Food Irradiation Current Research and State of the Art

1
Food IrradiationCurrent Research and State of
the Art

• Brendan A. Niemira, Xuetong Fan, Christopher H.
  Sommers, Ignacio Alvarez
• United States Department of Agriculture
• Agricultural Research Service
• Eastern Regional Research Ctr.
• Wyndmoor, PA, USA

2
Food Irradiation

• Overview and brief comparison of food irradiation
  technologies
• Research areas
• Microbiology of irradiated produce
• Biofilms
• Sensory and quality properties
• Shell eggs and liquid egg products
• Ready to eat meats and prepared meals
• Toxicology
• Summary

3
Food Irradiation - Overview

• Treatment of meats, seafood and produce with
  high-energy particles (gamma, X-ray, E-beam)
• inactivate insect pests
• eliminate spoilage organisms and human pathogens
• extend shelf life
• 60 years of research by governments, industry
  and academia
• Irradiated food is safe, wholesome and nutritious
• Endorsed by leading public health organizations
  (WHO, USDA, FDA, FSIS, ADA, CDC, etc.)

4
How is food irradiated?

• Product to be irradiated is handled with the same
  care and attention to cleanliness as ever
• Irradiation is intended to complement, not
  substitute for, proper food handling procedures
• Product is exposed to high energy electrons or
  high energy photons, either on-site, or at
  another location
• Contracting, shipment, transshipment add costs to
  final product

5
Electron beam
6
X-rays
High-density metal target (must be cooled)
7
Gamma rays
Radioactive material cobalt-60 or cesium-137
8
Technologies - Summary
9
Mode of Action

• Largest target in organisms is water
• High energy electrons break water molecules into
  OH and O radicals, which disrupt membranes,
  proteins and nucleic acids
• DNA is also broken directly
• High energy photons interact with atoms to eject
  high energy electrons
• Penetration of photons is much greater than for
  electrons - implications for how material is
  processed

10
The Max/Min Ratio
Maximum dose
(GROUND BEEF PATTIES)
Minimum dose
11
The Max/Min Ratio

• Packaging is appropriate
• complete penetration of e-beam from above and
  below
• relatively even dosage, low Max/Min ratio
• Improper packaging processing - too thick!
• incomplete penetration of e-beam
• uneven dosage, high Max/Min ratio

12
Microbiology of Irradiated Produce
13
Response and efficacy

• Lettuce
• D10 values on shredded iceberg lettuce
• E. coli O157H7 0.11 kGy
• Salmonella 0.2 kGy (Goularte et al., 2004, Rad
  Phys Chem 71155-159)
• D10 values on green leaf lettuce
• NalS E. coli O157H7 0.18 kGy
• NalR E. coli O157H7 0.10-0.12 kGy (Niemira
  2005. J. Food Sci 79(2)M121-4)
• 5.5 kGy chlorination 5.4 log reduction of E.
  coli O157H7 (Foley et al., 2002. Rad Phys Chem
  63391-396.)

B. Niemira
14
B. Niemira
15
Post-irradiation phenomena

• Endive
• L. monocytogenes regrew to control levels in
  storage following 0.42kGy (a 2 log10 reduction).
• Higher dose (0.84 kGy) suppressed the pathogen
  throughout the 19 d of the storage period
  (Niemira et al., 2003. J Food Prot 66993-998.)

L. mono.
TAPC
B. Niemira
16
Post-irradiation phenomena

• Respiration rates of most MAP vegetables are not
  significantly affected by low dose irradiation
• changes to packaging are not indicated
• Endive MAP
• Dose equivalent to 1-3 log10 reductions allowed
  regrowth of L. monocytogenes
• Irradiation reduced-O2, enhanced-CO2 packaging
  scheme effectively suppressed this capacity, and
  prevented the pathogen from regrowing. (Niemira
  et al., 2004. Rad Phys Chem 72(1)41-48.)

B. Niemira
17
L. mono. on endive Irradiation MAP
B. Niemira
18
Biofilms the great unknown

• Phytoplane bacteria are biofilm associated
• Biofilms protect against chemical and many
  physical antimicrobial processes
• Often requires 10x, 100x, 1000x exposure to get
  equivalent kill
• Planktonic and biofilm-associated Salmonella are
  equally susceptible to irradiation (Niemira and
  Solomon. 2005. Appl. Environ. Microbiol.
  71(5)2732-2736)
• Effect on structure? Attachment strength?
  Efficacy of co-applied antimicrobials?

