Chap 16 to 18 Flashcards
role of nitrite in colour formation
Nitrite - more common
- active form in nitrite
- proper colour/anti-botulinal properties
myoglobin - oxygen-binding protein in muscles
contains heme - Fe2+
changes to the oxidation state or new bonds/complexes made to iron atoms change the colour of the resulting product
- changes in myoglobin impact colour
Nitrite converts O2 to NO in meat - NO binds with myoglobin at low pH (purple-red colour)
minimize oxygen exposure - oxidation: negative impact on color
Nitrate - less common
- nitrate reductase needed in microbial
Role of nitrite to prevent C.botulinum growth
- the amount of nitrite added is inadequate to prevent the growth alone
- relies on hurdle technology: low pH, salt, organic acid (lactic acid, low water activity
Ascorbate and erythorbate
antioxidant
colour development
Microbial culture
requires LAB
Lactobacillus, Pediococcus
- make acid and lower pH
- produce desirable flavours/aromas
- outcompete pathogenic/spoilage organisms
Kocuria, Staphylococcus
- conversion of nitrate to nitrite
- can secrete lipases and proteases - release of flavours
- syringol: major smoke aroma
- guaiacol: major smoke flavour
North America sausages
- Nitrite
- fermentation is at higher temperatures/faster colour produced
- LAB only used
- more acid production
- time: <18 hours
- lactic acid is produced quickly + inhibits or outcompetes non-LAB
- 2% sugar
European/Asian sausages
Nitrate added and Kocuria, staphylococcus
- conversion using reductase enzyme
- process slow
- lower temperature
- more flavour + aroma
- less acid: minimal sugar added
- time: 2-4 days
What are the type of production process casing types?
helps prevent post-processing contamination
intestine casings - edible
collagen casings - edible
cellulose/fibrous casings - not edible
polymer casings - Not edible
surface mould
common on European saugases
- purpose: further flavour/texture development
- secretes:
-> proteases: ammonia, short peptide generation
-> lipases: ketone/other oxidized lipids
- influences organoleptic properties
Filamentous fungi -> Penicillium naglgiovense, P. camemberti
mould - sensitive to smoke
dry and humidity - facilitates the growth of mould
- low temp and humidity: less mould growth
- high temp, humidity: aw stays too high, spoilage growth
concern: growth of mycotoxin
Benefits:
- protection - light oxidation
- metabolize peroxides - rancidity, by-products of bacterial growth
- facilitates more even drying
hydrogen peroxide
made by LAB
- heme - oxidized by O2 or H2O2
- green/gray/brown colour
- induce rancidity
- undesirable
- broken down by catalase
-> LAB: -ve
-> Kocuria, Staphylococcus: +ve
Rice polishing
- husk already removed
- rid of the bran and germ - create off-flavours
- more polishing = higher quality - more expensive
- less potential for off-flavours
Tane koji
- spores of Aspergillus oryzae
- green in colour
- start to grow on rice - becomes white
- mix lightly polished streamed rice w/ wood ash (higher pH environment) and mineral growth - induce sporulation
koji enzymes secrete alpha-amylase and glucoamylase -> breaks down the stretch to glucose
Traditional method
Moto: fermentation starter culture - koji + water + microbes + steamed rice
- spontaneous
- generated by LAB
- not yeast added
Modern method
- inoculated and spontaneous
- added as pure lactic acid
- yeast added
- Lactobacillus sakei
- acidity moto - prevent the growth of undesirable bacteria
- produce bacteriocins - further aid in preventing the growth of undesirable organism
semi-continous fermenation
- fermentation rate high at first - then declines
- with each addition of rice + koji to moromi -> rate inc, again
- concentration of inhibitory substance are diluted by half each time substrates are added -> ethanol, organic acid diluted and temperature is reduced
multiple parallel fermentation
Fermentation 1: koji amylases/glucoamylase break down starch to glucose
- saccharification
- Aspergillus enzymes - stable + present in moromi
Fermentation 2: Yeast consuming glucose t- produces alcohol
occurs simultaneously
sake yeast
Saccharomyces cerevisiae - different strain
- metabolizes -> 1 glucose -> 2 CO2 + 2 ethanol + 2 ATP + heat
Foam - undesirable; takes up space so can’t ferment as much sake; loss of profit; if spills, so does the yeast - clings to foam and stuck, lower inoculum, sanitization concerns, extra labour
how does foam form: glycosyl-phosphatidyl-inositol anchored protein, coded by AWA1 gene - contains hydrophobic regions where the gas bubble forms - contains glycosylation sites -> glycans like to stick to glycans (other yeast cells) - these factors inc. foam
Foamless strains
- option 1: backslopping - sampled liquids part of sake + grew up and used for a new batch - over few batches foaming decreases
- Option 2: creation/identification of mutants - mutating AWA1 - not expressed led to dec. foam formation - dec in hydrophobicity
top-fermenting
Used for ale
- made in warmer areas
temperature: 18-27°C
Saccharomyces cerevisiae
- ale yeasts clumps/flocs are lower density and trap CO2 and rise
bottom-fermenting
used for lagers
- made in cooler regions
temperatures <15°C
Saccharomyces pastorianus
- lager yeast clumps are denser and sink
Malting process
Two purposes:
1) Source of both enzymes + their substrates
- starch + proteins -> amylases + proteases
2) source of colour, body, flavour
Barley - germinated to induce biochemical changes to prepare the seed growth - more activated form
dried mid-generation -> must be done gently: preserve enzyme activity for use later up rehydration and heating
3-step process:
1. steeping:
- moisture of grain inc.
