Institute for Food Safety and Hygiene
Airborne organisms in the
dairy processing facility
Prof. Angelika Lehner, PhD
Institute for Food Safety and Hygiene (Director: Prof. Dr. R. Stephan)
University Zurich, Switzerland
www.ils.uzh.ch
Dr. Claudia Fricker-Feer
Head of Food Safety, Hochdorf Nutritec Ltd., Switzerland
www.hochdorf.com
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Institute for Food Safety and Hygiene
Table of Contents
– Introduction
– A recent study
– Risk of airborne contaminations
–
Sources and routes of airborne organisms
–
Hygienic plant design
–
Air filters
– Control measures
–
General air quality control
–
Hygienic equipment control
– Recommended target values
– Summary
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Introduction
Bioaerosols: contaminants of biological origin; 0.5 to 50 mm ;may
include bacteria, fungi viruses, pollen; are easily translocated by air
currents within a food processing unit (Stetzenbach et al., 2004, Lee,
2011).
When associated with dust/solid particles and condensation
droplets potentially pathogenic organisms my come in contact with
food products, equipments and containers.
 May be of natural or artificial origin: surface waters, dry soils,
agricultural activities, food processing e.g. powder production
Transport and ultimate settling are affected by the physical properties
and environmental parameters (air currents, humidity, temperature
Chao et al., 2002)
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A recent study (Brandl et al., 2014)
A detailed study on particle concentration measurements along
with the characterization of total culturable airborne bacteria as well
as yeast and mold contaminants within a Swiss dairy processing
facility was performed.
94 samples were collected at seven selected defined locations at
two seasonally different sampling dates.
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A recent study – Methods (I)
Milk processing facility and selection of sampling sites: The
study was conducted at the milk powder processing unit of a Swiss
Dairy plant located in Switzerland. Air samples were collected from the
seven different sites (P1 to P7) within the milk processing line
representing different hygienic zones.
Particle counting: Three handheld laser particle counters were used
to determine particle numbers. Four different size classes (0.3 to 0.5
µm, 0.5 to 1 µm, 1 to 5 µm, and >5 µm) of particles were measured.
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A recent study – Methods (II)
Impaction air sampling and cultivation: three “MAS-100 eco” impaction
samplers were applied for the collection of bioaerosols onto solid agar (AMC:
aerobic mesophilic count agar) surfaces 100 liters were collected in time
intervals of approximately 3 min.
MALDI-TOF-MS and taxonomical classification: bacterial samples were
spotted in duplicates on MALDI steel target plates. Protein mass fingerprints
were obtained using a MALDI-TOF Mass Spectrometry AximaTM Confidence
machine with detection in the linear positive mode at a laser
frequency of 50 Hz and mass range from 2,000–20,000 Da.
16S rRNA and rpoB gene sequence based taxonomical classification: in
cases where species determination by MALDI-TOF-MS was not successful.
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A recent study – Methods (III)
Figure 1:
Flowchart of
milk powder
production. P1
to P6 denote
sampling sites
along the
processing
line, P7
represents an
outdoor
reference site.
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A recent study – Results (I)
Numbers of culturable microorganisms were generally very low (<100
colony forming units, per m3 of air) during milk powder and powdered
infant formula (PIF) production.
The highest particle loads were observed again during filling, bagging or
final packaging. Larger particles (size class 1 to 5 µm,>5 µm) were present
in higher concentration.
High total particle counts in these size classes are seen to be associated
with elevated bioaerosol concentrations.
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A recent study – Results (I)
Table 1: Details
on the particle
counting
performed
for the seven
sampling sites.
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A recent study – Results (II)
47 during the February sampling and 47 during the July sampling colonies
isolated from AMC primary cultivation, randomly picked and subjected to MALDI-TOF
MS and/or 16S rRNA and/or rpoB gene based taxonomical identification.
A total of 25 bacterial genera were observed, with the majority belonging to the
Gram-positive genera Staphylococcus spp. and Bacillus sp. During winter,
Staphylococcus sp. were the dominant bacterial isolates found in the indoor and
outdoor environment with most isolates belonging to the species Staphylococcus
arlettae. During summer sampling, members of the genus Bacillus were
predominant.
4 different genera of Gram-negative bacteria were observed during winter time
sampling, whereas 9 different genera were observed during the summer time.
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A recent study – Results (II)
Table 2: Details on the bacterial
genus/species identification.
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A recent study - Conclusions
 Due to strict hygiene precautions total airborne particle counts much
lower in this processing plant compared to other industrial or nonindustrial locations.
 Highest particle loads were observed in areas where anthropogenic
activities and handling of goods take place (filling, bagging, packing).
 Correlation of total airborne particles in the size range of 1 – 5 mm
with numbers of cfu observed indicate that use of a simple
surveillance system by laser mediated counting of airborne particles
within a specified size range may be used in helping to evaluate the
effectiveness of the dairy plant’s sanitation program.
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Risk of airborne contaminations – sources and
routes of airborne organisms
employees
personal and
material flow
air
possible
(re-)contamination
no process
validation
water
process
media
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no hygienic
design
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Risk of airborne contaminations – hygienic plant
design
No production area, e.g.
logistics, labs
Standard production
area
Pressure gradients of at least
10-15 pascals (0.1-0.15mbar) –
high hygienic area with positive
pressure
High hygienic area
No turbulences
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Risk of airborne contaminations – hygienic plant
design
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Risk of airborne contaminations – air
changes/hour
 Rule: the less the particle concentration needs to be, the
higher the air exchange must be!
