Blackwell Science, LtdOxford, UKFSTFood Service Technology1471-5732Blackwell Publishing Ltd, 200556776Original ArticleFood safety researchS. Rodgers
Peer review
Food safety research underpinning food service systems – a review
Svetlana Rodgers
School of Management, University of Western Sydney, Locked bag 1797, Penrith South DC, New South Wales, Australia
Abstract
Correspondence: Svetlana
Rodgers, Building 17,
Campbelltown campus,
UWS, Locked bag 1797,
Penrith South DC, New
South Wales and Australia
1797; Tel: +61 2 46 203522;
Fax: +61 2 46 203799; Email: s.rodgers@uws.edu.au
Keywords:
cook-chill, food safety, food
service systems, HACCP,
preservation hurdles
Food service systems allow the decoupling of food production from service and offer
economies of scale. However, the multiple steps in processing introduce additional
safety risks in comparison with the traditional preparation. Operators need to be
aware of the preservation principles and the type of data available in food safety
research. This paper provides justification and describes the link between different
types of studies in the field: surveys of background microflora, challenge studies, food
safety design, predictive modelling, hazard analysis critical control point (HACCP)
and good manufacturing practices (GMP). The needs and directions for further
research are identified.
Peer review
Modern food services are facing formidable and often
conflicting challenges: consumers demand higher quality food, governments require the guarantee of safety
and owners/shareholders seek increased profits. In
addition, environmental considerations are becoming
more important. Both the institutional and commercial
sectors rely heavily on economies of scale and the use
of ‘hard’ or equipment-based technologies. The developments in engineering and packaging offer a wide
range of options for bulk food production. Cook-hothold, cook-freeze and cook-chill (traditional and packaged) methods have been used to provide a ‘time buffer’
between production and consumption.
Often, central production units (CPUs) have spare
production capacity to supply external customers and
the retail sector (New South Wales Health Department
2005). The lack of confidence in food safety and limited
chilled distribution channels are some of the reasons of
this under-utilization. Consequently, even large organizations, such as Eurest Australia (http://www.eurest.
com.au/Home/index.html) and Gourmet Foods in the
US (Hauck 1992), freeze their products instead of
merely chilling them. In the UK, nearly 80% of sousvide (cooked-in-a-bag) products are frozen (Sheard
1999). Research on strengthening the food safety
design offers significant practical advantages in terms
of consumer confidence, prevention of overcooking and
potential reduction in processing/storage costs.
However, the legislative requirements are the main
drives of research in food safety. The Australian Food
Standard Code (ANZFA 2002) stipulates that all food
service businesses must develop a hazard analysis critical control point (HACCP) – based food safety programme. Numerous other bodies around the world, the
Canadian Code of Recommended Manufacturing Practices (Agriculture Canada 1990), the US Food & Drug
Administration (2001), the Advisory Committee on the
Microbiological Safety of Food 1995), the European
Chilled Food Federation Botulism Working Party
(Gould 1999) and the Food Linked Agro-Industrial
Research European Commission (1997), address the
food safety risks of long shelf-life (LSL) cook-chill technologies including sous-vide and hot-fill.
In general, the focus of studies on food safety followed the development of different systems – cookfreeze in the 1960s, traditional cook-chill in the 1970s
and LSL cook-chill in the 1980s. At present, there is no
journal dedicated solely to food safety aspects of food
service operations. However, leading mainstream food
science and technology publications (Food Control,
International Journal of Food Microbiology, Journal of
Food Protection, Food Safety and others) often cover
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
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Introduction
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Food safety research S. Rodgers
topics related to food services. In this paper the preservation principles, the need and pathways of research
on food safety are analysed in the context of food
service operations. The surveys of background microflora, challenge studies, studies on food safety design,
predictive modelling, (HACCP) and good manufacturing practices (GMP) are reviewed.
