Microbiological Specifications - Nestlé
Microbiological specifications
Table of contents22Purpose of this bookletFood Safety: Managing microbiological risks3445The definition of microbiological criteriaWhy do we use microbiological criteria/specificationsThree types of microbiological criteria: Codex AlimentariusAssessing adherence to microbiological specifications6Considerations for establishing microbiological specifications891013Components of microbiological specificationsMicroorganisms – PathogensMicroorganisms – Hygiene indicatorsMicroorganisms – Others141617Sampling plansThe stringency of microbiological specificationsSampling plans – Two- and three-class plans18Analytical Microbiological Methods19Frequently asked questions1
Purpose of this booklet:To help you understandFood Safety:Managingmicrobiological risks Why we use microbiological criteria/specifications for raw materials (RM),food ingredients, finished-products (FP)at various stages of the food chain. What are the main componentsof microbiological specifications. How Nestlé establishes microbiological specifications for rawmaterials.The safety of foodstuffs is neitherguaranteed nor controlled bymicrobiological testing.The safety of foodstuffs is primarilyensured by a preventative approach,such as implementation of GoodHygiene Practice (GHP) and applicationof procedures based on HazardAnalysis and Critical Control Point(HACCP) principles.The management of the microbiological risks at each stage ofmanufacturing process must beconsidered i.e. from farm to fork.This includes the quality of RM toreflect Good Agricultural Practices(GAP) and Good ManufacturingPractices (GMP).2
The Food Production ChainThe definitionof microbiologicalcriteriaMicrobiological criteria are used atany stage in the food chain to assessthe acceptance of lots of raw materialor finished product. They are basedon the absence / presence of certainmicroorganisms or quantitative limitsof these or other microorganisms, perunit(s) of mass, volume, area or ion3
Why do we usemicrobiological criteria/specificationsThree types ofmicrobiological criteria:Codex AlimentariusA large volume of food is exchangedworldwide between countries andshipped from sellers to buyers. Endproduct testing alone cannot ensuresafe foods, due to sampling planlimitations. Therefore, foods are notsystematically tested.Microbiological StandardsMandatory microbiological criteriawhich are written into law orgovernment regulations and specifiedby government to protect public health,e.g. European Hygiene and FoodSafety Criteria 2073/2005.Buyers, consumers or governmentsrely on the suppliers’ food safetymanagement systems to assure safefood throughout the food supply chain.To harmonise food safety and ensuretrading alignment, metrics such asmicrobiological criteria have beenestablished.Microbiological GuidelinesMicrobiological criteria which provideadvice to food manufacturers aboutacceptable or expected microbial levelswhen the food production processis under control when applying bestpractices.Microbiological SpecificationsMicrobiological criteria establishedbetween buyers and producers thatdefine product quality and safetyattributes required by the buyer.The scope of this bookletis limited to microbiologicalspecifications, describingthe approach taken by Nestléto establish and prescribespecifications to suppliers.4
Assessing adherenceto microbiologicalspecificationsAnalytical Microbiological Methodsare used to assess if RM or FP are inagreement with the microbiologicalspecifications. Microbiologicaltesting may be used by industry orgovernment. Lot testing, against thepre-defined specifications, is the mostcommonly used method. Furtherinformation on use of microbiologicalmethods is available on p.18.Defining a Lot: For Nestlémicrobiological specifications, a lotcorresponds to a specified quantityof product manufactured, filled andpackaged under the same conditions,thereby expected to have reasonablyuniform quality characteristics. Itshould never represent more than oneday filling/production.Frequency of Testing: Supplies of RMfrom suppliers are not systematicallyanalysed, but must comply withmicrobiological specifications. Testingis a verification of the effectivenessof food safety management systems,including prerequisite programmes andcontrol measures in place at suppliers.The frequency of analyses by thesupplier is dictated by their confidencein their prerequisite programmes andcontrol measures. A supplier approvalprocess and audit of suppliers willbe used to assess the prerequisiteprogrammes in place, with appropriatetest verification.Facility Environmental MonitoringSuppliers of RM should have inplace an adequate environmentalmonitoring programme (EMP). Aneffective EMP in a food processingfacility is an important component ofany food safety management system.It can act as an early warning systemfor microbiological hazards in boththe production and surroundingenvironment. It helps to identifyharbourage niches and ‘hot spots’ thatmay act as a source of contaminationand verify overall sanitary design,hygiene, personal practices andoperational methods in the facility.Target microorganisms in anenvironmental monitoring plan shouldinclude indicator microorganisms,pathogens and/or spoilage organisms.Such a plan defines zones to monitor,ranging from high risk to low risk (forproduct contamination).5
