Lecture 8 Flashcards
What are natural fats composed of?
Composed of Esters of glycerol with fatty acids
what are the components of a fatty acid?
Alcohol and carboxylic acid
What is the most common glyceride?
triglyceride
What is butyric fat in?
Give dairy products flavour
What is the difference in structures of stearic, oleic, linoleic.
Stearic straight line
oleic curved like U shaped
linoleic straight but soft curved like Z shaped
Where are the double bonds in oleic and linoleic fats?
oleic= 9C
linoleic= 9 and 12 C
What are the 2 classes of lipids?
Simple structure
Complex structure
What are simple lipids?
Fats (oils): Glycerol + F.A.
Waxes: Long chain alcohol + F.A.
What are complex lipids?
Phospholipids: Glycerol + F.A. + P + others
Example:
-Phosphatides: Lecithin found in egg yolk
What is the structure like of dry fats?
they are more complex
EX: Fat soluble vitamins, carotenoids, steroids
What is the difference between visible and invisible fats?
Visible: butter on toast
Invisible: cooked/baked into things
How do we name saturated and unsaturated fatty acids?
Saturated F.A. ………. Suffix “anoic”
Unsaturated F.A. …… Suffix “enoic”
What are the major groups of fats and oils?
1) Lauric Acid Group
2) Palmitic Acid Group
3) Oleic-Linoleic Acid Group
4) Linolenic Acid Group
5) Vegetable Butter
6) Marine Oils
7) Animal Fat
What are characteristics of Lauric acid groups?
Coconut oil, palm kernel oil
Highly saturated
High in medium chain fatty acids C:10-C:14
High content of Lauric acid C:12
Melting range 25-30oC
Solid at room temperature
What do we mean when oils are highly stable?
Highly stable, so wont oxidized as easily and maintaining all properties
What are characteristics of palmitic acid groups?
Palm oil
Highly saturated C:16:0,
Palmitic acid
Crude palm oil is bright red due to high conc. of carotenoids
Melting range 38-450C , solid at room temperature
What are characteristics of oleic-linoleic acid groups?
Olive, peanut, cotton, sesame, corn, safflower, sunflower
Liquid at room temp.
Unsaturated
Major fatty acid:
Oleic acid C:18:1, Linoleic C:18:2 (ω-6)
What are characteristics of linolenic acid groups?
Soybean, flaxseed, canola
Significant amount of linolenic C:18:3 (ω 3)
Susceptible to oxidation
What are characteristics of vegetable butter?
Enrobing fat
Cocoa butter (Melting Point:32-35oC)
Fats in cocoa butter, solid at room temp and melting temp close to body temp
What are characteristics of marine oils?
Long chain fatty acids: EPA C:20:5 and DHA C:22:6
What are characteristics of animal fats?
Fat derived from animal body
Cholesterol
-Fats contain cholesterol, for examplee lard
What are the physical properties of fats that can be altered?
Melting point
Viscosity
Iodine#
Stability
What factors affect melting point?
Natural fats vs. Pure fats
Chain length ↑ m.p. ↑
Unsaturation ↑ m.p. ↓
Melting range for natural fats and meelting poiint for pure fat (only one type)
• Natural fats have differeent kindds
What are the factors affecting viscosity?
Chain length ↑ η ↑
Unsaturation ↑ η ↓
What are the factors affecting iodine #?
Unsaturation ↑ I # ↑
Higher iodine value higher level of unsaturation
What properties affect stability?
unsaturated vs saturated
-Saturatde fats more stable than unsaaturated
vegetable vs animal fat
-Veg fats are more stable than animal fats although they are more unsaturated but its because they contain natural antioxidants and are therfore more stable than animal fats whiich can be oxidized more readily
What are the 3 ways fats can deteriorate?
Lipolysis (hydrolytic ranidity)
Flavour reversion
Auutoxidation
What is lipolysis?
Lipase cleaves Ester bonds > Free Fatty Acids
results in the production of a lot of Free fatty acids with:
- decrease smoke point (undesirable)
- creates off flavours
What is the flavour reversion?
Linolenic acid > Off Flavour
-by addition of UV
Visible, light, Heat
O2, Fe, Copper
results in a Beany, Painty, Fishy flavours
What is Autoxidation?
Oxidative rancidity most common
What are the 3 steps to autoxidation?
1)Initiation: RH R + H
(R = Free Radical)
-Formation of free radical. When oiil/fat comes into contact with oxidative properties, free radicals start
2) Propogation: R + O2 ROO
- Free readical reactiwith O2 and more free readicals form
3)Termination: R + R > RR RO + R > ROR ROO + R > ROOR -When free readical react with one another
Rate ↑ as the process goes on
What causes autoxidation (oxidative rancidity)?
Heat Light Ionizing Radiation Metals (Fe and Cu) Enzymes (Lipoxygenase)
To inhibit autoxidation keep away from all these
What are antioxidants relationship to fat?
Antiodxidants combinw with free radical react with fats and then no more ar being form
What are the synthetic antioxidants?
