Food Microbiology

beneficial microbes

microbes to make food (cheese, pickles, sauerkraut)

harmful microbes

microbe causing food spoilage, food poisonings, or foodborne infection (e.coli, listeria)

what does food spoilage result from

growth of microbes

what is microbial growth controlled by

intrinsic and extrinsic factors

intrinsic factors

factors related to the food

extrinsic factors

environment where food is stored

intrinsic factors example

food composition, pH, oxidation-reduction potential, physical structure

intrinsic: most favourable pH for growth

neutral

what takes over foods composed of carbs and how

mold, degrades food by hydrolysis

what takes over foods composed of proteins and fats

bacteria

bacteria taking over protein and fat foods: putrefaction

proteolysis and anaerobic breakdown of proteins, yielding stinky amine compunds

bacteria taking over protein and fat foods: unpasteurized milk spoilage

acid production followed by putrefaction

bacteria taking over protein and fat foods: butter

short chained fatty acid production results in rancid butter

intrinsic: how does lower water activity affect intrinsic factors

inhibits microbial growth

intrinsic: how does pH affect intrinsic factors

impacts make up of microbial community and types of chemical reactions that can occur when microbes grow

intrinsic: what does low pH favour

yeast and mold

intrinsic: what does neutral pH favour

bacteria

intrinsic: how is oxidation-reduction potential altered

by cooking

intrinsic: what does lower redox cause

more bacteria and anaerobes

intrinsic: how does physical structure promote microbial growth

grinding and mizing

antimicrobial substances: coumarins

fruits and vegetables

antimicrobial substances: lysozyme

cows milk and eggs

antimicrobial substances: aldehydic and phenolic compounds

herbs and spices

antimicrobial substances: allicin

garlic

antimicrobial substances: polyphenols

green and black teas

extrinsic: what does lower temp do

retards microbe growth

extrinsic: what does higher humidity do

promotes growth

extrinsic: how does the atmosphere promote growth

by oxygen

extrinsic: atmosphere: modified atmosphere packaging (MAP)

shrink wrap and vaccuum tech to control atmosphere

how much of global annual food is lost to spoilage

1/3 (microbes, insects, poor distribution)

what are the effects of food spoilage

bad taste, toxicity, infections, cost

where is filtration used to remove microbes

water, wine, beer, juice, pop

what does pasteurization do

kills pathogens but does not remove them

what does refrigeration at 5ºC do

slows microbial growth but does not stop it

what temp and time will kill spoilage microbes

115ºC for 25 to 100 minutes

how do canned foods spoil

spoiled before canning, underprocessing, leaking of water into containers while they cool

pasteurization

heating food kills pathogens and reduces number of spoilage organisms

how is water availability measured

in terms of water activity (aw)

what does water availability represent

the ratio of relative humidity of the air over a test solution compared with distilled water (where aw=1)

dehydration

preserves food by decreasing water and increasing solutes

GRAS

chemical agent: generally recognized as safe

what agents are included in GRAS

organic acids, sulfite, ethylene oxide gas, ethyl formate

how does sodium nitrite inhibit spores in meat

forms nitrosamines

what will impact the effectiveness of chemical preservatives

pH

HHP

high hydrostatic pressure

what is HHP

applies pressure without must change in temp

what is HHP effective at

eliminating eukaryotic microbes

what bad can HHP cause

highly detrimental to cell membranes, not effective at eliminating gram positive microbes

radapperization

use of ionizing radiation (gamma) to extend shelf life or sterilize

how is the food undergoing radapperization not radioactive

excellent penetrating power

how does radapperization kill microbes in moist foods

by producing peroxides from water (peroxides oxidize cellular constituents)

pro and cons of electron beams

are electrically generated so can be turned on and off

does not generate radioactive waste

does not penetrate foods as deeply as gamma

bacteriocins

bactericidal proteins active against related species

how do some bacteriocins act

disspiate proton motive force of susceptible bacteria, form pores in plasma membranes, inhibit protein or RNA synthesis

MAP

modified atmosphere packaging

polylactic acid

green alternative to plastic, made from wood and corn. it is embedded with slowly released nisin

how many cases of food-borne disease are there per year in U.S.

48 million

how many deaths of food-borne disease are there per year in U.S.

3000

how is food disease transmitted

bad hygiene, fecal oral route, fomites

what are the 2 primary types of food borne disease

food borne infections and food intoxications

food borne infection

ingestion of pathogen, followed by growth, tissue invasion, and release of toxins (listeria)

example of what can carry food borne infection

raw foods (raspberries, seafood)

who is most vulnerable to listeriosis

pregnant women, young and old, immunocompromised

food borne intoxications

ingestion of toxins in food where microbes have grown

when does food borne intoxications produce symptoms

shortly after food consumption because the microbe doesn’t need to grow

fungus toxins: aflatoxins

carcinogens produced in fungus infected grains and nuts

fungus toxins: fumonisins

carcinogens produced in fungus infected corn

what does algal toxin contaminate

fish and shellfish

what must testing be for food borne pathogens

rapid, sensitive, simple

what are PFGE, PCR, and RFLP used for

amplifying, specifying species

what are the major fermentations used

lactic, propionic, ethanolic

what do they majority of fermented milk products rely on

lactic acid bacteria

probiotics

live microbes that adda a health benefit to host

what types of microorganisms are probiotics

lactobacillus, bifidobacterium

what are the benefits or probiotics

immunomodulation, controls diarrhea, anticancer, treats enteric disease

probiotics: what do lactobacillus acidophilus and bifidobacterium improve

lactose intolerance, general gut health, lowers cholesterol in serum, anti-tumor activity

what type of fermentation is all cheese from

lactic acid

enology

wine production (separation and storage of liquid before fermentation)

what is fresh must treated with

sulfur dioxide fumigant

how long is fresh must fermented for

3-5 days at 20-28ºC

how are dry or sweet wines controlled

regulating initial must sugar content

what is racking

removes sediment from fermentation

malt

germinated barely graines having activated enzymes

mash

the malt after being mixed with water in order to hydrolyze starch to usable carbohydrates

mash heated with hops

hops assist in wort clarification, heating inactivates hydrolytic enzymes

where are bottom yeasts used

in beer production

where are top yeasts used

ale production

2 ways beer can be removed of microbes

pasteurized or filtered

distilled spirits: sour mash

mash inoculated with homolactic bacterium

what does bread production involve

growth of saccharomyces cerevisae (bakers yeast) under aerboic conditions

how is bread leavened

maximized CO2 production

how does bread spoil

bacillus species produce ropiness

sufu

from fermentation of tofu

sauerkraut (sour cabbage)

from wilted, shredded cabbage

quorn

a meat substitute made from fermented mycoprotein

mycoprotein

a protein from fungi

what are the length and width of hyphae from quorn similar too

animal muscle fibers