Notes for Exam 2

8/9/2019 Notes for Exam 2

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Lipids


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Class Presentations Will be

Discussed at the End of Class

Exams back next Monday

No class this Wednesday !!!!!


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Lipids

Main functions of lipids in foods

Energyand maintain human health

nfluence on food flaor "atty acids impart flaor

Lipids carry flaors#nutrients

nfluence on food texture $olids or li%uids at room temperatureChange &ith changing temperature

Participation in emulsions


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Lipids

Lipids are soluble in many organic solentsEthers 'n(alkanes)

*lcohols+en,ene

DM$- 'dimethyl sulfoxide)

.hey are generally N-. soluble in &aterC/ 0/ -and sometimes P/ N/ $


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LipidsNeutral Lipids

.riacylglycerolsWaxes

Long(chain alcohols '123 carbons in length)

Cholesterol esters

4itamin * esters

4itamin D esters

Con5ugated Lipids

Phospholipids/ glycolipids/ sulfolipids

6Deried7 Lipids "atty acids/ fatty alcohols#aldehydes/ hydrocarbons

"at(soluble itamins


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Lipids

$tructure

.riglycerides or triacylglycerols

8lycerol 3 9 fatty acids:12 different fatty acids


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Lipids ;2;

"atty acids( the building block of fats

* fat &ith no double bonds in it

"ats are named based on carbon number and number

of double bonds ';AB2/ ;AB;/ ;B1 etc)


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Lipids

-il( li%uid triacylglycerides 6-leins7"at( solid or semi(solid mixtures of crystalline

and li%uid .*8Many preseration and packaging schemes are

aimed at preention of lipid oxidation>


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Nomenclature

.he first letter Crepresents Carbon

.he number after C and before the colonindicates the Number of Carbons

.he letterafter the colon sho&s the Number of

Double Bonds .he letter n'or w) and the last number indicate

the Position of the Double Bonds


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$aturated "atty *cids


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$aturated "atty *cids

C09 C01 C01 C01 C01 C01 C01 C -0

-1245678 3

-ctanoic *cid


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Mono(=nsaturated "atty *cids


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Poly(=nsaturated "atty *cids


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"atty *cids

Melting Points and $olubility in Water

Solubility in H2O

Fatty acid chain length

2

Melting Point

,

Eespon

se


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=nsaturated "atty *cids

C09 C01 C01 C01 C01 C01 C01 C -0-1245678 3

C09 C01 C01 C01 C01 C01 C01 C -0

-1245678 3

9 ( -ctenoic *cid

9/ A ( -ctadienoic *cid


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Lipids

Properties depend on structure Length of fatty acids 'F of carbons) Position of fatty acids ';st/ 1nd/ 9rd) Degree of unsaturationB

Double bondstend to make them a li%uid oil $ignificantly lo&ers the melting point

0ydrogenationB tends to make a solid fat $ignificantly increases the melting point

=nsaturated fats oxidi,efaster Preenting lipid oxidationis a constant battle in the food

industry


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"atty *cids

Melting Points and $olubility in Water

Solubility in H2O

Fatty acid chain length

2

Melting Point

,

Eespon

se


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C? (

CA ( ? GH2

C ;A H@

C;2 9; A

C;1 ?? 2>@@

C;? @? 2>;

C;A A9 2>2

"atty *cids M>P>'C)mg#;22 ml

in 01-

C; H2 2>2?

Characteristics of "atty *cids


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"atty *cids

-

C -0

#1 Cabon !cid "ou

-

C -0

$on%ola &nd % Hydohobic &nd

'Fat%(oluble tail)

Pola &nd % Hydohilic &nd


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Lipids ;2;

"atty acid profile( %uantitatie determination of the

amount and type of fatty acids present follo&ing

hydrolysis>.o help orient ourseles/ &e start counting the

number of carbons starting &ith 6;7 at the

carboxylic acid end>O

C

OH

CCCCCCCCCCCCCCCCC

118


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Lipids ;2;

"or the 6;(series7 ';B2/ ;B;/ ;B1/ ;B9) the

double bonds are usually located bet&een carbons

GI;2 ;1I;9 ;@I;A>O

C

OH

CCCCCCCCCCCCCCCCC

118 91012131516


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Lipids ;2;

.he biomedical field started using the -ME8*'w)

system 'or 6n7 fatty acids)>

With this system/ you count 5ust the opposite>

+egin counting &ith the methyl end

No& the ;@I;Adouble bond is a 9I?double bond

or as the medical folks call itJ>an w(9 fatty acidC

C

OH

CCCCCCCCCCCCCCCCC

181 1097643


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.uning "ork *nalogy(.*8

.he top chain &ill then cure for&ard and form an h .hus the 6tuning fork7 shape

"ats &ill tilt and t&ist to the lo&est free energy leel


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Lipids

Lipids are categorized into two broad classes.

