| NA | NA |
| Heterofermentative LAB:
? --> propionate + acetate + CO2 | glucose or lactate
Propionibacterium shermanii in Swiss cheese production |
| Fermentation: definition | achieves food preservation via growth and metabolic activities of desirable microorganisms
- microbes breakdown fermentable substrates to produce ATP
- fermentable substrates (carbs, sugars) are oxidized
- organic compounds (pyruvate) are final electron acceptors
- end products: lactic acid, ethanol, propionic acid, CO2 |
| Fermentation: specific attributes | - microbes responsible for characteristics of fermented food (aroma, flavor)
- shelf-life usually longer than that of raw product
- preservation by acid, ethanol, other antimicrobials
- vitamin content and digestibility can be increased |
| fermentation: acid food + free sugar --> ? | yeasts (Saccharomyces cerevisiae) produce alcohol
- grape juice for wine production |
| fermentation: less acid + free sugar --> ? | bacteria (Lactobacillus bulgaricus, Streptococcus thermophilus) produce acids
- milk for yogurt production |
| fermentation: malt (germinating barley) inoculated with Saccharomyces cerevisiae --> ? | beer |
| fermentation: koji (cooked rice or soybean) inoculated with Aspergillus oryzae --> ? | Soy product (miso) |
| Acid producing organisms | - Lactobacillus
- Streptococcus
- Propionibacterium
- Pediococcus |
| Lactic acid bacteria: homofermentative | homofermentative LAB (ie yogurt cultures)
- Lactobacillus bulgaricus
- Streptococcus thermophilus
- Lactobacillus lactis |
| Heterofermentative LAB:
? --> propionate + acetate + CO2 | glucose or lactate
Propionibacterium shermanii in Swiss cheese production |
| Lactic acid bacteria: meats | fermented sausages, hams, fish
- Lactobacillus curvatus
- Pediococcus acidilactici |
| Saccharomyces | yeast that's used for beer, wine, bread
ex. Saccharomyces cereisae |
| Zygosaccharomyces | yest that's used for miso, soy sauce |
| Lactobacillus + Saccharomyces --> ? | sourdough bread |
| Lactobacillus + Acetobacter + yeasts --> ? | Keifer!
several yeasts: Saccharomyces cerevisiae, S. unisporus, Candida kefyr, Kluyveromyces marxianus |
| Soybean + aspergillus soyae --> ? | soy sauce |
| beet molasses (sucrose) + aspergillus niger --> ? | citric acid |
| Aspergillus oryze + rice/soybean --> ? | miso! cooked rice/soybean inoculated with Aspergillus oryzae is called koji |
| Typical fermentation process | - substrate decreases as cell mass increases
- primary metabolic products accumulate during cell growth
- pH of growth medium drops if acids are produced
- cell growth and product formation cease as substrate is depleted
- secondary products accumulate after growth stops
- easily metabolized substrates are depleted first
- microbial succession depends on substrate and acid levels |
| Health benefits of fermented foods | microbes fermenting the foods are associated with health benefits, lactic acid bacteria (LAB) is the most studied
- some produce B vitamins (folic acid, riboflavin, vitamin B12), these are easily destroyed during cooking so this fortifies the product with B vitamins
- enzymatic breakdown of proteins/peptides --> bioactive peptides (antioxidant, antimicrobial, blood pressure lowering, antiallergenic)
- exopolysaccharides stimulate the immune cells of intestinal tract
- competitive exclusion of pathogens in intestinal tract due to LAB colonization
- produce lactic acid, bacteriocins, sphingolipids (antimicrobials)
- reduced lactose intolerance
- lowered serum cholesterol |
