intro Flashcards
Why are foods fermented?
- texture, aroma, taste
- nutrient value
- preservation, storage
Microorganisms involved and eg of its products
Lactic acid bacteria (LAB): cheeses, yoghurt, salami, sauerkraut
Yeasts: bread, cider, beer, wine
Yeasts + LAB: African beers, sourdough bread, soy sauce, kefir (from Eastern Europe), kimchi (from Korea), miso (from Japan)
Fermentaion
= Metabolic process
= Condition determine outcome:
~ Substrate lv (raw product, additions)
~ Fermentation process (temp, pH)
~ Starter culture/ inoculation
= Resultant acidity and low pH inhospitable to many spoilage microorganisms
Traditional fermented food industry (9)
Small scales inconsistant quality Manual Insentive to time Safety is a minor concern Open Septic No sterile medium Significant exposure to contaminants
Modern fermented food industry
Time sensitive Aseptic Machinery / automated consistant quality Safety is a major concern Minimum exposure to contaminant Contained Large scale Pasteurised or heat treated medium
Bacteria size
1-10 um
Difference between Gram +ve & -ve bacteria
+ve has a thick peptidoglycan wall
-ve has a thin peptidoglycan wall, an outter membrane with periplasmic space in between
Bacteria cell shape
cocci bacilli spirilla (Spiral) spirochaetes (Cockscrew) vibrios (comma)
Bacteria cell grouping
Chain of rod and cocci
clusters of cocci
Pair of cocci
Tetra of cocci
Archaea
has no peptidoglycan wall
found in extreme environment
Fungi
Cell bound by cell wall composed mainly with chitin, some prtein and glycoprotein
Chitin
N- acetyl glucosamin residue - a Nitrogen containing polysaccharide
Yeast
- Saccharomyces cerevisiae
- egg shaped unicellular eukaryotic cell
- larger than bacteria
- reproduced by budding (asexually) (or sexually)
- No flagella
Moulds
- Fungi
- Hyphae - Long branched filaments- interwine to form mycelium
- Growth at tips
Microbes macronutrients (95%)
Carbon / Hydrogen / Nitrogen / Oxygen / Phosphorous
Sulphur
macronutrients can use to compose
carbohydrate, lipid, protein, nucleic acids
Other microbes macronutrients
Magnesium- enzyme cofactors, complex ATP, stablize membrane & ribosomes
Iron - electron transport, enzyme cofactors
Potassium - enzyme activity
Calcium - endospore heat resistance
microbes micronutrients
Copper / Cobalt / manganese / zinc /Nickel / Molybdenum
Mostly used in enzyme
Metabolism
Chemical reaction in cell to yield energy and material for growth
Each reaction need enzyme to speed up reaction and lower the energy needed
Specific for a given substrate
When a bond is broken, energy is released and used to run other reactions
Enzyme purpose
lower energy required for metabolic reactions and increase the rate
energy stored in cell as
ATP (adenosine triphosphate)
Catabolism
Breaking down complex molecules into small molecule Release energy( ATP) and heat and produce energy- poor end products (CO2, H2O), NH3)
oxidation, exergonic
Anabolism
Synthesis cell marcomolecules (Protein, Lipids etc) using precursor molecules (amino acids, fatty acid etc)
Energy required, reductive, endergonic
Oxidising agent
oxidise substrate and reduce itself
Reducing agent
reduce substrate and oxidise itself
Eg of Electron carrier (oxidized form & reduced form)
(Ox) (Re)
NAD+ 2e- + 2H+ NADH + H+
FAD + 2e- + 2H+ FADH2
NADP+ + 2e- + 2H+ NADPH + H+