The first, simple lipids, upon hydrolysis, yield up to two typesof primary products, i.e., a glycerol molecule and fatty acids!.

The other, comple" lipids, yields three or more primaryhydrolysis products.

#ost comple" lipids are either glycerophospholipids, or

simply phospholipids contain a polar phosphorus moiety and a glycerol bac$bone

or glycolipids, which contain a polar carbohydrate moietyinstead of phosphorus.


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Lipids


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-ther types of lipids

Phospholipids

$tructure similar to triacylglycerol

0igh in egetable oil

Egg yolks*ct as emulsifiers


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Where Do We 8et "ats and -ilsK

6Crude7 fats and oils are deried fromplantand animalsources $eeral commercial processes exist to extract food grade oils Most can notbe used &ithout first 6refining7 before they reach

consumers During oil refining/ &ater/ carbohydrates/ proteins/ pigments/

phospholipids/ and free fatty acids are remoed> Crude fats and oils can therefore be conerted into high %uality

edible oils n general/ fat and oil undergo four processing stepsB

Extraction

Neutrali,ation +leaching Deodori,ation

-ilseeds/ nuts/ olies/ beef tallo&/ fish skins/ etc> endering/ mechanical pressing/ and solent extraction>


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"ats and -ilsB Processing

Extraction

endering

Pressing oilseeds

$olent extraction

Peanut

Rape Seed

Safflower

SesameSoybean
http://rds.yahoo.com/S=96062857/K=soybeans/v=2/SID=e/l=II/R=2/SS=i/OID=698b5130b9e9ff52/SIG=1i73mdk6t/EXP=1111259636/*-http%3A//images.search.yahoo.com/search/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dsoybeans%26ei%3DUTF-8%26fr%3Dslv1-wave&h=125&w=153&imgcurl=www.unitoday.com%2Flibrary%2Fgold_directions%2F98Mar%2FImages%2Fsoybeans.jpg&imgurl=www.unitoday.com%2Flibrary%2Fgold_directions%2F98Mar%2FImages%2Fsoybeans.jpg&size=5.1kB&name=soybeans.jpg&rcurl=http%3A%2F%2Fwww.unitoday.com%2Flibrary%2Fgold_directions%2F98Mar%2F10.html&rurl=http%3A%2F%2Fwww.unitoday.com%2Flibrary%2Fgold_directions%2F98Mar%2F10.html&p=soybeans&type=jpeg&no=2&tt=19,362


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"ats and -ils

"urther Processing Degumming emoe phospholipids &ith &ater

efining

emoe free fatty acids 'alkali 3&ater)

+leaching emoe pigments 'charcoal filters)

Deodori,ation emoe off(odors 'steam/ acuum)


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Rendering Primarily for extracting oils from animal tissues>

-il(bearing tissues are chopped into small pieces andboiled in &ater>

.he oil floats to the surface of the &ater and skimmed>

Water/ carbohydrates/ proteins/ and phospholipidsremain in the a%ueous phase and are remoed from theoil>

Degumming may be performed to remoe excessphospholipids>

emaining proteins are often used as animal feeds or

fertili,ers>


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Mechanical PressingMechanical pressing is often used to extract oil from

seeds and nuts &ith oil :@2> Prior to pressing/ seed kernels or meats are ground into

small si,ed to rupture cellular structures> .he coarse meal is then heated 'optional) and pressed in

hydraulic or scre& presses to extract the oil> -lie oils is commonly cold pressed to get extra irgin

or irgin olie oil> t contains the least amount ofimpurities and is often edible &ithout further processing>

$ome oilseeds are first pressed or placed into a scre&(press to remoe a large proportion of the oil beforesolent extraction>


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Where Do We 8et "ats and -ilsKSolvent Extraction -rganic solents such as petroleum ether/ hexane/ and 1(propanol can be added to

ground or flaked oilseeds to recoer oil> .he solent is separated from the meal/ and eaporated from the oil>

Neutrali,ation "ree fatty acids/ phospholipids/ pigments/ and &axes exist in the crude oil

