Microbial spoilage, quality and safety within the context of meat sustainability

Linda Saucier

Department of Animal Science, Institute of Nutrition and Functional Foods, Faculty of Agricultural and Food Science, Université Laval, Quebec City, Québec, Canada, G1V 0A6

Prof. Linda Saucier PhD, agr, chmDépartment des sciences animalesFaculté des sciences de l’agriculture et de l’alimentationUniversité LavalPavillon Paul Comtois, local 42032425 rue de L’AgricultureQuébec (Québec)  G1V 0A6CanadaTel.: 418-656-2131 | 6295Fax: 418-656-3766E-mail: linda.saucier@fsaa.ulaval.ca

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ABSTRACT

Meat is a nutrient-dense food that provides ideal conditions for microbes to grow

and defines its perishable nature. Some organisms simply spoil it while others are a threat

to our health. In either case, meat must be discarded from the food chain and, being

wasted and consequently an environmental burden. Worldwide, more than 20% of the

meat produced is either lost or wasted. Hence, coordinated efforts from farm to table are

required to improve microbial control as part of our effort towards global sustainability.

Also, new antimicrobial systems and technologies arise to better fulfill consumer trends

and demands, new lifestyles and markets, but for them to be used to their full extent, it is

imperative to understand how they work at the molecular level. Undetected survivors,

either as injured, dormant, persister or viable but non-culturable (VBNC) cells,

undermine proper risk evaluation and management.

Keywords: Feeding strategies, Meat safety, Meat spoilage, Microflora management,

Near-death physiology, Survivors

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1. Introduction

Even if Lutz, Sanderson & Scherbov (2001) predicted that the world population

should stop growing by the end of the century, our number is expected to reach 9.6

billion by 2050. Demand for animal-based proteins will continue to rise, but to an extent

that will vary from country to country according to various factors such as geography,

culture, etc. (Sans & Combris, 2015). A fair part of our food supply will keep travelling

the world, but parallel to this, the need to maintain viable agricultural social communities

and to buy locally are still very much present. Food security during pandemic outbreaks

(e.g., Ebola in West Africa) and related land biosecurity protocols remind us that no one

should solely depend on others to feed its people. More than ever, agriculture and food

production remain vital economic activities.

Integration of agri-food activities from farm to table has closely linked

commercial partners and it takes, in this continuum, only one intermediate performing

poorly to destroy the efforts of a whole sector of activities. These interactions have

fostered traceability protocols, but also liability to one another. Consumer trends and

demands continue to drive the food industry whether as mass productions or niche

markets (Table 1). Challenges reside in designing safe food without compromising

quality and shelf life while responding to consumers’ demands for minimally processed

foods with fewer additives, but that remain easy to prepare. Development of novel

strategies and antimicrobial systems therefore requires thorough knowledge of the

physiological response expressed by microorganisms to be controlled.

Safety of our meat supply could be challenged in various ways. Except for

chemical contaminants build up through reaction with meat constituents (e.g.,

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nitrosamine), chemical contaminants are likely to remain at the same level or to decay

with time. This is a major distinction compared to microbial contaminants that have the

potential to increase in numbers if the conditions allow growth to occur or resume. With

respect to meat sustainability, it can be improved by increasing productivity, but

reduction of waste and spoilage is also part of the solution. In this context, microbial

control is a major issue. Novel interventions need to be integrated from farm to table and

based on a thorough understanding of microbe near-death physiology at the molecular

level. In this context, examples of effective microbial control are presented here.

2. Economic burden of safety, waste, and spoilage

WHO (2015) reported 420-960 million foodborne illnesses and 310,000 to

600,000 deaths in 2010 representing 25-46 million Disability Adjusted Life Years

(DALYs); amongst the culprits, namely Salmonella Typhi and non-typhoidal Salmonella

enterica, Campylobacter spp. Taenia solium, enteropathogenic Escherichia coli, hepatitis

