Fats and Oils Flashcards
Name examples of plant sources that are SOLID at room temperature.
coconut oil, palm oil (tropical fruit oils)
Name an example of animal sources that are liquid at room temperature.
Fish oil
How do we use fats?
- Food preparation (oil for frying)
- Food formulation (as an ingredient)
- Added directly to finished foods (butter on bread, salad dressing)
What % represent triglycerides?
95%
Define a triglyceride.
3 fatty acids chained to a glycerol
Define a fatty acid.
Chain of carbons with an organic acid (carboxyl group) on one end and a methyl group on the other
Name 2 factors that differ fatty acids.
1) Chain Length (2 to 22 carbons) - nbs are usually even
2) Degree of Saturation (0, 1, 2+)
Name the types of saturation.
- Saturated (0)
- Monounsaturated (1)
- Polyunsaturated (2+)
Compare cis and trans fatty acids.
Trans: Hydrogens are on either side of the
double bond
Cis: Hydrogens are on the same side of
the double bond
How do trans fatty acids occur?
Food procession - hydrogenation - dairy products, beef, lamb
What do cis fatty acids do?
Put a kink in the fatty acid chain
What do trans fatty acids behave like?
Like saturated fats
Name the 2 essential fatty acids.
1) Linoleic acid (omega-6)
2) Alpha-linolenic acid (omega-3)
What is alpha-linolenic acid a precursor for? What are they important for?
DHA and EPA
Important for brain and cardiovascular health
What is linoleic acid a precursor for?
arachidonic acid
Name sources of Omega-6 fatty acids.
Corn oil, peanuts, soybean oil
Name sources of Omega-3 fatty acids.
Fish, flax, walnuts, chia seeds, hemp hearts
How does fatty acid notation work? Where do you start counting?
Cn:xn-y
n = chain length (nb of carbons) x = nb of double bonds y = position of 1st double bond COUNTING FROM THE METHYL END
Define phospholipids.
1 glycerol, 2 fatty acids, 1 compound containing phosphate and a nitrogenous base
Name some sources of phospholipids.
egg yolks, liver, soybeans, wheat germ, peanuts (not found in great amounts in foods) - mono and diglycerides also act as emulsifying agents
What is the most important role of phospholipids?
Emulsifying agent (hydrophilic head and hydrophobic tail)
Name sources of saturated fats.
meat, poultry, milk/butter/cheese, egg yolk, lard
chocolate, coconut/coconut oil, palm oil, vegetable shortening
Name sources of monunsaturated fats.
avocado, peanuts, olives, canola oil
Name sources of polyunsaturated fats
Vegetable soils, margarine, mayonnaise, certain nuts (almonds, pecans, walnuts)
Name an example of oil in water emulsion.
Mayonnaise
Name an example of water in oil emulsion.
Butter
Name the 4 types of lipids.
1) Triglycerides
2) Phospholipids
3) Sterols
4) Waxes
Define sterols.
Interconnected carbon rings with a variety of side chains.
Give examples of sterols.
Cholesterol, phytosterols, steroic hormones, vitamin D
Where is cholesterol found? Is it essential?
Only found in animal sources (meat, poultry, fish, dairy, eggs)
- It is NOT essential
What is a bodily function of phytosterols in the body?
Block the absorption of cholesterol
Poorly digested, don’t contribute to raising your blood cholesterol levels
Define waxes.
Long fatty acid chain and alcohol hydrocarbon chains
How do waxes compare to triglycerides?
Waxes have a much higher melting point than triglycerides
Where are waxes found?
Waxy coatings are found on leaves and fruit of many plants and serve for protection
Why would fruits and vegetables be waxed?
Waxed to prevent moisture loss, protect them during shipping and increase shelf life
Name some common animal fats/oils used in cooking.
Butter, lard/tallow/suet, duck fat
Name some common plant fats/oils used in cooking.
Vegetable oils, fruit oils, nut oils, seed oils, margarine, shortening
What is the difference between lard, tallow and suet?
Lard: from pig
Tallow: from cow or sheep
Suet: specifically from the fat around the kidney and loin from cow or sheep
What affects the melting point?
1) Degree of Saturation (higher saturation, higher melting point)
2) Length of Fatty Acids (longer chain, higher melting point)
3) Cis-Trans Configuration (cis is more liquid at room temperature)
Where should lard, shortening and most oils be stored?
Room temp, away from light, tightly covered; will
keep longer in the refrigerator (esp. olive oil)
How long do MUFAs keep?
around 1 year
How long do unrefined PUFAs keep?
around 6 months
Define rancidity.
- Chemical deterioration of fats that gives off-flavours and rancid
odours - TG/fatty acids breakdown into smaller units
How is rancidity accelerated?
Accelerated by light, heat and oxygen -> oil used for cooking
Name the 2 types of rancidity.
hydrolytic and oxidative
How should unrefined polyunsaturated oils be stored?
refrigerator, dark glass bottle, airtight
Define hydrolytic rancidity. What is it catalyzed by?