B. Niemira
19
Irradiated biofilms

• Irradiation changes the internal structure of
  Salmonella biofilms
• shifts in region of highest density
• cell distributions
• Behavior of commensal background microflora
  biofilms not known

B. Niemira
20
Biofilms the great unknown

• Response of other pathogen biofims
• Complex microecologies
• mixed species biofilms of pathogens
  commensal/phytoplane background organisms
• recovery, injury repair, regrowth, predation,
  competition?
• Synergy of multiple interventions
• Substrate effects

21
Sensory and Quality Attributes of Irradiated Foods
22
Dose Threshold and Endogenous Antioxidant
Capacity of Fresh-cut Vegetables
X. Fan
23
X. Fan
24
Nutritional Quality of Alfalfa Sprouts Grown
from Irradiated Seeds
X. Fan
25
X. Fan
26
Volatile Sulfur Compounds from Turkey Bologna
Irradiated at 0 and at 3 kGy
5
4
2
3
1
6
X. Fan
27
Irradiation-Induced malondialdehyde,
formaldehdye, and acetaldehdye in Fresh Apple
Juice
X. Fan
28
Irradiation and Heat Treatment of Whole and
Liquid Eggs
29
Irradiation of eggs background
Eggs and egg products are responsible for an
estimated 230,000 cases of foodborne illnesses
each year, resulting in economic losses and
representing a consistent and serious obstacle to
the well-being of consumers Salmonella and mainly
serovar Enteritidis is the leading cause of all
egg-related foodborne illnesses Ionizing
radiation can inactivate Salmonella spp. in shell
eggs and egg products.
I. Alvarez
30
137Cs irradiator, dose rate of 0.095 kGy/min, 4ºC
I. Alvarez
31
137Cs irradiator, dose rate of 0.095 kGy/min, 4ºC
I. Alvarez
32
Shell eggs - US FDA Approves Irradiation of Shell
Eggs 3.0 kGy (21 CFR Part 179, vol. 65, No.
141, p. 45280) - Problem Internal quality
properties decreases with irradiation dose.
0 kGy
0.3 kGy
0.5 kGy
2.0 kGy
3.0 kGy
1.0 kGy
Will consumers accept IR shell egg?
I. Alvarez
33

• Egg products LIQUID WHOLE EGG
• Heat pasteurization to obtain Salmonella-free
  LWE 60ºC/3.5 min (FDA) (CFR 590.570, p. 765).
• Very heat resistant Salmonella serotypes
• More intensive treatments reduce LWE quality
  (57ºC coagulation of some soluble proteins)

I. Alvarez
34

• Egg products LIQUID WHOLE EGG
• 3.0 kGy enables to reduce 9 log cycles
  population of Salmonella.
• However, doses gt 1.5 kGy reduce LWE quality
  properties (color, off-flavor)
• HEAT followed by IRRADIATION additive lethal
  effect not available equipment for the
  industrial process
• - IRRADIATION followed by HEAT
• - synergistic lethal effect
• - most viable immediate industrial option
• - available equipment for the industrial process

LWE
Heat pasteurizer
Holding tuve
I. Alvarez
35
Egg products LIQUID WHOLE EGG COMBINING
TREATMENTS IRRADIATION followed by HEAT -
synergistic lethal effect - most viable
immediate industrial option available equipment
for the industrial process
I. Alvarez
36
Egg products LIQUID WHOLE EGG - COMBINING
TREATMENTS IRRADIATION followed by HEAT
MODELIZATION OF THE COMBINING TREATMENTS
Salmonellainactivation IR/0.67 kGy
Time/(299-9.8T0.08T24.4IR0.07IRT) T
temperature (55 57ºC) IR irradiation
dose (0.1 1.5 kGy)
Dotted and thick lines represents the TDT curves
for Salmonella Enteritidis-Typhimurium and for
Senftenberg, respectively.
Combinations time-temperature to inactivate 5 log
of any Salmonella Enteritidis, Senftenberg or
Typhimurium
I. Alvarez
37
Irradiation HeatSalmonella enteritidis

• (A) Non-treated native cells
• (B) subcultured cells after 1.5 kGy
• (C) subcultured cells after 1.5 kGy and 55ºC/21
  min
• (D) subcultured cells after 1.5 kGy and 60ºC/2
  min.

I. Alvarez
38
Egg products LIQUID WHOLE EGG COMBINING
TREATMENTS - IRRADIATION followed by HEAT in LWE
added with ADDITIVES - Nisin - Nisin
carvacrol - Carvacrol - EDTA carvacrol -
EDTA - EDTA nisin - Sorbic acid - EDTA
nisin carvacrol
I. Alvarez
39
Microbiological Safety of Irradiated Ready-To-Eat
Foods
40
Irradiated Ready to Eat Meals

• Reduction of pathogens in complex ready-to-eat
  (RTE) foods
• deli meats, assembled meals, sandwiches
• New challenge from a food safety standpoint
• highly processed
• typically eaten with little or no preparation
• must have a low in-package risk profile
• Influences on efficacy
• composition of meal
• physical location of the contaminating bacteria

