Oils + Fats: Refining

IS refining ususally done before or after Extraction?

After

What is the objective of the refining process?

To remove non-Triacylglycerol content from the oil, creating pure oil.

Outline the steps of refinery

1: clarification

2; Degumming

3; neutralising

4; Bleaching

5; Deodorisation

Outline the process of clarification

the crude oil from extraction settles, and the the particulate is filtered out. Centrifugation is often used to separate particulate material.

What is meant by particulate material?

material in crude oil from the extraction process, such as cell walls and tissue.

Which step is this?
‘the crude oil from extraction settles, and the the particulate is filtered out. Centrifugation is often used to separate particulate material.’

Step 1: Clarification

Outline step 2 of the refining process

Degumming: phosphoric acid (H3PO4) or brine (NaCl) is added to facilitate removal of resins, gum particles, proteins and phosphatides

which step is this?
‘phosphoric acid (H3PO4) or brine (NaCl) is added to facilitate removal of resins, gum particles, proteins and phosphatides’

Strp 2: degumming

Outline step 3 of the process

Neutralising: dilute caustic solution is added(NaOH or KOH), followed by bubbling water through the oil to wash it. This converts FAs to soaps (the bulk of which are removed through centrifugation)

Why do we want to neutralise FFAs, residual H3PO4, and traces of heavy metals such as iron or copper?

Because they are pro-oxidants, and removing them will increase shelf life.

How does the refining process increase shelf life

Neutralising: removes FFAs by making them into soapstock and heavy metals like copper and iron.

Bleaching: Uses fuller’s earth to remove pigments and traps peroxides

Deodorisation: Removes aldehydes and ketones

What are the oxidative products that limit shelf life?

FFAs, Heavy metals, peroxides, aldehydes and ketones

Outline step 4

Bleaching: Fuller’s Earth is a bleaching clay, used to remove non-TG residues, remove pigments, and trap peroxides and other oxidative residues. Clay is then removed by filtration.

Which step is this?
‘ Fuller’s Earth is a bleaching clay, used to remove non-TG residues, remove pigments, and trap peroxides and other oxidative residues. Clay is then removed by filtration.’

Step 4: bleaching

Outline step 5;

Deodorisation: Key flavour process, removing volatiles like aldehyde and ketones (also oxidative products), by vacuum steam distillation at 170-230C.

Why are volatiles removed for flavour in deodorisation

Because aldehydes and ketones cause off-flavours.