Food Microbiology Lecture Notes PDF

Food microbiology Dr. Arafat M. Goja Microbiological examination of foods Why we examine foods for microbiology? objec7ves: - To ensure that the food meet certain food safety standards - To ensure that the food meet internal standards set by processing company - To check...

Food microbiology Dr. Arafat M. Goja Microbiological examination of foods Why we examine foods for microbiology? objec7ves: - To ensure that the food meet certain food safety standards - To ensure that the food meet internal standards set by processing company - To check the materials entering the food meet the standards. - To examine the presence of speci:c organism or a group of microorganism. - Quality control 2 Methods for food microbiological examination Common methods used for food microbiological examina7on, categorized based on tradi7onal and modern approaches: 1. Culture-Based Methods These are classical techniques to isolate, enumerate, and iden7fy microorganisms. Plate Count Methods Standard Plate Count (SPC): Measures viable microorganisms in a sample. Spread Plate and Pour Plate Techniques. SelecBve and DiEerenBal Media Used to isolate speciIc types of microorganisms (e.g., MacConkey agar for coliforms). Enrichment Culture Techniques Enhances the growth of speciIc microorganisms in low concentra7ons. Most Probable Number (MPN) Method Sta7s7cal es7ma7on of microbial popula7ons in samples. 3 Methods for food microbiological examination 2. Microscopic Methods Direct Microscopic Count (DMC) Observes bacteria directly under a microscope (e.g., using a PetroM- Hausser coun7ng chamber). Fluorescence Microscopy Uses Puorescent dyes to iden7fy live/dead cells (e.g., acridine orange or DAPI stains). 3. Biochemical Methods Catalase and Oxidase Tests. FermentaBon Tests To iden7fy speciIc metabolic proper7es of microbes. API (AnalyBcal Pro:le Index) Systems. 4 Methods for food microbiological examination 4. Rapid DetecBon and EnumeraBon Techniques Immunological Methods Enzyme-Linked Immunosorbent Assay (ELISA). Latex Agglu7na7on Tests. Molecular Methods Polymerase Chain Reac7on (PCR): Detects speciIc DNA/RNA of microorganisms. Quan7ta7ve PCR (qPCR): Quan7Ies microbial DNA. Loop-Mediated Isothermal AmpliIca7on (LAMP). Biosensors Detects microbial metabolites or speciIc microbial ac7vity in food samples. 5 Methods for food microbiological examination 5. Advanced and Emerging Technologies Next-GeneraBon Sequencing (NGS) Provides a detailed microbial proIle of food samples. Microarrays Detect mul7ple genes simultaneously. Whole Genome Sequencing (WGS). 6. Physicochemical Methods ATP Bioluminescence Assay Measures ATP to es7mate microbial contamina7on. Mass Spectrometry (e.g., MALDI-TOF). 7. Rapid AutomaBon-Based Systems Automated colony counters (e.g., PetriIlm). Real-7me PCR-based systems. 6  Sampling - Sampling plan: One of the biggest problems associated with food microbial examinaBon - Number of samples: 5 - 10 samples per batch or square root of the number of packs per patch √ number of packs - samples must be representa7ves 7 Two design of sampling plans 1- Two –class sampling plans 2- Three –class sampling plans A two-class plans consist of speciIca7ons: n, c, m where: n = the number of sample units from a lot that must examined c = the maximum acceptable number of sample units that may exceeded the value of m. m = the maximum number of relevant bacteria per g, value grater than this are either marginally acceptable or unacceptable 8 Two design of sampling plans Ex. n = 10, c = 0 10 sample units are analysed for a speciIc pathogen (salmonella) if one contain salmonella the complete batch is unacceptable M = a quality used to separate marginally acceptable from unacceptable, Value at or above M at any sample are unacceptable. Ex. n = 5, c = 2, m =