Food science Flashcards
What does it mean when proteins denature?
This means the chemical bonds that hold their structure together break down
The proteins unravel and their shape changes
Proteins can be denature by:
- physical agitation
- changes in temperatures
- acids
What does it mean when protein molecules coagulate?
Protein molecules collide with other protein molecules and coagulate
Water gets trapped between the protein molecules
Changes appearance and texture
Overcooking-forces water out of molecules
How are foams formed?
When gas becomes trapped (aeration) inside liquid
When liquids containing proteins are agitated, proteins denature and stretch and air gets trapped in the liquid
When the proteins coagulate, this air becomes trapped, forming a foam
Over-whisking causes these new bonds to break-air escapes and the foam collapses
What is gluten?
Protein found in wheat flours
What is starch gelatinisation?
- Helps to thicken foods that contain starch
- Starch granules mix with liquid and become suspended in it
- When heated, bonds will break allowing water molecules to enter
- More water—->swell in size and soften
- When it gets hot enough, the granules burst open and release their starch into the liquid
- When cooled, it forms a solid gel
What is dextrinization?
- Occurs when starch is exposed to dry heat
- Starch molecules break down into smaller molecules called dextrins
-Gives food a browner colour and crispier texture and different taste
How does sugar caramelise when heated?
-Sugar molecules break down (brown and change flavour)
- First, liquids is very runny and sweet
- Time passes, smooth caramel
- Turns harder, more like candy
What is shortening?
- Flour has waterproof coating (fat)
- Prevents long gluten molecules from forming
- Dough cannot become strecthy (firm and crumbly)
Why do fats have plasticity?
-Mixture of triglycerides that all melt at different temps (gradually soften over a range of temperatures)
What are emulsifiers and what do they do?
Oil and water don’t mix so you use an emulsifier to keep them together
Molecules in an emulsifier have an hydrophilic end and an hydrophobic end
Water bonds to the hydrophilic end and oil bonds to the hydrophobic end which holds them together in a stable emulsion
Why do we cook food?
- To make it safe to eat
- To develop flavour
- To improve shelf life
- To improve texture
- To give variety in the diet
What is conduction?
Conduction is the transfer of heat energy through the vibration of particles
In a solid, the particles are held tightly together. So when one particle vibrates, it bumps into other particles nearby and quickly passes the vibrations on
When a pan is placed on a hob, heat energy from the hob causes particles in the pan to vibrate more and gain heat energy
When these particles collide with nearby particles, they pass some of their extra heat energy on to them
This process continues throughout the pan until the heat has passed all the way through
When food is placed into the hot pan, heat energy is transferred from the particles in the pan to the particles in the food in a similar way until the food is cooked
What is convection?
Convection is the transfer of heat energy through gases or liquids
When you heat up a liquid, the liquid near the heat source warms up faster
The warmer liquid rises above its colder surroundings-like a hot air balloon does
As the warm liquid rises, colder liquid takes its place
The colder liquid is heated and when it starts to rise, colder liquid takes its place
As this process continues, you end up with a circulation of fluid (convection currents)-after a while, this circulation of heat results in the whole fluid being heated
Convection also occurs in ovens-hot air rises and cooler air falls in the same way
What is radiation?
Radiation is the transfer of heat energy through waves of radiation
No direct contact between the heat source and food
Grills and toasters
They emit waves of radiation- when these waves reach the food, they are absorbed and heat the food up
How does boiling work?
Cook food by heating it in a pan of boiling liquid, usually water
Harsh method of cooking-can’t be used on delicate foods
Healthy way to cook as no fat is added however if veg is boiled for too long, colour, flavour and water-soluble vitamins are lost in the water
Not as attractive/boiling as food cooked by methods like roasting
Less energy
Heat is transferred by conduction (pan to water to food) and convection (liquid)