A virus, norovirus and aflatoxin. In terms of food waste, FAO (2011) indicates that 1.3

billion tons of food are lost or wasted every year. With respect to meat, more than 20% of

the 263 million tons of meat produced worldwide do not reach consumption, which

represents 75 million bovines raised for nothing (FAO, 2016). Animal products,

including meat, are nutrient dense, but highly perishable food commodities. In order to

reduce waste, spoilage, recalls linked to contamination with pathogens, etc. innovative

and effective strategies to improve microbial control have to emerge in order to improve

our sustainability towards meat and meat products. These new approaches may also

include tighter management systems. For example, Moisson Beauce, which is a non-for-

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profit organization, helps people living with difficult socio-economic situations. It carries

many activities like a food bank, reinsertion programs, etc. In partnership with a grocery

chain, they have implemented a meat recuperation program in order to reduce waste and

to provide beneficiaries with more nutritious foods (Fournier, 2015). In this case, meat is

frozen before the best before date and processed in provincially inspected kitchens before

being served to beneficiaries of charitable organizations. Alternatively, meat could be

sold at some point at a discount price before the end of shelf life. But if the product is not

handled properly by the consumer, poor eating experience and safety issues may arise.

3. Microbial control begins at the farm

With the exception of lymph nodes, muscles of healthy animals contain little to no

microorganisms (Huffman, 2002). Hence, the animal health status prior to slaughter is

paramount in securing meat quality and safety. On top of veterinary surveillance,

biosecurity measures at the farm must be established to protect the animal from diseases

and contamination by undesirable organisms. Obviously, reducing risk of economic

losses caused by animal death and herd dissemination is the logical reason to embark on a

biosecurity program. On top of biosecurity protocols, many producer associations have

developed a HACCP system at the farm. Although, these tend to be more of type 2

(minimizing microbial growth) than actual type 1 (procedures where cell counts are

reduced, in order to prevent or eliminate hazards), they are deemed valuable with respect

to microbial safety (Gill, 2000).

Free-range farming is seen as a less intensive system for animal production, but it

does, nonetheless, require stockmanship to be done properly and effectively with respect

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to welfare and productivity. Furthermore, higher incidence of parasitic infection was

reported when pigs are raised with access to outdoor facilities compared to more

conventional production systems (Eijck & Borgsteede, 2005). So, parameters such as

quality of pastures, feed, water facilities, pest and wildlife control, etc. remain important

to control disease and contamination that will lead to increased mortality, loss of

productivity and more carcass waste. Couple of years ago, pork producer associations in

Canada have promoted less severe cooking for whole muscle cuts as “pink cooking” for

customers to enjoy a more pleasing eating experience. It was deemed safe considering the

microbial quality achieved by producers but such practices would not be recommended

for free-range pigs as less severe cooking can lead to safety issues when incidence of

parasites is increased. Much to proof that new intervention must be studied thoroughly to

avoid introducing unsuspected risks.

Before being transported to slaughter houses, animals are submitted to a feed

withdrawal to reduce problems associated with motion/transport sickness, notably nausea,

vomiting, diarrhea, known to favour contamination to spread between them, but also

losses (death or non-ambulatory; Bradshaw et al., 1996; Isaacson et al., 1999; Ritter et al.,

2006). Pre-slaughter fasting is now a standard procedure and parameters for its proper

application vary not only amongst species but also amongst producers. That is why it is

deemed preferable to refer to fasting efficacy rather than fasting time. Conversely, a too

long fasting will affect animal welfare, as hunger makes them more irritable; fights are

more frequent leading to bruises on the carcasses. When they are properly fasted, the

volume of the gastro-intestinal (GI) tract is reduced along with risks of perforation during

evisceration as well as carcass and equipment contamination.

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Excessive feed withdrawal will also have a negative effect on carcass yield. With

pork, it takes four to eight hours before nutrients gets absorbed by the small intestine and

nine hours to reach blood stream. Hence, it takes 10 to 12 h before the feed consumed

materialized into carcass gain (Faucitano et al., 2010b). Undigested material left in the

digestive tract is an unnecessary expense for the producer and represents an extra waste

to manage at slaughter (Murray, 2001). Effective feed withdrawal reduces the incidence

of Pale, Soft and Exudative (PSE) meat. If unduly extended, muscle reserves will get

exhausted leading to Dark, Firm and Dry (DFD) meat (Faucitano et al., 2010b). Its high

pH favours microbial growth, leads to early spoilage of the meat and reduces shelf life.

