food microbiology

microorgs mostly involved in fermentation

lactic acid bacteria and variety of yeasts

what are lactic acid bacteria

gram +ve, aerotolerant anaerobes, rods/cocci

what are 2 types of lactic acid bacteria

homofermentative and heterofermentative

what are homofermentative lactic acid bacteria

fermentation yields primarily lactic acid

what are heterofermentative lactic acid bacteria

fermentation yields lactic acid and variety of flavorful compounds

lactic acid reduces…and improves…

food spoilage, storage qualities (lowers pH)

what process is carried out on milk

pasteurization to remove potential pathogens

what is usually added to milk

desired microorgs

2 bacterias that make yogurt

S. thermophilus and L. bulgaris

what temperature is yogurt incubated

43ºC

What is the role of Streptococcus thermophilus in yogurt production

produces acids and promotes growth of L. bulgaris

Which bacteria produces most of the acid in yogurt

Lactobacillus bulgaris

What does acid do to casein in milk during yogurt production

denatures casein, causing the milk to thicken

what may raw milk cheese contain

pathogens

how does curdling happen

lactic acid bacteria precipitates proteins

how does ripening happen

through lactic acid bacteria and other ogranisms

what does ripening result in

flavor

what do starter cultures in cheese making do

ferment lactose and produce lactic acid

what does lactic acid do in cheese making

forms curds by precipitating proteins and fats

what is the liquid left after curds form

whey