Saran's Learn Microbiology

  MICROFLORA OF FOOD 1) Meat Natural/Typical Microflora Pseudomonas , Acinetobacter , Moraxella , Micrococcus , Flavobacterium Spoilage Organisms Pseudomonas , Shewanella , Lactic Acid Bacteria, Clostridium spp. Sources of Contamination Slaughterhouse environment, intestinal contents, knives, workers, tables, water, air Spoilage Characteristics Sliminess, sour smell, discoloration, putrid odor, rancidity Preservation Methods Refrigeration, freezing, vacuum packing, drying, curing, irradiation, canning 2) Fish and Seafood Natural/Typical Microflora Pseudomonas , Acinetobacter , Moraxella , Bacillus , Flavobacterium , Vibrio Spoilage Organisms Pseudomonas fluorescens , Proteus , Serratia , yeasts, molds Sources of Contamination Water, slime, gills, gut, fishing boats, nets, ...

FOOD AS A SUBSTRATE FOR MICROORGANISMS Factor Description Effect on Microbial Growth Examples / Notes 1) pH (Hydrogen-ion concentration) Each microbe has minimum, optimum, maximum pH Low pH inhibits bacteria; yeasts & molds more tolerant Fruits, pickles, soft drinks resist bacteria Foods with low pH (<4.5) Natural or fermentation acidity Prevent bacterial spoilage Spoilage mainly by yeasts & molds Buffering capacity Some foods resist change in pH Strong buffers allow longer microbial growth Milk (high buffer), fruit juice (low buffer)   Microbe Type Preferred pH Outcome Bacteria Near neutral (6–7) Grow widely in many foods Yeasts Slightly acidic (4–5) Fruit juices, fermented foods ...