lips/triglycerides- week 3/4 Flashcards
what is the melting point of a triglyceride based on
its dependent on its fatty acids & its crystal structure (polymorphism)
1) TG with high melting points are ………. at room temp.
2) TG with low melting points are ……. at room temp.
1) solid
2) liquid
when do fatty acids melt
occurs when intermolecular (van de waals) are broken
by heat energy (not intramolecular bonds)
what decreases the melting point of a fatty acid
increasing unsaturation
The more C=C bonds the lower the melting point
what increases the melting point of fatty acids
increases with chain length (number of carbons)
The longer the chain, the higher the melting point
Longer chains = more intermolecular bonds = more heat energy needed
how does the unsaturation of the fatty acid influence the melting point (2 points)
-trans C=C bonds introduce a slight kink and lower intermolecular bonds and thus less heat energy needed to melt
-cis C=C bonds introduce a larger kink (~42o
) and lower intermolecular bonds even more and thus even less
heat energy needed to melt
Triglycerides are polymorphic, what is it meant by polymorphic
means that TG can exist in more than one crystalline form
what are the three main polymorphic forms
α : alpha
β’ : Beta prime
β : Beta
what is the melting range of MP of fats dependent on
on the arrangement of TG molecules
i.e. their crystal structure
What are the properties of α-types (3 points)
- Limited applications in foods and food processing (don’t form solids)
- Randomly formed
- Melts very easily
what are the properties of β’ -types (2 points)
- Form small needle like crystals
- Form soft plastic fats for use in margarine
what are the properties of β -types (3 points)
- Form large crystals giving grainy texture (cocoa butter, lard)- too hard
- Well ordered; hard texture
- Not good for margarine
what is the definition of Tempering explain in terms of chocolate
controlled crystallization that is necessary to induce the desired form
of cocoa butter in the finished product (Used to Prepare Food with Desired
Polymorphic State of a Lipid)
what are the 3 states that lipids can exist depending on temperature
-solid (All TGs liquid)
-plastic (TGs with short chain FA liquid TGs with long chains solid)
-liquid (All TGs liquid)
Outline the difference between a simple and mixed triglyceride
In a simple triglyceride such as palmitin or stearin, all three fatty-acid groups are identical. In a mixed triglyceride, two or even three different fatty-acid groups are present; most fats and oils contain mixed triglycerides.
how is the process of tempering used to form chocolate
-Liquid cooled to initiate crystallisation
-Reheated to 32 degrees (just below the mpt of β-3 type) and
held – this melts out unwanted crystals
-Stir at 32 degrees, allow formation of very small β-3 crystals
and then finally solidify
what are the natural commodities lipids are obtained from (3 points and give examples of each)
-plants-
Oil Seeds (Rape, Sunflower, Palm Kernel, Soybean,
Cottonseed, Corn germ, Peanut, Coconut)
Fruit Pulp (Olive, Palm Fruit)
-animals & Fish-
* Lard (rendered from pig kidney fat, fatback, caul fat)
* Tallow (The rendered form of fat from sheep and cattle)
* Marine oils (Fish, Whales)
-Milk fats-
produced from churning whole milk or cream
Describe how lipids are purified from natural commodities from FRUIT (4 points)
-Grinding to a paste
-Pressing
-Separation (decantation or vertical centrifuge)
-Heating/Solvent Extraction
Describe how lipids are purified from natural commodities from seeds (5 points) - Milling
-Cleaning
-Breaking
-Cooking 70-100oC (to denature the enzymes like lipase & killing microbes)
-Expelling
-Solvent Extraction (hexane/heptane)
what are the 2 ways of Oil/Fat Extraction from Lipid-Rich Animals
wet rendering and dry rendering
what are the steps for wet rendering (5 steps)
- Tissue heated with steam (high temp of about 100-110oC)
- Lipid melts
- Lipid separated by decanting or centrifugation
- White lipid with neutral flavour, e.g., Lard
