# Emulsions: Principles and preparation - Physical characteristics of emulsions - Droplet size, droplet size distribution

## 6 important questions on Emulsions: Principles and preparation - Physical characteristics of emulsions - Droplet size, droplet size distribution

### Which properties of an emulsion are quite dependent on size?

- Larger droplets cream/sediment easier due to gravity
- The appearance of a product
- Small droplets (<50 nm) --> almost transparent
- Larger droplets (50 nm - 10 um) --> scatter light (milky white)
- Even larger --> scatter light much less (yellowish)

### What are 2 different ways of counting particles to obtain the distribution curve?

- Count the number of particles smaller than a size --> particles that are much larger also count for 1
- Total interfacial area present on the particles --> smaller droplets count less than larger droplets --> more realistic
- Volume of the particles smaller than the specific size --> total amount of oil present in small, medium or larger droplets

### Which 4 ways can be used to determine the average droplet size?

- By looking at the frequency distribution and taking the size at which the distribution is maximal --> modal size
- Summing up the size of all particles and dividing by number of particles --> number average diameter (d10)
- Sum up the volumes of all particles and divide this by the total number of particles --> volume average diameter (d30)
- Summing up the volume of the particles and dividing it by the surface are of the particles --> Sauter diameter (d32)

### Which 3 things about droplets can be measured?

- Droplet size distribution
- Average droplet size
- Width/span of the distribution

### What is the difference in stability of droplets with a different distribution width?

Polydisperse (smaller and larger) --> less stable, larger droplets can initiate creaming

### What are 4 different methods to measure the droplet size distribution?

- Microscopy
- Droplets larger than 1 um --> optical microscopy
- Droplets smaller than 1 um --> electron microscopy
- Light scattering
- Following the dynamics of the droplets (dynamic light scattering) --> Doppler shift, larger droplets slower Brownian motion
- Count droplets individually --> Coulter counter method

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