Final Exam (Chapters 4-6) Flashcards
What is the most abundant molecule in food?
Water (H20)
Almost all foods contain what?
Water
What is polarity?
An atom / molecule that exhibits opposite powers in opposite directions
Is water polar?
Yes
What is solubility?
The ability to be dissolved (especially in water)
What are the substances called that easily dissolve in water?
Hydrophilic (hydra - fill - lick)
What are the substances called that don’t easily dissolve in water?
Hydrophobic (hydra - phobe - ic)
What is boiling point?
The temperature where vapour pressure = atmospheric pressure
What is water’s normal boiling point?
100 degrees celcius
Why does water boil at lower temperatures at higher altitudes?
Since vapour pressure = atmospheric pressure, when you increase your altitude (go higher) there is less atmospheric pressure… therefor there is less vapour pressure required to get to boiling point
What happens to the boiling point of water when salt is added to it?
The boiling point will increase (aka it will need to be a bit hotter to boil)
What happens to the boiling point of water when sugar is added to it?
Adding sugar will raise the boiling point of water. This means that the water will need to be a little bit hotter than 100 degrees to boil, therefor food will cook a little bit faster due to the higher temperature
What is freezing point?
The temperature at which a liquid becomes a solid
What is pure water at sea level’s freezing point?
0 degrees Celsius
At which temperature is water its most dence at?
4 degrees celsius
Water is the only molecule that is ____ at a frozen state than at a liquid state.
less dense
What does solutes (sugar…) do the waters freezing point?
lowers the freezing point of water
what happens to the ice crystals when they are fast frozen?
the ice crystals are smaller (less chance to migrate)
what happens to the ice crystals when they are frozen slowly?
the ice crystals are bigger (more time for them to migrate)
What size of ice crystals do you want?
you want smaller ice crystals because you can taste bigger ones
What temperature should you never thaw your food in?
Room temperature
What is freezer burn
it is dry and burnt in places
cannot hold onto the juices
texture is awful
What is the best way to thaw food?
move it from the freezer to the fridge
put the item in cold tap water (must change water regularly to keep temperature low)
What is water activity?
the partial vapour pressure of water in a substance divided by the partial vapour pressure of water at that same temperature
aka vapour pressure of the water in the food compared to vapour pressure of pure water
What is the consequence if you reduce the amount of water activity in a food?
you prolong the shelf life of that item
(make the shelf life longer)
what water activity level will cease the growth of all microorganisms?
0.6
What does low water activity do?
Inhibits microbial growth
also provides crispness and crunchiness textures (snack foods and cereals)
What does highest specific heat mean?
it can absorb and lose the most heat when temperature increases or decreases by 1 degree celsius
What liquid has the highest specific heat than all known liquids?
Water
What does high specific heat do in regard to cooking?
Contributes to faster cooking
What cooks food faster, food boiling at 100 degrees or in the oven at 100 degrees Celsius?
food boiling at 100 degrees celsius cooks food faster.
because dry heat has much lower specific heat than water
What is osmosis?
Water moving from higher concentration of solutes to lower concentration of solutes
What is the fluid in a cell maintained by?
a phenomenon known as osmosis
what does the crispiness of vegetables and fruits depend on?
the osmotic pressure of their cells
What helps prevent fruits from losing water (why would this be a good thing)
many fruits are coated with wax that seals the pores on the fruit to prevent evaporation
this helps keep the crispness of fruits (keeps the fruit’s osmotic pressure)
How are carbohydrates formed?
in green plants through photosynthesis, the suns energy converts carbon dioxide from the atmosphere and water from that soil into glucose
What are carbohydrates?
Hydrates of carbon
Thus made up of carbon, hydrogen, and oxygen
What does photosynthesis produce?
glucose
what are the carbohydrates classified as (the ones produced from glucose from photosynthesis)
sugars:
monosaccharides
diaccharides
oligosaccharides
What is a saccharide
A sugar molecule
How many sugars is a monosaccharide?
one sugar molecule
what is glucose an example of?