Considerations forestablishing microbiologicalspecificationsMicrobiological specifications for RMare derived from those establishedfor the corresponding FP. Thesealready take account of the products’Ready to Eat (RTE) /Non Ready to Eat(NRTE) status. The FP microbiologicalspecification must also consider theconsumer group for which the FP isdestined (e.g. infants versus adults).At the outset, it should be consideredif there is a need to establish a microbiological specification for a RM. Whenit is deemed necessary, the definitionand limits of the microbiologicalspecifications must consider the usageof the RM i.e. the application or notof a microbial kill step. If a kill step isto be applied then the nature of thismicrobial kill step will influence the RMmicrobiological specifications:Influences on the stringency ofraw material microbiologicalspecifications1. Is a microbiological specificationrequired?In some circumstances, e.g. syntheticallymanufactured ingredients, microbiologicalspecifications are not required.2. Where a microbiological specificationis required, the usage of the RM mustbe considered.If the RM is to be used without anyfurther microbial kill step, stringentmicrobiological requirements willapply. However, if a kill step is appliedto RM before inclusion in the finishedproduct, less stringent microbiologicalspecifications will apply.3. The nature of the microbial kill stepapplied impacts RM microbiologicalspecificationsFor example, the application ofpasteurisation compared to Ultra HighTemperature (UHT) will impact themicrobial parameters and stringencyrequirements of RM used for the differentprocessing methods.Stringency of RM microbiologicalspecifications6
Raw Material (RM)NoYesFor example flavours(without carrier matrix)No furtherKill StepApplicationof Kill StepFor examplePasteurisationFor exampleUHTInfant FormulaIce CreamReady-to-drink productHighMediumLow7
Componentsof microbiologicalspecificationsSampling PlansStringencyLimitsMicrorganismsPathogensHygiene indicatorsOthers8Analytical MicrobiologicalMethods
Microorganisms –PathogensA considerable number of foodbornepathogens exist. FP microbiologicalcriteria / RM specifications includea limited number of these asmicrobiological parameters.Factors influencing the selectionof microbiological components ofspecifications are: Is the pathogen known to be linkedwith this specific RM or foodproduct? Is this link well established? Have similar RM or food productsbeen involved in foodborneoutbreaks? Is the pathogen likely to be found inthe processing environment? Is pathogen applicable/included inFP microbiological specificationsthus dictating inclusion in RMmicrobiological specifications?Factors influencing the selection of microbiological components of specificationsFoodborne pathogens includethose which cause gastrointestinalillness after ingestion and invasion/colonisation of host tissues, forexample, Salmonella, Listeriamonocytogenes, Shiga toxin-producingEscherichia coli (STEC).A number of pathogenic bacteria e.g.Bacillus cereus, Staphylococus aureusand Clostridium perfringens causeillness through intoxication. Theirtoxins can be preformed in food whenbacterial numbers increase to highlevels ( 105 cfu/g).Salmonella, Listeria monocytogenesand Cronobacter sakazakii are generallythe only pathogens stipulated inRM specifications by Nestlé. WhileSalmonella will be included in themajority of specifications, the inclusionof L. monocytogenes and C. sakazakiiwill be dependant on FP for which theRM is to be used and type of process.9
Microorganisms –Hygiene indicatorsHygiene indicators are frequentlyincluded in microbiologicalspecifications and are widely acceptedwithin the scientific and regulatorycommunity. Their purpose are: To help in the verification of GMP/GHP and HACCP. To indicate deviations in hygiene orsanitary conditions – Unacceptablelevels will indicate an increasedrisk of the presence of associatedpathogens. Many hygiene indicatorsdescribed in scientific literaturehave overlapping characteristicsand therefore can be consideredredundant or beyond requirements. Enterobacteriaceae (Eb) and aerobicmesophilic count (AMC) are thehygiene indicators of choice for NestléRM microbiological specifications.The applicability and suitability ofAMC and Eb are illustrated below. Food processors may includealternate hygiene indicators inmicrobiological specifications.Nevertheless, while acceptable, theseare only included if deemed necessaryin Nestlé RM microbiologicalspecifications for the reasons given.Internationally recognised hygiene indicators applied in Nestlémicrobiological specificationsHygiene