Class 6: Fat and Oils
fat are found in the form of _____________
triglyceride
true or false: Storage conditions depend on type of fat
true
what differ fiat from oil?
Fats: solid at room temp; usually from animal sources Oils: liquid at room temp; usually from plant sources
what are some fat replacement?
- apple sauce - beans - shredded zucchini - bananas - tofus
what are some advantage of cooking with coconut oil?
- good for frying (high smoking point) - give food a nutty flavour
formation of ω-6, ω-3 eicosanoid
- linoleic acid: elongation: arachidonic-->ω-6 - linolenic acid (ALA): elongation: EPA --> ω-3 eicosanoid or another elongation --> DHA
shredded zucchini
- lock in moisture in muffins and bread
how degree of saturation is related to melting point?
- low degree (unsaturated): lower MP - saturated: high MP
what are some other sterol apart from cholesterol?
- phytosterol : in plant
what differ refined and unrefined oil?
- unrefined oils are not processed further after pressing - Refined oils are chemically and physically processed to remove undesirable components from the oil
how antioxidant prevent oxidative stress?
1. Being oxidized themselves 2. Donating their hydrogen to a FA 3. Sequestering metals (chelating agent)
what is the recommended intake of unsaturated fat each day you need to take? including oil used for cooking, salad dressing, margarine, mayonnaise.
2-3 tbsp (30 - 45 mL)
what is the most common fatty acid chain length?
4-24 most common: 16 or 18
where can you find cholesterol in diet?
ANIMAL ONLY: meat, poultry, fish and fish roe, organ meats, dairy products, egg yolk
what is fatty acid notation for linoleic acid?
C18:2n-6
what is rancidity
Chemical deterioration of fats that gives off-flavours and rancid odours
what are some tips and tricks for low fat cooking?
Choice of equipment: § Non-stick frying pans : eliminates need for oil (or at least not as much) § Parchment paper: eliminates need for greasing Choice of cooking methods: § Steaming § Grilling, Baking, or Poaching instead of Frying choose ingredient wisely, use low fat replacement preparation
what are oil that are high in saturated fat
coconut oil, butter , palm oil
how hydrolytic rancidity happen?
Exposure to water, catalyzed by heat and lipase enzyme--> hydrolyze TG into smaller subunit --> rancid flavour (deep-frying, butter left at room temperature)
How do we use fats?
In food preparation (oil for frying) food formulation (as an ingredient) added directly to finished foods for flavour(e.g.. butter on bread, salad dressing)
what is waxes composed of?
Long fatty acid and alcohol hydrocarbon chains
is cholesterol an essential nutrient?
NO!
how length of fatty acid is related to melting point?
Shorter carbon chains - more liquid at room temp (lower MP)
what cause rancidity?
TG/fatty acids breakdown into smaller units Accelerated by light, heat and oxygen --> oil used for cooking
what is intersterification
The rearrangement of the fatty acid portion in a triglyceride on the glycerol backbone
how winterization and fractionation are similar to each other ?
The separation of oils into two or more fractions based on melting point
what is the function of waxes, where can we find it?
Waxy coatings are found on leaves and fruit of many plants --> protection fruit and vegetable are artificially waxed to prevent spoilage, water loss and increase shelf-life
how winterization differ to fractionation ?
Winterization: • Oils are cooled and kept at low temperatures for some time, liquid and solids are separated by filtration Fractionation: • Same principle as winterization however it is a more sophisticated process of cooling and separating fractions with much greater control
how long should you keep your refined/monosaturated fat?
about 1 year
what are some origin of lipid?
animals, seeds, nuts, some fruits
how long should you keep your unrefined/polysaturated fat?
around 6 month
what are some good fat for frying ?
beef tallow, palm oil, ghee(high smoke point) - peanut, canola, sunflower, safflower, cottonseed. (350-450 F),
what is the main advantage of intersterification?
can modify the physical properties of a fat without production of trans-fatty acids
what are some food sources of linolenic acid
canola oil, chia seed, flaxseed product, leafy green, ω-3 egg
what are oil that are high in oleic acid?
canola oil, safflower oil, olive oil
how to extract oil?