.hesepromotelipid oxidation and off(flaors 'in due time) emoed by heating fats and adding caustic soda 'sodium hydroxide) or soda ash

'sodium carbonate)> mpurities settle to the bottom and are dra&n off> .he refined oils are lighter in color/ less iscous/ and moresusceptible to oxidation

'&ithout protection)>

+leaching .he remoal of colored materials in the oil> 0eated oil can be treated &ith diatomaceous earth/ actiated carbon/ or actiated

clays> Colored impurities include chlorophyll and carotenoids +leaching can promote lipid oxidation since some natural antioxidants are

remoed>


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Deodori,ation .he final step in the refining of oils> $team distillation under reduced pressure 'acuum)> Conducted at high temperatures of 19@ ( 1@2C>

4olatile compounds &ith undesirable odors and tastescan be remoed>

.he resultant oil is referred to as refined and is readyto be consumed>

*bout 2>2; citric acid may be added to inactiate pro(oxidant metals>


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"ats and -ils

"urther Processing0ydrogenation

*dd hydrogen to an oil to 6saturate7 the fatty acid

double bonds Conducted &ith heated oil

-ften under pressure

n the presence of a catalyst 'usually nickel) Conerts li%uid oils to solid fats

aises melting point


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0ydrogenating 4egetable oils can

produce trans(fatsC C

H H

C C

H

H

Cis-

Trans-

.h i d f f f tt id


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.he cis( and trans( forms of a fatty acid


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d -il i d


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"ats and -ils in "oods $-LD "*.$are made up of microscopic fat crystals> Many fats

are considered semi(solid/ or 6plastic7> PL*$.C.is a term to describe a fat

Een a fat that appears li%uid at room temperature contains a small number ofmicroscopic solid fat crystals suspended in the oilJ>>and ice ersa

PL*$.C "*.$are a 1 phase systemB $olid phase 'the fat crystals) Li%uid phase 'the oil surrounding the crystals)>

Plasticity is a result of the ratio of solidto li%uidcomponents> Plasticity ratio I olume of crystals # olume of oil Measured by a Osolid fat index< or amount of solid fator li%uid oilin a lipid

*s the temperature of a plastic fat increases the fat crystals meltand the fat &ill soften and eentually turn to a li%uid>


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"at and -ilB "urther Processing

Winteri,ing 'oil)Cooling a lipid to precipitate solid fat crystals

D""EEN. from hydrogenation

Plastici,ing 'fat)Modifying fats by melting 'heating) and solidifying

'cooling)

.empering 'fat)

0olding the fat at a lo& temperature for seeralhours to seeral days to alter fat crystal properties

'"at &ill hold more air/ emulsify better/ and haea more consistent melting point)


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Lipid -xidation


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Oleic acidOleic acid

Radical Damage,Radical Damage,HydrogenHydrogen

AbstractionAbstraction

Formation of aFormation of aPeroxyl RadicalPeroxyl Radical


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$implified scheme of lipoxidation

C C

H H

CC R

H

H

H

H

R C C

H

CC R

*

H

H

H H

R C C

H

CC R

O

H

H

H H

O

R

+ Oxygen+ Catalyst

i i


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.emperature(basicrxn kinetics

Water *ctiity+oth high and lo& *&

*t lo& *&/ peroxides decompose faster and metal ions

are better catalysts in a dry enironmentMetalons(catalysts

Light(energy source

$inglet-xygen( -$/ highly electrophiliceacts ;/@22 times faster at CIC than ground state -1

En,ymesie> Lipoxygenase 'L-)

Primary Driers


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nitiation of Lipid -xidation

.here must be a catalytic eent that causes the initiation of

the oxidatie process En,yme cataly,ed

6*uto(oxidation7 Excited oxygen states 'i>e singlet oxygen)B ;-1

.riplet oxygen 'ground state) has 1 unpaired electrons in the samespin indifferentorbitals>

$inglet oxygen 'excited state) has 1 unpaired electrons of oppositespin in thesameorbital>

Metal ion induced 'iron/ copper/ etc) Light 0eat "ree radicals Pro(oxidants Chlorophyll

Water actiity

C id ti f Li id - id ti


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Considerations for Lipid -xidationWhich hydrogen &ill be lost from an unsaturated

fatty acidK.he longerthe chain and the moredouble

bondsJ>the lo&er the energy needed>


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Bond %trength

Fatty acid

OH or other

Free radicals

..

.