- Exposure to water
- Catalyzed by heat and lipase enzymes
What happens chemically during hydrolytic rancidity?
Bonds in TG are hydrolyzed -> smaller subunits (off flavour)
Name examples of hydrolytic rancidity.
Deep frying, butter left at room temperature
Define oxidative rancidity. What increases susceptibility?
- Exposure to oxygen
- More unsaturated the fat, more susceptible since the double bonds are being attacked
Name the 3 steps in oxidative rancidity.
1) Initiation: free radical is formed
2) Propagation: oxygen + free radical = peroxide-free radical -> domino effect until all double bonds have been used
3) Termination : no more H at double bonds to react with
What are the health concerns to oxidative rancidity?
lipid peroxides and free radicals (in the long term are toxic to our body)
How do antioxidants prevent oxidation?
1) Being oxidized themselfs
2) Donating their H to a FA
3) Sequestering metals such as a chelating agent
Name some examples of antioxidants.
Vitamin C, vitamin E, beta carotene
Vitamin E is found in many vegetable oils
What are the fat recommendations from Health Canada?
- Add 30 to 45 mL (2-3 Tbsp) of ADDED unsaturated fat each day. (oil used for cooking, salad dressing, margarine, mayonnaise)
- Limit butter, hard margarine, lard, shortening
Compare expeller pressed vs. cold pressed.
Expeller pressed: squeezing the seeds at very high pressures
Cold pressed: yields less oil, more nutritious, much better quality, expensive, less stable - mechanically pressing the seed
Compare refined vs. unrefined oils.
Refined: chemically and physically processed to remove undesirable components from the oil
Unrefined: not processed further after pressing (generally pressed)
Name 4 ways to modify fats.
- Hydrogenation
- Interesterification
- Winterization
- Fractionation
Define hydrogenation.
- Process used to harden vegetable oil
Refined vegetable oil + H2 - catalyst -> semi solid or solid oil - Unsaturated fat to saturated fat
Define interesterification.
- The rearrangement of the fatty acid portion in a triglyceride on the glycerol backbone
Define winterization.
- The separation of oils into two or more fractions based on melting point
- basically oils are cooled and kept at low temperatures for some time, liquid and solids are separated by filtration
Define fractionation.
- same principal as winterization
- more sophisticated of cooling and separating fractions with much greater control
What are the 3 types of ways to produce oils?
- Chemical (uses solvents like hexane)
- Mechanical (expeller pressed and cold pressed)
- Using both chemical and mechanical
Name the advantages and disadvantages of producing oil chemically.
Advantages: highest yield, therefore highest profit, more affordable
Disadvantages: loss of nutrients due to heating of oil
Name the advantages and disadvantages of producing oil mechanically.
Advantages: highest quality oil, maintains integrity
Disadvantages: small yield, more expensive
What is the main advantage of interesterification? What is the disadvantage?
advantages: can modify the physical properties of a fat without production of trans fatty acids.
disadvantages: still uses heat, no conclusive evidence that it is or isn’t healthy
Name some functions/uses of fats/oils in food.
- Heat transfer
- Shortening
- Emulsion
- Flavour
- Texture
- Satiety
- Nutrients
Name some tips and tricks for low fat cooking.
Choice of equipment: non-stick frying pan, parchment paper
Choice of cooking methods: steaming, grilling, baking, poaching
Choice of ingredients: low-fat versions, lean cuts of meats, healthier versions
Preparation: trimming visible fat off of meat, bake pies with only a bottom crust or top crust
How do you replace fat in baking?
- Apple sauce: use in place of oil in cakes, cupcakes and some cookie recipes
- Beans: can work well in replacing fat and brownies (and other items with a fudge-like texture)
- Shredded Zucchini: can help lock in moisture in muffins and breads
- Bananas: mashed bananas can help reduce the amount of fat needed in muffins and cookies
- Tofu: can replace cream
What is coconut oil mostly made up of?
Medium-chained fatty acids that are very high in saturated fats
What’s the significance of a medium chained fatty acid? And how does it relate to coconut oil?
- Are not incorporated into chylomicrons
- Doesn’t effect LDL levels like other saturated fats might
- Primary source of fuel for liver cells
Compare the melting and smoke points of refined and unrefined oils.
Oils that are unrefined tend to have a lower melting and smoke points
The more refined it is, the more stable it is
What is shortening?
Fat that tenderizes or shortens, the texture of baked products by impeding gluten development, making them softer and easier to chew
Milk, cream, egg yolks, mayonnaise, salad dressings, gravies, puddings are what kind of emulsion?
Oil in water
Butter and margarine are examples of what kind of emulsion?
Water in oil
How is mayonnaise made? What is the dispersed and continuous phase?
- Vegetable oil (dispersed)
- Vinegar or lemon juice (continuous)
- Egg yolk with lecithin (emulsifier)
Peanut and olive oils are examples of what kind of oils?
Unrefined, cold-pressed