The pathways in food safety research
There are three types of food service products in terms
of their microbial status. The first type is chilled
uncooked products (salads, sandwiches, etc.) with the
whole range of food-associated microflora (bacteria,
moulds and yeasts), which are often harmless and even
can have a bio-protective effect against food poisoning
or spoilage microorganisms (FPSOs) (Jay 1995). The
second type is the traditional or ‘open tray’ products
(cooked and not packaged). Cooking would destroy
indigenous yeast, moulds and the majority of vegetative
bacteria. Such products would have some surviving
indigenous spore-formers, which can germinate during
inadequate storage, as well as the microflora introduced
during consecutive handling. The third type is the packaged LSL cook-chill products, which together with
controlled atmosphere packaging (CAP) and modified
atmosphere packaging (MAP) are classified as ROP
(reduced oxygen packaging) products by the US Food
& Drug Administration (2001). The Administration
recognizes Bacillus cereus, Salmonella spp., Staphylococcus aureus, and Vibrio parahaemolyticus as the
FPSO of significance for ROP and warns that Salmonella spp., Campylobacter spp., and Brucella spp. can
survive in such products for long periods of time. All
these species except the spore-forming B. cereus would
not survive pasteurization in the LSL cook-chill foods.
The microbial status of the LSL cook-chill foods
would depend on the degree of heating – each increase
in the processing severity (cooking time-temperature
combinations) results in the destruction of more species
of pathogens. If the heating is lower than 10 min at
90∞C, any temperature abuse is extremely dangerous as
psychrotrophyc Clostridium botulinum, one of the
spore-forming pathogens capable of surviving mild pasteurization, can grow and produce toxin under refrigeration (Brown & Gaze 1990; Brown et al. 1991;
Rodgers 2002). Consumption of as little as 30–100 ng
of botulinum neurotoxin can be lethal (Peck 1997).
Food service operators should be able to differentiate
between the risks associated with the type of raw materials (Salmonella spp. in chicken, Vibrio parahaemolyticus in seafood, etc.) and preparation technologies
(vegetative microflora in traditional vs. spore-formers
in LSL cook-chill). When managers commission micro-
biological tests or verification studies they need to
appreciate the hierarchy of different levels in food
safety research – the data generated from studies at the
lower levels form a base for the higher level. Figure 1
shows that there are two streams of research: the studies analysing the microflora in the product itself and
the studies describing the surrounding environment
such as air, water and food contact surfaces. The
former are developed on the knowledge of background
microflora and the effect of preservation factors (challenge studies). Both shelf-life studies and HACCP are
based on such information. Predictive modelling is a
statistical tool, which is used to quantify these effects.
The studies on the effectiveness of cleaning programmes, product flow (facility design), personal
hygiene rules and staff training support GMPs, which,
in turn, support HACCP (Fig. 2). The lack of proper
equipment and incorrect layout, for example, were the
main obstacles to efficient HACCP management
(Panisello & Quantic 2001).
Background microflora surveys
Unlike managing food safety risks from chemical pollutants, when the simple removal of the source of contamination is sufficient, managing microbiological risks
requires the knowledge of the types and population
levels of ubiquitous bacteria. The studies on background microflora are conducted to enumerate and
identify FPSOs in raw materials and the final product;
sometimes the sources of contamination are traced by
matching the strains with those isolated from raw
materials or the environment. Post-process contamination of cook-hot-hold meals prepared and distributed
by a CPU to schools in Argentina (Tessi et al. 2002),
for example, originated from food handlers and kitchen
environment. The spore-forming bacteria in LSL cookchill meals, which represent pathogenic and spoilage
risks (Lopes et al. 1999), were traced to dry ingredients
such as milk powder and starch (Carlin et al. 1999). In
sous-vide fish-based products, C. botulinum and Listeria monocytogenes (in the case of under-processing)
were identified as the most important pathogens
(Rosnes et al. 1999).
The ROP products are protected from re-contamination by packaging. In general, studies show negligible
background microflora in a wide range of LSL meals
(Nyati 2000; Rybka et al. 2001). However, the population levels depend on the storage temperature.
Hansen et al. (1995) showed the difference in counts
of spore-formers in sous-vide beef during storage at 2
and 10∞C (Fig. 3). Another type of bacteria, lactic acid
bacteria (LAB) are frequently isolated from a variety of
LSL meals (Shamsuzzaman et al. 1995; Simpson et al.