Furthermore, hungry animals may drink more in order to reduce discomfort and water fill

up the stomach (Saucier et al., 2007), which is counterproductive with respect to reducing

GI tract volume (Rabaste et al., 2007).

Many factors are susceptible to influence meat quality including pre-slaughter

stress, truck design, seasons, roads, animal density, duration of transport, feed

withdrawal, etc. (Faucitano & Schaefer, 2008; Weschenfelder et al., 2012, 2013a, 2013b).

In fact, stress inflicted on animals before slaughter may interfere with their health and

welfare leading to poor meat quality and microbial contamination (Faucitano et al.,

2010b). After death, muscles remain metabolically active until reserves are exhausted in

anaerobic conditions since breathing has ceased. If the animal is submitted to a prolonged

stress before slaughter (e.g., long transport), reserves will get exhausted prior to

slaughter, limited production of lactic acid will occur and ultimate pH (pHu) after 24 h of

chilling will be higher leading to DFD meat. This higher pH is favourable for microbial

growth (Faucitano et al., 2010a), the meat will spoil faster and shelf life will be reduced.

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However, when pH is higher, myofibrillar proteins are far from their isoelectric point

producing a net charge causing repulsion between the fiber networks. Water then has

more space and meat retaining it will have a dry appearance. This improved retention

leads to reduced cooking losses, better yield and quality in processed meat (Interbev,

2006).

If stress is inflicted shortly before slaughter (e.g., use of electric prod), it leads to

poor quality PSE meat as well as low cooking yield although its low pH refrain microbial

growth compared to DFD meat. More recently, intermediate quality classes have been

defined in pork, namely, Red, Soft and Exudative (RSE) and Pale, Firm and Non-

exudative (PFN). Much remains to be unveiled with respect to this newly suggested

classification, but we have demonstrated that, after DFD, RSE meat spoils the fastest

(Faucitano et al., 2010a). So, proper pre-slaughter management is important to control

contamination and to obtain quality meat with optimized shelf life.

4. Improving quality and shelf life while reducing waste

Many small fruits (e.g., cranberry, strawberry, etc.) and plants (e.g., tea leaves,

onions, etc.) contain large amounts of phenolic compounds, including ellagic and gallic

acids, which are known for their antimicrobial and antiviral activity in vitro as well as in

vivo (Buzzini et al., 2008; Leusink et al., 2010; Rozoy et al., 2013). Cranberry is very rich

in proanthocyanidins, which have inhibitory effects on Staphylococcus aureus and

Escherichia coli growth in meat (Daglia, 2012) and lipid oxidation in fresh turkey and

ground pork meat (Lee, Reed & Richards et al., 2006; Raghavan & Richards, 2006).

Essential oils from herbs and spices also demonstrate antimicrobial (Oussalah et al.,

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2007) and antioxidant properties (Botsoglou et al., 2002, 2003, 2004). However, when

directly applied to meat, organoleptic concerns arise.

It is well documented that feed supplementation with vitamin E improves the

oxidative stability of meat (Schaefer et al., 1995). Addition to feed is more effective than

on meat (Mitsumoto et al., 1993; Houben & Gerris, 2002; Lahucky et al., 2010) and its

action is immediate upon surface exposition to air. By a similar feeding strategy, Soultos

et al. (2009) demonstrated that adding oregano oil to the diet of rabbits reduced total

mesophilic aerobes, Pseudomonas spp. and Enterobacteriaceae of the carcass after 12

days of refrigeration under aerobic conditions. As well, Fortier, Saucier & Guay (2012)

improved the microbial quality of pork meat when rations were supplemented with

oregano oil and cranberry pulp. The idea here is not to feed farm animals with fruits and

plants, but rather with feed enriched with bioactive compounds extracted from plant by-

products to improve meat quality and shelf life. Effective use of polyphenols and other

bioactive molecules aligns with a global vision for sustainable agriculture and economic

efficiency.

