Fermentation - Fermented products Flashcards
What is the importance of the addition of salt in the process of sauerkraut production? And how much salt is added?
1.5-2.2 % w/v
- Selective properties on microbiota.
- Inhibition of pectolytic enzymes.
- Extraction of cabbage juice which acts as the brine.
What is the usual succession of MO in the primary fermentation step? What metabolites do they produce?
Gram-negative bacteria –> Formic acid, Acetic acid, CO2
Leuconostoc bacteria –> LA, Acetic acid, ethanol. CO2, mannitol, dextran
Lactobaccillus plantarum –> LA
Pediococcus, Enterococcus, Lactobacillus brevis –> LA, diacetyl
What went wrong in production when the sauerkraut is discoloured (pink/grey)?
- Manganese deficiency.
- NaCl or temp too high, air leakage.
What went wrong in the production of sauerkraut when the product has a greyish discolouration?
Gram-negative bacteria are too abundant.
What went wrong in the production of sauerkraut when the product is too soft?
- Insufficient salt added (should be 1.5-2.2% w/v).
- Pressure too high.
What went wrong in the production process of sauerkraut when the product is sour but has no flavour
Temp too high.
What went wrong in the production process of sauerkraut when the product is not sour enough?
Temp too low.
What went wrong in the production process of sauerkraut when the product has a musty smell?
Surface spoilage has occurred, yeast growth was facilitated by air leakage.
What went wrong in the production process of sauerkraut when the product is rotting?
This is caused by pseudomonas, proteolysis and pectinolysis after the degradation of the acid.
What are the two main MO in sausage fermentation and what are their roles?
- Micrococcus spp.
pH > 5.5 nitrate reduction –> nitrite which prevents spoilage MO
pH < 5.5 nitrous acid is in equillibrium with nitric acid and NO (latter has a stabilizing effect on colour) - LAB
acidification
flavour
What is the MO used in beer fermentation?
Saccharomyces cerevisiae (yeast)
Which MO are used in the fermentation of Kinema?
- Bacillus subtilis
- B. lichenformis
Why do soy beans need to be fermented to be edible?
- They have bitter tasting compounds
- They have ANF:
1. Trypsin inhibitor, inhibits digestion
2. Phytic acid, reduced bioavailability of minerals
3. Haemagglutinins, cause red blood cell to clump together
4. Stachyose which is poorly digestible oligosaccharide, which is further degraded to raffinose which is also hard to digest (flatulence)
What sets the fermentation of kinema apart from all the other products?
It is an alkaline perfentation. pH will go from 5 to 7. It is driven by Bacillus subtilis which is specialized in degrading proteins –> releasing ammonia –> increases pH
Why is boiling a crucial step in Kinema production?
All MO but spore formers are inactivated. Because bacilli are the most abundant spore formers, after cooling the remaining spores germinate and predominate. This is a natural fermentation process.