C. Sommers
41
Proliferation of L. monocytogenes on beef fine
emulsion sausage at 0. 1.5 and 3.0 kGy during 8
weeks refrigerated storage (9oC).
L. monocytogenes can proliferate following a
radiation dose of 1.5 kGy, that provides a 2.5
log reduction, but not at 3.0 kGy, a 5 log
reduction. Sommers et al. 2003. J Food Prot.
66(11)2051-2056
C. Sommers
42
Proliferation of L. monocytogenes on beef fine
emulsion sausage that contains sodium diacetate
and potassium lactate at 0. 1.5 and 3.0 kGy
during 8 weeks refrigerated storage (9oC).
Use of 0.15 sodium diacetate and 2 potassium
lactate prevents growth of L. monocytogenes and
spoilage bacteria in combination with irradiation
during long-term storage. Sommers et al. 2003. J
Food Prot. 66(11)2051-2056
C. Sommers
43
How virulent is irradiated Listeria
monocytogenes? L. monocytogenes inoculated onto
beef frankfurters, irradiated, and plated on
blood agar to assess function of the hylA
(hemolysin) virulence gene.
Significant inactivation of hlyA was achieved
only at radiation dose (gt2 kGy) sufficient to
achieve a 3-4 log reduction of the pathogen.
Sommers et al. 2003. J Food Prot.
66(11)2051-2056
C. Sommers
44
Toxicological Safety of Irradiated Foods
45
Toxicological Safety

• Irradiated foods have tested exhaustively
• Numerous short-term, medium-term and long-term
  (multigenerational) animal feeding studies
• Chemical and biochemical analyses
• WHO determined in 1998 that foods treated at any
  dose posed no exceptional risk to consumers
• As chemical analysis methods improve, the debate
  on the toxicological safety of irradiated foods
  continues.

C. Sommers
46
Toxicological Safety

• IR induces changes in the chemistry of treated
  foods
• formation of chemical byproducts, some of which
  are known toxins
• Vast majority of radiolytic products are also
  found in unprocessed foods and in foods treated
  with conventional processing techniques
• Unique radiolytic products, i.e. chemicals
  byproducts which are only formed in foods by IR,
  have been a topic of recurrent attention.

C. Sommers
47
Toxicological Safety

• 2-alkylcyclobutanones (2-ACBs)
• Generated at low levels in irradiated meats and
  poultry
• Observed to cause damage to DNA under certain
  laboratory conditions
• Most significant is 2-dodecylcyclobutanone (2-DCB)

C. Sommers
48
Genotoxicity of 2-dodecylcyclobutanone (2-DCB)

• Produced by irradiation of fat containing
  foods.1
• 0.1 0.2 mg/g of fat in meats.
• Produced equivocal results for genotoxicity in
  the Comet Assay.2, 3

• LeTellier and Nawar. (1972) Lipids. 1 75-76.
• Delincee and Pool-Zobel. (1998) Radiat. Phys.
  Chem. 52 39-42.
• Delincee et al. (1999) Lebensmittelbestralung 5.
  Deustche Tagung, Kahlruhe, Behichte der
  Bundesforcheshungsanstalt fur Ernarung.
  BFE-R99-01. 11- 12 Nov. 1999, pp 262 269.

C. Sommers
49
Toxicological Safety

• 2-dodecylcyclobutanone (2-DCB)
• review of literature suggests that improper tests
  do not allow any conclusions to be drawn(Smith
  and Pillai. 2004. Food Technology. 58 (11),
  48-55.)
• analysis using more appropriate tests indicates
  no meaningful risk posed (Sommers and Mackay.
  2005. J Food Sci. 70C254-257)
• In vitro toxicology is one piece of information
• accurate, appropriate tests are essential
• Many factors determine actual potential for risk

C. Sommers
50
Summary

• Irradiation has shown promise to improve the
  safety, sensory properties and shelf-life of a
  wide variety of foods
• An underutilized tool
• Consumer understanding, acceptance is key
• Challenge for processors and food scientists
  derive benefits within limitations of technology
• Singly or in combination with other treatments
• Varying preparation methods, storage conditions,
  and market forces

51
Resources for more information

• IFT - Scientific Status Summary
• http//www.ift.org/publications/docshop/ft_shop/11
  -04/11_04_pdfs/11-04-sss-irradiation.pdf
• USDAs Food and Nutrition Service
• www.fns.usda.gov/fdd/foodsafety/irradiation
• CDC
• www.cdc.gov/ncidod/dbmd/diseaseinfo/foodirradiatio
  n
• FDA
• www.fda.gov/opacom/catalog/irradbro
• American Medical Association, National Food
  Processors Association, American Dietetic
  Association, many others

52
Resources for more information

• USDA-ARS-ERRC Food Safety Intervention
  Technologies Research Unit
• Dr. Howard Zhang, Research Leader
• http//www.arserrc.gov/www/fsit/
• Food irradiation group
• Dr. Brendan A. Niemira (bniemira_at_errc.ars.usda.gov
  )
• Dr. Xuetong Fan
• Dr. Christopher Sommers

53
USDA-ARS - Eastern RegionalResearch Center,
Wyndmoor, PA
54
(No Transcript)