A monosaccharide
Are monosaccharides sweet in taste?
yes
how many sugar molecules are in disaccharides?
two sugar molecules
are disaccharides also sweet like monosaccharides?
yes
What is an example of a disaccharide?
Lactose
Is lactose intolerance an allergy?
No, its a sensitivity
What is used as a reference for sweetness?
Table sugar
What are humectants?
substances that hold moisture in foods?
what is an example of humectants?
sugars
What is caramelization?
When sugar is dry heated at high temperatures, the sugar melts and turns brown (caramelization)
Leads to brown colour plus caramel flavours
What is maillard reaction?
a reaction between reducing sugar (all monosaccharides and most disaccharides), and an amino acid
when heated they react and lead to the complex mixture of brown compounds called melanoidins
This is the colour, flavour, and aroma of baked bread
Does sugar increase the freezing point?
No, it reduces the freezing point
the higher the concentration of sugar, the lower the freezing point
What does sugar also reduce in frozen foods?
It reduces the risk of large ice crystals forming in frozen desserts
What are oligosaccharides?
3-10 sugar molecules connected
Are oligosaccharides water-soluble?
yes
What can oligosaccharides lead to an excessive amount of?
gas
This happens in beans
Why do oligosaccharides cause so much gass?
Becuase humans cannot digest oligosaccharides due to the lack of enzymes. so they just pass through humans and go out as gas
How can you get rid of oligosaccharides in beans?
Soaking them in tap water before cooking the beans
What is butter (oil in water emulsion, or water in oil emulsion)?
Water in oil emulsion
What are polysaccharides?
complex carbohydrates that contain 10+ (typically hundreds) of sugar molecules connected
What are examples of polysaccharides?
Starches, fibers, and glycogen
Does starch have an odor?
No, it is odorless
Is starch soluble in water?
No starch is insoluble in water
What are the starches called that contain no amylose?
Called zero-amylose or waxy starches
What are sources of starch?
Plant foods (potatoes, yam, cereal grains, beans…)
What does starch provide lots of for very cheap?
Starch provides lots of energy for very cheap
What is starch used for in food?
used as a thickener in food
in soups and gravies
also great at binding for meat or plant patties
What is dextrinization?
when starch is heated in the absence of water, the starch breaks down and becomes sweeter, has flavour, color, and aroma
It also reduces starches ability to form a gel
What is glycogen?
a polysaccharide (hundreds / thousands of glucose molecules)
highly branched, not linear
humans do produce enzymes to break these down
What does glycogen provide energy to that nothing else does?
Our brain receives its only energy from glycogen
What is dietary fibre?
a polysaccharide that is part of plant material
our digestive system doesn’t produce the enzymes to break these down
What is the definition of water-soluble fibres?
Dissolve in water and increase the viscosity of the water. Leads to slow movement through our digestive system, this keeps our stomach full for a longer period of time
it also slows down the absorption of nutrients which prevents sharp increases in glucose levels
Is it true that water-soluble fibres increase the chance of heart diseases?
No, in fact they may reduce the risk of heart diseases by lowering the blood cholesterol levels
What are sources of water-soluble fibres?
Beans, vegetables, fruits, and some cereal grains (oats, barley, rye)
What is the definition of water insoluble fibres?
they do not dissolve in water and have no impact on the viscosity of the water
Where are insoluble fibres found in foods?
Are present on the outer layers of all plant foods (fruit peels, vegetables, whole grains, beans…)
what can you add to improve the texture of foods?
soluble fibres retain water in the baked goods, therefore slowing things down (somehow good for improving the texture)
Can fibres add colour?
Yes, insoluble fibres are bound to many colour compounds
What are lipids?
they are organic macromolecules that are generally insoluble in water, but are soluble in non-polar solvents (like alcohol)
What are lipids broadly classified as?
They are broadly classified as fats and oils
Where do fats come from?
Most animal foods contain lipids (beef, chicken, turkey, pork…)
Are fats solid or liquid at room temperature?
solid
Are oils solid or liquid at room temperature?
liquid
What are sources of oils?
most plant lipids come from canola, olives, sunflower seeds…
What are lipids broadly classified as?
triglycerides, phospholipids, and sterols