exercise 11 (part 1: sauerkraut)

lactobacillus species

-Found in final stage of fermentation, homolactic fermenter -Strictly fermentative, salt tolerant, acid producing, Gram (+) rods. -Higher acid tolerance than previous bacteria.

leuconostoc species

-found in intermediate stage -heterolactic fermenters -Strictly fermentative, salt and acid tolerant, acid producing, Gram (+) cocci.

list the three natural flora of cabbage

1. enterbacter colacae, Erwina herbicola 2. leuconostoc species 3. lactobacillus species

three conditions that favor sauerkraut growth

1. lactic acid production only takes place under anaerobic conditions 2. salt creates an evr that these lactic acid thrive in producing bacteria preferred for fermentation 3. bacteria use the sugars from the cabbage to produce the lactic acid

describe final stage

After 4 to 6 days Lactobacillus species are the only bacteria in our system able to tolerate the low pH. More lactic acid is produced by fermenting the sugars in the cabbage and the pH eventually reaches around 1.5 to 2. Organic acids are also produced at this stage providing a lot of the unique flavor in sauerkraut.

describe intermediate stage

After two or three days only bacteria able to grow in high salt and low pH are growing. As heterolactic fermenters they produce equal parts carbon dioxide, lactic acid and ethanol.

describe early stage

Naturally occurring bacteria on the cabbage use up all remaining oxygen in the can. This creates an anaerobic environment where the facultative anaerobes carry out the fermentation.

enterbacter colacae, Erwina herbicola

found in early stage, facultatively anaerobic, acid producing, gram negative rods

sauerkraut is produced through...

microbial succession (this is carried out by normal microbiota found in cabbage)

why can acid fermentation be used as a way to preserve food?

most bacteria can't live in the highly acidic evr

microbial succession

situation in which different types of microorganisms grow up and then die off one after another as conditions in the evr change over time