Dair pt 3 Flashcards
effect of temperature on casein complexes?
increased temp –> increased aggregation due to increased hydrophobic interaction
effect of acidity on casein complexes?
increased acidity –> increased aggregation due to proteins being brought to their isoelectric point
effect of calcium on casein complexes?
increased calcium –> increased aggregation due to increased insoluble calcium caseinate formation
effect of chelating agents on casein complexes?
increased chelating agent –> decreased aggregation due to binding of calcium
micelle formation leads to (solvation/aggregation)
aggregation
what keeps k-casein from interacting to form curds?
CHO portion
what is the protein portion of k-casein called?
para-k-casein
role of para-k-casein in cheese making?
para-k-casein precipitates via hydrophobic interactions and calcium-caseinate formation; this is enabled by the removal of the CHO moiety
what sugars are present in milk?
- lactose (alpha and beta form)
- lactose oligosaccharides
why are isomers of lactose possible?
anomeric carbon of galactose engages with glucose. glucose’s anomeric carbon is free to exist in either alpha or beta form.
true or false: the alpha form of lactose crystallizes at a higher temperature than the beta isomer
false: lower temperature
which isomer of lactose increases in solubility at a greater rate with increased temperature?
alpha
high temperatures favor which form of lactose?
alpha
list the minor components of milk
- organic acids
- minerals
- vitamins
- indigenous enzymes
- growth factors
what organic acids can be present in milk?
lactic, acetic, citric, carbonic
what minerals can be present in milk?
Ca2+, Na+, K+, Mg2+, I, Se, Zn2+
what vitamins can be present in milk?
C, B2, B3, B5, E
what enzymes can be indigenously present in milk?
catalase, lysozyme, B-galactosyl transferase, aldolase
what growth factors and hormones can be present in milk?
insulin, estradiol
why do we process milk?
- destroy pathogens
- inactivate enzymes
- prevent phase separation
briefly describe the 6 steps of the processing of milk
1) collect milk and store cold (<4C)
2) send to processing facility in refrigerated trucks
3) take QC measurements
4) Clarify
5) Homogenize
6) heat treatment
what would happen if you left raw milk at room temperature?
within 13-14 minutes, you’d get phase separation, which may or may not be desirable
what QC measurements are taken? what are their significance?
- fat content: milk value
- total solids: milk value
- microbial load: shelf life
- sediments present: no one wants hair and sand in their milk
- freezing points/moisture: indicator of fraud
- flavor profiles: verifies onset of rancidity
what does clarification of milk accomplish?
removal of sediments like hair of cattle, sand, feed, stones, feces; gives index of farm contaminants
list some heat treatments
- pasteurization (batch , HTST)
- thermization
- ultra high temperature
- sterilization
what does thermization accomplish?
it’s like pasteurization but less hot. it’s good for priming the milk for certain cheeses which require certain microbes.
what’s the temp and time for UHT?
2-8s, 136-138C
sterilization takes a (longer/shorter) time than pasteurization
much longer