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
Food safety research S. Rodgers
GMP
- Cleaning/hygiene
- Facility and process design
- Staff training
Environmental tests
- Food contact surfaces
- Air quality
- Water supply
HACCP
- Processing parameters/practices verification
- Hazard assessment
- Legislation/policy effectiveness
Shelf-life studies
Predictive modelling
- Risk identification/quantification
- CCPs identified
- Limits established
- Model verification
Challenge studies
- FPSO's resistance to processing factors
- Effect of additional inhibitory hurdles
- Food safety design
Figure 1 Pathways in food safety
research. CCP, critical control point;
FPSO, food poisoning or spoilage microorganisms; GMP, good manufacturing
practices; HACCP, hazard analysis critical control point.
Surveys of microbiological populations
- FPSOs identified
- Factors (food type, temperature and contamination
sources) established
- Raw data for predictive models
The HACCP Plan can
never be a stand-alone
document.
Premises
&
Equipment
Vendor
Assurance
Scheme
Figure 2 GMP programmes supporting
HACCP. Adopted from J Hourigan, personal communication. GMP, good manufacturing practices; HACCP, hazard
analysis critical control point.
Product
Recall
Protocols
HACCP
Plan
Lab.
Manual
Waste
Control
Sanitation
& Hygiene
Training
1995; Nyati 2000). These are unexpected results as
LAB do not form spores, but being Gram-positive are
relatively heat resistant.
It should be noted that studies on the incidence of
pathogens are rarely commissioned by food services as
they require a large sample size, which is often cost
prohibitive. The data on a prevalent commodity type
(seafood, chicken or minced meat, for example) can be
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
Air &
Water
Supply
Clothing
Pest
Control
Complaints
Procedures
Maintenance
Standard
Operating
Procedures
found in the mainstream food microbiology research
or the published results commissioned by food
manufactures.
Challenge studies
Challenge studies involve the inoculation of food with
FPSOs, which are usually identified in the background
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Food safety research S. Rodgers
Figure 3 Psychro-trophic aerobic counts on the surface of
sous-vide cooked roast beef prepared from 3∞C, 17 day stored
raw material and kept at 2∞C (––) or 10∞C (––). Adapted
from Hansen et al. (1995).
microflora surveys. An inoculated product can be subjected to the intended steps in processing – cleaning,
peeling, cutting, heating, portioning, storage, distribution, rethermalization, retailing, service, etc. Alternatively, FPSOs can be challenged with additional
controlling factors, which are physical, chemical or
biological in nature. With the developments in the LSL
cook-chill technologies, non-thermal preservation hurdles, such as lactate, irradiation, bacteriocins and
protective cultures, have been tested (Rybka-Rodgers
2001). In practice, challenge studies are used to establish processing parameters, such as those described in
the industry codes (New South Wales Health Department 1998a,b,c,d), verify the adequacy of processing
and extend the shelf-life of a product.
The examples include the adaptation mechanism of
Basillus spp. to thermal stress (Arinder et al. 1999;
Carlin et al. 1999) as well as the survival and growth
of Escherichia coli, L. monocytogenes, Salmonella and
B. cereus at chilled temperatures (Gibbs 1999). The
minimal heating requirements of 2 min at 70∞C for
traditional cook-chill system (New South Wales Health
Department 1998c) are based on the survival of
L. monocytogenes tested by Gaze et al. (1989); the
storage temperature of 3∞C and the shelf-life of 28 days
for LSL meals (New South Wales Health Department
1998d) on the study on the minimal growth temperature (3.3∞C) and ‘time to toxin’ (30 days) for
C. botulinum by Hatherway (1992).
Challenge studies require complex experimental protocols and are not commissioned by food services routinely. Only when the process does not have the proper
time/temperature controls to guarantee the safety of the
product, as can be the case with the LSL cook-chill
meals, such studies are needed. Consequently, reports
addressing the danger of botulism dominate the field.
