Bacterial Inactivation in Apple
Juice by UV-light and Radio
Frequency Electric Fields
Processing
Eastern
Regional
Research
Center
Dike O. Ukuku Ph.D.
FSIT-ERRC-ARS-USDA
Wyndmoor, PA 19038
Human bacterial pathogens
 Escherichia coli O157:H7, Listeria
monocytogenes and Salmonella are
recognized foodborne pathogens and are
capable of surviving in low acid foods like
fruit juices
 Outbreaks involving E. coli O157:H7 in apple
cider and Salmonella in orange juices have
raised concerns about the safety of
consuming unpasteurized fruit juices
2
Foodborne Illness in the U.S.
 76 million illnesses each year
 325,000 hospitalizations
 5,200 deaths
 $3 Billion in hospitalizations
 $20-40 Billion = lost productivity
3
Recent outbreaks of E. coli O104:H4 linked to
contaminated organic bean sprouts
(Bill Marler, 23, June , 2011)
The European Union
 3798 sickness, 865 with HUS cases, 2,930 with non-HUS
cases, 44 deaths reported
 Source : http://www.marlerblog.com/legal-cases/new-world-wide
4
USA
 5 confirmed cases (Three with HUS) connected to
the outbreak (Michigan, Massachusetts, Wisconsin
and North Carolina)
 * 1 death in Arizona linked to the outbreak
Japan
 In May of 2011 there was E. coli O111 outbreak
 90 people sick, 23 with hemolytic uremic syndrome
4 deaths tied to a raw beef dish called yukhoe
5
Processing treatments for juices
 Physical and chemical treatments have been
used in food processing to eliminate or at
least reduce the presence of pathogenic and
spoilage microorganisms in foods
 Thermal processing is used by the juice
industry to inactivate food borne pathogens
however; it impairs the characteristic flavor
of juices
6
Objective
 To develop, evaluate, validate, recommend
and transfer post-harvest handling
intervention technologies to enhance the
quality and safety of the nation’s food
supplies
7
Fig 2: Enhancing Food Safety
An Integrated Approach
Outbreaks /
Contamination
Detection
Processing
and Interventions
Characterization
Safe Foods
8
Technologies in use
 Pulsed electric fields
 Radio frequency electric fields
 UV and pulse light
 Super-critical carbon dioxide
 High hydrostatic pressure
 Ohmic heating
 HTST/UHT, TDT devices
 Aseptic Processing and Packaging
9
Fig 3: Radio Frequency Electric Fields
Processing
80 kW RFEF Unit –
World’s most powerful
Operates at 20, 30,
and 40 kHz
Voltage
Eastern
Regional
Research
Center
Voltage
Similar to Pulsed
Electric Field
Time
Time
Modification of UV-light equipment
 A UV apparatus was assembled at the Eastern
Regional Research Center, Agricultural Research
Services of United States Department of Agriculture
with slight modification (Geveke, 2008)
 The UV lamp was surrounded by a coil of tubing
instead of having the tubing surrounded by UV lamps
 The apple juice flowed through the UV transparent
Chemfluor tubing. One, two, three, or four UV bulbs
were used in series, depending on the experimental
condition.
11
Ultraviolet light equipment
12
Effect of RFEF treatment on the survival and injured
populations of E. coli cells in apple juice
Ukuku et al., 2008 J. Food Prot.71:684-690
Injured populations in apple juice
9
80
8
70
7
6
5
TSA
60
SMAC
50
4
3
2
% Injury
Survivors (log10 CFU/ml)
Survival of E. coli cells in apple juice
No-RFEF
RFEF
40
30
20
1
10
0
0
27
40
45
Temperature (oC)
50
55
0
0
27
40
45
50
55
60
Temperature (C)
13
Damage to membrane surface structure of bacteria by
RFEF treatment led to leakage of intracellular ATP
[SEM (Figure 1, A= Control, B=40C, C= 50C and D= 55C)] Ukuku et al., 2008 J. Food Prot.71:684-690
Extracellular ATP (log10 fg/ml)
6
Log/ATP (fg/ml)
5
4
3
2
1
0
23
27
40
45
50
55
60
Temperature (oC)
14
Inactivation, log cfu/ml
UV-light inactivation of E. coli in liquid eggs
5
4
D = 37 s
3
2
1
0
0
50
100
150
200
Treatment Time, s
15
Survival and percent injury by RFEF treatment
9
120
100
7
6
80
5
60
4
Log CFU/mL
3
40
Percent injury
Survivors (log CFU/mL)
8
Percent injury
2
20
1
0
0
0
23
30
40
16
Effect of combined UV-light and RFEF treatment
9
120
8
7
6
80
5
60
4
3
40
Percent injury
Survivors (log CFU/mL)
100
2
RFEF+UV-light
20
Percent injury
1
0
0
0
23
30
40
Treatment temperature C
17
TEM observation of E. coli cells
C= RFEF+55C
(A= control; B= Heat@75C;
A
B
C
___
0.5 µm
18
Leakage of UV-materials at 260 nm
0.4
R² = 0.865
Absorbance at 260 nm
0.35
0.3
R² = 0.9676
0.25
R² = 0.9304
0.2
0.15
RFEF
0.1
UV-light
0.05
UV-light & RFEF
0
0
5
10
15
20
25
30
35
40
45
-0.05
-0.1
Temperature C
19
CONCLUSION
 The results of this study clearly showed the
differences in bacterial inactivation by UV
light alone, RFEF treatment and a combine UV
light + RFEF treatment
 Proper modifications of treatment parameters
is likely to improve process treatment and
enhanced the microbial safety of treated
juices

20
 A combination of the two processing
treatments did not increase cell injury or
leakage of UV-substances
 Mechanism of bacterial inactivation by RFEF
treatment is different from UV-light treatment
 RFEF treatment caused more membrane
injury and cellular leakage of UV-substances
than UV-light treatment
21
Process commercialization/products
22
Acknowledgments
 Dr. Howard Zhang
 Dr. John Phillips
 Dr. David Geveke
 Dr. Ms. Donyel M. Jones,
 Mr. Lee Chau
For more information
Contact:
Dr. Dike O. Ukuku
Senior Scientist, FSIT- ERRC- ARS-USDA
600 E. Mermaid La, Wyndmoor, PA 19038
215-233-6427, Fax 215-233-6406
[email protected]
http://www.ars.usda.gov/naa/errc
24