Indicator Organisms

To monitor conditions in a particular environment, ecosystem, area, habitat or consumer product. Examples: Coliforms, Yeast $ Mold count, Aerobic Plate count, E-coli

Pathogens:

A bacterium, virus, or other microorganisms that can cause disease. Example: Salmonella, Listeria monocytogenes.

    Growth characteristics

Yeast & Mould:

            Grow in food (pH 2-9) temperature ( 5-35°C), able to grow at a of aw 0.85 or below.

Aerobic plate count:

            These are mesophilic, growth temperature range (15-37°C)

Thermoduric bacteria:

Survive heating range (60-80°C) but growth at mesophilic temperature range.

Psychrotroph:

            Growth temperatures (0°C-7°C) but have temperature optima above 20°C.

Thermophilic:

            Extremophile – that thrives at relatively high temperatures, between 41 and 122°C

Halophilic & Halotolerent :

            Halophiles require saline conditions to grow while halotolerant can grow under these conditions but donot require elevated conc.of salt

Acidophilic:

            Thrive under highly acidic conditions (usually at pH 2.0 or below)

Salmonella spp:

            High environmental resistance the range of temperatures for growth can be between 2 and 54°C. broad pH range of 3.8 -9.5

Listeria monocytogenes:

            Generally multiplies at temperature ranging from 1-45°C, is acid tolerant and can survive in acidic foods for days or weeks. It can grow at a water activity of 0.90. growth in media with 10% sodium chloride (NaCl).

Vibrio spp:

            Facultative anaerobes and grow best in alkaline conditions, halophilic.

   Milk and Milk products:

• Raw milk, as it leaves the udders of healthy animals, normally contains very low numbers of microorganisms.
• Total counts usually are less than 1000 per mL. Micrococcus, Staphylococcus, Streptococcus, and Corynebacterium spp. are the most common bacteria.
• Microorganisms associated with foodborne illness may enter the raw milk supply through infected animals, milking personnel, or the environment.
• If lactating cows have mastitis, large numbers of the infectious organisms might be shed into the milk.
• Pasteurized, dehydrated, fermented and concentrated
• The microbiological quality is influenced by the initial flora of the Raw milk, the processing conditions, and post-pasteurization contamination.
• Efforts should be made to minimize microbial numbers in raw milk supplies, because processing does not eliminate quality defects.

Pasteurized milk:

• The initial microflora of freshly pasteurized milk consists primarily of thermoduric bacteria and spores.
• The presence of coliforms and other Gram-negative bacteria in freshly pasteurized milk is normally an indication of post – pasteurization contamination.
• Outbreaks of salmonellosis and listeriosis in pasteurized milk have been linked to post – pasteurization contamination.
  • Process hygine & Food safety criteria:
    • Coliform count
    • Aerobic plate count
    • Salmonella spp
    • Listeria monocytogenes

Fermented Products:

• Yogurt, fermented milks(cultured milk), and cultured cream (sour cream) are unripened, cultured dairy products low pH <4.5 generally prevents the growth of most spoilage and pathogenic organisms
• Normally contain hight numbers of starter microorganisms or secondary ripening flora
• Process hygiene & Food safety criteria:
  • Coliform count
  • Yeast & Mold count
  • S. aureus ( Coagulase +ve)
  • E.Coli
  • Salmonella spp
  • Listeria monocytogenes

Frozen milk products:

Microbial content of frozen products largely reflects the quality of the ingredients used for their manufacture: milk, cream, nonfat milk solids, sugar, chocolate, fruits and nuts, etc.

• Milk, cream, and the soluble components are normally blended and pasteurized, therefore, microbial counts of the pasteurized mix are generally low (<100 per mL).
• Sporeformers (Bacillus soo.) and some of the hardier thermoduric bacteria originating from the fluid or dry components are usually the only survivors.
• Process hygiene & Food Safety criteria:
  • Coliform count
  • Aerobic plate count
  • S. aureus ( Coagulase +ve)
  • E.Coli
  • Salmonella spp
  • Listeria monocytogenes

Dried milk products:

• Because of their low water activity (aw), dried products rarely spoil or deteriorate because of microbial growth.
• The typical microflora of dried milk consists of thermoduric micrococci, thermoduric streptococci, and aerobic sporeformers
• Psychrotrophic bacteria, coliform bacteria, and yeasts and molds are reduced to very low levels during pre—heating
• Process Hygiene & Food safety criteria:
  • Yeast & Mold count
  • Aerobic plate count
  • S. aureus ( Coagulase +ve)
  • E.Coli
  • Salmonella spp
  • Listeria monocytogenes
  • Cronobacter spp.

