First experiment: How does the acid used affect the emulsion formed in the vinaigrette?

Posted by Anonymous March 13, 2020

First experiment: How does the acid used affect the emulsion formed in the vinaigrette?

How does the acid used affect the emulsion formed in the vinaigrette?

Introduction:

Imagine having a salad that is super oily but lack of flavor, hmm...that doesn't sound appetizing right? As vinaigrette consists of mainly oil and acid, which are immiscible in nature, thus this undesirable scene will happen when the emulsion of the vinaigrette is not properly formed. As oil has a higher density than the acid, it will sit on top of the acid layer, and will flow out of the container before the acid is poured out. This explains why the salad is oily but tasteless, as most of the oil is poured out but not the acid which gives the salad its flavor.

Aim of the investigation:

We don't want to have an oily salad with barely any taste right? Therefore, I'm here to help you investigate which acids form the best emulsion by measuring how long does it take the oil and acid layer to separate.

The 5 "W"s:

Who?

Chan Wing Sze Kelly

What?

To investigate the effect of using different acid on the formation of the emulsion in vinaigrette.

Where?

In my kitchen.

When?

To carry out the tests after preparing seven vinaigrettes with different acids.

Why?

To find out the best acid to form the most stable emulsion with oil.

How?

By measuring the time taken for the shaken mixture to separate into 2 layers after it is left alone. The longest time taken indicates the best emulsion formed.

The science behind the formation of emulsion:

acid molecule (polar)

In vinegar, the acetic acid and water molecule are polar in nature. In a polar molecule, one or a group of atoms have a stronger pulling force on the electrons in the molecule. As there is an uneven share of electrons between the atoms, weak charges are formed on the opposite ends of the molecule.

oil molecule (non-polar)

Dipole moments formed between oppositely-charged weakly positive and negative charges in the acid molecule, making it slightly electronegative; on the other hand, oil molecule (a lipid) is non-polar, and composed primarily of long molecules called fatty acids. The electrons are distributed evenly across the fatty acid molecule, making it non-dipole, the overall compound is neutral.

Polar molecules are hydrophilic (water-loving), while non-polar molecules are hydrophobic (water-fearing), thus they cannot mix and combine well under normal circumstances. When the vinaigrette is shaken vigorously, the two initially form an emulsion, a mixture of polar and nonpolar compounds. However, this emulsion is unstable and will very quickly form layers in what’s known as phase separation. The solutions separate into layers according to their respective densities due to an aversion to each other. Since oil has a lower density than vinegar, it sits/ floats on top of the acid layer.

However, with the addition of an emulsifier/ emulsifiers, which contains both hydrophilic and hydrophobic groups within the compound, they are able to introduce and combine the oil and acid molecules together to form a more stable "emulsion", which does not separate quickly nor easily.

THE BASIC FRENCH VINAIGRETTE RECIPE

Preparation time: 5 minutes

Servings: 4

Ingredients:

- 120g of olive oil

- 40g of white wine vinegar

- 15g of dijon mustard

- 20g of honey

- 2 medium garlic cloves, minced

- 1.5g of fine sea salt, to taste

- ground black pepper, to taste

Utensils used: whisk, glass bowl, glass jar, timer, measuring scale

Method:

1. In a jar or a bowl, add in all the ingredients. If you are using a jar, close the jar with the lid and shake it vigorously to combine; if you are using a bowl, whisk the mixture using a whisk or a fork until the ingredients are combined and an emulsion is formed.

2. Taste the mixture, and adjust as necessary. If it is too acidic, add in more honey; if it is too bland, just add in more salt and pepper.

3. Either serve immediately or cover the vinaigrette well and refrigerate for future use. Homemade vinaigrette can be kept in the fridge well for around 7 to 10 days.

Independent variable	The type of acid used
Dependent variable	The time for the separation of the oil and acid layer
Controlled variable	à Volume of acid and oil used à The type and brand of oil used à The amount and type of seasonings (i.e. mustard, honey, salt, pepper, and garlic) added to the vinaigrette à The shaking/ mixing time for combining the vinaigrette àThe utensils used in the preparation of the vinaigrette à The temperature of all the ingredients used à The equipment used to store the vinaigrettes