C1a Flashcards Preview

Chemistry > C1a > Flashcards

Flashcards in C1a Deck (9):

What are additives and what are some?

-substances added to foods improve flavour, colour or prolong expiry
*food colours make food look more appetising
*flavour enhancers bring out the taste and smell of food without adding their own taste
*antioxidants help to preserve food
*emulsifiers help oil and water blend together in foods


What is the structure of an emulsifier?

-hydrophobic (likes oil) tail
-hydrophilic (likes water) head


What is an emulsion?

-a mixture of oil and water
-made up of lots of droplets of one liquid suspended in another liquid


How do emulsifiers work?

-stops oils and water separating
-when you shake a oil and water together the oil with an emulsifier the oil forms droplets, bonded to a coating of emulsifier
-the hydrophobic end is bonded to the oil, and the hydrophilic end is facing onward
-other oil droplets are repelled by the hydrophylic head, while water latches on
-the emulsion won't separate


Why are many foods cooked?

-better texture and taste
-easier to digest cooked
-high temperature kills microbes that cause diseases
-some foods are poisonous raw, e.g. kidney beans


How are eggs and meat changed in cooking?

-egg and meat are proteins
-energy from cooking breaks some chemical bonds in the protein and allows its molecules to change shape
-this is denaturing
-a chemical change and irreversible
-giving food a more edible texture


How are potatoes changes during cooking?

-potato cells have rigid cell walls made of cellulose
-human's cannot digest cellulose
-cooking potatoes ruptures the cell walls and the starch grains inside the cell swell up and spread out
-making the potato softer, more flexible and easier to digest


What happens when baking powder is is heated?

-thermal decomposition
-sodium hydrogencarbonate--->sodium carbonate+carbon dioxide+water


What is thermal decomposition?

-a substance breaking down into a simpler substance when heated
-many thermal decomposition need catalyst