65 kCal10 kCal

65 kCal!5 kCal

Propagation eactions


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Propagation eactions

"n#t#at#on $round state oxygenPeroxyl rad#%al

&ydroperox#de 'ew

Rad#%al

&ydroperox#de

de%ompos#t#on

&ydroxyl rad#%al((

Start all o)er aga#n*

lkoxyl rad#%al


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Mechanism of Photooxidation

ChlorophyllChlorophyll 3O21O2

or


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$inglet -xygen -xidation

HOOC

O2

1

HOOC

OOH

HOOC

OOH

HOOC

OOH

HOOC

OOH


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*utoxidation

14

1312

11

109

8

HOOC

H

H

14

1312

11

109

8

14

1312

11

109

8 14

1312

11

109

8

O2

14

1312

11

10

9

8

OO

+

+


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$inglet -xygen -xidation

HOOC

O2

1

HOOC

OOH

OH

O

'onanal


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$econdary ProductsB *ldehydes


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$econdary ProductsB *ldehydes


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Lipid &"idation

Peroxide decomposition can generate aldehydes/ ketones/ alcohols/ arioushydrocarbons/ and epoxides> Many are olatile/ and many are unappealing>


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elatie -xidation ates

0o& fast is lipid oxidationK

"atty *cid elatie ate$teric acid ';B2) ;

-leic acid ';B; nG);22

Linoleic acid ';B1 nA) ;/122Linolenic acid ';B9 n9) 1/@22

. i ti f Li id - id ti


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.ermination of Lipid -xidation *lthough radicals can 6meet7 and terminate propagation

by sharing electronsJ>

.he presence or addition of antioxidants is the best &ay ina food system>

*ntioxidants can donate an electron &ithout becoming a

free radical itself>


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*ntioxidants and Lipid -xidation

+0. Q butylated hydroxytoluene

+0* Q butylated hydroxyanisole

.+0R Q tertiary butylhydro%uinone

Propyl gallate

.ocopherol Q itamin E

ND8* Q nordihydroguaiaretic acid

Carotenoids


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Polar *ntioxidants

Most effectie in

nonpolar or less polar

enironment

+ulk oils Located at the oil(air

interface or in reerse

micelles 0igh amount of

oxidants present here

,ellow O#l

-lue water

Pospol#p#ds


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Non(polar *ntioxidants

Most effectie in polarenironment -il(in(&ater emulsions

Located at the &ater(oil

interface Dissoled in oil droplets

of the emulsion *llo&s access to

oxidi,ing agents located

in the &ater phase Peroxides -xidi,ing metals


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Chemical .ests for

Lipid Characteri,ations


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'odine (alue

Measure of the degree of unsaturationin an oilor the number of double bonds in relation tothe amount of lipid present

Defined as the grams of iodine absorbedper;22(g of sample>

.he higher the amount of unsaturation/ the

more iodine is absorbed>.herefore the higher the iodine alue/ the

greater the degree of unsaturation>

'odine (alue


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'odine (alue* kno&n solution of Sis used to reduceexcess Cl

'or +r) to free iodine(C(C I C(C(3 Cl(C(C(CCl(C(3 Cl

TExcessU 'remaining)

eaction schemeBCl3 1SSCl3 S3 1

.he liberated iodine is then titrated &ith a

standardi,ed solution of sodium thiosulfateusing astarchindicator

13 $tarch 3 thiosulfate I colorless endpoint

'+lue colored)


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Iodine value: g absorbed I !"" g fat


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Iodine value: g absorbed I2 !"" g fat

#$at can %e conclude about t$e &O'PO(I)IO*#$at can %e conclude about t$e &O'PO(I)IO*or ()R+&)+R of eac$ of t$ese oil ty-es.or ()R+&)+R of eac$ of t$ese oil ty-es.

Hig$ly saturatedHig$ly saturated

Hig$ in !/:!Hig$ in !/:!

Hig$ in !/:! and !/:20Hig$ in !/:! and !/:20

!/:!, !/:2, !/:1!/:!, !/:2, !/:1

!/:!, !/:2, !/:1!/:!, !/:2, !/:1longer c$ains0longer c$ains0

d


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(tandard Iodine 3alue(tandard Iodine 3alueA 4 21A 4 215 4 665 4 66

& 4 78& 4 78D 4 /9D 4 /9 4 !!! 4 !!!