indicatorDescriptionWhere applicableCommentAerobic MesophilicCount (AMC)Refers to the totalload of viablemesophilic, aerobicmicroorganisms.Often applied to verifythe application ofprocessing steps suchas heat treatment. Itcan also be used as anindicator for adherenceto GMP/GHP.Also referred toas Aerobic ColonyCount (ACC),Standard Plate Count(SPC) and AerobicPlate Count (APC).EnterobacteriaceaeA large group ofbacteria, with similarproperties, includingspecies originatingfrom the intestinal tractof animals and humansas well as plants andthe environment.The interrelationshipbetween Eb andother frequently usedhygiene indicators isillustrated.As they are killed byheat processes usedin food productionand are readilyremoved fromfactory equipmentand environmentby appropriatecleaning, theirpresence is indicativeof post process (re)contamination in heatprocessed material.One of the mostfrequently appliedhygiene indicator.Now commonlyapplied as processhygiene criteria inEU regulations andthus in many casesreplaces previouscoliform criteria.10
The relationship between Salmonella, pathogenic E. coli(E. coli O157/STEC) and the commonly used Enterobacteriaceaehygiene indicator, and related hygiene indicatorsEnterobacteriaceaeTotal coliformsE. coliE. coli 0157STECFaecal coliformsSalmonella11
Internationally recognised hygiene indicators not generally appliedin raw material specifications by NestléHygiene indicatorDescriptionWhere applicableCommentColiformsA functional subgroup of Eb’s butmay also containorganisms outside theEb group.As for Eb group.Coliforms are a poorlydefined group andthere is variabilitybetween detectionmethods thus they arebeing systematicallyreplaced by Eb (seepreviously).Faecal coliforms/E.coliA functional subgroup of Eb, mostcommonly used asan indicator of faecalcontamination.While low levelsof faecal coliformsand E. coli may bepresent on raw foods(produce, meatnuts seafood), highlevels are indicativeof substantial faecalcontamination.Faecal coliformsand E. coli shouldnot be present inhighly processedready to eat foods.They tend to die offquickly in dry foodsand therefore are notconsidered useful fordry products.Listeria spp.May provide agood indication ofthe likelihood ofcontamination withL. monocytogenes.Generally appliedto wet plantenvironments andequipment (e.g.chilled and frozen).Their presence canindicate hygienestatus of processenvironment.Can be present andpersist in drains/water-containingenvironments – mayindicate inadequaciesin sanitation.12
Microorganisms – OthersFour categories of bacterial sporesare commonly included in Nestlé RMmicrobiological specifications.The application of these and the setlimits (m) depend on the nature of the FP.The 4 combinations of bacterial spore-formers usedin raw material microbiological specifications by NestléSpore Parameters (in MicrobiologicalSpecifications)Where and When appliedAerobic mesophilic sporesCan be included where it is deemednecessary that the subsequent thermalprocess applied to RM may be insufficientto destroy spores and therefore could impactfinal product AMC. Spores of Bacillus spp.is the common target microorganism.Anaerobic mesophilic sporesMay be used as a hygiene indicator in RM atrisk of Clostridial spore contamination, e.g.C. botulinum. Sulphite reducing Clostridia(SRC) are often specified for similar reasons.Aerobic thermophilic sporesMay be included to specify quality of RM,where those RM are used to manufacturelow-acid commercially sterile products(e.g. retorted/UHT) and thus will helpminimize insterility rates.Anaerobic thermophilic sporesMay be occasionally used where subsequentquality defects can be attributed tothermophilic Clostridia spp.Thermo-resistant molds may survivethermal processing and thereforemay be included in specifications toavoid the risk of spoilage in high-acidproducts.aureus and/or Bacillus cereus inRM microbiological specifications.Stringent FP specifications withrespect to these bacteria will drive theirinclusion in RM specifications.Exceptionally, Nestlé may includecoagulase positive Staphylococcus13
Sampling plansThe sampling plan summarises therequirements (limits) and definestheir stringency. It is the basis for thedecision on release / acceptance oftested lots.Sampling plans are expressed by 3 or4 parameters and are defined astwo- or three-class plans respectively.Every sampling plan has a certainamount of risk by which a good lot isrejected or a bad lot is accepted, dueto microbiological testing limitationand the heterogeneous distribution ofmicroorganisms in the sample.Parameters defining sampling plans:n number of samples or unitsanalyzed.c maximum allowable numberof sample units yielding marginalresults, i.e. results betweenm and M.m microbiological level thatseparates good quality fromdefective, or in a three-classplan good from marginallyacceptable quality.M microbiological level in a threeclass plan that separatesmarginally acceptable fromunacceptable (defective)quality. Note: In a two-class planM is assimilated to m.The analytical unit is includedin the sampling plan.Nestlé uses two-class plans formicrobiological specifications ofRM’s, therefore n, c and m aredefined.14
