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What are characteristics of lactic acid bacteria?
gram-positive
aerotolerent anaerobes

Two types:
Homofermentative
Heterofermentative

Used in fermented products (saurkraut, pickles)

Lactic acid production reduces pH and improves storage quality
Homofermentative
fermentation yields primarily lactic acid

used in PICKLES!!!!!
Heterofermentative
fermentation produces lactic acid AND a variety of flavorful compounds

used in CHEEEEESE!!!
What does lactic acid due to food?
reduces pH
increases shelf life
What are yeast used for?
alcoholic beverages and breads

commonly use saccharomyces strains
Whey
water in milk
casein
milk protein that causes thickening in yogurt and other milk products when DENATURED
What are the two main processes in making cheese?
curdling and Ripening
What is curdling? Process?
1) curdling is when lactic acid bacteria and/or Rennin precipitate proteins and fats == curd formation
starter culture ferments lactose to produce lactic acid

2) Whey is drained off and treated like sewage (cuz of high BOD) or used for other processes

3) Curd is heated to extract more whey

4) salt added to promote extraction of water and inhibit growth of unwanted organisms

5) Packing or Pressing and Ripening
Rennin cleaves caesin, resulting in curd formation
What is Ripening?
leads to texture and flavor change due to organisms added in starter culture or added after onto surface

cheese is pressed and packed and allowed to age for long period of time

Different methods for different cheeses
How are hard cheeses ripened?
wrapped

no additional bacteria added to cheddar cheese

Swiss - innocculated with propronibacter to produce bubbles
longer you ripen-- the higher the acidity and sharpness
What is the process of ripening in Semi-soft cheese (blue) ?
Curd is innoculated with penicillium roquefortti that creates blue spores in wholes
What is the ripening process if soft cheese (Brie) ?
Curd is left UNWRAPPED and additional bacteria is added to surface

bacteria excrete proteases that are responsible for softening

Needs to be very sanitary
Process of Making Vinegar?

Bacteria used?
Use acetobacter-- STRICT AEROBE

oxidizes ETHONAL--> acetaldehyde --> ACETIC ACID

oxidation produces pmf and ATP!!
How is Wine made? Whats the difference between dry and sweet wine? red and white?
MUST (grape juice) used

Metabisulfide added to prevent growth of WILD yeast

resistant yeast S. cervisia and S. elliposideus added and grow until 12-14% alcohol content

Dry wine= all sugars fermented
Sweet = sugars left or added

Red= fermented with skins
White= no skins
Metabisulfide
Na2S2O2

added to wine to prevent growth of wild yeast
What are the 5 steps of brewing??
1. malting
2. Mashing
3. Boiling
4. Fermentation
5. Polishing
What is Malting
First step of brewing

grains are allowed to germinate producing amylase, amylase breaks down starch (cannot be digested by yeast) into fermentable sugars (activated in mashing)

Grains are then dried and crushed to create MALT
What is Mashing?
second step of brewing, after malting

malt is soaked in 60 C water for 1-2 hours to allow activation of amylase to convert starch into sugars ( glucose and maltose) that could be fermented

malt is filtered to create WORT
What is Boiling?
Third step of brewing, after mashing

HOPS is added to WORT and wort is boiled for several hours (NEAR STERILIZATION)

Flavor and ANTIMICROBIAL compounds extracted from hops during boiling

Hops prevents lactic acid bacteria from growing

Filtered (commercial) and then cooled to 20 C
What is Fermentation?
Fourth step of brewing, after Boiling

Yeast is added to wort- vary depending on type

Lager = top yeast (saccharomyces carlsbergensis)

Ale = bottom yeast (S. cerevissia)
What are factors that effect taste during brewing?
malt source
hops
yeast
time and temp of fermentation
What is polishing?
Last step of brewing, after fermentation

filtration, pasteurization and carbonation

in bottle carbonation is when sugar is added before bottling and additional fermentation is carried out, which produces bubble! bubbles dissolve into liquid when under pressure
How is light beer made?
with Genetically modified yeast that uses all sugar in wort
When and why is hops added to brew?
During boiling (3rd step)

added for taste and antimicrobial compounds that prevent the growth of lactic acid bacteria