1. Plant oils What do we use plant oils for?
Why add chemicals to food and what do they do?
How do we make sure the food we eat is safe?

2. What are additives?
Traditionally, herbs and spices have been added to food to improve its flavour.
Lemon juice (citric acid), salt and vinegar have also been used to help food last longer.
Today, a wide range of natural and artificial ingredients are used in small quantities to enhance or preserve food. These are called additives. The main groups of additives are:
Photo credit: © 2006 Jupiterimages Corporation
flavourings
emulsifiers and stabilizers
preservatives and antioxidants
colourings.

3. What is an emulsion?
Oils and water are insoluble in each other and do not naturally mix. These liquids are immiscible.
Adding oil to water in a particular way forms an emulsion.
Fine droplets of oil become dispersed through out the water, This give the emulsion a thick and creamy texture.
Milk, salad dressings and paint are all examples of emulsions.
Salad dressings often have to be shaken before use because the ingredients have separated.
Teacher notes
The images show an emulsion of oil and vinegar. Other water-based ingredients that can be used to make emulsions include lemon juice.

4. What stops emulsions from separating?
Mayonnaise is an emulsion. Unlike salad dressings it does not separate when it is left to stand. Why is this?
Mayonnaise is made using egg yolk. This contain lecithin, which is a natural emulsifier.
emulsifier
Emulsifiers have a hydrophilic (‘water loving’) part and a hydrophobic (‘water hating’) part.
water
Natural and artificial emulsifiers are used to stop oil and water separating in emulsions.
oil

5. What are E-numbers?
Food labels often contain E-numbers. Nearly all additives, including natural products like citric acid, have E-numbers.
E-numbers are often blamed for health problems, including hyperactivity in children, but what exactly are they?
The ‘E’ stands for ‘European Community’. To be given an E-number, additives are tested to make sure they meet safety requirements set by the European Community.
Teacher notes
Flavourings do not have E-numbers because they are regulated through other systems.
A full list of E-numbers is available at
More information about the associated health risks of E-numbers is available at
However, not everyone agrees that these additives are safe. Some additives with E-numbers that are used in the UK are banned in other countries. For example, the food colouring E104 (quinoline yellow) is banned in Australia and the USA.

6. What are plant oils?
Plant oils are types of fat and can provide the body with energy. They are also good sources of vitamins.
Oils can be made by crushing the seeds, beans and nuts of some plants, including olives and sunflowers.
First the plant material is crushed to make a paste. The paste is then pressed to remove water and other impurities. Oils obtained in this way are often labelled “virgin” or “cold pressed”.
Photo credit: © 2006 Jupiterimages Corporation
Teacher notes
More information about making plant oils is available at:
Distillation and chemical processes can also be used to make plant oils. Oils obtained in this way are often labelled “refined”.

7. What are the differences between fats?
Saturated fats contain no carbon-to-carbon double bonds. The straight fatty acids chains pack closely together.
Unsaturated fats contain at least one carbon-to-carbon double bond. This bends the fatty acid chains and they cannot pack closely together.
Saturated fats are less healthy than unsaturated fats because the dense packing makes them harder for the body to digest.

8. How is margarine made?
Margarine was originally made using buttermilk, a waste product from making butter.
Most modern margarines are made from plant oils. The oil is heated and hydrogen is pumped through it. This is called hydrogenation.
Some of the carbon-to-carbon double bonds in the plant oils are broken and extra hydrogen atoms are added. This hardens the oil to make it a solid at room temperature.
Not all the carbon-to-carbon double bonds are broken. This means that margarines still contain unsaturated fats. The oil is partially hydrogenated.
Nickel is used as a catalyst for this reaction. It is filtered out before the margarine is packaged and sold.

