Food Microbiology Exam 2- module 5

3 types of antimicrobials

Synthetic, natural extracts, GRAS (ex. vinegar)

What acids are antimicrobials (high activity)

acetic, lactic, propionic, sorbic, benzoic acids and parabens

What acids have low activity

citric, malic, and fumaric acids

When "ic acid" loses a H, it becomes ___

"ate"

pKa and acid strength have a

inverse relationship

How is acid resistance mitigated?

ATPase pumps out H+ to maintain the ideal pH of the cell

How do nitrosamines form in foods

under acidic conditions or when fried, nitrates and amines combine

what animal do nitrosamines form tumors in

rats, in their liver

What is the additive that reduces the formation of nitrosamines

sodium erythorbate

What is the additive/preservative used for wine

sulfites and bisulfite

What preservative is used for baked goods

phosphates

name ways to utilize biopreservation in foods

addition of LABs, probiotic bacteria, and bacteriophages

How does LAB preserve food

acidify the food below 4.8 pH and produce bacteriocins

What do bacteriocins do

disrupts cell membrane, increase permeability, pore formation, detergent

Bacteriophages in biopreservation

lytic cycle lyses cells quickly, destroying bacterial populations

What are challenges to using bacteriophages

large scale production, delivery, stability, specificity, mutation, regulations

What is a D value

the time it takes to reduce CFU/mL by 1 log

What is a Z value

the temperature increment needed to shorten the D value by a factor of 10

What is the most important extrinsic parameter to controlling spoilage in foods

temperature

What bacteria class grow at refrigeration temperatures?

psychrotrophs

how do bacteria respond to lower temperatures

membrane increases in unsaturated fatty acids, prevents membrane crystals and maintains fluidity

freeze drying

freezing followed by vacuum sublimation of ice, a very low water activity

MAP packaging encourages the growth of

anaerobes

Explain how HHP works

cold pasteurization, uniform high hydrostatic pressure in a sealed vessel which limits microbial growth via lysis and inactivation of enzymes

benefits of HPP

no impact on flavor or nutrients

What is the water activity of dried fruits and powdered products

0.2 to 0.6

What is infared drying used for

high moisture foods

How does UV radiation damage microbes

DNA damage via thymine dimers, viruses are resistant

How does ionizing radiation damage microbes

inhibits DNA synthesis due to DNA breaks

How do microbes adapt to these treatments

heat/cold/osmotic shock proteins, Spores and viruses are usually most resistant, Salt/pH/nutrients, Stationary phase are more resistant, VBNC induced in Salmonella by high salt