Dair pt 3

Question 1

effect of temperature on casein complexes?

Answer 1

increased temp –> increased aggregation due to increased hydrophobic interaction

Question 2

effect of acidity on casein complexes?

Answer 2

increased acidity –> increased aggregation due to proteins being brought to their isoelectric point

Question 3

effect of calcium on casein complexes?

Answer 3

increased calcium –> increased aggregation due to increased insoluble calcium caseinate formation

Question 4

effect of chelating agents on casein complexes?

Answer 4

increased chelating agent –> decreased aggregation due to binding of calcium

Question 5

micelle formation leads to (solvation/aggregation)

Answer 5

aggregation

Question 6

what keeps k-casein from interacting to form curds?

Answer 6

CHO portion

Question 7

what is the protein portion of k-casein called?

Answer 7

para-k-casein

Question 8

role of para-k-casein in cheese making?

Answer 8

para-k-casein precipitates via hydrophobic interactions and calcium-caseinate formation; this is enabled by the removal of the CHO moiety

Question 9

what sugars are present in milk?

Answer 9

• lactose (alpha and beta form)

- lactose oligosaccharides

Question 10

why are isomers of lactose possible?

Answer 10

anomeric carbon of galactose engages with glucose. glucose’s anomeric carbon is free to exist in either alpha or beta form.

Question 11

true or false: the alpha form of lactose crystallizes at a higher temperature than the beta isomer

Answer 11

false: lower temperature

Question 12

which isomer of lactose increases in solubility at a greater rate with increased temperature?

Answer 12

alpha

Question 13

high temperatures favor which form of lactose?

Answer 13

alpha

Question 14

list the minor components of milk

Answer 14

• organic acids
• minerals
• vitamins
• indigenous enzymes
• growth factors

Question 15

what organic acids can be present in milk?

Answer 15

lactic, acetic, citric, carbonic

Question 16

what minerals can be present in milk?

Answer 16

Ca2+, Na+, K+, Mg2+, I, Se, Zn2+

Question 17

what vitamins can be present in milk?

Answer 17

C, B2, B3, B5, E

Question 18

what enzymes can be indigenously present in milk?

Answer 18

catalase, lysozyme, B-galactosyl transferase, aldolase

Question 19

what growth factors and hormones can be present in milk?

Answer 19

insulin, estradiol

Question 20

why do we process milk?

Answer 20

• destroy pathogens
• inactivate enzymes
• prevent phase separation

Question 21

briefly describe the 6 steps of the processing of milk

Answer 21

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

Question 22

what would happen if you left raw milk at room temperature?

Answer 22

within 13-14 minutes, you’d get phase separation, which may or may not be desirable

Question 23

what QC measurements are taken? what are their significance?

Answer 23

• 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

Question 24

what does clarification of milk accomplish?

Answer 24

removal of sediments like hair of cattle, sand, feed, stones, feces; gives index of farm contaminants

Question 25

list some heat treatments

Answer 25

• pasteurization (batch , HTST)
• thermization
• ultra high temperature
• sterilization

Question 26

what does thermization accomplish?

Answer 26

it’s like pasteurization but less hot. it’s good for priming the milk for certain cheeses which require certain microbes.

Question 27

what’s the temp and time for UHT?

Answer 27

2-8s, 136-138C

Question 28

sterilization takes a (longer/shorter) time than pasteurization

Answer 28

much longer