The examples include the survival of C. botulinum during cooking (Fernandez & Peck 1997) and storage
(Brown & Gaze 1990; Brown et al. 1991). The poor
growth of this pathogen in sous-vide meals was
reported by Hyytia-Trees et al. (2000) and Rodgers
(2002); the low temperature (<5∞C) and pH (<5.5) were
adequate to control growth and toxin production.
Food manufactures have long been designing products to suit their operational requirements (mostly
shelf-life) by application of preservation hurdles. This
is a novel concept for food service operators accustomed to cooking and serving meals without delay. The
concept of LSL in food services allows limitless opportunities in terms of centralized food production. The
extension of shelf-life can be achieved by a variety of
methods. The ‘double-heating’ method was used commercially by Naka system (Light & Walker 1990) in
the 1960s – it resulted in the over-cooked and ‘tired’
product quality. ‘Intelligent’ combinations of hurdles
are possible when several antimicrobial factors of low
intensity provide safety without affecting the sensory
quality of products.
The ROP meals can be irradiated after the packaging
step (Grant & Patterson 1995). The main advantage of
irradiation is that it does not cause significant quality
deterioration; the main disadvantages are the need for
expensive equipment and the fact that it is not compatible with the ‘fresh’ image of food service products. For
the same reason, the use of chemical preservatives is
excluded. Other non-thermal processing technologies,
such as MAP and hydrostatic pressure, are not effective
against spore-forming FPSOs. The use of natural ingredients with antimicrobial properties or their derivatives
is a more ‘natural’ solution. Spices (clove, thyme, black
pepper, pimento, origanum, garlic, onion, cinnamon)
(Ismael & Pierson 1990a,b), essential oils of sage, turmeric, mustard and fenugreek (Packiyasothy & Kyle
2003) as well as sodium lactate (Meng & Genigeorgis
1994) have been tested. However, high effective concentrations of terpenoid compounds in spices (Packiyasothy & Kyle 2003) and the aftertaste of sodium lactate
affect the flavour of food.
Bio-preservation, on the other hand, can be applied
to any product. Bacteriocins (substances produced by
Gram-positive bacteria against closely related species)
are effective at very low concentrations. In many developed countries, the use of bacteriocins is limited by
legislation. In the US, for example, only Nisiplin (nisin)
is allowed in cheese and liquid eggs. Fermented products that are less concentrated can be added to meals
without approval. However, like spices and lactate,
such applications may cause sensory changes. Live
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
Food safety research S. Rodgers
Predictive microbiology
Figure 4 Cook-chill seafood chowder inoculated with
103 CFU/g of non-proteolytic C. botulinum after 10 days of
storage at 10∞C (left – control, toxic, visually spoiled; right –
protected with L. lactis spp. lactis, non-toxic, visually sound).
Adopted from Rodgers (2003).
LAB, on the other hand, do not affect taste (Rodgers
et al. 2002), are recognized as safe and offer the unique
temperature-sensitive inhibition – inhibitory substances
are produced only when a product is subjected to temperature abuse.
Protective cultures, the bacteriocin-producing Lactococcus lactis spp. lactis and Pediococcus pentosaceus,
prevented the botilinum toxin production in seafood
chowder stored for 10 days at 10∞C (Fig. 4). The main
disadvantage of bio-preservation is the need for a complex development process starting with the screening of
potential ‘candidates’ for protective cultures and finishing with sensory evaluation and scaled up production
(Rodgers 2003). The practical difficulties include the
heat sensitivity of LAB (during the hot-filling step) and
the need for legislative approval in such countries as
Australia.
Thus, operators need to be aware of the existence of
other controlling factors apart from time/temperature
combinations. The potential benefits include the ‘relaxation’ of processing parameters – decreased heating and
increased storage temperature. This would result in the
cost of energy savings. A CPU would be able to deliver
the product to the satellite kitchens through refrigerated (5–7∞C) distribution channels rather than keeping
a fleet of specialized chilled (<3∞C) tracks. The reduction in the severity of cooking would also improve
the quality attributes of meals with heat sensitive
ingredients (eggs, cheese, poultry, seafood and leafy
vegetables).
