Bacterial Counts on Food Products

BIOL315L Session 22

sanitary control of food quality

concerned with testing food products for the presence of specific microorganisms

food products

primary vehicle responsible for transmission of microbial diseases of the gastrointestinal system

heterotrophic plate count

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

the larger the count, the greater likelihood that specific pathogens capable of causing disease will also be present cause food spoilage

limits of heterotrophic plate count

only bacteria capable of growing in a culture medium under the environmental conditions provided will be counted

food microbiology

study of microorganisms that create, contaminate or cause the spoilage of food and the pathogens that may cause disease if food is improperly stored and/or handled

ways in which food changes after harvest

residual enzymatic processes in the meat or plants, chemical reactions with the environment, and microbiological processes that can induce desirable or undesirable changes in the flavor of the food

(as soon as food is harvested)

food spoilage

associated with microorganisms; is caused by the generation of metabolic byproducts that are typically considered unpalatable and/or unhealthy

ex. rancidification of milk, putrefaction of meat, oxidation of fats, production of amines

processing

food often becomes contaminated during this stage

ex. meat in the slaughterhouse with dirt from hooves and hides or intestinal contents

muscle tissue

has high water-content and supports the growth of bacteria and provides a rich source of protein, glycogen, and amino acids

origin of most pathogens that contaminate commercial food

come from intestines of the slaughtered animals or in feces used for crop fertilizer

members of Enterobacteriaceae family are responsible for most disease (Salmonella, Shigella, E. coli) and other genera (Campylobacter, Gram-positive Listeria monoctyogenes, Clostridium spp.)

different methods for food preservation

cooking, salting, adding spices, fermentation, refrigeration, freezing, freeze-drying, pasteurization, canning, use of chemical preservatives

number of bacteria recovered from each food

given in units of CFU/100 g of food