Chemistry AQA C1b

Seeds, Nuts and Fruits are rich in vegetable oils

Pressing-followed ny removing water and other impurities   Distilling-(plants which are mixed with water and oil)-because this mixture is easier to separate.

Molecules in veg oils have hydrocarbon chains. Those with carbon-carbon double bond (=) are unsaturated.......... Poly-means many>>>and so these are called Polyunsaturated

unsaturated oils will react with bromine or iodine (solution will go colourless)

Veg oils produce a lot of energy when eaten or burnt as fuels

Boiling points of veg oils are higher than water (so oily foods to be cooked faster must be cooked in higher temperatures) Oily foods also have a different taste, texture and colour. Energy content of the food is also higher because some of the oil is absorbed by the food.

Hydrogenation- is an addition reaction done at 60 degrees C in a nickel catalyst.................Unsaturated oils can be reacted with hydrogen so that some/all double carbon bonds become single bonds. Hydrogenation can be used to increase melting points of oil so they harden and become solid fats at room temperature.

Solid fats can be spreads and can be used to make cakes, biscuits and pastries.

Remember:in a hydrocarbon...the carbon (C) CAN ONLY have 4  bonds( - )joined to it !!!!

Emulsions are made from liquids which usually separate from each other. They are made from vigorous shaking, stirring or beating to form tiny droplets of the liquid. The droplets go so small that thy remain in each other and a slow to separate.

Emulsifiers  help stop the liquids from separating (usually the tail is attracted to the oil and the circle/heat is attracted to the water in a diagram)

Emulsions are usually thicker than the liquids they form from>>>> this improves their Texture, Appearance and ability to stick to solids.

Emulsions take place in: milk, sauces, salad dressing and ice creams

Additives may be natural or synthetic chemicals.......They are added to improve appearance, flavour, texture and to keep quality.

There are 6 main additive which are given E-numbers:

E1-Colours >>>appearance of food                                                                                            E2-Preservatives>>>Help food keep longer                                           E3-Antioxidants>>>Help stop food from reacting with oxygen  E4-Emulsifiers>>>Improve texture of food                                                       E5-Acidity Regulators>>>Help control pH                                       E6-Flavourings>>>There are only 5 flavours: sweet, sour, bitter, salt, savoury                                   

Foods ar5e checked by Chemical analysis Chromatography and mass spectrometry