| Processed meats: pros | - extended shelf-life
- convenience, ready to eat
- variety
- flavor enhancement (salt, spices)
ex: hot dogs, bologna, sausages, salami, lunch meats |
| Processed meats: contamination sources | - the fresh meat itself
- seasonings and formulation ingredients |
| Typ. microorganisms in hot dogs | - Micrococcus spp
- Bacillus spp
- Lactobacillus spp
- Streptococcus spp
- some yeasts |
| Processed meats: 3 types of spoilage | slime, souring, greening |
| Processed meats: slime | - outside of sausage casings
- lactic acid bacteria (aerotolerant) and yeast |
| Processed meats: souring | - underneath the sausage casing
- Lactobacillus spp, Enterococcus spp
- lactic acid produced |
| Processed meats: greening | - on surface or in the center of sausages
- microbial production of H2O2 or H2S
- some Lactobacillus spp produce H2O2
H2O2 or H2S + nitrosohemochrome (cured meat pigment) --> green color |
| Bacteria that cause greening in processed meats | - Weisella viridescens
- Enterococcus faecium, faecalis
- Leuconostoc spp
- Lactobacillus fructivorans, jensenii, sake |
| Low acid canned foods | - pH > 4.6 (red meats, poultry, seafood milk, corn, lima beans, meat & veggie mixtures)
- thermophilic flat-sour spoilage (souring, no gas, cans remain flat): Bacillus stearothermophilus, coagulans
- sulfide spoilage (odors from volatile sulfide compounds): Clostridium nigrificans, bifermentans
- gaseous spoilage (gas production, swollen cans): Thermoanaerobacterium spp., Clostridium sporogenes, botulinum |
| Acid canned foods | - pH 3.7-4.6 (fruits ie. tomatoes, pears, pineapple, fruit cocktail)
- less heat needed for microbial safety
- acid (low pH) + heat = more lethal to Clostridium botulinum spores
- thermophilic spoilers: sporeformers, Bacillus coagulans
- mesophile spoilers: mostly sporeformers, Bacillus polymyxa, Clostridium butyric, Clostridium pasteurianium, some Lactobacillus spp (survive pasteurization, thermoduric) |
| High acid canned foods | - pH < 3.7 (some fruits/veg ie. grapefruit, sauerkraut, pickles, tomato ketchup)
- naturally high acid or acidified by processor, much less heat needed for microbial safety
- spoiled by thermoduric lactic acid bacteria (survive pasteurization), yeasts, and molds
- yeast ex: Byssochlamys fulva produces heat-resistant ascospores, pectinolytic enzymes degrade pectin
- Clostridium botulinum spores are sensitive to high acid and heat during canning, survivors cannot germinate in high acid environment |
| Factors influencing population and composition of microflora on seafood | - environment: [NaCl], water temp. influences prevalent bacteria type
- season: increased populations during warmer months
- harvesting conditions: more microbes in trawling vs. line caught
- handling and processing: cleanliness of deck, rough handling of nets causes fish compaction/bruising/fecal material expulsion
- storage on ships: ice or chilled brine, frozen storage |
| Seafood spoilage | mostly caused by Pseudomonas, Acinetobacter, Moraxella
- sulfide odors
- discoloration
- softening
- purge
- gas production |
| Spoilage of fruits | - low pH limits bacterial growth (exception: Erwinia spp can cause rot in pears)
- mostly yeast and molds spoil fruits, yeasts grow faster
- yeast ferment sugars
- molds degrade high MW constituents of fruits
- spoilage defects: softening, discoloration, exudate, moldy odor |
| Spoilage of vegetables | - generally higher pH, water, and protein content than fruits
- can support growth of bacteria, yeast, and molds
- relatively high REDOX potential
- bacterial soft rot: soft, mushy, water-soaked appearance
- spoilage defects: discoloration, exudate, off odors, gas production
- bacterial spoilage caused by Pseudomonas, Erwinia (cause bacterial soft rot)
- spoilage molds: Botyritis cinerea, Geotrichum spp, Rhizopus stolonifer |