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
Predictive microbiology is one of the modern developments which can make food safety design feasible in
food service settings. It is based on the principles of
statistics and food microbiology. The fact that the
microflora of non-preserved foods is dynamic – it reacts
to temperature changes – offers the possibility to construct predictive models describing the growth patterns
of bacteria. The latter depends on a relatively small
number of factors, for example, temperature, food
composition, initial contamination level and the presence of any additional antimicrobial factors.
The models used in predictive microbiology, such as
the Modifed Gomperts equation, reflect the non-linearity of microbial inactivation and growth as a function
of time. The scarcity of raw data on microbial populations in food services can be overcome by the application of artificial neural networks (Geeraerd & van Impe
1999). The interconnections between different factors
affecting microbial growth are treated similarly to the
responses of the human nervous system.
Miles & Ross (1999) listed potential applications of
predictive modelling in HACCP management: (i) to
show which FPSO can grow on the product; (ii) to
define the processing parameters to achieve death or
stop the growth of a FPSO; (iii) to test ‘what-if’ scenarios with different product formulations and processing
parameters to see if alterations will allow a new hazard
to emerge; and (iv) to establish the suitability of a
product after a loss of control at a CCP, such as undercooking or a break-down of a cool room.
The accuracy of the models is the major limiting
factor in the practical applications of predictive microbiology. Despite the latest developments, the programmes are not reliable enough to verify a new food
service system without ‘real-life’ challenge studies. The
main fundamental problem is the fact that the data
used for the model development are mostly derived
from microbiological broths. Robins & Wilson (1994)
demonstrated that the growth pattern of bacteria in
solid and semisolid media would be slower. On the
other hand, it would be impossible to develop a separate model for each product type. Consequently,
commercial programmes such as the FMM (Food
MicroModel, UK), PMP (Pathogen Modelling Program, USDA http://www.arserrc.gov/mfs/pathogen.
htm) and Food Spoilage Predictor© include a warning
that the users have to validate the models for each
product. In food services, this would be impossible with
ever-changing range of recipes, preparation methods
and storage conditions.
The studies on accuracy and validation of the models
comprise one of the fields of research in predictive
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Food safety research S. Rodgers
Population (log cfu/g)
72
10
9
8
7
6
5
4
3
2
1
0
0
1
2
3
4
5
6
7
Storage (days)
microbiology. The FMM predictions, for example, were
conservative when tested in the variety of LSL cookchill meals (Hyytia-Trees et al. 2000; Rodgers 2002).
In general, the shelf-life predicted by the FMM was
shorter than those by PMP (Hyytia-Trees et al. 2000).
The PMP showed a good ‘fit’ in seafood chowder only
after nine days of storage at 10∞C (Fig. 5) and was more
sensitive to pH than the FMM (Rodgers 2002).
Operators should also be aware of the wider range
of possible applications of modelling: (i) operation
design; (ii) heat penetration patterns based on the shape
of a heating unit and the properties of food; and (iii)
functional properties of new ingredients in terms of
their effect on product texture or health benefits based
on their chemical structure, and so on.
Haccp
The field of research on HACCP covers the ways of
controlling FPSOs. In tourism, for example, two types
of pathogens are recognized in this respect: those controllable by the tourism industry through maintaining
high standards of food safety; and those whose control
does not lie primarily in the domain of the tourist
industry, such as street vendors or rural farm visits
(MacLaurin 2001). HACCP deals with the ‘fate’ of the
product during processing and should not be confused
with hygiene and sanitation and other GMP programmes (Fig. 2). HACCP is situated at the core of the
pathways in food safety research (Fig. 1). The whole
field of food microbiology concerned with studying
pathogens is relevant to HACCP. The codes mentioned
earlier (New South Wales Health Department
1998a,b,c,d) are the prototypes of a HACCP table specifically designed for different food service systems. The
verification of HACCP typically involves final product
testing against recognized microbial standards. Such
validation is needed for a new or modified food service
system not described in the industry codes.
