Unit 4: Food Chemistry

Question 1

what contains more water fruits and vegetables or meats in grains

Answer 1

fruits and vegetables

tomato is 94% water

Question 2

Polarity and solubility

Answer 2

o Polarity
 Water is a polar molecule,
 Means water can form hydrogen bonds with other molecules
o Solubility
 Water dissolves a variety of molecues and is thus nearly a universal solvent

   •	Water dissolves molecules 2 ways
  o	Ionization
          	Ex: salt
 o 	Hydrogen bonding
          	Ex: Sugar
   •	Substances that dissolve in water
          o	Hydrophilic
      •	Substances that do not dissolve in water
          o	Hydrophobic

Question 3

Suspensions in water

Answer 3

• Such as starch in water

* Do not dissolve

Question 4

Emulsions

Answer 4

• Oil-in-water (milk)

* Water-in oil (butter)

Question 5

water boils when

Answer 5

atmospheric pressure = vapour pressure

• ( higher altitude boiling temp is lower)
• can increase boiling temp if you add sugar or salt

boils at 100C at sea level

Question 6

Water Freezes

Answer 6

freezes at 0C at sea level

• adding sugar lowers the freezing temperture
• the lower the freezing temp the smaller the ice crystal and thus less damage to texture

Question 7

Water activity (Aw)

Answer 7

 Is the relative humidity of food
 Is not the amount of water but amount of solute in the mixture

 Low Aw
• Inhibits microbial growth,
• Gives texture characteristics such as crispness and

high Aw
- allows for more bacterial growth

Question 8

Specific heat of water

Answer 8

 In foods high specific heat of water contributes to fater cooking
• Ex: food cooks faster in 100C water than 100C oven
• Is the reason why steam feels hotter

Question 9

Carbohydrates

Answer 9

• Made carbon hydrogen and oxygen and are from green plants trhough photosynthesis (C6H12O6)
• Photosynthesis produces glucose

Question 10

Carbs are classifies as

Answer 10

1.	Sugars; monosaccharides, 
	Sweet to taste
	1 sugar molecule
	Ex: glucose, fructose, and glactose
	Do not need digestion and rarely occur in freeform

2. Disaccharides
    Simple sugars are sweet to taste
    Require digestion
    Ex: sucrose, maltose, lactose
    Sugars are naturally present in fruits and honey
    Milk is the only non plant source of sugar
3. Oligosaccharides
    3-10 sugar molecules (oligo means few)
    Ex: raffinose (3), stachyose(4), and verbascose(5)
    No enzyme to digest so they pass through the large intestine and create gasses
    Ex: kidney beans, black bean, lima beans
   • Can soak in water to get ride of oligarchies in beans
4. Polysaccharides
    Complex= more than 10 sugar molecules
    Ex: startches, fibers, and glycogen

Question 11

Sweet scale (5)

Answer 11

	Table sugar= 1 and is the reference for sweetness
	Lactose is lower= 0.16
	Maltose= 0.33-0.45
	Glucose= 0.74-0.8
	Fructose is much sweeter= 1.17-1.75

Question 12

Carbs act as a Humectant

Answer 12

hold moisture in food

Question 13

dextrination

Answer 13

when starch is heated with no water
turns brown and has a sweet taste
ex: gracy

Question 14

water soluble dietary fibres

Answer 14

 Dissolves in water and increases viscosity of water (viscous fibers)
 When we eat it increases the viscosity of chyme in out digestive and slows the movement of chyme thus makes us feel full longer

Question 15

water insoluble dietary fibres

Answer 15

 Do not dissolve in water and have no impact on viscosity (non-viscous fibers)
 Present in fruit peels and outer layer of plant food
 Canada food guide recommends

Question 16

Pectin use

Answer 16

 In the cell walls and form a transparent gel
 Used in fruit jam and jelly
 Two types high methoxy and low methoxy
• HM forms a gel at pH below 3.5 and at least 55% sugar
• LM pectin can form a gel between pH 2-7 without sugar (low sugar jams and jellies)

Question 17

Fats vs oil

Answer 17

• Fats
o Solid at room temp
o Most animal foods beef, chicken, pork, coconut oil, palm oil

• Oils
o Liquid at room temp
o Ex; fish oil, rapeseed oil, grapeseed oil, duck oil

Question 18

reasons for lipids in food

Answer 18

1. frying
   - can heat higher than water
2. plasticity
   - how it spreads
3. flavouring property
4. tenderness

Question 19

ways to denature proteins

Answer 19

• means irreversible change to the proteins shape

• pH ch- ange (acid)
ex:hydrochloric acid is used in stomach to denature food proteins

• heat

•	Alcohol
- We drink it penetrates our cells and denatures our cell proteins
- Alcohol is considered a toxin
•	UV radiations
Ex: sun burn

• Heavy Metals (mercury)
ex: Mercury poisoning