Microbiology

Name one of the key bacteria responsible for kefir.

Lactobacillus kefiranofaciens, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus acidophilus, and Lactobacillus delbrueckii subsp. bulgaricus

Name the five genera of lactic acid bacteria.

Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Streptococcus

What cheese is associated w/ the following major microorganisms: lactococcus, propionibacterium shermanii, penicillium roqueforti, Lactic streptococci

Lactococcus= cheddar (or mozzarella); propionibacterium shermanii= Swiss; penicillium roqueforti= Blue; Lactic streptococci= Edam, Gouda

In the development of toxicity data for seeking approval of a new food additive, explain the difference between an LD50 and NOAEL and what are the typical units for these?

LD50 is the dose that kills 50% of test animals;NOAEL is the highest dose that cause No Observed Adverse Effects Level; amount is mg or micrograms per kg body weight

Define LD50 in the context of toxicology, and explain what a lower LD50 value indicates about the toxicity of a substance compared to a higher value.

LD50 stands for the Lethal Dose, 50%, which is the dose of a substance required to kill 50% of a test population. A lower LD50 value indicates that the substance is more toxic (or more potent), as a smaller dose is required to cause 50% mortality.

Name three obligate heterofermenters.

Lentilactobacillus brevis (formerly L. brevis) – Found in kefir and late-stage vegetable ferments. Limpasilactobacillus reuteri (formerly L. reuteri) – Probiotic found in breast milk. Lacticaseibacillus fermentum (formerly L. fermentum) Lactobacillus sanfranciscensis (The primary sourdough starter) Leuconostoc mesenteroides (The "pioneer" of sauerkraut fermentation) Oenococcus oeni (Used for malolactic fermentation in wine)

Which genus of bacteria are used in the production of kimchi?

Leuconostoc gelidum, Weissella koreensis, and Lactobacillus sakei

Name 4 major causes of food spoilage.

Microbial growth, enzyme activity, insects, parasites, & rodents, temperature fluctuation, moisture fluctuation, air, particularly O2, light, time

Name 4 classes of potential hazards of concern during food processing as defined by FSMA.

Microbial, Chemical, Physical, Radiological

What is the log reduction required for milk and what pathogen are they controlling for? What about egg shells?

Milk - 6D process targeting Coxiella burnetii (the most heat-resistant non-spore-forming pathogen in milk). Eggs - 5D process and they are controlling for Salmonella seftenberg

Name 5 organelles of cells.

Mitochondria, nucleus, vacuole, ribosome, Golgi apparatus, cell wall, cell membrane/plasma membrane, endoplasmic reticulum (SER, RER), lysosomes, peroxisomes, cytoskeleton

Explain how water activity differs from moisture content and why it matters in food safety.

Moisture content measures total water present, while water activity measures the availability of water for microbial growth and chemical reactions. Foods with high moisture but low water activity (e.g., jams) may be shelf-stable, whereas foods with lower moisture but higher water activity may still support microbial growth.

In terms of food fermentation, what does the acronym NSLAB stand for and name four.

Non-Starter Lactic Acid Bacteria; Lactiplantibacillus plantarum, Lacticaseibacillus casei, L. curvatus, Pediococcus

Top 3 microbial causes of foodborne illnesses.

Norovirus, salmonella, clostridium perfringes

Describe the Big Six pathogenic E. coli, their primary food associations, and why they are regulated similarly to O157:H7.

O26, O45, O103, O111, O121, O145; associated mainly with beef and produce. They produce Shiga toxins and cause severe illness, warranting equivalent regulatory control.

What are some disadvantages of using the formula (ball) method to calculate lethality?

Only can use at a constant retort process temperature, the cooling portion modeling is empirical and may over/under estimate lethality

Name three types of shellfish poisoning.

Paralytic, neurotoxic, amnesiac, diarrhetic

What do the following media stand for, what organisms do they select for and how do the colonies appear on the media? (ask any 5) PCA, PDA, MacConkey, McBride, MRS, XLD, VRBA, VRBGA, Baird-Parker, Cetrimide, Blood, SS, EMB, MYP, BHI, Oxford, BS, TSC, HE, PIA

PCA: Plate Count Agar, total viable bacteria, creamy/white colonies PDA: Potato Dextrose Agar, yeasts (smooth colonies) and molds (filamentous colonies) MacConkey Agar: Gram negative bacteria, enterobacteriaceae, lactose fermenters (pink/red) vs non-fermenters (colorless) McBride agar: Listeria monocytogenes, small, translucent, blue-gray colonies (when viewed with Henry illumination) MRS: de Man, Rogosa and Sharpe agar, LAB, white/creamy XLD: Xylose Lysine Deoxycholate agar, salmonella (red with black center) and shigella (red w/o black centers) VRBA: Violet Red Bile Agar, coliforms, red/purple colonies with red-purple halos VRBGA: Violet Red Bile Glucose Agar, Enterobacteriaceae, red or purple Baird-Parker: Staphylococcus aureus, black shiny colonies with clear zones/halo Cetrimide: Pseudomonas aeruginosa, large flat colonies producing greenish blue pigment Blood agar: hemolytic bacteria, colonies with different hemolysis: alpha: greenish, beta: clear, gamma: none SS: Salmonella-Shigella agar, Salmonella (colorless with black centers), Shigella (colorless) EMB: Eosin Methylene Blue agar, Gram negative enteric bacteria, lactose fermenters; E. coli (metallic green sheen), other lactose fermenters (purple), non-fermenters (colorless) MYP: Mannitol egg Yolk Polymyxin; Bacillus cereus, large, pink to red colonies surrounded by a distinct zone of precipitation (cloudiness) BHI: Brain Heart Infusion; Listeria monocytogenes, small, smooth, creamy white or translucent colonies Oxford: Listeria monocytogenes, small, black colonies surrounded by a black halo BS: Bismuth-Sulfite; Salmonella, black or metallic green colonies, often with a "rabbit eye" appearance (a black center with a clear edge) and a dark "halo" in the surrounding agar TSC: Tryptose Sulfite Cycloserine, Clostridium perfringens, black colonies HE: Hektoen Enteric Agar, Differentiates Salmonella and Shigella from other Enterobacteriaceae, Salmonella: Blue-green colonies with black centers (H2S production).Shigella: Green to blue-green colonies without black centers.Coliforms (like E. coli): Large, yellow to salmon-orange colonies. PIA: Pseudomonas Isolation Agar, Pseudomonas aeruginosa, typically producing blue to blue-green, convex, and often smooth or mucoid colonies

Name three of the main antimicrobials used in aquaculture throughout the world.

Penicillins (like amoxicillin, ampicillin), phenicols (florfenicol), macrolides (erythromycin), tetracylcins (Oxytetracycline), aminoglycosides (streptomycin), sulfonamides, fluroquinolones

List 5 genera of bacteria and molds that produce antimicrobial agents.

Penicillium ,L. lactis, Lactobacillus, Pediococcus,Streptomyces