- Process milder than dry rendering
what are the steps for dry rendering (4 steps)
- Uses high heat alone
- A harsher process than wet rendering
- Browner lipid with stronger flavour
- Non food uses e.g. soap
what are the 2 ways of refining oils
- Caustic or chemical refining
- Physical refining
what are the steps for caustic or chemical refining (6 steps + define each step)
-Crude Lipid (TGs, water, protein, phospholipids)
-DEGUMMING (Removal of phospholipids + some protein)
-NEUTRALISATION (Removal of free fatty acids)
-BLEACHING (Removal of colour and pro-oxidants)
-DEODORISATION (Removal of volatile compounds and flavours)
-Crude Lipid (TGs, water, protein, phospholipids)
Refined Oil (one of the purest foods known)
Refining Steps in Detail
DEGUMMING
2-3% water added + agitation at ~50 degrees
Water phase removed after phase separation
what are the steps for physical refining (5 steps + explain each step)
-Crude Lipid (TGs, water, protein, phospholipids)
-DEGUMMING (Removal of phospholipids + some protein)
-STEAM DISTILLATION UNDER HIGH VACUUM (Removal of free fatty acids and deodorisation in one step)
-BLEACHING (Removal of colour and pro-oxidants)
-Refined Oil is produced
give in DETAIL the process of DEGUMMING in Caustic or Chemical Refining
2-3% water added + agitation at ~50 degrees
Water phase removed after phase separation
give in DETAIL the process of NEUTRALISATION in Caustic or Chemical Refining
Caustic soda added to heated fat
Aqueous solution (soap stock) removed; Washed with hot water
give in DETAIL the process of BLEACHING in Caustic or Chemical Refining
Heated to 85 degrees and absorbents added
(Fullers earth or activated carbons); The bleaching earth removed by filtration
give in DETAIL the process of DEODOURISATION in Caustic or Chemical Refining
Steam distillation-steam passed through oil under reduced pressure
Citric acid is often added to sequester metals
What is lipid modification
The alteration of one or more fatty acids in a lipid, resulting in a change in the properties of the lipid
Why are lipids modified (5 points)
Most of our food products is oil/ 75% of world edible oil is vegetable oil
Melting point not suitable for processing
Crystal structure not fit for production
Cloudy when cooled
Unstable (oxidation)
What are the 3 different methods of lipid modification
Hydrogenation
Fractionation
Interesterification
Explain hydrogenation
(What does it do to FAs/what does it produce/characteristics of hydrogenated FAs)
-removed double carbon bonds- end up with trans fatty acids(increase HDL
-means it increases the melting point
-can convert cheap vegetable oils into plastic fats
-improves stability
-Generates hydrogenated vegetable oils (HVO)/trans fats
What is Interesterification/ what can it do to the lipid/ what’s its properties
- Rearranges fatty acids on the glycerol
backbone of TGs - Can change melting point
- Can change crystal structure
- Improves properties (more plastic)
(Can change to what you what the product you want, and it doesn’t produce trans-fatty acids)
*Converts cis bonds into trans double bonds
what are the importance of lipids in food
-Nutrition (essential FAs, e.g linoleic acids & lipids are essential of bilayers)
-Palatability (flavour, texture, solubility)
-Processing (heat transfer)
what are lipids
Compounds that are soluble in non polar solvents and are insoluble in water
what are the major classes lipids can be classified into
» Simple lipids (waxes, fatty acids, mono-, di-, triglycerides)
» Compound lipids-structural lipids (phosphoglycerides, glycolipids- all are polar)
» Derived lipids (sterols, fat soluble vitamins)
what is it meant by a lipid is polar
it has a hydrophobic tail and hydrophilic head
what is the structure of glyceride and how can you tell if its a simple or mixed triglyceride
glycerol + FA = triglyceride
in the triglyceride has the SAME variable regions = SIMPLE
if 2 are a least DIFFERENT it means its MIXED
what is the difference between a phosphoglyceride and a triglyceride
Similar to triglycerides (TGs) but are polar (eg.
