Microbiology

Name three major causes of food deterioration

Growth and activity of microorganisms (yeasts, bacteria, molds); Natural food enzymes; Insects, parasites, and rodents; Temperature, both hot and cold; Air, oxygen; Light; Moisture and dryness

Describe the purpose of HACCP and list its first two principles.

HACCP is a preventive food safety system designed to identify, evaluate, and control hazards. The first two principles are hazard analysis and identification of critical control points (CCPs).

Please rank the size of bacilli, cocci and helicoidal bacteria.

Helicoidal>bacilli>cocci

What are some viruses that cause foodborne human illness?

Hepatitis, rotavirus, norovirus

What is the difference between Homofermentation and Heterofermentation?

Homofermentation is when bacteria produce mostly lactic acid; Heterofermentation is when bacteria produce lactic acid, butyric acid, acetic acid, Carbon Dioxide, and other end products.

Differentiate between homofermentative and heterofermentative lactic acid bacteria in terms of their products, and name two examples of each.

Homofermentative Lactic Acid Bacteria: These species are "specialists" that focus on producing lactic acid quickly. They are essential when the goal is a rapid drop in pH to inhibit spoilage organisms. Eg. Lactobacillus acidophilus: (Dairy/Probiotics), Pediococcus acidilactici: (Fermented meats/Sausage), Lactococcus lactis: (The primary starter for Cheddar and most hard cheeses), Lactobacillus bulgaricus: (One of the two mandatory bacteria required to make Yogurt), Streptococcus thermophilus: (The second mandatory yogurt bacteria; also used in Mozzarella) Heterofermentative Lactic Acid BacteriaThese species are the "flavor and texture artists." Because they produce CO2, ethanol, and esters, they provide the characteristic "tang," carbonation, and "eyes" (holes) in various foods. Eg. Leuconostoc mesenteroides: (Sauerkraut/Kimchi/Kefir), Lactobacillus brevis: (Vegetable fermentation/Sourdough), Lactobacillus sanfranciscensis: (The specific bacterium that gives San Francisco Sourdough its famous flavor), Oenococcus oeni: (Crucial in winemaking for "Malolactic fermentation," which softens the acidity of the wine), Leuconostoc citreum: (Commonly found in fermented seafood and kimchi)

Explain the difference between indicator organisms and index organisms, with examples.

Indicator organisms signal general sanitary quality (e.g., total coliforms), while index organisms indicate the possible presence of specific pathogens (e.g., E. coli as an index for enteric pathogens).

Food infection vs Food intoxication.

Infection has microorganisms living in the food, intoxication is when a biological end product (toxin) is in the food. Intoxication can be fatal

Describe tyndallization and how it works.

Intermittent heating (usually at 100 C for 30 minutes) over 3 consecutive days. The first heating kills vegetative cells. During the incubation period between heatings, the surviving spores germinate into vegetative cells, which are then killed by the subsequent heating.

Differentiate between food intoxication and infection and classify the following microorganisms if they cause intoxication or infection regarding foodborne illness: Clostridium botulinum, Campylobacter jejuni, Staphylococcus aureus, Aspergillus flavus, and salmonella species.

Intoxication is ingestion of toxins produced by certain pathogens in a food. Intoxication: Clostridium botulinum (botulinum toxin), Staphylococcus aureus (amongst the more common toxins secreted by S. aureus are hemolysin, leukotoxin, exfoliative toxin, enterotoxin, and toxic-shock syndrome toxin-1 (TSST-1).), Aspergillus flavus (aflatoxin) Food infection is when the food contains bacteria or other microbes which infect the body after it is eaten. Infection: Salmonella, Campylobacter jejuni

Explain the difference between intrinsic and extrinsic factors affecting microbial growth in foods.

Intrinsic factors are inherent to the food, such as pH, water activity, nutrient content, and natural antimicrobials. Extrinsic factors include environmental conditions like storage temperature, relative humidity, and surrounding atmosphere.

Name four intrinsic and four extrinsic factors that affect microbial growth in foods.

Intrinsic: pH, water activity, nutrient content, natural antimicrobials Extrinsic: temperature, relative humidity, atmosphere (oxygen), storage time

What are the intrinsic and extrinsic factors for microbial growth in food?

Intrinsic: pH, water activity, redox potential, biological structure, moisture content,animicrobial component , competitive microflora, nutrient content Extrinsic: temperature and time, relative humidity, gaseous environment, presence of other organisms, processing operations, type of packaging

Name names three intrinsic factors and three extrinsic factors that affect microbial growth in food products.

Intrinsic: water activity, pH, nutrient content; Extrinsic: temperature, storage environment, humidity.

A product has a pH of 4.2 and water activity of 0.97. Discuss classification and safety concerns.

It is an acidified food (pH < 4.6). Primary concerns include acid-tolerant pathogens and spoilage organisms such as yeasts and molds. Appropriate strategies include pasteurization, preservatives, or refrigeration.

What are the core messages of the five keys to safer food outlined by the World Health Organization?

Keep clean, separate raw and cooked, cook thoroughly, Keep food at safe temperatures, use safe water and raw materials

Name three facultative heterofermenters.

Lactiplantibacillus plantarum (formerly L. plantarum) – Found in sauerkraut, pickles, and olives. Lacticaseibacillus casei (formerly L. casei) – Used in Yakult and aged cheeses. Lacticaseibacillus rhamnosus (formerly L. rhamnosus) – Common probiotic strain. Lactobacillus curvatus (Fermented meats/sausages) Lactobacillus sakei (Kimchi and fermented meats)

Name three obligate homofermenters.

Lactobacillus acidophilus (Common in probiotics and human gut) Lactobacillus delbrueckii subsp. bulgaricus (Essential yogurt starter) Lactobacillus delbrueckii subsp. lactis (Hard cheese production) Lactobacillus helveticus (Emmental and Gruyère cheese) Lactobacillus salivarius (Found in the digestive tract) Lactococcus lactis (Though not a Lactobacillus, it is an obligate homofermenter used in cheddar)

Name five probiotic microorganisms.

Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus plantarum, Lactobacillus rhamnosus, Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium animalis, Streptococcus thermophilus, Enterococcus faecium, Kefir (mixture of Lactobacillus and Bifidobacterium), Saccharomyces boulardii (a yeast), and Limosilactobacillus reuteri.

Name three key bacteria responsible for kefir.

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