5. Microflora management

One technology that has ship-shaped meat microbial shelf life in the past few

decades is most certainly modified atmosphere packaging. Without any additives or other

interventions, but simply by changing composition of the gaseous environment around

the meat, we have been able to modulate its microflora in order for less spoiling lactic

acid bacteria to prevail over psychrotrophic Pseudomonas, provided that the cold chain is

maintained throughout storage and transport (Saucier, 1999). So, this fine-tuning of

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microbial ecology has led us to keep the microorganisms that we want, at the level that

we want, and with the timing that we want. Rather than having a “bazooka” approach,

where everything is wiped out, a more targeted “sniper” one eliminating the bad and

leaving the good microbes to thrive has proved to be beneficial. In any case, microbial

void created by reducing or eliminating endogenous microflora is at risk to be

recontaminated and recolonized by opportunistic organisms at post treatment.

In 2008, the Canadian meat processing industry was shaken by a listeriosis

outbreak where elderly people actually died. Luncheon meat had been contaminated with

Listeria monocytogenes from a biofilm found on a slicer (Weatherill, 2009). This incident

has led to the implementation of new reforms including approval of two antimicrobials

for processed meat (sodium acetate and sodium diacetate) and new regulations with

respect to microbial control on surfaces near or touching meats got implemented. One of

the hypotheses proposed to explain the presence of L. monocytogenes in meat plants fits

with the improvement of sanitation, where only psychrotrophs like L. monocytogenes can

survive in cold processing rooms. Drains are difficult to decontaminate since water and

organic matter are constantly being flushed through them. Zhao et al. (2006) reported that

Listeria sp. can reach 3.6 to 7.5 CFU/1000 cm2 in drains of poultry processing plants and

that use of Lactococcus lactis subsp. lactis with Enterococcus durans at 107 CFU/mL in

an enzyme-foam-based cleaning agent can reduce Listeria sp. population after four weeks

of treatment. Similarly, a commercial biological product design to control odors in grease

traps and drain was tested for its ability to exert a competitive exclusion on Listeria

innocua (Fig. 1). Even the way plant activities are laid out will influence the spread of

contamination. Lundén et al. (2003) reported that facilities with more compartmentalized

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activities are less susceptible to contamination spread compared to large processing

rooms.

6. New technologies to improve meat quality and processing efficiency

Biological control using bacteriophages infecting and killing undesirable bacteria

have been studied against Pseudomonas in meat (Geer & Dilts, 1990). It was soon

realized while controlling a wide group of bacteria, such as members of a whole genus,

host range coverage and specificity were important criteria. Although the use of cocktails

provides a larger host range and reduces the emergence of phage resistant clones, better

success was obtained when phages were used to target specific bacterial species such as

E. coli O157:H7 (Table 2; Saucier, Moineau & Fairbrother, 2001), L. monocytogenes

(Hagens & Loessner, 2014) and Brochothrix thermosphacta (Greer & Dilts, 2002). To be

effective, lytic, not temperate, phages must be used and since most bacterial viruses only

multiply in viable and active cells, growth limiting conditions, such as refrigeration,

reduce its efficacy. Transducing phages are to be avoided since genetic material could be

transferred from cell to cell. Furthermore, contact between phages and bacteria should be

optimized otherwise high titers of phages are necessary to provide a significant effect.

Commercial phage preparations are available, notably Listex™ consisting of a broad

range phage, P100, and ListShield, a cocktail of phages (Hagens & Loessner, 2014).

Phage-encoded enzymes, such as endolysins, have been also tested as anti-

microbiological agents against Listeria biofilm, although their stability remains an issue.

The absence of the outer membrane in Gram positive organisms allows its application

externally on Listeria.

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High efficiency meat tenderizers as well as brine or marinade injectors have been

developed to improve eating qualities of less noble cuts. By piercing meat surface with

blades or needles, it compromises its integrity allowing microorganisms on the surface to

penetrate the core of the muscle similarly to ground beef. It was only a matter of time

before meatborne outbreaks got linked to such process. Indeed in 2012, 18 cases of

Escherichia coli O157 were linked to such products in Canada (Catford et al., 2013) and

prompted the implementation of guidelines for mandatory labelling to provide proper

cooking information (Health Canada, 2014). So, on the package of non-intact muscles, it

must be indicated: “mechanically tenderized”, “cook to a minimum internal temperature

of 63°C (145°F)” and, in the case of steak, “turn steak over at least twice during

cooking”. Gill et al. (2014) demonstrated that if steak is turned twice or more while being

cooked to 63°C, a 5 Log reduction is obtained. Again, this emphasizes the need to study

thoroughly the behavior of microorganisms in food systems when new technologies are

introduced and to establish their efficacy and safety. Apart from the O157 serotype, other

Shiga-toxin producing E. coli (STEC) namely, O26, O45, O103, O111, O121, O145,

commonly referred to as the “Big Six”, are now considered adulterants in meats and must

be controlled as well.