emulsifying agents
what is the structure of a phosphoglyceride
it has:
-choline
-glycerol
-phosphate
-Fatty Acid
what is a Fatty Acid
FAs are chains of carbon and hydrogen atoms with a terminal carboxyl group
How are saturated Fatty acids named
Named in accord with the number of C atoms including the COOH group
i.e: CH3CH2 CH2 CH2 CH2COOH —–>HexANOIC (Caproic acid)
CH3CH2 CH2COOH
ButANOIC (Butyric acid)
anoic -means its a saturated FA
in unsaturated fatty acids what are the 2 types of methylated double bonds
-Methylene interrupted
-Conjugated (where this there is no CH2 in between the double bounds- Rare)
what is it meant by methylene interrupted
FA is interrupted by a CH2 in between the double bonds
what are the influence of TG structure in the nature/use of lipids
-Type of FA and arrangement responsible for the varied properties of TGs in foods
—->TG melting point is dependent on its fatty acids & its crystal structure (polymorphism)
give examples of lipid rich foods and the content of TG in them (4)
-Ruminant Milk Fat TGs
* Short chain FAs (C4
-C12) + trans FAs
-Vegetable Fat and Oil TGs
* Seed oils-low in sat FAs
* Vegetable fats, High sat/unsat ratio
No fully saturated TGs
- Animal Fats
* Fully saturated TGs present; solid at room temp (20oC)- some unsat
- Marine Oils
* Low in saturated FAs; liquid at room temp
* High in long chain polyunsaturated (PU) FAs
describe how the Fatty acid structure influence TG properties (3 points)
-Melting of fatty acids occurs when intermolecular (van de waals) are broken
by heat energy (not intramolecular bonds)
-Melting point increases with chain length (number of carbons)
The longer the chain, the higher the melting point
-Melting point decreases with increasing unsaturation
The more C=C bonds the lower the melting point
what influence does the chain length have on the Melting point of FAs
Longer chains = more intermolecular bonds = more heat energy needed
rank in Oder from the highest MP to the lowest MP:
TGs have C18 Saturated FAs
TGs have C4-C12 Saturated FAs
TGs have Unsaturated FAs
highest —>lowest MP
TGs have C18 Saturated FAs
(solid- e.g Lard)
TGs have C4-C12 Saturated FAs
(semi-solid- e.g butter)
TGs have Unsaturated FAs
(liquid- e.g oils)
define polymorphic and give an example of one
Triglycerides are polymorphic meaning they can exist in more than one crystalline form
what are the three main polymorphic forms
α - alpha
β’ - beta prime
β - beta
what causes the different polymorphic forms to form
The forms that grow depend on HOW the liquid is cooled
how does α-types affect the application of Lipids/ what’s its characteristics
- Limited applications in foods and food processing
- Randomly formed
- Melts very easily
how does β’-types affect the application of Lipids/ what’s its characteristics
- Form small needle like crystals
- Form soft plastic fats for use in margarine
how does β-types affect the application of Lipids/ what’s its characteristics
- Form large crystals giving grainy texture (cocoa butter, lard)
- Well ordered; hard texture
- Not good for margarine
define Tempering
Used to Prepare Food with Desired
Polymorphic State of a Lipid—->controlled crystallization that is necessary to induce the desired form
of cocoa butter in the finished product
» This is the last stage in the process
» Ensures that chocolate is in the correct crystalline state
Which polymorphic state exists in chocolates and margarine?
small β-3 crystals
what are the natural commodities lipids are derived from
-Plants: Oil SEEDS(i.e sunflower ,rapeseed, soybean) & fruit PULP (olive, palm fruit)
- Animals & Fish: Lard (rendered from pig kidney fat), Tallow (The rendered form of fat from sheep and cattle), Marine oils
-Milk fats: butter produced from churning whole milk or cream.
*rendering =product that is melted in order to separate out the impurities.
