Unformatted text preview:

CHAPTER 9Terminology of Microbial ControlSlide 3Slide 4Slide 5Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Disk-Diffusion MethodSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20CHAPTER 9CONTROL OF MICROBIAL GROWTHTerminology of Microbial Control•Sepsis/ Asepsis–Aseptic techniques•Sterilization •Commercial Sterilization•Sanitization•Antisepsis vs Disinfection –Biocide vs Biostatic •Degerming•ChemotherapyFactors that influence the effectiveness of anti-microbial procedures: 1. microbial characteristics 2. number of microbes–Decimal reduction time (D value) 3. environmental influences4. time of exposure5. concentration or intensity of treatment1. Heat (moist & dry)2. Filtration3. Low temperature4. High pressure5. Desiccation & Osmotic pressure6. Radiation Physical or Mechanical Methods1. Heat• Moist Heat –Boiling kills most vegetative forms in 10 min –Autoclave – steam under pressure–Sterilization - 15 psi, 121OC for 15 min–Pasteurization–Standard methods do not sterilize –higher temp, shorter exposure time•Dry heat •Incineration•Flaming •dry heat sterilization•Requires higher temp and longer exposure •170°C for 2 hours is equivalent to autoclaving2. Low Temperatures –Slows metabolic rate –Freezing forms ice crystals that can damage cells–Slow freezing then thawing does most damage 3. Filtration –Mechanical sterilization of heat-sensitive material –HEPA filters (high efficiency particulate air filters)–Membrane filters have pores as small as 0.01 microns4. High Pressure–Up to 130,000 psi –Endospores are resistant–Commercially pasteurize foods –Preserves flavor, taste, appearance, and nutritional value5. Desiccation–Resistance varies by species•can’t reproduce or grow, but may remain viable–Osmotic pressure•create a hypertonic environment; dehydrates cells•Preserved fruits (sugar), cured meat (salt), and pickles (salt)6. Radiation •depends on wavelength, intensity and duration•Ionizing vs non-ionizing•Sterilization of food products and disposable medical equipment; water treatmentEvaluating Anti-microbial Compounds •Phenol coefficient test•Use-dilution test–Current industry standardDisk-Diffusion MethodTypes of Anti-microbial Chemicals–Phenol (carbolic acid)•Rarely used, irritating qualities and bad odor•Penolic compounds more common•Disinfect for surfaces (Lysol) and antiseptic (antimicrobial soaps and lotions)–Halogens •Iodine – antiseptic or disinfectant–May be available as a tincture or iodophore •Chlorine - disinfectant (water treatment)–Alcohols•Affect vegetative forms of bacteria, fungi, and enveloped viruses•ethanol and isopropanol - degermer (hand sanitizer) and disinfectant •70% solution typically is most effective –Heavy metals •Silver; mercury; copper •antiseptic, algicide, mildew control paints, placed in newborn’s eyes to prevent spread of gonorrhea–Surfactants •Soap –Emulsification; degerming–Least effective of all chemical methods•Anionic Detergents–Commercial sanitizers•Cationic Detergents–disinfectant and antiseptic–Peroxygens •Disinfectants •Ozone – supplements chlorine in water treatment•Hydrogen peroxide – good disinfectant not antiseptic–Where do the bubbles come from? –Aldehydes •Disinfectant and preservative•Formaldehyde – formalin –Irritating and carcinogenic •Glutaraldehyde–Liquid chemical sterilant–Biguanides •Chlorohexidine most effect class•antiseptic in lotions, soaps and impregnated into surgical meshes and plastics –Ethylene oxide •Gaseous chemo-sterilizer •4 -18 hours exposure kills all microbes•Useful for heat sensitive materials–Food preservatives •Organic acids – Sodium benzoate, Sorbic acid–Inhibit mold growth in acidic foods•Calcium propionate - fungicide used in bread–Inhibit mold growth•Nitrates- added to many meat products –prevents germination and growth of botulism endospores–preserves the pleasing red color ????–Antibiotics •Nisin- added to cheese to inhibit growth of endospore formers•Natamycin – antifungal used in food (mostly cheese) •Why should medical antibiotics not be used in food


View Full Document

Southern Miss BSC 381 - CONTROL OF MICROBIAL GROWTH

Download CONTROL OF MICROBIAL GROWTH
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view CONTROL OF MICROBIAL GROWTH and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view CONTROL OF MICROBIAL GROWTH 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?