Dairy Flashcards
how does the blood carrying nutrient get to secretory cells
capillaries
within secretory cells what organelles synthesise milk components
Endoplasmic reticulum and ribosomes
what can be considered as milk components
proteins and lipids
in what form are the milk components moved out of the cell
vesicles
what organelle facilitates the transport of milk components out of the cell
Golgi
where are the vesicles deposited
the lumen of the alveoli
after the lumen of the alveoli where does the milk components go
milk cistern
where are the milk components stored
milk cistern
what hormone stimulates muscle contraction that results in milk excretion
oxytocin
where does the milk move to after muscle contraction
teat cistern
percentage of water in milk
87%
Percentage of fats in milk
2.4-5.5%
percentage of milk solids
9%
what is meant by the term milk solids
vitamins, minerals, proteins, carbohydrates and enzymes
how do milk fats exist and how are they stabilised
in fat globules
by a membrane
what gives the milk a yellowish tinge
Beta-carotene
triglyceride to fatty acid/sterols/phospholipids composition of milk fats
98% to 2%
fats in milk are a major source of and
energy and nutrients
what three things causes milk to go rancid when exposed to them
lipases, light and oxygen
protein composition of milk
18% Whey
80% casein
2% other
what enzyme breaks down lactose
beta-galactosidase
what are the fat-soluble vitamins found in milk
A
D
E
K
What are the water-soluble vitamins found in milk
B
C
4 reasons to process milk
safety
preservation
variety
economic or convience
reasons why milk has high spoilage
water activity
nutrition value
source
four spoilage enzymes of milk
lipases
phospholipases
proteinases
lactase
what do lipases in milk do?
hydrolyses the fats causing rancidity
What do proteinases in milk do?
hydrolyses proteins giving age gelation (lumps) and off-flavours
What does lactase do?
turns lactose into lactic acid
what do phospholipases do
break down milk fat globule causing creaming
the temperature required for LTLT(low temp, long time) processing
63 degree
the temperature required for HTST(high temp, short time)
72 degrees
the temperature required for HHST(higher heat, short time)
100
the temperature required for UHT
138-150
what enzyme is used to test the sufficiency of pasteurisation
alkaline phosphatase
Why is alkaline phosphatase used
> heat stability than milk pathogens
3 alternatives to pastuerisations
ultraviolet light, high-pressure processing and pulsed electric fields
why must milk be pasteurised before homogenisation
to inactivate lipases to stop rancidity
what does homogenisation do to milk?
reduces fat globule size
prevents separation
what is the isoelectric point signify
the point at which a protein is least soluble
how does adding acid coagulate milk
changes the pH to the isoelectric point of the wanted protein
how does adding salt coagulates milk
when added in excess the salts aggregate together drawing water away from the protein and it ppts
how does chymosin coagulate milk
chymosin enzyme cuts off the negatively charged K-casein micelle tails reducing the repulsion like charges and allowing them to coagulate
