Plant oils Flashcards
What are some examples of oily foods?
- Fish
- Meat
- Vegetables
- Plants (e.g. sunflower oil)
- Chips/fast food/crisps
What does saturated mean?
There are no double bonds
What does polyunsaturated mean?
There are many double bonds
What does monounsaturated mean?
There is one double bond
Explain how oils are extracted from plants… (lavender oil)
Steam distillation
- Lavender plants are put in a flask
- Steam is passed into the flask
- Lavender oil and water evaporate
- Lavender oil and steam is condensed
- Lavender oil separates from water
- Lavender oil and water are collected
Why do we cook with vegetable oil?
- Higher energy content
- Contrast of crispy outside and fluffy/soft middle from cooking at a higher temperature so the food cooks faster
- Different/better taste from cooking at a higher temperature with oil
- Food absorbs the oil
(- Vegetable oils contain essential fatty acids which the body needs for metabolic processes)
How do we harden oils into spreads?
- Add hydrogen to unsaturated vegetable oil
- Nickel is used as a catalyst in this reaction at about 60 degrees C
- Reaction replaces some or all of the carbon=carbon double bonds with single carbon bonds
- Molecules fit next to each other better so the forces between the molecule increases and the melting point is raised
- With a higher melting point it becomes a solid at room temperature
- This is called HARDENING or HYDROGENATION
Where can plant oils be found?
Anywhere:
- petals
- Leaves
- Stem
- Roots etc.
How are plant oils extracted mechanically?
Known as cold-pressing where a material is squeezed to extract the oil
What is an example of a plant oil which is extracted mechanically?
- Olive oil
- Coconut oil
(essential cooking oils)
How are plant oils extracted by distillation?
(For oils more difficult to extract)
Material is dissolved in a solvent and impurities are removed when distilled
What is an example of a plant oil which is extracted by distillation?
- Sunflower oil
- Soy oil
How are plant oils extracted by steam distillation?
Steam is passed through the petals and the oils are able to evaporate because they are small and they form an emulsion with water- the oils are then extracted by distillation
What is an example of a plant oil which is extracted by steam distillation?
- Rose oil
- Lavender oil
(floral oils)
What are the properties of saturated fats?
- Solid at room temperature
- (vegetable fats e.g. palm oil)
- Only carbon-carbon single covalent bonds
- Addition of bromine water means the orange bromine remains the same colour (no possibility of free bonds)
What are the properties of unsaturated fats?
- Mostly liquid at room temperature (due to carbon=carbon double bonds in their molecules which stop molecules fitting together well)
- Have carbon=carbon double bonds
- Monounsaturated= 1 double bond
- Polyunsaturated= more than 1 double bond
- Can be hardened/hydrogenated to make spreads
- Addition of bromine water decolourises the orange of bromine (bonds with free bonds)
What fuel can be made from vegetable oil?
Biodiesel
Similar properties to ordinary diesel
What kind of saturation are vegetable oils and animal fats?
Vegetable oils tend to be unsaturated
Animal fats tend to be saturated
Which type of fat is less healthy an why?
Saturated compared to unsaturated because saturated fats increase the amount of cholesterol in the blood, which can block arteries and increase the risk of heart disease
Which unsaturated fat is healthier: monounsaturated or polyunsaturated?
Polyunsaturated
The more double bonds there are, the easier it is for our body to break down and digest the fat
What is a health benefit of natural unsaturated fats such as olive oil and sunflower oil?
Help reduce the amount of cholesterol
Are trans fats (partially hydrogenated vegetable oil) healthy?
No
Increases the amount of cholesterol in the blood increasing the risk of heart disease
This is due to the fact that the double carbon bonds have been lost
What is an emulsion?
A mixture of oil and water where the oil droplets are very small
How is milk an emulsion?
- Contains proteins, which are emulsifiers
- Emulsifiers separate the oil and water so they combine evenly
What are examples of where emulsifiers are used?
- Mayonnaise (sunflower/olive oil and vinegar)
- Ice cream
- Paints
- Cosmetics
What are the pros and cons of using emulsifiers?
Pros:
- Stop emulsions separating out, giving them a longer shelf-life
- Allows food companies to produce foods which are lower in fat but which still have a good texture
Cons:
- Some people are allergic to certain emulsifiers e.g. egg yolk
How do emulsifiers help oil and water mix?
- The molecule has a hydrophilic head which is attracted to water
- It also has a hydrophobic tail which is attracted to the oil
- The hydrophilic head has a negative charge in order to repel other molecules so there is an even spread of the emulsion
What are emulsifiers?
Chemicals that can help break down fats up into smaller globules so they don’t settle out of suspension
What are E numbers?
The code on additives for different purposes- each single additive has its own code so that it can be identified internationally (in Europe)
What are additives?
Chemicals added to improve food (appearance, shelf-life, taste etc.)
What is an E1 additive? What does it do? What is an example?
Colour
- Improves food appearance
- Classes of colour: 1- natural, 2- browning (cooking and processing) 3- additives
- e.g. E150- caramel, a brown colouring
What is an E2 additive? What does it do? What is an example?
Preservatives
- Helps food keep longer
- Foods go bad quickly without and wastage of food is a big problem so they are added
- e.g. E211- sodium benzoate
What is an E3 additive? What does it do? What is an example?
Antioxidants
- Helps stop food reacting with oxygen which can affect food badly (apple turns brown when it reacts with oxygen)
- e.g. E300- vitamin c
What is an E4 additive? What does it do? What is an example?
Emulsifiers, thickeners and stabilisers
- Helps improve food texture (an example in jam and soya proteins used for making vegetarian products)
- e.g. E440- pectin
What is an E5 additive? What does it do? What is an example?
Acidity regulators
- Helps to control pH
- Essential part of taste (all fruits contain sugar but without acid they would be sickly and dull)
- e.g. E501- potassium carbonate
What is an E6 additive? What does it do? What is an example?
Flavourings
- 5) sweet, sour, bitter, salty, savoury
- Subtle blend together with smell released
- e.g. E621- monosodium glutamate
How can we separate dyes in food colouring?
Chromatography
Why do we use chromatography to test food colourings?
- To see how well they dissolve in a particular solvent
- To check the colourings are safe by matching up to already known substances
How can we analyse food colourings?
Mass spectrometer
- identifies elements
- measures the relative formula mass of the substances given
- then you can identify the sample to check it is legal and safe
What is the texture of an emulsion relative to its counterparts of oil and water?
It is generally thicker than either
