MILK Flashcards
Can indicate pus, colostrum, or late milk
yellowish creamy
Can indicate the addition of water for adulteration or skimming
blue thin/ thin creamy
Milk is produced under unhygienic conditions
visible dirt and impurity
Can indicate fermentation by yeast
bubbs, coagu, why separation
Can also indicate mastitis milk or milk adulterated by flour and/or skim milk powder.
It can also indicate early spoiling
small white clot
Can indicate the presence of blood in the milk
red/pink
Can indicate sour milk or mastitis milk
large clots
Result of growth of acid-producing bacteria that reduces lactose to lactic acid.
acid flavors
characterized by sweet and sour smell, thin and waterish appearance could be a result of bacterial activity and storage in closed container without proper ventilation
blue souring
Pure bitter flavor is detected by taste only
true
rancid flavor is detected by taste only
both senses
___ taste is a result of peptonizing of milk by Streptococcus liquefaciens
bitter
is a result of lipolysis (deterioration) of fat
rancidity
like garlic, onion, beets, poorly made silage, as well as certain plants and pastures can
cause off-flavor milk
feed flavors
Suggest very slight oxidation as well as low solids and/or low-fat milk
flat flavor
Suggestive of malt. Result of the growth of bacteria??
Steptococcus lactis var. maltigenes
Sometimes described as “oily”, “stale”, “tallowy”, or “cardboard”
oxidized flavor
Associated with milk from cow in an advanced stage of lactation or mastitis milk.
salty milk
salty milk is caused by an increase in ____ and low in ___ levels
chlorine; lactose
Suggest mustiness, staleness and foul stable air
unclean flavor
Caused by Pseudomonas producing esters
fruity aroma
aIndicate the presence of capsule producing bacteria such as Aerobacter aerogenes
slimy milk
slimy milk is caused by bacteria ___
aerobacter aerogenes
why milk clots?
high acidity) or high protein percentage like colostrum
some bacterial contaminants of the milk can attack the milk sugar (____) to form acid
lactose
primary
acid produced.
lactic acid
a dye which is colorless in acid environment and changes to red in alkaline solution
phenolphthalein
natural constituents of milk making it slightly acidic
protein and phosphates
the addition of phenolphthalein to milk will not change the color of the milk rather the addition of an alkali like sodium hydroxide neutralizes the acid, and adding an excess amount will turn the phenolphthalein red
true
acidity test is used to ascertain large amount of lactic which reduces milk heat stability, and thereby its suitability for milk product manufacture.
titratable acidity test
Normal milk acidity ranges from _____ to ___ lactic acid
0.10% to 0.20%
Values ___ and above should be rejected for pasteurization as it will clot in the pasteurizer.
0.25%
The acidity is due to ____, while alkalinity to ____
hydrogen ions (H+)
hydroxyl ions (OH-)
is a measure of quantity of acid present
titratable acidity
is a measure (numerically inverse) of intensity of that acidity
pH
The pH of the milk is dependent on the ____ concentrations in the milk
hydrogen ion
The pH meter is standardized using ___solutions. T
standard buffer
Normal cow’s milk has a pH of
6.5-6.8
tests done in the dairy farm or dairy plant’s laboratory
routine tests
routine tests can only be done on raw milk
false
Routine tests of raw milk consist of the following
DMC, TPC, presumptive Coliform test, dye reduction, Determining of keeping quality of the milk
Routine test on pasteurized milk consist of the following
- Phosphatase test
- Coliform Test
- Methylene Blue Reduction test
most used micro exam in milk
TPC
no single method could give the total viable population in milk.
true
The average number of bacteria is per microscopic field is determined after examining 5 and 40 fields.
50
Grade A raw milk should not have more than
100k/mL
Grade A pasteurized milk should have a count of not more that
20k/mL
This method is especially suited in low bacterial densities sample such as pasteurized milk wherein most of the bacteria have been killed during the process.
TPC
other factors influence the reduction time
bacterial growth phase
generation time
presence of somatic celsls
he decoloration is due to the reduction of methylene blue (blue color) to
leucomethylene
is an indirect method of bacterial count and ability of the bacteria to propagate
MBDR
Because of the unknown lag phase and generation time, the reduction time is a good measure of the initial bacterial index
poor measure
commonly used to assess the keeping quality of producer’s milk.
dye reduction test
rhe lower the bacteria present in a given milk sample, the longer it will take to reach a count of 50-100 million
true
milk rich in somatic cells have a longer reduction time
shorter
If the reduction test is carried out on heat-treated milk, the reduction does not start until the ____is present, as the ____ of the milk was destroyed by the treatment.
double quantity of microorganism is present
hypoxanthin dehydrogenase
Pasteurization supposedly kills all coliform bacteria in milk. Therefore, the presence of coliform bacteria in pasteurized milk is assumed to be acquired before and after pasteurization
after only
Coliform test is performed on producer milk as well as during the transport of milk.
falase - not done
Ice cream contains 12% saccharose. At such concentration, when ice cream is inoculated in the media, lactose negative but saccharose-positive bacteria can form acid and assume the characteristic appearance of coliform bacteria.
true
number of colonies per ml of satisfactory grade coliform values
<5
number of colonies per ml of not quite satisfactory grade coliform values
5-30
number of colonies per ml of unsatisfactory grade coliform values
> 30
test to detect presence of chlorine-containing substances such as hypochlorites and chloramines.
wode’s
In Wode’s test, ___ is added to the sample, and would result to the liberation of ___ if present
hydrochloric acid
chlorine,
The chlorine could then react with ____ that could result to free iodine.
potassium iodide
tests for milk adulteration
indole/iodine test
resorcinol
hehner
Test used to detect starch/rice-wash in milk.
indole/iodine
Test used to detect the addition of coconut in milk.
resorcinol
Test to detect the presence of formaldehyde in the milk.
hehner
indicates the presence of formaldehyde. (positive rxn)
yellowish colored middle