7. Efficacy of antimicrobial systems and cell physiology

Various antimicrobial systems are used to control microorganisms in food, including

meat, and heat treatments are amongst the oldest and the most widely studied. Métris et

al. (2008) demonstrated that recovery time increases with severity of heat treatment. Cell

recovery and growth have been traditionally used to assess severity and efficacy of

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antimicrobial systems (e.g., commercial sterility of canned food). For recovery and

detection to happen, however, survivor cells must be able to grow and form colonies on

culture media. Injured cells do not grow on selective media (Oliver, 2005; Li et al.,

2014). To be detected, they must deal first with their injuries in non-selective growth

conditions. Stress, including commonly used food preservatives, can induce a viable but

non-culturable (VBNC) state (Oliver, 2010; Li et al., 2014). Contrary to injured cells,

those in VBNC state cannot grow on any media (Oliver, 2005; Li et al., 2014) but they

remain metabolically active whereas dormant cells are not (Pinto, Santos & Chambe,

2015). As stated by Li et al. (2014), little is known about the genetic control of these

VBNC cells and their age also influences resuscitation time, which can take days or years

depending on strains and conditions. Furthermore, they are known to be more resistant to

physical and chemical stresses (Li et al., 2014). VBNC state is seen as an adaptive

strategy to survive longer under unfavourable conditions. Also, persister cells have been

described as a subpopulation of phenotypic non-growing variants associated with

antibiotic resistance (Yamaguchi & Inouye, 2011; Li et al., 2014; Leung, Dufour &

Lévesque, 2015). Through a toxin-antitoxin (TA) system, they control cellular growth

and death that can lead to a “dormant” state. Under stress, induced proteases eliminate the

less stable antitoxin and free the toxin. There are three groups of TA systems (I, II and

III) based on the antitoxin function and they have been identified in many bacteria;

E. coli K12 is known to have 36 TA systems (Yamaguchi & Inouye, 2011). Survivors,

either as injured, dormant, persister or VBNC cells, can resuscitate when the conditions

are right, notably during storage and transport. So, there is always a possibility that those

conditions favouring resuscitation may not be known, and risks associated with

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undetected survivors remain; they could be dangerous if they are pathogenic and ingested

(Olivier, 2010, Rowan, 2004). The efficacy of antimicrobial systems is traditionally

evaluated by cell enumeration on solid growth medium during challenge studies. Hence,

when viable cells cannot grow to be detected, we overestimate the efficacy of

antimicrobial treatments indicating that other markers should complement cell count

enumeration to assess risk properly.

In order to survive, microorganisms react to antimicrobial systems used to control

them and initiate a variety of physiological responses to modify metabolic activity

(transcriptome, proteome, etc.), cell structure (e.g., membrane fluidity) or genetic make-

up. For example, when exposed to antibiotics, cells can develop tolerance or acquire

resistance at genetic level, depending on concentration of antibiotics encountered.

General, as well as specific, stress responses have been described in many organisms

(Storz & Hengge-Aronis, 2000; Dodd & Aldsworth, 2002; Jones, 2012). The general

stress response, under the control of factor RpoS in E. coli, leads to cross protection

against other stresses (Lemay et al., 2000; Blackman, Park & Harrison, 2005; Jones,

2012). At the molecular level, stress proteins, induced by sub-lethal heat treatment, have

been described in several eukaryotes and prokaryotes. The stress response associated with

heat shock can also be induced by other factors (ethanol, UV, DNA-gyrase inhibitors) in

E. coli and many proteins induced by various stresses have already been identified (Storz

& Hengge-Aronis, 2000; Jones, 2012). Organism survival to an inhibitory treatment, such

as heat or acid, can be improved by prior exposure to sub-lethal conditions (Storz &

Hengge-Aronis, 2000; Seyer et al., 2003; Jones, 2012). Interestingly, heat shock proteins

protect E. coli cells against freezing but not chilling conditions (Chow, & Tung, 1998).

