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Milk Lab Report
Kim chi nguyen
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2/26/2013
Section 12768
FOS4041L
Tuesday 6-9pm
Kim chi nguyen Section 12768 1
Milk Lab Report
Purpose: The purpose of this experiment is to determine the effect of pH, temperature on the
coagulation of milk. For the 2nd experiment, the purpose was to evaluate on taste, texture, and
appearance on various dairy product
Principle of food:
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Homogenized milk are richer in taste than pasteurized because of fat particle.
Yogurt are tart from the bacteria
Whey protein coagulate at 150 Degrees Fahrenheit
Casein usually not affected by heat but if concentration is high, it can curdle more readily.
A pH of 5.2 or lower, casein coagulate from the negative charges that stabilized calcium
phosphocaseinate micelles are neutralized by the positive charges of the hydrogen ion from
acid.
Curds form by acids are soft and fragile with high moisture content
Low in calcium in curds
Increasing viscosity will increase the stability of the foam
Increase Concentration of fat will increase the ease of formation and stability of the foam
Cool temperature cause fat droplet to harden and clump together more easily than when they
are warm and soft
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Data collected:
Table 3
Experiment III - Data Worksheet Effect of pH and Temperature on the Coagulation of Milk
Taste
Condition
pH
Formation of
curd
Plain curds
Creamed curds
Acid, chilled
5
No curd
No curd
No curd
Heated
7
Yes
Milky, sour,
cheesy
Creamy,milky,cheesy,rich
8
No curd
No curd
No curd
Alkaline
Kim chi nguyen Section 12768 2
Milk Lab Report
Table 4
Sensory evaluation table for various dairy products
Product:
Appearance
Texture
(Mouthfeel)
Flavor
Sour cream
appearance,
white,
Tannish yellow
Very,very thick
Sour, tart,
Thick, heavy,
Soy bean, sweet, aromatic, vanilla
White,
Liquidy, little thick
Super sour,plain, acidic, tart
Lifeway Kefir,
Lowfat Raspberry
Meyenberg Goat
Milk
Light pink
liquidy
sour
Super white
Liquidy,thick
Creamy
Good Karma Flax
Milk Beverage with
Omega-3
Horizon Organic
DHA-Omega Milk
Ice Cream
Silky white
Light, very liquidy,
clear
Creamy,sweet, aromatic, rich,
Bright White
Liquidy, kind of thick
Sweet,
Cloudy white
Icey, melt in mouth
Light sweet, milky, and vanilla
Chobani Non-Fat
Greek Yogurt
Silk Live! Vanilla Soy
Yogurt
Lifeway Kefir, NonFat Plain
Question and answer:
Questions for Egg and Milk Lab
FOS 4041L
1.
What effect does pH have on the coagulation of milk?
Acid will cause the milk pH to decrease. When the pH is 5.2 or lower, the casein will coagulate because
the negative charges that stabilized calcium phsphocaseinate micelles are neutralized by the positive
charges of the hydrogen ions from the acids.
2. What is the effect of temperature on the coagulation of milk?
Denatures whey protein and causes complex interaction among denatured whey protein,casein micelles, minerals
and fat globules. Whey protein denatures at 150 degrees Fahrenheit and the protein form a precipate along the
Kim chi nguyen Section 12768 3
Milk Lab Report
sides and bottem of the pan and surface of the heat milk. Casein is unaffected by the heating during normal
cooking temperature.
3.
Discuss the nutritional content of goat milk, flax milk, DHA-fortified milk and acidophilus milk. Be sure
to at least mention: calories per serving, fat, sugar, protein, vitamin D, B12 and calcium.
Goat milk: 150 calories, 7 g of fat,11 g of sugar, 8 g of protein,100 I.U of vitamin D, 300 mg of calcium
Flax milk:50 calories,2.5 g of fat,7 g of sugar,0 g of protein,50% vitamin D,
DHA-fortified:150 calories, 9 g of fat, 12 g of sugar, 8 g of protein, 30% calcium, 25% vitamin D
In comparision, goats DHA- fortified milk are very similar in nutritional content. Both have about the same calories,
fat, sugar, protein. However, it is the DHA fortified milk that has more mineral and vitamins. Flax milk however, is
lower than both of the remaining milk. They have less calories, sugar, fat, protein. They don’t even more
noticeable mineral and vitamins.
4.
Discuss the scientific principles of using salt when making ice cream.
Salt lowers the temperature freezing temperature of water. When salt is pour on the ice, it creates a briny
mixture that has a temperature nearing 0 degree. The brine is so cold that it freezes the mixture in the
bag (ice cream!)
5.
How does sugar affect the quality of frozen desserts, such as the ice cream made in lab? Explain in
detail. (see chapter 22 in lab manual; chapter 14 in text)
Sugar lower the freezing point of water. One mole of sucrose decreases it 3.35 degree Fahrenheit. Too
much sugar lowers the freezing point too much and decreases overrun.
Conclusion:
The concept of food principle on milk coagulation was support by the data in table 3. However, 2 one of
our experiment were support. The pH effect on milk was supposed to curd. The pH we measure were 5.
According to the food principle, pH at 5.2 or lower supposed to create a coagulation of the casein to
tangle and create a solid. Some of the reason why it went wrong was because through human error,
amount of acid, or maybe some fat was dropped in the pan. To make it curd, I would of add more lemon
juice and see it that would work. The other experiment “heated” was successive. It was added with an
acid and heated, therefore it had a higher chance of curding. For alkaline factor, the pH was 8 so that is
not acidic. Therefore, it makes sense that it did not curd. Overall, the data supports and display the
science of coagulation in milk.
Kim chi nguyen Section 12768 4
Milk Lab Report
Reference:
1. Foods, Experimental Perspectives, by Margaret McWilliams, 7th Edition, 2012
2. Principles of Food Preparation, A Laboratory Manual, 2nd Edition, by Freeland-Graves.