surface decontamination
treatment
0, 1, 3, 5, 10, 20 min
TUVP
UVC
Chlorine
Water bubble
Recovery
Enumeration
TUVP-Surface
UVC-Surface
Chlorine-Surface
Water bubble-Surface
24
Microbial analysis of surface decontaminated oranges
Orange
Washing/drying
Inoculation
Initial count of E. coli O157:H7
Immersion: 5.0 log CFU/mL
Surface decontamination
treatment
0, 1, 3, 5, 10, 20 min
TUVP
UVC
Chlorine
Water bubble
Squeezing
Packaging
Orange juice
TUVP treated juice
UVC treated juice
Chlorine treated juice
Water bubble treated juice
HHP treatment
TUVP-HHP treated juice
UVC-HHP treated juice
Chlorine-HHP treated juice
Water bubble-HHP treated juice
Orange juice
25
Results & Discussion
26
Surface decontamination effects of TUVP, UVC,
chlorine, and water bubble on E. coli O157:H7
inoculated orange surfaces
1
TUVP
UV
Water bubble
Chlorine (200 ppm)
0
log N / N0
-1
-2
-3
-4
-5
0
5
10
15
20
Time (min)
 TUVP treatment inactivated E. coli O157:H7 to 4.08 log CFU/mL, whereas
UVC, chlorine, and water bubble treatment inactivated 3.63, 3.90, and 1.51
log CFU/mL, respectively.
27
Surface decontamination effects of TUVP, UVC,
chlorine, and water bubble on orange juice from E. coli
O157:H7 inoculated orange
0.5
TUVP
UV
Water bubble
Chlorine (200 ppm)
log N / N0
0.0
-0.5
-1.0
-1.5
-2.0
0
5
10
15
20
Time (min)
 After surface decontamination treatment, oranges were freshly squeezed
to evaluate the cross-contaminated E. coli O157:H7 in orange juice.
 TUVP inactivated 1.67 log CFU/mL, whereas, 0.95, 1.39, and 0.93 log
CFU/mL was inactivated by water bubble, chlorine (200 ppm), and UVC
treatment, respectively.
28
Effects of TUVP+HHP on the inactivation of E. coli
O157:H7 in fresh squeezed orange juice
Initial count: 4.7 log CFU/mL
TiO2-UVC photocatalysis (
), HHP (
), synergistic effect (
).
TUVP treatment prior to HHP, total E. coli O157:H7 inactivation (4.7
log CFU/mL) was achieved at 400 MPa, whereas, at the same
pressure 2.79, 3.83, and 3.29 log CFU/mL reduction was achieved
when treated with water bubble, chlorine (200 ppm), and UVC,
respectively (P < 0.05).
29
Modeling the inactivation kinetics of E. coli O157:H7 on surface
decontaminated oranges
Biphasic model
Initial count:
7.0 log CFU/cm2
Inoculated orange
Surfaces
𝒌𝒎𝒎𝒎𝒎
𝑹𝟐
MSE
Water bubble
0.9514±0.0062
3.71±0.35
0.02±0.01
0.9978
0.0419
Chlorine
0.9959±0.0006
5.84±0.29
0.17±0.01
0.9995
0.0481
UVC
0.9963±0.0032
8.91±1.86
0.13±0.05
0.9789
0.2839
TUVP
0.9987±0.0011
5.29±1.03
0.15±0.05
0.9856
0.2816
Model parameter ± SD
𝒌𝒎𝒎𝒎𝒎
𝒌𝒎𝒎𝒎𝒎
𝑹𝟐
MSE
Initial count:
5.0 log CFU/mL
Orange juice from
inoculated oranges
𝒇
Model parameter ± SD
𝒌𝒎𝒎𝒎𝒎
𝒇
Water bubble
0.8956±0.0547
2.41±0.35
0.02±0.01
0.9949
0.0397
Chlorine
0.9663±0.0094
4.07±0.76
0.00±0.02
0.9907
0.0907
UVC
0.9215±0.0123
2.80±0.54
0.00±0.01
0.9347
0.0510
TUVP
0.8956±0.0547
2.56±1.13
0.08±0.03
0.9666
0.1707
All data were the means±SD, n=3. Different lowercase letters in the same column indicate a significant difference (P < 0.05).
 The 𝑓 values had no significant difference (P > 0.05) between four different
treatments, which means that the fraction of the sensitive population was
not influenced by the treatments.
 UVC showed highest 𝑘𝑚𝑚𝑚𝑚, demonstrating that it showed fastest
inactivation rate of the sensitive population.
30
Modeling the inactivation kinetics of E. coli O157:H7 on surface
decontaminated oranges – Inoculated orange surfaces
Water bubble
Chlorine
0.00
5.00
10.00
15.00
20.00
-1.00
log (N/N 0)
log (N/N0)
-1.00
0.00
0.00
-2.00
-3.00
-4.00
0.00
20.00
15.00
20.00
-3.00
-5.00
Time (min)
Time (min)
TUVP
0.00
0.00
0.00
5.00
10.00
15.00
20.00
-1.00
log (N/N 0)
log (N/N 0)
15.00
-2.00
UV
-2.00
-3.00
0.00
5.00
10.00
-2.00
-3.00
-4.00
-4.00
-5.00
10.00
-4.00
-5.00
-1.00
5.00
-5.00
Time (min)
Time (min)
31
Modeling the inactivation kinetics of E. coli O157:H7 on surface
decontaminated oranges – Orange juice from inoculated orange
Water bubble
Chlorine
0.00
0.00
0.00
5.00
10.00
15.00
20.00
0.00
-1.00
-1.50
15.00
20.00
15.00
20.00
-1.00
-1.50
-2.00
-2.00
Time (min)
Time (min)
UV
TUVP
0.00
0.00
0.00
5.00
10.00
15.00
0.00
20.00
5.00
10.00
-0.50
log (N/N 0)
-0.50
log (N/N 0)
10.00
-0.50
log (N/N 0)
log (N/N 0)
-0.50
5.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
Time (min)
Time (min)
32
Pesticide (carbaryl) reduction by TUVP
70
Reduction (%)
60
50
40
30
20
10
0
40
70
80
Time (min)
 Over 60% of carbaryl reduction was observed after TUVP reaction
for 80 min.
33
Conclusion
34
 TUVP is a promising non-thermal technology for surface
decontamination of fruit surfaces.
 TUVP surface decontamination treatment prior to combined
treatment of HHP of freshly squeezed orange juice increased the
efficacy for the inactivation of E. coli O157:H7.
 A TUVP surface treatment (17.2 mW/cm2) of 20 min and HHP
pressure 400 MPa allowed reaching 5-log reductions of E. coli
O157:H7 in the final orange juice product.
 Inactivation kinetics of surface decontaminated treatment on E.
coli O157:H7 inoculated oranges were well fitted to the biphasic
model.
 Carbaryl residues were reduced to over 60% of initial dose after
treating with TUVP for 80 min.
35
Thank you
for your attention!

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