There are other ‘soft’ aspects of HACCP, which are
not directly based on research in microbiology and,
consequently, not listed in Fig. 1. These aspects reflect
the nature of HACCP as a quality management tool
8
9
10
Figure 5 Comparison between the actual
(
) and predicted by Food MicroModel (FMM) (
) growth of nonproteolytic C. botulinum in seafood
chowder at 10∞C. Adopted from Rodgers
(2003).
and include the elements of risk assessment as well as
studies on the effectiveness of food safety legislation
and HACCP-based policies, the link with the ISO 9000
and TQM (Total Quality Management) programmes,
the organizational measures (Snyder 1995) and the
implications on human resource management.
The quantification of potential risks would guide
operators in the allocation of funds to CCPs with
higher impacts. The methods in risk assessment include
sophisticated statistics coupled with computation. The
‘Monte Carlo’ simulation, for example, is capable of
generating the probabilities of the range of possible
outcomes. Bayesian Belief Networks (Barke et al. 1999)
provide transparent representation of complex scenarios with many uncertain quantities. These tools are
important when managers have to prioritize the spending of limited resources.
Managerial protocols for HACCP in food services do
not differ fundamentally from generic risk assessment
approaches used in other sectors of hospitality – on
cruise ships, for example (Fig. 6). Although, the
matrixes for risk assessment in food service applications would have the hazards of different nature. The
scores are allocated for the categories of food (higher
for seafood and lower for mayonnaise, for example),
the way food is prepared (higher for a process with
many steps) and the frequency of use (Coleman &
Griffith 1998).
The managerial aspects extend to practical (staff
reluctance to work in low temperature environments,
inability to monitor core temperature of cooking for
the cooked-in-a-bag products, cool-room alarm activation set at higher temperatures to account for the
defrost cycle, etc.) (Rybka 1999) and technical
(Table 1) barriers in HACCP implementation. There
are also human resource management aspects of
HACCP: (i) the development of mutual understanding
between the staff and environmental health officers
(UK) or food inspectors (Australia); (ii) the need for
leadership and the change of old habits/attitudes; and
(iii) staff motivation and supervision (Panisello &
Quantic 2001). It can be concluded that research on
HACCP is positioned on the interface between funda-
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
Food safety research S. Rodgers
Figure 6 The formal safety approach for
cruise vessels. Adopted from Lois et al.
(2004). Hazard identification (HAZID).
Table 1 Technical barriers in HACCP implementation in food services
Barrier
Factors
Illusion of control
Company size
Type of product
Managers without appropriate training are unaware of the risks
Thinking in terms of productivity rather than safety
Diversity of raw materials
Many processes are without a final lethal step (salads, sandwiches, etc.)
The lack of well-defined product flow
The wide diversity of the workforce
The constant turnover of employers
The variations in demands and workloads
The evidence that HACCP is being complied with is needed to supply
supermarkets and hotel chains, airlines and other large businesses
Industry sector (hotels, restaurants,
public houses, canteens and others)
Company’s customer
Compiled from Panisello & Quantick (2001)
mentals of food microbiology and management
practices.
Good manufacturing practices
Environmental microbiological studies are not unique
to food services; food industry and infection control
agencies use similar approaches. Filtration is used for
enumeration of bacteria in water. Swabs are taken from
different surfaces to assess the effectiveness of hygienic
practices including cleaning. For example, the critical
areas harbouring pathogens were personal protective
equipment including oven mitts and potholders
© Blackwell Publishing Ltd. 2005 Food Service Technology, 5, pp. 67–76
(Michaels et al. 2002). Floor mats and footbaths were
contaminated with L. monocytogenes, a pathogen of
particular significance in cook-chill processing (Klausner & Donnelly 1991).
Surfaces can be inoculated or challenged with an
indicator organism, subjected to cleaning and then
swabbed. Meredith et al. (2001) used this approach to
study the potential spread of pathogens during preparation of chicken casserole. Considerable contamination was found with hand washing being an effective
prevention measure. Plate count is the technique most
often used to assess the effectiveness of cleaning, the
validation of rapid methods in testing for microbial
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Food safety research S. Rodgers
contamination (ATP bioluminescence or analysis for
proteins) as well as the accuracy of visual inspections
(Valcarcel et al. 2003).
