LAB WEEK 13 (Bacterial Counts of Foods)

What are foods prepared by microbial fermentation and therefore have high bacterial counts?

yogurt, sauerkraut, summer sausage

what treatments significantly reduce bacterial counts in foods?

pasteurization and smoking

which foods have naturally associated bacteria?

green beans, potatoes, beets

what causes the chalky appearance of grapes?

naturally appearing yeasts

what bacteria is introduced into cows milk from the udder?

Streptococcus and Lactobacillus

T/F- Pasteurization does not kill all the bacteria in milk, because some can survive the temperatures. These bacteria can eventually cause spoilage or souring of milk

True

what do high bacterial counts in foods suggest?

the potential for rapid spoilage of food

coliform counts

method to determine fecal bacterial counts in food

botulism food poisoning

ingesting a toxin produced by Clostridium botulinum when its endospores occur in the soil and the environment that contaminate the prepared vegetables

Salmonella and Campylobacter are associated with what foods?

poultry and eggs

Echerichia coli O157: H7 is associated with what foods?

meat from intestines of infected cattle

fecal contamination in foods can result in diseases such as _____

typhoid fever, bacillary dysentery, cholera, intestinal viral diseases

heterotrophic plate count (HPC)

can be used to determine the number of viable bacteria in a sample of food

the larger the count of the HPC, the more likely that….

specific bacteria capable of causing disease are present, and that the food will spoil

saprophytes

organisms that live on decaying plant and animal material

limitation of the HPC method

only organisms that can grow on the medium and conditions are counted

TFTC

too few to count (<30)

TNTC

too numerous to count (>300)

how to calculate average number of bacteria per gram of food

count the colonies on each plate and multiply by the dilution factor

pasteurization

heat process that destroys pathogenic organisms in milk while preserving the milks physical and nutritional properties

two most common methods for pasteurization

heating milk at 62.9 C for 30 min

heating milk to 71.6 C for at least 15 seconds

coliforms

gram negative bacilli (commonly E.coli) whose presence indicates high possibility that milk is contaminated with pathogenic organisms

what are the primary vectors responsible for transmission of microbial diseases in the GI tract?

food products

Methylene blue

dye used to test presence of oxygen or lack thereof

The longer it takes for the blue color to disappear in the MBRT test, the ____________ the bacterial count

lower

Methylene Blue Reductase Test

test used to screen quality of milk in finding the concentration of coliforms and Lactococcus lactis

what are the most common bacteria food-borne pathogens?

campylobacter, Salmonella, Listeria, Clostridium, Vibrio, and Staphylococcus aureus

what are the dominant protozoa causing food infections?

Giardia, Cryptosporidium, and Toxoplasma

common viral infections of food are?

Norwalk and hepatitis A viruses

Food products are the primary vehicle for the transmission of microbial diseases of the gastrointestinal system?

True

Increasing counts in food samples indicates food spoilage.

True

Differentiate between food poisoning and food intoxication.

food poisoning occurs with food containing micro organisms while food intoxication means microbes may no longer be alive but the toxins it produced are still in Food.

Milk is pasteurized, rather than sterilized

True

what are the human diseases that might become milk borne via contaminated milk handler?

streptococcal infection, shigellosis, and salmonellosis

What are some animal diseases transmitted to humans through unpasteurized milk?

tuberculosis, brucellosis, listeriosis, and Yersinosis

Why was methylene blue added to our milk samples?

Its a redox indicator, It loses its blue color in an anaerobic environment and is reduced.