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Using reporter gene assays, Purushottam et al. (2005) demonstrated that cold

temperatures (5°C) prevent induction of the general stress genes uspA and rpoS upon

osmotic shock. Similarly, in starved E. coli O157:H7 cells, the GrpE general stress

protein is most abundant at 5°C, whereas UspA is most abundant at 37°C. Bacteria also

sense and communicate (e.g., quorum sensing, “scout”/suicide hypothesis) their exposure

to stresses (Leung, Dufour & Lévesque, 2015; Pinto, Santos & Chambe, 2015). For

example, upon alkali or acid exposure, extracellular induction components are produced

and can act as alarmones to warn unstressed cells to prepare for the upcoming danger

(Lazim & Rowbury, 2000; Rowbury & Goodson, 2005; Li et al., 2014; Leung, Dufour &

Lévesque, 2015,). Stress-inducible alarmones are small signaling molecules that diffuse

readily and can be activated by more than one stress (Leung, Dufour & Lévesque, 2015).

The level of (p)ppGpp is also involved in RpoS transcription (Jones, 2012). So far,

research on bacterial stress responses have focused on the period when physiological

changes are at their peak and geared towards survival (Storz & Hengge-Aronis, 2000).

DnaK is a chaperone protein implicated in the folding of nascent polypeptides, repair of

denatured proteins, and degradation of non-functional ones (Georgopoulos, & Welch,

1993); it represents 1% of the total proteins under optimal growth conditions. It is also

known as a heat shock protein which may increase up to 13% of the total proteins when

cells are grown at 30°C and then exposed to 42°C (Herendeen, VanBogelen, Nedhardt,

1979). Residual DnaK after heating was found to be necessary for cell recovery, and

additional DnaK was produced during the recovery process. Furthermore, resistance to

the same lethal heat treatment was better in cells that went to a recovery process than in

exponentially growing cells as if, through some epigenetic process, daughter cells

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remembered the stress their mother cells were exposed to (Seyer et al., 2003). Real-time

PCR measurement of heat shock gene expression also indicated that dnaK and groEL

mRNA levels decreased significantly above 60°C to become similar to control cells at

37°C suggesting that above 60°C, cells’ ability to adapt to heat treatment declined and the

treatment begins to be effective (Guernec, Robichaud-Rincon & Saucier, 2013). Hence,

as stress severity approaches cell death, stress response drops, suggesting a shift towards

a “near-death physiology state” (Seyer et al., 2003; Guernec, Robichaud-Rincon &

Saucier, 2013). In practice, this means that for heat treatment to be effective, it must be

severe enough to avoid bacterial stress response and adaptation.

Processed meat cooking (e.g., ham, bologna, etc.) aims to control non-spore

formers. Therefore, the product is not sterile and must be kept refrigerated to secure a

decent shelf life that reaches 30 days under modified atmosphere packaging (e.g.,

vacuum), depending on the product and its formulation. Historically, processed meat

products are cooked to a temperature of 71°C at their geometric center to be considered

effective and should provide a 6.5-log reduction of Salmonella in meat products that do

not contain poultry, and a 7-log for those that do (Martin, 1984, Sallami et al., 2006).

However, an extremely heat-resistant E. coli has been isolated from a beef processing

facility (Dlusskaya, McMullen, & Gänzel, 2011). Heat resistance is associated with a

14 kb genomic island containing 16 predicted open reading frames which share >99%

sequence identity with sequence in Cronobacter sakazakii and Klebsiella pneumonia

known to be linked to heat resistance (Mercer et al., 2015). Our microarray results reveal

that although cells of E. coli K12 treated at 58 or 60°C for a pasteurization value (PV) of

3 min could not resume growth after treatment, their gene expression was significantly

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different from those treated at a core temperature of 71°C (Fig. 2). In fact, eight genes

were still expressed differentially between treatments (Guernec, Robichaud-Rincon &

Saucier, 2013). The biological significance of the presence of those transcripts remains to

be tested since residual metabolic activity does not necessarily mean viability. For

instance, when an animal is slaughtered, eviscerated and carcass dressing is completed,

muscle cells remain metabolically active until cellular reserves are exhausted, even

though there is no more vascular circulation. So, it is important to discriminate when

bacteria are still fighting adverse conditions and when residual metabolic activity is

sustained beyond cell survival ability. Membrane integrity has been suggested as a key

component to assess viability and cell wall strengthening by increased peptidoglycan

cross-linking has been observed in VBNC cells (Li et al., 2014).