Kassa et al. (2001) described a numeric rating scale
derived from matching the results of swabbing different
surfaces (hand washing sinks faucets, freshly cleaned
and sanitized food contact surfaces, coolroom and
freezer door handles) with the results of visual inspection. Such ratings can be used to assess the effectiveness
of staff training or articulate the need for food safetyrelated competencies (a detailed knowledge of the likely
reservoirs of hazards; the nature, formulations and processing conditions in foods; and the factors that will
enable an increase in the number/level of hazards)
(Mayes 1994).
The results can also lead to the development of GMP
(cleaning programs, hygienic practices and facility
design) as well as cleaning/sanitation assessment criteria such as the acceptable level of contamination of
food contact surfaces or the desirable reduction of bacterial populations after cleaning – a five decimal reduction within 30 seconds for Listeria (Chamber 1965),
for example.
Future directions
Although the area of food safety represents the bulk of
research on food service systems, some processing
parameters still do not have theoretical justification.
The notion of ‘playing safe’ often leads to the acceptance of over-conservative regimes such as the chilling
time of 90 min recommended by New South Wales
Health Department 1998c,d). In practice, cooked beef
cooled to 7.5∞C within 15 h did not support the outgrowth of C. perfringens (Juneja 1999). Furthermore,
the need for six decimal reduction of C. botulinum
during cooking (New South Wales Health Department
1998d) can also be questioned – the high populations
of this pathogen are extremely rare (Murall & Stewart
1983). Psychotrophic B. cereus is more heat resistant
than C. botulinum – which of these pathogens should
be targeted in the process selection?
In order to ‘strengthen’ the food safety design, the
application of natural antimicrobials (spices, salt,
sugar, organic acids, bacteriocins and lactate) in a synergistic combination of subtle preservation hurdles can
be investigated. The effectiveness of protective cultures
in traditional cook-chill foods against such pathogens
as Salmonella and Listeria can be tested. In LSL processing, microencapsulation or the development of a
release mechanism from the packaging material can
protect the cultures from heat. Furthermore, the whole
process of LSL meal production can be re-engineered –
a hot-fill method can be replaced with aseptic packag-
ing. This would facilitate the incorporation of protective cultures and other beneficial bacteria such as
probiotics. The chilling of the product before pumping
would prevent overcooking of the product during
pumping, and cheap recyclable packaging can be used.
The enrichment of meals with bacteria stimulates consumers’ immunity (Perdigon et al. 1999) and fits with
the ‘better food safety through nutrition’ concept.
Further improvements in validity and accuracy of
predictive models would reduce the need for challenge
studies. In commercial practices, operators often innovate by modifying traditional and LSL cook-chill methods. Some upmarket food services use prime cuts of
meat/fish, which are only sealed/browned on the day
prior to consumption, the core temperature never
reaches the requirements of the codes of practices. In
some cases a product is ‘hygienically’ packaged without
the pasteurization step. Companies supplying recyclable packaging are experimenting with LSL meals plated
at a CPU. All these new processes should be validated.
It can be concluded that the knowledge of food safety
should match the growing complexity of modern food
service systems. Rough assumptions of parameters/limits are no longer satisfactory. Theoretically justifiable
boundaries are needed in order to make informed
choices. The fine-turning of processing parameters by
means of predictive models and sophisticated preservation systems offers the potential for delivery of less
processed meals, which are safer and have superior
sensory and nutritional quality at the same time.
References
Advisory Committee on the Microbiological Safety of Food
(1995). Report on Vacuum Packaging and Associated Processes. Her Majesty’s Stationery Office, Department of
Health: London. UK.
Agriculture Canada (1990). Canadian Code of Recommended
Manufacturing Practices for Pasteurised/Modified Atmosphere Packaged Foods. Agri-Food Division, Agriculture
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