Extracting Vegeable OIl
Some seeds, nuts and fruit are rich in vegetable oil. The oils can be extracted by pressuring followed by removing water and other impurities. Some oils are extracted by distilling the plants mixed with water. This produces a mixture of oil and water from which the plants can be seperated.
The molecules in vegetable oil have hydrocarbon chains. Those with carbon carbon double bonds are unsaturated. Unsaturated oils will react with bromine or iondine. Bromine water is used as a test for an unsaturated compound.
Vegetable oils produce a lot of energy when eaten or when we burn them as fuels.
Cooking With Vegetable Oil
The boiling points of vegetable oils are higher than water, so food is cooked at a higher temperature in oil. This means it cooks faster and also changes the flavor, colour and texture of the food. Some of the oil is absorbed and so energy content of the food increases.
Unsaturated oils can react with hydrogen so that some or all of the double carbon carbon bonds become single bonds. This is an additional reaction called hyrdogenation and is done at about 60 degrees using a nickel catalyst. Hydrogenation is used to increase the melting points of oil so they harden and become solid fats at room temperature.
Solid fats can be spread and can be used to make cakes, biscuits and pasteries.
REMEMBER: Oils are liquid at room temperature and fats are solids at room temperature.
Emulsions are made from liquids that usually separate from each other. They are made up by vigorously shaking, stirring or beating liquids together to form tiny droplets of the liquids.
Emulsifiers help keep the droplets to stay suspended and stop the liquids from separating. They do this because different parts of their molecules are attracted to different liquids.
Emulsions are opaque and usually thicker than the liquids they were made from. This improves their texture, appearance and ability to stick to soilds.
Milk, sauces, salad dressing and ice cream are examples of emulsions
What is Added to Our Food?
Substances added to food to improve its appearance, flavour, texture and keeping qaulities are called additives. Additives may be natural products or synthetic chemicals.Some substances, like salt, vinegar and sugar have been used for hundreds of years.
There are six main kind of additive:
- Acidity regulators.
The European Unoin only permitted substances may be added to food and these are given E numbers. Additives must be included in the list of ingredients on food labels, it can be labelled as there full name or as there E number. Foods are checked by chemical analysis to ensure only permitted additives have been used. The methods of used include chromattography and mass spectormetry.
Vegetable Oils As Fuel
Vegetable oils produce a lot of energy when they burn. They can be treated to remove some chemicals and then used as fuel in diesel engines. We can use waste vegetable oils from food frying as well as fresh oils.
Biodiesel can replace some or all of the diesel fuel produced from crude oil. Biodiesel is renewable because plants are grown to produce vegetable oils . The plant material left after removing the oil can be used for food for animals.
Biodiesel is less harmful to the enviorment than fossil fuels. The plants remove carbon dioxide from the air as they grow and so when we burn it there is no more additional carbon dioxide released. Biodiesel produces no sulfur dioxide and it is more biodegradable than diesel oil.