'easures I5r or I&l'easures I5r or I&l

&onsum-tion neg -ea;0&onsum-tion neg -ea;0

&onsum-tion overtime

AutomatedAutomatedIodine 3alueodine 3alueDeterminationDetermination


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Chemical .ests

$aponification 4alue

Saponification Value


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$aponification is the process of breaking do&n or

degrading a neutral fat into glyceroland fatty acidsby treating the sample &ith alkali>

0eat

.riacylglyceride (((: "atty acids 3 8lycerol S-0

DefinitionB mg S-0 re%uired to titrate ;g fat

'amount of alkali needed to saponify a gien amount of fat).ypical aluesB Peanut I ;G2/ +utterfat I 112




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.he mg S-0 re%uired to saponify

triacylglycerides into glycerol plus fatty acids

is related toB

aerage fatty acidchain lengthor

aerage fatty acidmolecular &eight

Diide molecular &eight by 9 to get aerage ofthe fatty acids present


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Chemical .ests for -xidationLipid -xidation

0ydrolysisPeroxide 4alue

-xidation .ests


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Degree of hydrolysis'hydrolytic rancidity)

0igh leel of ""* means apoorly refined fator fat breakdo&nafter storage or use>

+ree +atty *cids ++*s!


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Peroxide Value


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Measuresperoxides and hydroperoxidesin an

oil &hich are the primary oxidation products'usually the first things formed)>

.he peroxide alue measures the 6present

status of the oil7> $ince peroxides are

destroyed by heat and other oxidatie

reactions/ a seriously degraded oil could hae

a lo& P4>

Peroxide Value


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S 3 peroxyl radical yields free odine '1)

.he iodine released from the reaction is measured in the

same &ay as an iodine alue>

1in the presence of amylose is blue>

1

is reduced to S and the endpoint determined by loss ofblue color>

? 3 -13 ?0 113 101-


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.hiobarbituric acid 'reactie substances) .+* - .+*$

.ests for end products of oxidation Q aldehydes/ Malonaldehyde'primary compound)/ alkenals/ and 1/?(dienals

* pink pigment is formed and measured at V@92 nm>

.+*$ is firmly entrenched in meat oxidation research and is a

method of choice>

.+*$ measure compounds that are olatile and may react further

&ith proteins or related compounds>

0igh .+* I 0igh -xidatie ancidity

HEXANAL Determination


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8ood indictor of the end products of oxidation

'if there are any)>

$tandard method in many industries>

*ldehyde formation from lipid oxidation>

Nonenal is also a common end-product

HEXANAL Determination


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Conugated +atty *cids

During o"idation, double bond migration

occurs and conugated fatty acids are

formed.

They absorb light efficiently and can be

monitored in a spectrophotometer.

C C C C C C C CR R

T/C0N'12/% &+ #/*%23'N4 &)'D*T'(/


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T/C0N'12/% &+ #/*%23'N4 &)'D*T'(/

%T*B'L'T5

'nduction Period6is defined as the length of time

before detectable rancidity or time before rapid

acceleration of lipid o"idation

#/*%23'N4 &)'D*T'(/ %T*B'L'T5


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#/*%23'N4 &)'D*T'(/ %T*B'L'T5

Active Oxygen Method- *ir is bubbled through oil or fat atGH>C> .ime re%uired to reach peroxide alue of ;22 me%#kg

fat determined> 'method replaced by -$)

Oil Stability Index automated ancimat 'instrumental

method)> *ir bubbled through sample ';;2C)> -il degrades to

many acidic olatiles 'e>g> formic acid) &hich are carried by

the air into a &ater trap> Conductiity of the &ater can then beassessed>


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"ree adicals


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What are free radicalsK

Where are free radicals fromK

0o& damaging are free radicalsK0o& do &e control free radicalsK

Wh t f di l K


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What are free radicalsK

!ny *olecula (ecie( caable o+ independente,i(tence- .hich contain( one o *oeunaied /alence electon( not contibuting tointa*olecula bonding0i( a +ee adical

The most frequent ra!"a#s are o$%&en'er!(e free ra!"a#s) a#so

*non as rea"t!(e o$%&en s,e"!es -RO./

.u,ero$!e -O2'/

ero$%# -ROO/

#*o$%# -RO/H%ro$%# -HO/

5!tr!" o$!e -5O/

Other RO. are non'ra!"a#s su"h as s!net o$%&en-O2/) h%ro&en

,ero$!e-H2O2/) an h%,o"h#orous a"!-HC#O/6

7here o the% "ome from


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7here o the% "ome from

Fee adical( ae oduced by o,idationeductioneaction( in .hich thee i( a tan(+e o+ only one electonat a ti*e- o .hen a co/alent bond i( brokenand oneelecton +o* each ai e*ain( .ith each ato*

