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Nutrition and Food Services
NFS 2000
All Professors

What are Microorganisms Simply microorganisms are living entities that are too small to be seen by the naked eyeThose important to food include bacteria viruses protozoa andmold and yeast All organisms are classified as eitherbacteria have no nucleusmost other organisms having a nucleusViruses are neither but are considered a life formMost important and troublesome May excreteSingle cell microscopic Several shapes and forms Bacteria are classified based on whether or not they can retain the pigment crystal violet in their cell membrane the gram staintest is one of the first done to characterize bacteria Classified as either gram positive or gram negativeReproduction of Bacterial Cells Reproduced by division fission Referred to as growth Under optimum conditions a cell divides every 2030 minutesWhat are Microorganisms Some bacteria form spores Spores are produced in response to unfavorable growing conditions Allows them to start growing spore germination again when favorable conditions returnFungi include both mold and yeastMolds may be unior multi cellular form a tangled mass called mycelium composed of hyphae which facilitate their growthMost molds also form spores on the top of the hyphae which allow for the spreading of mold culturesMolds can produce toxins Can be beneficial by producing antibiotics or enzymes that are used in food processing Ex flavor in blue cheeseMolds Largerthanbacterialongerthanyeasts Widelydistributedinnature Surviveonmanysubstances Moretoleranttocoldthanheat MayalterpHofacidfoodssothatCbotulinum cangrow Mosthavelowheatresistance AerobicYeastareunicellularthatgrowoverawidesetofconditionswithgenerallyrapidgrowthratesTheyaremostoftenassociatedwithpositivefoodprocessingapplicationsbreadwineetc CanalsobedetrimentaltofoodcauseoffodorflavorsetcYeasts Smallerthanmoldslargerthanbacteria Reproducebybudding Widelyfoundinnature Liquidfoodswithsugarandacid Moretoleranttocoldthanheat Littleresistancetoheat alcoholandcarbondioxidearebyproductsofgrowth Nopublichealthproblem Aerobic WhatareMicroorganisms ProtozoaaresinglecelleucaryotesthatmostoftenaffectfoodareparasitesTheydontgrowinfoodbutoccurduetoinfectionoffoodanimalsorcontaminationoffoodbyinfectedanimalsincludinghumansTheytypicallyformcystsinfoodanimalsthatmaybeconsumedbyhumanswhichbecomesickwhentheprotozoapenetratestheintestinallining ExGiardialambliaGiardialamblia Frequentlyassociatedwiththeconsumptionofcontaminatedwater5outbreakstracedtofoodcontaminationbyinfectedfoodhandlers Possibilityofinfectionsfromcontaminatedvegetables MostfrequentcauseofnonbacterialdiarrheainNorthAmerica Foundinintestinaltractofanimals WhatareMicroorganisms VirusesareobligateparasitesmeaningtheyabsolutelyrequireahosttosurvivebecausetheyusethehostsbiochemicalmachineryTheyarecomposedofaproteinaceouscapsuleinwhicheitherDNAorRNAresideusuallyRNAinvirusesthatareofconcerninfoodsOncetheyattachtohostscellstheyinjecttheirnuclearmaterialorbecomeengulfedinthehostcell TheyallowthehostcelltoreplicatetheirproteinsthatformnewvirusparticlesultimatelykillingthehostcellcauseofdiseasesymptomsFactorsAffectingMicrobialGrowth Environmentalfactorssuchasallhavemajorinfluencesonthegrowthofmicroorganisms Availabilityofnutrients Wateractivity pH Temperature Oxygen
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