Microbiology

Koch's postulates to determine disease causing microbes

(1) The microorganism must be found in diseased but not healthy individuals; (2) The microorganism must be cultured from the diseased individual; (3) Inoculation of a healthy individual with the cultured microorganism must recapitulated the disease; (4) The microorganism must be re-isolated from the inoculated, diseased individual and matched to the original microorganism.

What are the four C's of food safety?

1. Clean hands, equipment, utensils and work area with soap and hot water. 2. Cook food until the temperature reaches at least 140 F. 3. Chill foods immediately after purchasing and after serving. Maintain at a temperature of less than 40 F. 4. Avoid cross-contamination from bacteria by keeping raw foods away from cooked and ready-to-eat foods.

In order list the 7 steps of HACCAP.

1. Conduct a hazard analysis, 2. Identify CCP, 3. Set critical limits, 4. Establish monitory procedures, 5. Establish corrective actions, 6. Verification, 7. Establish record keeping

State the seven principles of HACCP.

1. Conduct a hazard analysis. 2. Determine Critical Control Points (CCPs). 3. Establish critical limits. 4. Establish monitoring procedures. 5. Establish corrective actions. 6. Establish verification procedures. 7. Establish record-keeping and documentation.

What are the five steps used in the traditional isolation of Salmonella species?

1. Preenrichment 2. Selective Broth Isolation 3. Selective Plate Isolation 4. Biochemical Test 5. Serology.

Name three pointers to avoid salmonella.

1. Wash your hands carefully before handling food. 2. Clean the cutting board and use a sanitizing solution, before and after use. 3. Heating foods to at least 155 F. 4. Refrigerate or freeze leftovers immediately. 5. Keep pet feeding dishes and toys out of the kitchen.

A food sample was analyzed for aerobic plate count by diluting 100 and 1,000 times separately. the # of colonies on plate w/1:100 dilution was 240 with 1:1,000 was 35. What is the exact aerobic plate count of the food sample?

25,000 CFU/ml

An initial population of 50,000 bacteria grows with a generation time of 30 minutes. About how many bacteria will be present 3 hours later?

3,200,000 [Nt= N0 * 2^(t/G)]

If the total plate count is 500 CFU/ml, with the generation time of 30 min., what will the total plate count be after 3 hours?

32,000 CFU/ml

Give characteristics of Clostridium Botulinum.

A bacteria found in foods that produces toxins that are harmful when consumed. Very heat resistant, won't grow in acidic foods

What is patulin, with what food products is it associated, and how is it usually analytically determined?

A mycotoxin formed by Penicillium, Aspergillus and Byssochlamys genera associated with apple juice products; determined by High Performance Liquid Chromatography

Name 6 of the 8 (or 7?) pathogenic types of botulinum toxin.

A, B, C1, C2, D, E, F, G

What are five mycotoxins, and what is one food each is commonly found in?

Aflatoxin- (peanuts, tree nuts, corn), Patulin- (apples), Roquefortine c (blue cheeses), Ochratoxin a (grain, pork, coffee, wine grapes), Citrinin (grains)

Describe aflatoxins and their source.

Aflatoxins are toxic secondary metabolites produced by Aspergillus flavus and A. parasiticus, commonly found in peanuts, corn, and other stored crops.

Name 3 molds that cause spoilage in vegetables.

Alternaria, Penicillium, Fusarium, Aspergillus, Rhizopus

Name 3 strains of mold that produce mycotoxin.

Aspergillus flavus, Aspergillus parasiticus, Claviceps purpurea, Penicillium citrinin, Penicillium expansum, Fusarium spp.

What 3 microorganisms are involved in the production of soy sauce?

Aspergillus seed starter, soy yeast, lactic acid bacteria

What are the three major genera of mycotoxin producing fungi?

Aspergillus, penicillium, fusarium

What are three genera of fungi commonly used in food production?

Aspergillus, Penicillium, Fusarium, Saccharomyces

What four genera of molds can cause rotting in fresh fruits?

Aspergillus, Penicillum, Alternaria, Botrytis, rhizopus, monilinia, Colletotrichum, Fusarium, Cylindrocarpon, Mucor, Cladosporium