 Examples:
 Class C (acc. to PIC) = ISO 7 = Class 10’000 (acc. to US-FS
209b): 25-60 changes/hour
 Class D (acc. to PIC ) = ISO 8 = Class 100’000 (acc. to USFS 209b): 15-25 changes/hour
 Production areas: 10-30 changes/hour
 Lab: 8-15 changes/hour
 Storage rooms: 4-10 changes/hour
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Risk of airborne contaminations – hygienic plant
design
 Flow of goods  gates, de-wrapping
 Personnel flow  gates, change of shoes, clothes
 Elevators  separate for material and personnel
 Strict separation between dry and wet zone
 Air filtration systems (change of filters is related to differential
pressure according to supplier)
 Technical media (steam, water, air,…)
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Risk of airborne contaminations – air filters
 Air filters
Source: http://www.fischer-luftfilter.de/en/filter-classes/
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Risk of airborne contaminations – air filters
G1-G4
F5-F9
H11-H13
Coarse dust
Fine dust
High performance
particle filters
Filters for cooling of
large machinery,
compressors, air
conditioning and
ventilation systems.
Often used as prefilters for F-Filters
Filters for room
ventilation, switchgear
in food production,
spray drying towers
for milk powder
production. Often
used as pre-filters for
clean room facilities in
pharmaceutical
industry
Filters for spray drying
towers for infant
formula production,
micro-technology,
sterile benches in labs
and electronics. It’s
recommended to use
H-Filters for vacuum
cleaners
Source: http://www.fischer-luftfilter.de/en/filter-classes/
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Control measures – general air quality control
Sedimentation
Impaction
Sieve
Samplers
Impinger
Passive, nonvolumetric method
with petri dish which
is exposed to the
atmosphere (3060min)
Jet which draws air
into the sampler and
leads a known
volume of air to a
rotating petri dish.
1-6 stages of
perforated plates are
in front of an agar
plate. Constant flow
with defined volume.
Glass impinger
which leads the air
through a curved
tube. A suitable
liquid at the bottom
of the impinger
captures the
particles
Most primitive
method for sampling
airborne microorganisms;
Possible
desiccation; no
validation possible
Very common
method for air
sampling, e.g. 100l
of air. Possible
desiccation can
occur with higher air
volumes
With stacked sieve
impactors you can
collect data on
particle size as well.
Possible inefficiency
in collecting small
particles
Not a convenient air
sampling method,
glass in the
production, time
consuming, very low
flow rate  no
reliable validation
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Control measures – general air quality control
– Different systems in use  ISO 14698-1/2, Appendix B
provides a procedure to compare different systems (very time
consuming and expensive). Therefore it is important that you
always measure with the same system!
– Possible sampling procedure: outside air and defined
production areas, e.g. in dry zones (filling areas) but also in
microbiological labs  in minimum monthly measures
– Analysis for total plate count, yeast/moulds,
Enterobacteriacea
Source: http://www.micro4compounding.com/
cmss_files/attachmentlibrary/Micro4Compounding4.jpg
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Control measures – hygienic equipment control
– Analytics of vacuum cleaners: in minimum monthly for
Enterobacteriaceae, Salmonella spp., Cronobacter spp. (for
milk products for powdered infant formula)  risk based
analysis
– Tolerance values:
– Enterobacteriaceae: <100cfu/g  normal values, <1000cfu/g
 hygienic improvements necessary, >1000cfu/g  high
probability of pathogens
– Salmonella spp.: nd/25g
– Cronobacter spp.: nd/25g
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Control measures – hygienic equipment control
– Analytics of pressured air: once per month for total plate count
and oil traces (if there are not oil-free filters in use)
 risk based analysis
– Tolerance values:
– Total plate count: <10cfu/10l of air
– No oil traces on filter
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Control measures – hygienic equipment control
– It’s highly recommended to install not only a hygienic
monitoring for air borne micro-organisms (vacuum cleaners,
pressed air) but also for the following items:
– Different water qualities (drinking water, processing water,
condensed steam, iced water, rinsing water)
– Drains
– Employees (clothes, hands)
– Swabs after cleaning
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Recommended target values
– No official target values for food industry! (in Europe)
– Background: food processes don’t need sterile environment,
only sterile processes, e.g. aseptic filling lines with SIP/CIP
– Proposal of internal target value: e.g. outside bacterial load or
double outside bacterial load
– Pharmaceutical industry: clearly defined recommendations for
microbiology and for numbers of particles  Annex I of PIC/S
(Pharmaceutical Inspection Convention, Guide to Good
Manufacturing Practice for Medical Products, 1 March 2014)
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Recommended target values
Grade A = high risk operations, e.g. filling zones, open ampoules
Grade B = aseptic preparation and filling, environment of Grade A zones
Grade C/D = clean areas for carrying out less critical stages of sterile products
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Recommended target values
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Recommended target values (unofficially)
– Values < than double of outside air (outside air: Yeast and
Moulds: <1000cfu/m3, TPC: <500cfu/m3, EB: <10cfu/m3)
– These reference values are suitable for rooms without any
conditioned air, e.g. no filters.
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Summary
– Air borne re-contaminations are complex and influenced by
several factors, epidemiological studies are recommended to
provide.
– Beside airborne contaminations other factors such as water,
material flow, hygienic design and employees are relevant,
too. Therefore it’s necessary to establish a thorough
environmental monitoring.
– For milk powder use at least F7/9-filters, for high risk products
HEPA-filters are recommended.
– Use impaction or sieve sampling method for air sampling.
– Due to missing tolerance values in food industry, PIC
guidance can be helpful.
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