Lipids Flashcards
What is the trans isomer of Oleic acid, and what does it do in the body, where is it found
Eladic acid, raises vldl, low HDl and up cetp. Majorly found in hydrogen veg oils
Three kinds of lipids
Triacyl
Phospho
Sterols
Excluding butyrate, these are assumed to be 8+ carbons long
What desaturated do humans have, and what do they make
9 654, Oleic acid is a desaturated form of steric acid, which comes from palmitic acid.
Steps in gas crom analyzing lipids
Extraction, saponification, methylation, volatility
What do phospholipids contain, and what is their function
3 kinds, where are they found
They contain po4, 2 tags on sn12, and a nitrogen containing group, when n is gone it is phosophtidic acid
They are emulsifiers. Lecithin is an example. Can have choline as a head group, found in eggs and soybeans, extrCted with hexane
Ethanol amine, cephlin . In Pufas and bilayers
What are sterols, what do they make
Alcohol derivatives, d, bile, cholesterol
Types of fat rancidity
Oxidative, lipolytic
Oxidative rancidity- mechanism, products ( factors affecting ) auto oxidation
Heat, light, oxygen, ionization, loss of flavour and efas, toxic compounds, breaks fas from glycerol, intermediates formed = nasty odour , which condensates. Forms lipid hydroperoxides
Aldehydes provide Roma
Lipolytic rancidity, brought Bout, where found, mechanism
More prone to oxidation then o2, hydrolysis by oxy, gen free fas , produces various aromas, lipase activity in fluid phases very active - more in homogenized milk since finely dispersed
Hydrolysis of lipids generated by
Acid, bases , enzymes, thermal , gen short chain fas , lipase. Moisture in lipid
Oxidative rancidity mechanism.
Form lipid hydroperoxides , breakdown lipid hp. I,p,t
Initiation
Unsaturated lipids lose a hydrogen, forming a lipid radical, in the presence of an initiator, can also be incorporated into a ROOH, forms a hydroperoxide
Propagation
The lipid radical reacts with oxygen to form a lipid peroxyl radical LOO
Will attack fatty acid double bonds to get a h, produces another one of itself
TerminAtion
Can combine with another radical to terminate, or can run into an anti oxidant lool o2, or loo + ah – looh + a
How to stop auto oxidation,
Avoid initiators, saturate or hydrogenated fat , add vitamin e
Hydroperoxides function
Central mechanism of lipid breakdown, easily decompose to form hydroperoxide free radicals, breaks double bonds forms aldehydes , ketones carboxylic acids
Environmental factors in lipid oxidation
Oxidation, temp, light, moisture, analysts, nit oxidants, moisture
antioxidants
Slow rancidity, does not stop production of aldehydes and ketones rom hydroperoxides
How do ntioxidants work
Retardation auto oxidation. Compete for oxy binding retardation free radicals inhibition of catalysts , stabilize hydroperoxides most importants is blocking of propagation.
Blockage of propagation mechanism via anti ox
Ah acts as a hydrogen donor to loo or l, a does. A does not act as an initiatior itself enters a termination reaction. Can be regenerated if favourable
What should food grade anti oxidants hAve. Also what is a contributor to lipid oxidation thru catalytic action
Should be fat soluble. Metallic ions, cu, iron.
Citric acid sequesters metals , enhance phenolic antiox activity
Browning of fruits and veg when cut
EnzymTic action of phenolic compounds . Ascorbic acid prevents this , critic acid enhances the effectively of Ascorbic acid in preventing browning
E numbers
300-399
Synergism
The two nit oxidants together and greater then when used sepErately mixed free radical quenchers, mixed free rad and a metal cheating agent . A synergist may have more then one role , electron donor as well as Metal Che.ator
Measuring lipid oxidation
Rate of oxy uptake , formation of per oxides, ydroperoxidsz , mall aldehydes conj dienes , free fatty acids
Rte of oxygen uptKe tbars
Oxidized fat reacts with tba, forms tba acid, gives red coloured complex , correlates with degree of rancidity
Types of fat in foods
Milk fat, Lauric acid ( coconut oil) , veg butter , Oleic linoleic, linolenic, animal fat Marine oils
Milk fat
Palmitic Oleic , steRic, short chain , branched, odd numbered
Lauric acid
Coconut oil. Babassu large number of saturated , low melting point
Cocoa butter, narrow melting range, no tri saturated , large number of saturated
Above lol
Lonoleic
Canola, olive, safflower, most abundant, less then 20 saturated
Linolenic
Hemp, soy, whet germ
Animal fats
C16, 18, some oleic and linoleic , mostly fully saturated tag , high mp. Small amounts of odd numbered
Marine oils
Long chain Pufas up to 6 dbl bonds, a and d , less resistant to oxidTion usually have dha and EPA at sn2
Plant tags
Seed oils have unsaturTed fatty acids at sn2 13 are sat
Animal tags
Varies among animal/ where on animal , depot fat can be altered by changing dietary fat c16 at sn1, c14, sn2, short chain in milk is at sn3
Pig fat
Unique
Sn1and 3 c18, sn2 c16
Impurities in refining , steps in refining,
FFA, phospholipids, carbohydrates,proteins, water, pigments, fat oxidation products Settling degumming Neut using base Bleaching Deodorizing Hydrogenation
Settling and degumming
Water, protein materials and cho, oil is heated and allowed to stand
Neutralization
Uses NaOH, created rootstock or soapstock, removes phospholipids and colouring materials
Bleaching
Removes residual soapstock , phospholipids and oxidation products , oil is then filtered with activated carbon,
Deodorization
Steam distilization , used to remove volatile compounds , critic acid is often used to bind metals
Hydrogenation
Adding h+ to double bonds aids in stability
Liquid oil is converted to semi solid fat or plastic fats , shortening or margarine
Improves oxidative stability , decrease in the number of unsat fas