- sprayed or submerged and aerated
the process stops when small roots emerge showing ‘chit’
2. Germination:
- Enzymes become active and begin to breakdown starch
- produce heat - may start a fire, constant flow of humid air + frain turners used to keep the temperature as the required level
- 3-5 days, 10-16°C
-produce ‘green malt’
3. Kilning:
- stops the germination process
- dries + stabilizes malted grain
- enzyme activity preserved
- moisture 5-10%
- aw ~0.3
- adds flavour and colour - controlled by temperature and time
- reduces the microbial level
- diastatic power -> higher kilning temp -> darker grain -> lower diastatic power - denatures enzyme
- low heat at first -> so no destruction occurs - then increase
- higher heat is more destructive
- lastly hours done @>80°C removes dimethyl sulphide from malt
Beer ingredients
water + ions:
- water is treated via reverse osmosis and then desired minerals are added back in
- the mineral is needed as key enzyme cofactors
malted barley:
- light beers -> lighter malts
- darker beers -> lighter malts + darker malts
- need enzymes from lighter malts
- the primary source of CHO -> maltose -> ethanol
hops: Humulus lupulus
- preservation -> alpha-acid type
- flavour + bittering agent -> terpenes
Yeast
- industrial -> hops extracted
- iso-a-acids can cross the membrane -> dissociate + energy wasted pumping out extra proton
- an ionophores -> dissociate a-acid helps chelate Mg2+
Adjuncts: non-malted barley grain-derived
- the source of CHO (cheaper)
- no amylase activity
- includes sugars/syrups -> malt syrup + hydrolyzed starch
- can be as high as 60% of fermentable CHO
Mashing
Purpose:
- rehydrate and activate the enzyme in the grain
- enzyme converts starches into maltose
- solubilize needed substrate for fermentation
- extract and react
- temperature 60-65°C to raised incrementally in stages - mixed w/ water and heat
using multiple temperatures extracts starches, and allows multiple endogenous enzymes to catalyze reactions
- α-amylase/β-amylase: breakdown of amylose and amylopectin to maltose
- β-glucanase: breakdown β-glucan (contributes to poor viscosity/haze) - β-1-4 linked glucose monomers
- Proteolytic enzymes: release amino acids for yeast growth and help to make a clarified beer
Beer microorganisms and fermentation
Saccharomyces cerevisiae and saccharomyces pastorianus
Aeration: wort (liquid part) is aerated or sparge (lautering-rinsing step) with sterile air/O2
addition of O2 - jumps starts yeast’s logarithmic growth phase and ethanol production starts
- cell respiration
- required for synthesis of cell membrane lipids
Microorgnism - Saccharomyces cerevisiae
- MAL3 locus - maltose usage
Microorganism - Sachharomyces pastorianus
- a hybrid of S. cerevisiae and S. eubayanus -> cold-sensitive
- efficient use of maltose at lower temperatures - more maltotriose and growth/ferments slower
glucose consumed first
maltose + maltotriose -> transporter + enzyme to break them down α-glucosidase are repressed by glucose
Potential issues of Fermentation
- high glucose adjuncts can stall fermentation
- glucose levels always high enough to inhibit maltose utilization
- poorly attenuated beer
- less attenuated = more sugars left
- more attenuated = less sugars left
Post-fermentation
conditioning/resting
- yeast consumes secondary metabolites to bring beer its final profile
- off-gassing of undesirable volatiles
Hazy appearance
- clarification -> remove haze
- filtration -> fining agents -> additives that induce flocculation of proteins and yeast cells -> gelatin, isinglass, Irish moss
carbonation
- adding extra sugars - allowing carbonate
- “secondary fermentation”
- direct injection of CO2 gas - amount added dictated by style
Pasteurization
- before/after packaging
- 5D processing -> drops the # of microorganism