1/ 5orma# on&o!n& metao#!sm) es,e"!a##% from the

e#e"tron trans,ort s%stem !n the m!to"honr!a an

from a numer of norma##% fun"t!on!n& en:%mes

2/ ;n(!ronmenta# fa"tors su"h as ,o##ut!on) ra!at!on)

"!&arette smo*e an to$!ns "an a#so s,an

!o#o&!"a##%'er!(e free ra!"a#s6


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-ur +ody s> -ur "ood

+iological radicals

"ood(based radicals

Where do these 1 areas crossK


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"unctional "oods Concept

Certain food ingredients hae health benefits

beyond basic nutrition

ecent deelopment onlyB since V;GH@

.he concept that Onon(nutrients< &ere beneficial

has taken off since then

"irst idea in scientific communityB antioxidant

compounds may protect against chronic

diseases


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"ree adicals

Early ;G@2


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eactie -xygen $pecies '-$)

Primary target listB protein/ lipid/ DN*/ and

carbohydrates

End resultsB cancer/ C0D/ stroke/ arterial

disease/ rheumatoid arthritis/

Parkinsonmany more

*ging by slo& oxidationK


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.he Defense

Minimi,e contact bet&een free radicals andimportant systems 'like cellular components)

Cell membranes are one of our best barriers

Metal chelation system in(placeProtease en,ymes are in place to remoe

damaged proteins for replacement by ne&

6epair en,ymes7 help to restore DN*6*ntioxidant en,ymes7(superoxide dismutase/

catalase/ glutathione peroxidase


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+est DefenseJ* 8ood -ffense

6Nutrients7 that cane> decreased immune

response/ enironmental factors/ hypertension/

poor diet)>


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"oods and the *ntioxidant Link

$oy( isoflaones/ polyphenolics

.ea( polyphenolics/ flaans

Coffee( polyphenolicsWine( polyphenolics

osemary( carnosic acid/ rosmaric acid

Citrus( flaonoids

-nions( sulfur cpds/ flaonoids +erries( flaonoids/ polyphenolics

4egetables( carotenoids/ polyphenolics


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*ntioxidants in "ood $ystems

-xidatie $tress(the food remedy


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y

DietB

nflammation( tocopherol

$moke( ascorbic acid

Physical stress( carotenoids

Pollution( carotenoids

EnironmentB

adiation( glutathioneCarcinogens( antioxidant en,ymes/ diet

modification


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-xidatie $tress and "oods

.ocopherol(egetable oil/ &hole grains/

egetables/ fish#poultry

*scorbic acid(citrus/ berries/ tomato/ leafy

eggies/ brassicas 'broccoli/ cauliflo&er)

Carotenoids(yelloorange fruits and

eggies/ tomatoes/ green leafy eggies>

Polyphenolics(coffee#tea/ grains/ all fruits

and egetables


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Magic +ulletsJfor our foodsK

Will increasing the use of antioxidants in foods

modulate all oxidatie damageK

Will food products 6lie7 longer &ith no %uality

problemsK Pro(oxidant nature of ascorbic acidB WhoaJ

*scorbic acid does not al&ays act linearly in food

systems

n the presence of metal ions 'ie> "e#Cu) it can

generate reactie oxygen species 'peroxides) or free

radicals 'hydroxyl radicals)

Causes and Effects


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Causes and Effects

Y(carotene and lung cancerB small/ but significantincrease &ith smokers

.ocopherols and C0DB protect lipoproteins or inhibit

blood clotting '&hich initiates heart attacks)

.ocopherols and *l,heimer


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$tructure(+ased *-

Polyphenolics


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+(ing $ubstitutions

OOH

OH O

OH

OH

OH

OOH

OH O

OHOH

OH

OH

OOH

OH O

OH

OH

Saempferol

Ruercetin

Myricetin

-

C

Ruercetin


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Ruercetin

? Q-0 groups

OOH

OH O

OH

OH

OH

?(oxo function

9(-0

1(9 db

Catechin


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Catechin

? Q-0 groups

OOH

OH

OH

OH

OH

9(-0

Cyanidin


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Cyanidin

? Q-0 groups

OOH

OH

OH

OH

OH

+


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mportance of the OHOH


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p

9(-0 group

OOH

OH O

OH

OH

OH

O

O

O

OO

O

OOH

OH O

Ruercetin*- I ?>H

Ruercetin(9(glucoside

*- V 1>@

OOH

OH O

OH

OH

Luteolin

*- I 1>;