chemical methods mechanical methods
how cis, trans configuration affect melting point?
cis : more liquid at room temperature, lower MP
what's so special with coconut composition ?
contain mostly medium-chain fatty acids which are metabolized differently by our body
what are oil that are high in linoleic acid?
cottonseed oil, corn oil, soy bean oil
apple sauce work best in
cut calories and fat. replace half butter with apple sauce. use to replace oil in cake, cupcakes and cookies recipes
where we can find naturally occurred trans fatty acid?
dairy product, beef, lamb
where we can find phospholipid in food?
egg yolks, liver, soybeans, wheat germ, peanuts, mustard
what is phospholipid's role (e.g. lecithin) in cooking?
emulsifying agent
glycerol and fatty acid are attached by ___________ linkage to form TG though _________________
ester dehydration synthesis
how oxidative rancidity happen?
exposure of fatty acid to oxygen Three steps: 1. Initiation: free radical is formed --> slow, triggered by light, heat, salt, food particles in frying oil, certain metals (Fe, Cu, Ni) 2. Propagation:oxygen combines with the free radical & peroxide free radical is formed --> domino effect until all double bonds have been used 3. Termination: no more hydrogens at double bonds to react with oxygen
what are some food sources of DHA and EPA?
fatty fish
what is an exception of oil from animal source that is liquid at room temperature?
fish
what areoil that are high in linolenic acid?
flaxseed oil
prune puree
good with chocolate and cinnamon. replace all butter with prune to give low-kcal and low-fat treat
does refined oil tend to have a higher or lower smoke point?
higher
what are two type of rancidity?
hydrolytic and oxidative
what are lard, tallow and suet
lard: pig fat tallow: rendered suet suet: cow, sheep fat
what increase oil's susceptibility to oxidative rancidity?
level of unsaturation (more unsaturated, more susceptible)
beans
mashed or pureed, can replace fat in brownies to give judge like structure. low Kcal, low-fat
banana
mashed, help to reduce fat in muffins and cookies
are ω-6 eicosanoids and ω-3 eicosanoids fatty acid?
no
is consumption of sterol bad?
no, sterol also include phytosterol which can lower cholesterol level in adult
what are some food sources of linoleic acid?
nuts, seeds, vegetable oils, meat
phospholipids have similar in structure to triglycerides --> one FA is replaced by a compound containing ___________ and a _____________________
phosphate nitrogenous base
how do you store butter and margarine?
refrigerator
how do you store unrefined, polyunsaturated oil?
refrigerator, dark glass bottle, airtight
avocado
replace half butter with avocado for a softer and chewier cookies
canola oil
replace half cup melted butter with 1/2 cup canola oil for snack with less saturated fat, ch and na
greek yogurt
replace half cup of butter with 1/4 cup of full fat plain greek yogurt to reduce kcal and saturated fat
how do you store lard, softening, most oil?
room temp, away from light, tightly covered; will keep longer in the refrigerator (esp. olive oil)
tofu
silken tofu replace crea,. low fat and vegan alternative
why coconut is very easy to melt at room temperature?
since coconut oil contain fatty acid that have very short chain length
why flax seed and hemp seed is very hard to be pressed?
since they contain high proportion of omega 3, so very sensitive to heat
how to overcome oxidative stress in food?
use antioxidant
what are some example of antioxidant ?
vitamin E, vitamin C, lecithin, beta-carotene, flavonoid, sulfite, BHA, BHT
what are ways to modify fat?
§ Hydrogenation § Interesterification § Winterization § Fractionation
what are advantages of using solvent to extract oil (chemical)?
• Advantages: highest yield, therefore highest profit, more affordable (most bottled oils and those sold in food products) • Disadvantages: loss of nutrients due to heating of oil (to remove solvent), up to 25ppm of solvent often remains in final product, lower quality oil
what are methods of mechanical extraction?
• Cold-Pressed : highest quality oil, small yields, more expensive, maintains integrity of oil and other compounds within it • Expeller-Pressed: very high pressures, therefore more heat generated
what unrefined oil contain?
• pigments (ex: chlorophyll) • odors and flavors • waxes • Can also contain heavy metals and pesticide residues