Working with a food matrix is complex and a whole array of antimicrobial

systems is used in carcass dressing (e.g., organic acid showers (1.5% lactic or acetic

acid), carcass pasteurization, cold storage, etc.) and during meat processing (e.g., nitrite,

acidification/fermentation, drying, salt content, etc.). This multitude of processes can

actually lead to various cross protections (Lemay et al., 2000; Li et al., 2014). Our

previous work (Lemay et al., 2000), on different antimicrobial systems applied in

different sequences, like it is often seen in industrial food preparation (e.g., chilling after

cooking), indicates that cells survive better after exposure to a sub-lethal osmotic shock

(NaCl) followed by an acid stress (lactic or glutamic acid), compared to reverse order.

Lowest survival is obtained when treatments are applied simultaneously. Hence, the

sequence of events during food processing is important and will influence both the

overall efficacy of treatments and the level of microbiological control obtained.

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Furthermore, using irradiation treatments (0.3 kGy) applied at different rates (8x10-2 and

3x10-3 KGy/min) on E. coli cells, we demonstrated that treatment applied at a slower rate

initiated a stronger stress response (Saucier et al., 2012). Even though a lot is known

about individual hurdles, little physiological information is available with respect to

various combinations, sequences and rates of application in real food/meat systems.

As the industry thrives to provide both good quality and safe foods, and to answer

consumers’ demands, it is important to acquire the necessary knowledge and tools to

improve our understanding of near-death physiology in order to sustain the vitality of our

agri-food sector. A new technology or antimicrobial system cannot be used to its full

potential if we do not understand how it works. Such knowledge is important for

improving food safety and product quality, and to reduce economic losses in the agri-

food industry due to microbial spoilage, loss, waste as well as recalls.

8. Conclusion

Nature is resilient and all living organisms thrive to survive. Survival strategies

and physiological make up do exist, and continue to evolve, even amongst

microorganisms and these pose challenges in terms of risk assessments related to safety.

So, when we abuse our agricultural resources to a point of no return, it is a sign that we

have went too far. Ocean garbage patches, the recurrent presence of smog in major cities,

the recent burst of toxic mining waste in Brazil are all signs that we are running towards a

wall. It is not a matter of if, but when, and at what speed we are getting there. Economic

growth based on demography and productivity alone no longer holds. Agricultural

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sustainability, wise natural resources management, reduction of waste will have to

become part of the equation.

Acknowledgements

This review manuscript and associated presentation at the 62nd International

Congress on Meat Science and Technology in Bangkok, Thailand are dedicated to the

memory of a colleague and dear friend Dr. C.O. Gill (1943-2014) Research Scientist at

the Lacombe Research Centre, Agriculture and Agri-Food Canada.

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Figure Captions

Fig. 1. Competitive exclusion study between a commercial biological product containing a live non-pathogenic consortium of bacteria designed for odour treatment of grease trap and drain in agri-food facilities against Listeria innocua at Log103 CFU/ml of each. Cell enumeration (Log10 CFU/ml) was performed over time after incubation in Brain Heart Infusion at 10°C with or without agitation (WA and NA, respectively).

Fig.1 Hierarchical clustering of differential gene expression upon various heat treatments. Only E. coli cells heated at 58°C PV2 were able to resume growth. Pasteurisation value (PV) is defined as the time needed at a given temperature to control the reference organism, here Enterococcus faecalis (D value of 2.95 min at 70°C and z value of 10°C).

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Table 1Consumer trends and demands as defined by Fread (2014).

Designations Description

Foodies curious, variety of foods, pleasure

Healthies healthy foods, more natural, less preservative

Greenies socially responsible (ethic, environment)

Speedies convenient food, minimal preparation

Cheapies value-conscious, limited spending

Newbies immigrant with “culinary culture”

701702

703