Infant nellaC. sakazakii6030000025g10gHygieneindicatorsAerobic mesophilic almonella100025gHygieneindicatorsAerobic mesophilic countsEnterobacteriaceae550010 4101g1gConfectioneryAn illustrative example of different stringencies applied to microbiological specifications.RM – sucrose used for infant formula (no further kill step) and used for confectionery(used as wet mix; further microbial kill step applied).15
The stringencyof microbiologicalspecificationsThe choice of n and c varies with thedesired stringency. This stringency isguided by the level of risk associatedwith the RM/FP and how the material isto be used/processed/consumed.compromise between what is anideal probability of acceptance andthe work load the laboratory canhandle as sampling plans should beadministratively and economicallyfeasible.For high stringency n is high andc is low. Choice of n is usually ancHigh stringencyLow stringencyInterrelationship between n and c for microbiological specification stringency16
Sampling plans –Two- and three-class plansA concentration (m) may also beassigned in a two-class plan, e.g.1000 cfu/g, above which the sample isconsidered unacceptable.There are two widely acceptedtypes of sampling plans as definedby the International Commission forMicrobiological Specifications for Food(ICMSF):Three-class plans are frequently usedto examine for hygiene indicator whereenumeration of microbes in a unitvolume or mass is possible. Such planscan be used to separate the qualityof a lot into acceptable, marginallyacceptable and unacceptable.Two-class plans are used essentiallyfor pathogens and where a presence/absence test is to be performed (e.g.presence/absence of Salmonella). In thecase of a presence /absence analysis,c 0 and m 0. The presence of thetarget microorganism is unacceptable.Two-class planmAcceptableUnacceptableThe microbiological limit (m) separates the quality of a lot between acceptableand unacceptable in a two-class planThree-class planmAcceptableMMarginalUnacceptableThe microbiological limits (m and M) separate the quality of a lot between acceptable,marginally acceptable and unacceptable in a three-class plan17
Analytical MicrobiologicalMethodsFor each of the microorganisms orgroup of microorganisms included inthe microbiological specifications, atleast one analytical method should beavailable. Ideally, the analytical methodused should be readily available andeasily applied on a routine basis. Theyshould be based on internationalstandards (e.g. ISO methods). Alternatemethods should be validated againstsuch standard methods. If pooling (ofsamples) is considered as a means ofreducing the number of analytical units,evidence must be available to confirmequivalent performance of a poolingstrategy.FoodstuffSample analyticsDiagnostics18
Frequently asked questionsDo all microbiological parametershave to be analysed for each batch?No, the supplier must have thenecessary control measures andprerequisite programmes in placewith their corresponding analyticalverification as deemed necessary(monitoring). A vendor approval systemand audit will assess compliance.An increased frequency of testing(’positive release’) may be required ifnon compliance is demonstrated.Is the probability of detectingpathogens the same if we reducethe number of analytical units andpropotionally increase the samplesize (e.g. equivalence of 3 x 500g;60 x 25g; 1500 x 1g)?No, drawing greater numbers ofsmaller samples provides greaterprotection than drawing the sametotal weight of sample in fewer sampleunits. There is an increased chanceof detecting contamination due touneven distribution of contamination.A calculation table is available fromICMSF (www.icmsf.org) which candetermine equivalence. However, thefeasibility of analysing larger volumesmust be considered and suppliers areencouraged to seek advice from Nestléexperts.Is analytical pooling possible forSalmonella or Eb and what are thelimits? Why have we have stated375g for S, 100g for Eb?Yes, pooling is acceptable up to 375gfor Salmonella and up to 100g for Eb.Pooling up to these analytical volumeshave been validated. The 100g poolinglimit for Eb was established based onthe fact that for many microbiologicalspecifications n 10, hence 10 x 10gsamples could be pooled, compared to15 x 25g for Salmonella.What is meant by wet mix, dry mix,MR2, EB10 and MR1?Wet mix ingredients are those where afurther kill step will be applied to thembefore finished product is produced.Dry mix ingredients will be usedwithout any microbial kill step beforefinished product product
Analytical Microbiological Methods are used to assess if RM or FP are in agreement with the microbiological specifications. Microbiological testing may be used by industry or government. Lot testing, against the pre-defined
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