1. Introduction



Names: Ang Liya, Rishita Subnavis, Kho Hannah

Class: S2-01

Group Reference: D

A.    Indicate the type of research that you are adopting:

[    ] Test a hypothesis: Hypothesis-driven research
e.g. Investigation of the antibacterial effect of chrysanthemum

[    ] Measure a value: Experimental research (I)
e.g. Determination of the mass of Jupiter using planetary photography

[ X ] Measure a function or relationship: Experimental research (II)
e.g. Investigation of the effect of temperature on the growth of crystals

[    ] Construct a model: Theoretical sciences and applied mathematics
e.g. Modeling of the cooling curve of naphthalene 

[    ] Observational and exploratory research
e.g. Investigation of the soil quality in School of Science and Technology, Singapore  

  1. Type & Category

Type of research: 3

Category  –  10

Sub-category –  e (Organic Chemistry)

Application of project relevant to SST Community, Society or the World:
Casein that is found in milk can be used to create plastics, fibres and paints. By using this protein, people can make use of milk to make biodegradable plastic and fibres that would not harm the environment when unwanted. The project can tell us which acidic liquid would work most well to create the casein from the milk so that the milk can be used to its maximum potential and create as much casein as possible.
Our project can be useful to the industry because people can use this idea to make other materials with milk, which is easily found.
It can also be useful to create paint, which can benefit artists. The casein-milk can be homemade, and helping to make use of the casein in milk, will allow people to use the paint and create art.

C.    Write down your research title:

Investigation of the effect of acids on curdling of milk

D.   (a) Aim / question being addressed 

 To find out about how the amounts of vinegar and other acids will affect the amount of curdling of casein in milk.

Q: How does the acidic liquid make the casein from milk?
A: Casein is a protein in milk which is insoluble, and when the vinegar is poured into the milk and turning it acidic, the casein reacts by precipitating and turning into clumps which can be separated from the rest of the milk.

Background research:
 In milk, casein is not dissolved, just suspended, so it can be filtered out of milk. Heating and boiling milk does not alter its state but dilute acids and rennet cause it to precipitate, stronger ones dissolve it.

 Casein is a protein that is commonly found in mammalian milk, making up at least 80% of the proteins in cow’s milk and between 20% to 45% of protein in human milk. Casein has a wide variety of uses, from being component of cheese, to use as a food additive, to a binder for safety matches. As a food source, casein supplies amino acids.

 Casein contains a fairly high number of proline residues, which do not interact. It is rather hydrophobic, making it poorly soluble in water. It is found in milk as a suspension of particles called “casein micelles” which show only relatively limited resemblance with other micelles in a sense that the hydrophilic parts reside at the surface and they are spherical.

 The isoelectric point of casein is 4.6. Since milk’s pH is 6.6, casein has a negative charge in milk. The purified protein is water-insoluble. While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as sodium oxalate and sodium acetate.

 Casein can also be used and/or found in paint glue, cheese making, plastics and fibre, protein supplements and other medical and dental uses.

 There is evidence that it has been used during the middle ages and it has been identified in 18th century ceiling paintings. However, there are problems using casein as paint because it is brittle and can become moldy.

(b) Independent variable

Acidic liquids:
  • Cider vinegar        (3.10 pH level)
  • Yuzu juice          (2.00 - 2.60 pH level)
  • Apple juice            (3.35 - 4.00 pH level)
  • Red wine               (2.90 - 3.90 pH level)
  • Aloe vera juice      (6.00 - 6.80 pH level)
  • Cola                      (2.30 - 3.50 pH level)
And the amount of acid added.

(c) Dependent variable

Weight of curd (casein)

(d) Controlled variables

(a)The starting amount and concentration of casein of the milk (same brand and type of milk) (eg. Marigold full cream milk)
(b)The temperature of the milk (49 degrees Celsius) after the milk is heated
(c)The beakers used

      (e) Hypotheses

The higher the pH of the liquid is, the more curds is present.
The higher the volume of acid, the more curd is present.

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