Food Fermentation 1 Flashcards
What is fermentation in LAB?
fermenting CHO to LA (change in ph) decreases.
What are LAB? gram + or gram -? spores? gaseous environement?
LAB are gram + with nonsporulating, nonmotile. with low DNA content.
- anaerobic meats
What are the conditions that LAB will grow in?
approperiate ph (low) and CHO preesnt. fermented foods such as: dairy, wine, sourdouhs, and spoilage foods such as off odors from H2S and off flavors from organic acid.
What is one thing LAB has to compete with during fermenation in beer?
YEAST!
What are the two groups of LAB?
Homo-fermentative and heterofermentative.
What is homo-fermentative?
Use ONLY 6C sugars. Produces NO gas, and ends with lactic acid.
What is hetero-fermentative?
Ends in Lactic acid, acetic acid, and CO2 given off as well as ethanol. Can use 5C
- NO CO2 given off if using 5C.
ONLY CO2 if
What causes slime?
dextran from sucrose
What amines can be produced by LAB?
Tyramine, histamine
Tell me about Streptococcus thermophilus
Thermophile grows at 45-50C NOT found in fridge. Limited proteolytic activity.
What are three things about Lactobacilli?
- fastidious.
- Can be aciduric or acidophilic
- Rarely pathogenic
Obligate homofermentative lactobacilli
glucose--> Lactic acid. Acidophilus. does NOT use 5C. NO CO2. 2 ATP produced.
Faculative heterofermative
Can use 5C as well as 6C Glucose--> LA (no gas) Pentose--> LA or acetic acid 1 or 2 ATP (2ATP if go to acetic acid) 2 NADPH produced.
Obilgate heterofermative
Must use C6
- CO2!!!!
1 or 2 ATP produced depends if create acetic acid then 2. If go to ethanol 2 NAD is proced and 1 ATP.
What lactobacillus is used in swiss cheese?
Lactobacillus helveticus
What lactobacillus is used in yogurt??
delbrueckii
Why doe you need two colonies to make yogurt
- Lactobaacillus delbueckii subsp. bulgaricus
- Has strong proteolytic activity (provides AA) - Streptococcus thermophilus
- produces flavor
diacetyl Butter flavor
acetaaldehyde green apple flavor.
acetic acid vinager
Citrate fermentation pathway in LAB has 5 products and three flavors….what are they?
- Acetic acid- vinager
- acetylaldehyde- green apple
- diacetyl- butter
- acetoin
- 2,3-butylene glycerol no flavor
What are some examples of heterofermenatative?
Leuconostoc
- Key in veggie fermenation with Less than 5% NaCl.
- grows in refrigirator, vacuum packed foods.
Propionibacterium shermanii.. a little about this bacteria..
anaerobic LA produces CO2 and acetic aicd. nutty flavor and swiss cheese.
What are other organisms used in fermentation?
FUNGI Penicillium spp. geotrichum candidum.
What else in food fermentation?
Protein and fat degratdation (increase pH) RISK
4 things for a starter culture
- rapid fermentation of lactose
- Proteinase activity
- Production of inhibotory compounds
- Phage resistance
- Rapid fermentation of lactose
Use PEP/PTS to uptake the CHO into the cell and now need something ot break lactose into glucose and lactose.
Proteinase activity
Break down proein for energy. PRT-
Can use other organisms such as L. delbruekii subsp. bulgaricus
Phage resistant
Inactive phase!
block RNA/DNA injection,
Production of inhibitory sustances
bacteriocins- slows down growth
organic acids
