Lipids 1 Flashcards
Oil uses in ancient Egypt, Greek/Roman, and medicinal uses
Egypt 7000 - 2000 BC: base for lotions, perfumery
Greek/Roman 700 BC -1000 AD: distillation and seed pressing, olive oil, Athena offered olive tree to Athens
1000 - 1500 AD: Chinese medicine, purified sex hormone from urine
Saponification
Developed during industrial rev (1600-1800)
- first industrialized lipid transformation process
Boiling of animal fats + strong alkali + salts
Led to sperm whale hunting for oil in head (1982 illegal)
Lipid definition
3 Types in human body:
Glycerol formation
Insoluble organic compounds with a greasy feel
triglycerides, phospholipids and sterols
carboxyl group of FA reacts (esterification) with hydroxyl of glycerol form mono, di or triglyceride
- ester bond is between the 2 O molecules
Examples of monounsaturated FA sources
Examples of polyunsaturated FA sources
ω-3 and ω-6 definitions
Trans isomer of oleic acid
olive, canola, almonds, walnuts
safflower, sunflower, corn oil
designate 1st position of double bond from methyl end (nutritional convention)
Elaidic acid
How to check FA composition of a fat/oil
FA melting point increases with
Hydrolyze ester bonds with strong base and analyze
1) increasing chain length
2) decreasing cis double bonds
3) isomerization from cis to trans bonds
Catalytic hydrogenation
Addition of H2 across double bonds, converting cis –> trans
negative health consequences of trans fat
Switch to interesterification for conversion of oils to fats
Advantages of hydrogenation: longer shelf life, stability, cheaper, faster dissolving and setting in chocolate
Functional properties of oils (7)
1) Good heat transfer agent: >200°C
- Fry oil drives off water as steam on food surface –> maillard rxn
2) Tenderize baked goods - shorten gluten strands ↓ chewiness/toughness
- fat to flour ratio determines flakiness
- Oil for liquidy batter, fats for pastry and biscuits
3) Lubricating agent: emulsions
- oil in water (dressing) or water in oil (butter)
4) Aeration: incorporation of hydrophobic air bubbles
5) Flavor enhancer: dissolve and disperse flavor compounds
6) texture, mouthfeel, satiety
7) Plasticity: solid fat content determines ability to be spread/molded due to range of TAG types
- no single melting point
Autoxidation
Lipolysis
Smoke Point
Flash Point
Autoxidation: reactions with lipids in presence of O2 - becomes unpalatable due to off flavors (rancidity, chemical spoilage)
- More double bonds - faster autoxidation
- Antioxidants like vitamin E added to delay autoxidation
Lipolysis: hydrolysis of TAG at high temps in presence of water (ie. frying)
- free FA reduce BP and smoke point (must discard oil)
Smoke point: temp FA break apart and produce smoke
Flash point: temp FA flame
Degradation of oils health concerns
Free radicals, aldehydes and peroxides produced by spoilage
Increased inflammatory response and disease
Protect from heat and light to avoid deterioration (opaque bottles)
Applications of saturated fats
Butter, lard and tallow
High temp resistant: frying and deep frying
Solid at room temp: baking and aeration
Applications of monounsaturated oils
Olive, safflower and canola oils
Moderate heat resistance: low temp sautéing
High flavor profile: dressing/cooking
Applications of unsaturated oils
Flax, cottonseed and walnut
Heat vulnerable: cold applications
Liquid at room temp: liquid baking applications
Applications of solid unsaturated fats
avocado, margarine
Good plasticity: toast spread, side dish
Applications of saturated tropical oils
palm and coconut
Heat stable: good for cooking and frying
High yield and low cost (palm especially): industrial uses
Characteristic flavor (coconut): distinct flavor for cuisines like Thai
Fat substitutes
Lipid based, low cal, lb for lb, many not authorized in Canada
- can be used for cooking
Dur-Lo: mono/diglyceride emulsifier
EC-25: emulsion of TAG, proplylene glycol, monoester, aqueous phase with starches and gums