FRUIT & VEGETABLES

Fresh fruits and vegetables are susceptible to contamination with a variety of microbial pathogens, spoilage microbes, fungi.

• Plants harbor bacteria and fungal microflora that utilize carbohydrates, protein, and inorganic salts
• Fruits flora differ from vegetables because of low pH levels which limit bacterial growth
• Spoilage of vegetable occur due to fungal species while fruits by molds.
• Contamination of produce with foodborne pathogens can occur during pre-  and postharvest handling of the products.

Dried fruits & Vegetables:

• Due to decreased aw, the normal flora of dehydrated fruits and vegetables consists predominately of yeast and molds.
• Black aspergilla are the most common fungi responsible for spoilage
• Spore – forming bacteria are also often found in the spore state on dehydrated fruits and vegetables
• Non- sporulating microorganisms like E.coli or Salmonellae are destroyed by blanching,
• But dried vegetables not previously blanched could contain these microorganisms if they had been grown in soils contaminated with animals or human wastes.

Frozen & Fermented vegetables:

• Spoilage of fermenting vegetables can occur in a number of ways. One of the principal causes is uneven distribution of salt, sugar, low pH
• Pathogenic microorganisms are not a significant issue for fermented vegetables
• Frozen vegetables are rarely involved in food poisoning incidents.

Fish and Fish Products

• Fish is a generic term to encompass all edible aquatic and marine finfish, molluscan shellfish, and crustaceans.
• These are more perishable than other high – protein foods, changes in flavor, odor, texture, and color reflect freshness.
• Muscle tissue of live, healthy fish is considered bacteriologically sterile, the largest concentrations of microorganisms are found in the intestine, gills and surface slime.
• The circulatory system of some crustaceans is not “closed” and the hemolymph of crabs can harbor substantial levels of bacteria, particularly members of the genus vibrio.
• Pathogens & sources:

Frozen cooked crustacean:

• The cooking process can be blanching. Boiling, or steaming under pressure ( lobsters, crabs, > 100°C).
• Reduces significantly the bacterial counts in crustaceans, destroying vegetative cells of both spoilage and pathogenic species.
• Causes for presence and growth of pathogenic bacteria: inadequacy of the thermal process, post-processing contamination, improper storage
• Vibrio parahaemolyticus, a common member of the microflora associated with raw shrimp and crab, is a cause of food poisoning associated with these products.

Smoked fish:

• Traditionally been used as a preservation method; and gives fish a distinct flavor.
• Are classified according to the temperature maintained during smoking (i.e., cold-smoked or hot-smoked) the salt content, and the duration of smoking and /or drying.
• For hard-smoked products with high heat input, the more heat-stable organisms such as Bacillus, Micrococcus, and yeasts will be predominant.
• For milder smoked fish, a number of gramnegative organisms will survive; Pseudimonans and Moxaxella-Acinetobacter are common in the microflora of such products.
• The potential for growth and toxin production by Cl.botulinum type E is a safety concern with smoked seafood products.
• L.monocytogenes is a microbial hazard for cold-smoked seafood where smoking temperature of less than 30°C and water phase salt concentration of less than 5% are insufficient to inactivate the organism.

Fermented Fish:

• Fish are heavily salted and allowed to stand at natural atmospheric conditions for several months.
• The high salt content retards microbial growth, hydrolysis of the fish protein is belived to occur by natural tissue enzymes.
• For low salt products, halophilic or halotolerant populations consisting of gram-positive organisms will prevail.
• One of these products, izushi, which is fermented by various strains of lactic acid bacteria, has been associated with food poisoning outbreaks from toxin produced by C.botulinum type E.
• Scombrotoxin (i.e., histamine) Poisoning is also a concern, fermented fish products can be a source of histamine.

Reference: E-Learning – AOAC India (aoac-india.org)