Physico chem prop of milk Flashcards
book by Sukumar De
Outlines of Dairy technology
physical state of components of milk are all in solution
No
dissolved or suspended
Protein
Fat
Minerals
Lactose
physical state
Colloidal suspension
Emulsion
Solution like lactose / colloidal suspension like protein
solution
Physica; state of mineral salt is emulsion and solution?
No
Colloidal supension and solution
…..is used to assess perishability of milk
acidity
fresh milk is …….
amphoteric
if basic red lithmus turns
blue
what contributes to apparent accidity
Citrates
Acid phosphates
Casein
What is apparent acidity
Natural/ Apparent/ Titrable acidity
TAN
TAN is due to
casein
Acid phosphate
Citrate
Real acity is actually NAtural acidity?
No
real acidity= Developed acidity
Total acidity is expressed as percentage of ….
Lactic acid
what is the titrable acidity and pH of cow’s and
Buffaloe’s milk
0.13-0.14 - 6.4- 6.6
0.14-0.15 - 6.7-6.8
what does a lower pH than normal indicates
What does more alkaline pH indicate
bacterial spoilage
sub clinical mastitis
why pH of sub clinical mastitis cow milk is alkaline
Na ion seaps into mik from blood in udder
temperature doesn’t affect specific gravity of Milk
false
the standard temp at which Specific gravity is measured in milk
15.6 degree celcius
60 deg fahrenheit
Hydrostatic balance is used to measure ….. of milk for which … is also used
Specific gravity
Pycnometer
principle or method used by hydrostatic balance is : determining ….. of known …..
weight of known vol
principle behind pyconometer
determining Weight of known Vol
working principle of Lactometer
determining Vol of known weight
Sp gravity can be measured using …/…. and ….
pycnometer= hydrostatic balance & lactometer
Sp gravity of cow’s milk
buffalo’s milk
skimmed milk
1.028- 1.030
1.030- 1.032
1.035- 1.037
Mean value of Sp gravity of milk at market
1.030
relation between fat, SNF and Sp gravity
fat~1/Sp gravity
SNF~ Sp gravity
SNF and Natural acidity and why
SNF~ Natural acidity
SNF= casein, Citrate, acidic phosphate
Fat and Sp gravity are inversely proportional yet buffalo with higher fat perc than cow still has higher sp gravity ….why?
Buffalo has Higher SNF content than cow’s
to increase Sp gravity cream / water can be added ?
false
cream= fat decreases Sp gravity
water addition reduces SNF/ solute conc which also reduces Sp gravity
dding whey/ skimmed milk …sp gravity
increases
skimmed milk is low in fat..lower fat means higher Sp gravity
freezing temp of milk is > water
false
milk freezes at a lower temp
-5 deg celsius
why freezing temp of milk is lower than 0 deg celsius
more solutes more lowering of temperature needed
Depression in freezing point of milk indicates
milk freezing at a temp lower than (-5) that of water (0 deg)
usual relation between Freezing point and Freezing point Depression is direct?
false
inverse
Adding water increase / decreases fp? what about Freezing point depression
adding water increases Fp and Decreases FPD
adding water….. more water like so shifts from -5 to more positive or higher temp
what all can increase FP (decrease FPD) of milk
increase fp means more positive
adding waterhat
can reduce FP
reduce means more negative/ more cold
(more milk like)
souring
boiling (solutes increases -lowers temp)
sterillisation “