BHA [Butylated hydroxy anisole]
BHT [Butylated hydroxy toluene]
What are the natural antioxidants?
Vit E. Tocopherol, α, β, γ, δ
Vitamin C,
Beta-Carotene
What does citric acid do?
Citric Acid is a chelating agent which binds with iron and copper and inhibit oxidation
-When Fe and Cu are bound with citric acid they are no longer in the fre forma nd cant cause oxidation
What are the different ways of extracting fats/oils?
Pressing
Solvent Extraction
What is oil pressing?
Oil Seeds Machine (screw press) Squeeze the oil out Crude Oil
-physical pressing
What is solvent extractions?
Uses hexane to dissolve oil from the oilseed flakes
Two types:
1) Immersion: Seed-Flakes are totally submerged in Hexane
2) Percolation: Seed-Flakes are placed into baskets and Hexane is sprayed on top (hexane percolates through)
What is a micelle?
(solvent + oil) is then collected
- The crude oil is recovered from micella by distilling off the solvent
What are the things that we want to remove from fats/oils when they are processed?
Suspended solids Gums, pigments Lipoproteins, phospholipids Mycotoxins Others
What are the different ways to remove unwanted particulate matter?
Settling and Degumming Neutralization Bleaching Deodorizing by Steam Distillation Winterization
What is settling and degumming?
By adding dilute H3PO4, Brine…
Removes: Non-Oil Impurities Protein Phospholipids: Lecithin Vegetable Gums
Cude oiil put in the cone, so impuritiessetle to the bottom and theen open the valve and remove the bottomm
What is neutralization?
Alkali (NaOH) added to oil
Free Fatty Acids Insoluble soaps (i.e. Na-salt) are filtered out
What is bleaching?
Elimination of undesirable colours
Involves filtering through activated charcoal & clay
Also removes pigments, traces of gums, soaps
What is Deodorizing. by steam distillation?
Removes flavour and odour compounds
Mild odor desired
Pump oil into chamber and pump stream in and vacuum the odors out
What is winterization (Winterizing oil)?
is the process of holding fat at cold temp until cloud formation and then filtering high melting point fats.
The final oil stays clear at cold temp.
The winterized oils are used in salad dressings that need to stay clear in the refrigerator.
How can we modify fats and oils?
Hydrogenation
Partial hydrogenation
What is hydrogenations effects on melting point, stability, viscosity, Iodine #?
Increease melting point stability and viscosity because you have less double bonds
Iodine value would decrease because less double bonds
What is partial hydrogenation?
Partial: don’t convert all double in to single, if they did complete the final fat would be hard and brittle and not very functional which Is why this is common in industry
What is hydrogenation?
To icrease stability of fats and oils
Adding H to convert double bonds to single bonds , at high temp with a catalyst
What is selective hydrogenation?
Used in manufacture of ? …. Margarine
Requires high temp (200oC) & low pressure (6psi)
Hydrogenation of Linoleic Oleic predominates over hydrogenation of Oleic to Stearic
-Selective hydrogenation of these, higher trans fats and a softer fat
What does selective hydrogenation result in?
Result> Softer Fat and high amount of Trans Fats
What is non selective hydrogenation?
Used in the manufacture of ? …. Frying Fat
Requires lower temp (135oC) & higher pressure (40psi)
Oleic and Linoleic are hydrogenated simultaneously
Result Harder Fat
What is interesterificatoin?
Modify the physical properties of oil by randomizing the order of fatty acids on glycerol backbone
What are the 2 ways we can achieve interesterification?
1) Heating the fat in the presence of Sodium Methoxide under anhydrous conditions
- Breking ester bonds to replace unsaturated FA with a searin asid, increeaseing the solid conted of fat
2) Biological Catalysts (Enzyme)
Lipase can replace Sodium Methoxide
Milder Condition
-Don’t have to use high heat with this
What is polymorphism in fats?
Liquid Fat >Diff. patterns of molecular packing
Chilled at different rate > Diff. Crystal Structures
What are the 3 main forms of fat crystal structure?
Hexagonal
- randomly oriented
- 5 micron
- alpha
Parallel
- 20-30 micron
- beta
Needle shaped
- alternating
- 1micron
- beta prime
What do beta crystals result in?
Coarse and Grainy Texture (Not Desirable)
-i.e. Margarine, Shortening
What is shortening?
Fat + Entrapped Air
What is the best fat crystal structures?
Beta prime
Has smallest size and will be a smoother and creeamier fat
What type of air bubbles are in beta and beta prime fat crystals?
Beta prime: Lots of small air bubbles (Desirable)
beta: Few large air bubbles (Not Desirable)
What kind of mix is margin?
Water in oil emulsion
a Controlled Crystallization = Better Texture
What is enrobing fats?
Found in Cocoa Butter
At Room Temp Hard and Brittle
Absence of Liquid Fat
At Mouth Temp Rapid Melting
(Cocoa Butter)
What is tempering?
Process of holding fat at selected temp. to allow interconversion of crystalline forms
-Mke sure you have beta prime crystals