mportance of the ?(-xo "unction


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Works &ith the 1(9 double bond in the C(ring and

is responsible for electron delocali,ation from the+(ring>

9(-0 and @(-0 substitutions &ith the ?(oxo

function are best for maximum *- properties

OOH

OH O

OH

OH

OH

$tructurally/ %uercetin has

all the right components to

make for the 6perfect7 antioxidant>

t f th 1 9 db


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mportance of the 1(9 db

OOH

OH O

OH

OH

OH

Ruercetin*- I ?>H

.axifolin

*- I ;>G

OOH

OH O

OH

OH

OH

M h Ph li * id


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More on the Phenolic *cids

COOH

1

2

3

4

Ortho

?eta

ara

COOH

1

2

3

4

COOH

12

3

4

0ydroxyben,oic

*cid

'0+*)

0ydroxyphenylacetic

*cid

'0P*)

Cinnamic

*cid

'C*)


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COOHOH

COOHOH

OH

COOHOH

?eO

COOH

OH

COOH

OH

OH

COOH

OH

?eO

p(-0(ben,oic

p(coumaric

Protocatechuic

Caffeic

4anillic"erulic

2>2 1>11

;>;G ;>1A

;>?9 ;>G2


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*ntioxidants in "ood $ystems

What Makes a 8ood *ntioxidantK


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Polyphenolics( adical scaengersNumber of hydroxy groups '(-0)Location of hydroxy groups 'on ben,ene ring)

Presence of a 1(9 double bond 'flaylium ring)

?(oxo function 'flaylium ring)

$ynergistic#antagonistic reactions &ith other

antioxidant compounds

OOH

OH O

OH

OH

OHCOOH

COOH

OH

OH

What Makes a 8ood *ntioxidantK


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Carotenoids .he number of con5ugated double bonds 'G3is best)

$ubstitutions on Y(ionone group 'on the end)

adical scaengers3;< C*3 8= 3- < C*3;eta'Carotene

.ocopherol


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*lpha(tocopherol I 4itamin E

beta and gamma forms also $ynergist &ith carotenoids and selenium and is

regenerated by itamin C

Efficiency determined by the bond dissociation energy

of the phenolic (-0 bond

.he heterocyclic chromanol ring is optimi,ed for

resonance stabili,ation of an unpaired electron>

O

OH

*ntagonism($ynergism(Metals


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Many antioxidant &ork for and against each other

*n antioxidant in a biological system my beregenerated

n mixed -$Jinefficiency of one antioxidant to

%uench all the different radicals>

No &ay of kno&ing if the 6better7 antioxidant for a

particular radical is doing all the &ork or not>

Will a better antioxidant for a gien food system 6beat

out7 a lesser antioxidant 'antagonistic response) inorder to %uench the radicals>

Example: Factors AffectingExample: Factors Affecting


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p ff gp ff g

AOX of Bell PeppersAOX of Bell PeppersChemical interactionsChemical interactions

In vitroIn vitromodelsmodels

"ind synergistic#antagonistic effects"ind synergistic#antagonistic effects

"ree metal ions"ree metal ions

Diluted isolatesDiluted isolates*dd metal chelator*dd metal chelator

"laonoid"laonoid *scorbic*scorbic

*- K*- K

AOX with uercetin InteractionsAOX with uercetin Interactions'Y Carotene +leaching)'Y(Carotene +leaching)


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'Y(Carotene +leaching)'Y(Carotene +leaching)

?@2 ppm Caffeic I ?H ?@2 ppm Caffeic I ?H

2 ppm *scorbic I ;@2 ppm *scorbic I ;@

OOH

OH O

OH

OH

OH

AOX with !uteolin InteractionsAOX with !uteolin Interactions'Y(Carotene +leaching)'Y(Carotene +leaching)


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'Y(Carotene +leaching)'Y Carotene +leaching)

?@2 ppm Caffeic I ?H ?@2 ppm Caffeic I ?H

2 ppm *scorbic I ;@2 ppm *scorbic I ;@

OOH

OH O

OH

OH

"heoretical uercetin"heoretical uercetin


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#$egeneration% &cheme#$egeneration% &cheme

Delocali,ationDelocali,ationof C(ringof C(ring educed resonation in * and + ringseduced resonation in * and + rings