9. What are trans fats? Trans fats are a type of fat that the body
finds difficult to break down. These molecules can block the arteries of the heart.
Trans fats can be formed by the partial hydrogenation of plant oils.
Partially hydrogenated oils were used to make margarine. Today, most margarines are made using other methods and contain less trans fat.
However, partially hydrogenated plant oils are commonly used in food products, such as biscuits and ready meals.
Teacher notes
More information about trans fats is available at:
Medical organisations in the UK have campaigned to get trans fats clearly labelled on food. Most supermarkets have banned trans fats from their own-brand foods.

10. What are essential fatty acids?
Essential fatty acids (EFAs) can be found in plant oils. They are needed by the body but it cannot produce them.
Some research has shown that EFAs can help lower blood pressure and decrease the risk of blood clots.
There are two main types of EFAs:
omega-3 – found in flax seeds (linseed), pumpkin seeds, walnuts and oily fish
omega-6 – found in corn, sunflower and soya oil
Teacher notes
Recent research suggests that although oily fish are beneficial to health, some oily fish can contain high levels of toxins, such as mercury.
Current government advice recommends that girls and women who are pregnant, breast feeding or intend to have children at some point should only have 2 portions of oily fish a week. More information is available at
It is easy to get enough omega-6 because corn and soya oil are often added to processed food.
However, most people eat fewer foods containing omega-3.

11. How can food risks be studied?
It can be hard for scientist to prove or disprove that there is a risk of consuming a food. Can you think of any problems of testing ingredients on humans?
Most research works by controlling all the factors in the experiment. Is it possible to control the diet of a human?
It many take many years for side effects to show in humans. How long should new ingredients be tested for?
Genetics means that some people are more likely to react to substances than others. On how many people should an ingredient be tested before it is declared safe?
Recent studies have suggested that combinations of additives might cause health problems. Should scientists
test foods as a whole or the individual chemicals?

12. What are biofuels?
Biofuels are renewable fuels produced from plant material, such as agricultural crops.
Two types of biofuel used in vehicles are bioethanol and biodiesel.
They can be safely combined with normal petrol or diesel and used in conventional engines to reduce levels of harmful emissions without causing engine damage.
Photo credit: Ana Schaeffer

13. What is bioethanol?
Bioethanol is an alcohol produced by the natural fermentation of the carbohydrates (such as starch) in sugar beet/cane or wheat crops.
Photo credit: Ivana De Battisti
‘Flexi-Fuel’ vehicles, fitted with modified fuel injection systems, can run on E85 fuel (85% bioethanol, 15% petrol), which cuts carbon dioxide emissions by 70% compared to normal petrol-engine cars.

14. What is biodiesel?
Biodiesel is produced by chemically reacting vegetable oils or animal fats with alcohol and a catalyst. The process can be completed in 12 hours.
Biodiesel can be mixed with conventional diesel, which significantly reduces emissions, especially toxic hydrocarbons, particulates and carbon monoxide.
Photo credit: Andre Veron
There are few garages in the UK that sell biodiesel. Home-made fuels, usually from waste vegetable oils, are heavily taxed.

15. Advantages of biofuels
What are some of the advantages of using biofuels?
Biofuels are carbon neutral: the carbon released during combustion comes from the carbon dioxide the plants took in when they were growing.
Storage, transport and distribution costs are low as biofuels can be handled in the same way as conventional fuels.
Photo credit: Charles Bensinger/Renewable Energy Partners of New Mexico/NREL
Triple biofuels dispenser at Baca Street Biofuels Stations.
By-products of production, such as pressed seedcake, can be burnt in power stations instead of fossil fuels or used a
animal feed.

16. Disadvantages of biofuels
What are some of the disadvantages of using biofuels?
Although biofuels themselves produce relatively little when combusted, their production needs energy from fossil fuels.
There are few UK producers of biofuels, and only small quantities of fuel are made. Biofuels therefore need to be imported, mainly from Brazil and South-East Asia.
The high demand for land to plant biofuel crops can lead to deforestation and habitat loss, for example in Malaysia.