Minor regeneration by ascorbic acidMinor regeneration by ascorbic acid

Minor regeneration by caffeic acidMinor regeneration by caffeic acid

RuercetinRuercetin


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Antioxidant Activit' after (ilutionAntioxidant Activit' after (ilution


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' f' f

>'

nhibitionofCaroteneBleaching

Antioxidant Activit' with )helatorAntioxidant Activit' with )helator


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''

>'

nhibition

ofBleaching


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*ntioxidant Methods

0*. and $E. eactions


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0*. and $E. eactions

0ydrogen *tom Transfer 0*T! 7s. %ingle/lectron Transfer %/T!

*ntioxidants can &ork in one of t&o &ays '0*.

or $E.)>End result is the same for both/ differing in

kinetics and side rxns>

0*. and $E. rxns may occur in parallelDetermined by antioxidant structure and properties

$olubility and partition coefficient

$ystem solent/ system p0

0*.


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0*.

*A"+based methods measure the classical

ability of an antioxidant to %uench free radicals

by hydrogen donation '*0 I any 0 donor)

$E.


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&E"+based methods detect the ability of a

potential antioxidant to transfer one electron to

reduceany compound/ including metals/

carbonyls/ and radicals>

*lso based on deprotonation/ so p0 dependent

0*. s $E.


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0*. $electiity in 0*. rxs are determined by thebond dissociationenergyof the 0(donating group in the antioxidant

*ntioxidant reactiity or capacity measurements are thereforebased on competition kinetics>

eactions are solent and p0 independent and are ery fast Common reducing agents '4itamin C) are an interference

$E. =sually slo&and can re%uire long times to reach completion *ntioxidant reactiity is based on apercent decrease/ rather than

kinetics 4ery sensitie to ascorbic acid and other reducing agents> .race amounts of metal ions&ill interfere/ and cause oer(

estimation and inconsistent results>

*ntioxidants and adicals


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"our sources of antioxidantsB

En,ymes $uperoxide dismutase/ glutathione peroxidase/ and catalase

Large molecules albumin/ ferritin/ other proteins

$mall molecules ascorbic acid/ glutathione/ uric acid/ tocopherol/ carotenoids/ phenols

0ormones estrogen/ angiotensin/ melatonin

Multiple free radical and oxidant sources -1/ -1(/ 0-[/ N-[/ -N--(/ 0-Cl/ -'-)[/ L-'-)

-xidants and antioxidants hae different chemical andphysical characteristics>

Complex $ystemsB $inglet -xygen


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p y g yg

Carotenoids are not good peroxyl radical %uenchers compared to

polyphenolics Carotenoids are exceptional singlet oxygen %uenchers compared

to polyphenolics

0o&eer/ singlet oxygen is not a radical and does not react ia

radical mechanisms $inglet oxygen reacts by its addition tofatty acid double bonds/

forming endoperoxides/ that can be reduced to alkoxylradicals/that initiateradical chain reactions>

No& &e hae multiple reaction characteristics and multiple

mechanisms No single assay &ill accurately reflect all of the radical sources

or test all the antioxidants in such a complex system>

Method $elections for *ntioxidants


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Controersy exists oer standard methods for antioxidantdetermination

0istorical use and peer(reie& acceptance is critical =se my multiple labs to highlight strength/ &eakness/ and

effectiness Ne& methods take time to adopt and accept

*n 6ideal7 methodB Measures chemistry actually occurring in potential application =tili,es a biologically releant radical source $imple to run =ses a defined endpoint and chemical mechanism nstrumentation is readily aailable 8ood &ithin(run and bet&een(day reproducibility *daptable for both hydrophilic and lipophilic antioxidants *daptable for multiple radical sources *daptable for high(through(put analysis =nderstanding of the range of use and recognition of interfering agents

0*. assays


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0*. assays

-*C-xygen adical *bsorbance Capacity

Measures inhibition of peroxyl radical induced

oxidations in chain breaking actiity by 0 atomtransfer

.*P

.otal adical(.rapping *ntioxidant ParameterMeasures the ability to interfere &ith peroxyl

radicals or stable free radicals

$E. assays


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$E. assays

"*P "erric educing *ntioxidant Po&er

.he reaction measures the reduction capacity of a

ferric compound to a color end(productC=P*CCopper eduction *ssay

4ariant of "*P assay using Cu instead of "e

"olin(Ciocalteu assay

Notes for Exam 2

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