Antioxidants Application 2

8/3/2019 Antioxidants Application 2

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OBJECTIVE

METHOD

ANTIOXIDANTSAPPLICATION

To solve the rancidity and shelf-life reducing problem in currentsnack products

From general knowledge aboutoxidation, applying antioxidantsinto frying oil and doing shelf-lifeactual test


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CONTENT:

1. Oil deterioration

2. Oxidation and anti-oxidation

3. Antioxidants

4. Applying and testing method


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1. OIL DETERIORATION

i. Oil deterioration

ii. Chemical reactions specification

iii. Factors influence oil deterioration

iv. Oil deterioration measure

v. Monitoring oil deterioration methods


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1. OIL DETERIORATIONi. Oil deterioration


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i. Oil deterioration


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ii. Chemical reactions specification: 3 main reactions Hydrolysis:

breaking down triacylglycerols

releasing mono-, di-acylglycerols and FFA

Oxidation:

reaction of atmosphere oxygen and lypid causing rancidity, bleaching, nutrients loss &

reducing shelf-life

Thermal decomposition:

both saturated and unsaturated FA undergo

produce acids, hydrocarbons, acrolein, ketones, acyclic acidsand dimers


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2. OXIDATION & ANTIOXIDATIONi. Oxidation

Mechanism of oxidation

Factors influence oxidation

Oxidation catalysis mechanism

Oxidation impacts on products Oxidation measurement

ii. Anti-oxidation

Anti-oxidation method

Anti-oxidation mechanism Factors influence anti-oxidation

Choosing anti-oxidation method


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2. OXIDATION & ANTIOXIDATIONi. Oxidation: (also autoxidation)

Definition: Spontaneous reaction of atmospheric

oxygen with lipid

Objects: Both saturated and unsaturated fatty acid.

Unsaturated possess higher oxidative

potential

Catalysis: Light sensitizer and metal trace.

Products: Mainly volatile ketones and aldehydes.

Influential factor: Fatty acid composition,

temperature, moisture, surface area, pro-oxidants


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2. OXIDATION & ANTIOXIDATION

i. Oxidation (also autoxidation) Oxidation mechanism: 2 stages

- Hydroperoxides forming ( without off-flavour)- Hydroperoxides decomposition and volatile compoundsforming (causing rancidity)

Initiation X.RH

R. ROO-

O2

ROOH RH

RO.ROOR,ROR

keto, hydroxyde

cleavage

Aldehydes Alkyl Radicals

Oxoacid

Dimer, polymer, cyclic,peroxide compounds

cleavage

Aldehydes, ketones,furans, acids


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2. OXIDATION & ANTIOXIDATIONi.

Oxidation (also autoxidation) Oxidation products

o Initial stage: hydroperoxides

o Second stage: hydroperoxides decomposition


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2. OXIDATION & ANTIOXIDATIONi.

Oxidation (also autoxidation) Oxidation products: Final products

Fatty acid HydroperoxidesAldehyde formed

Name Flavour

Oleic (18:1) 8-OOH2-undecenal

decanal

9-OOH 2-decenal, nonanal10-OOH Nonanal

11-OOH Octanal

Linoleic (18:2) 9-OOH2,4-decadienal

3-nonenalFatty, waxy

13-OOH Hexanal Green

Linolenic (18:3) 9-OOH2,4,7-decatrienal Painty, fishy

3,6-heptadienal soapy

12-OOH2,4-heptadienal

3-hexenal green bean

13-OOH 3-hexenal Green bean

16-OOH propanal


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2. OXIDATION & ANTIOXIDATIONi. Oxidation (also autoxidation)

Factors influence rate of lipid oxidation in foodso Fatty acid composition: number, position and geometry of

double bonds Cis-acids: oxdise more rapidly than its trans isomers Conjungated double bonds more reactive than non-

conjungated

o Temperature: Autoxidation of saturated fatty acid isextremely slow at room temperature but rapid at hightemperature

o Moisture: oxidation inversely depends on moisture

o Surface area: oxidation rate increases when surface area oflipid exposed to air raise

o Pro-oxidants: metals posses 2 or more valency states actingas catalysts

o Antioxidants


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Catalysis:o Light sensitizer (sens): oxygen raised to excited state(1O2) by

light energysens sens*sens* + 3O2 sens +

1O2o Metal trace

Acceleration of hydroperoxide decompositionMn+ + ROOHM(n+1)+ + OH- + RO.

Mn+ + ROOHM(n-1)+ + H+ + ROO. Direct reaction with the unoxidized subtrate:

Mn+ + RHM(n-1)+ + H+ + R.

Activate of molecular oxygen to give singlet oxygen peroxide

radicalMn+ + O2

O2. + e

Mn+ + O2 + H+

H.O2

light


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Effects of lipid oxidation

o Flavor quality loss: Rancid flavorChanges of color and textureConsumer acceptanceEconomic loss

o Nutritional quality loss: Essential fatty acidsVitamins

o Health risks: Toxic compoundGrowth retardationHeart diseases


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2. OXIDATION & ANTIOXIDATIONii. Antioxidation Preventing singlet oxygen (1O2):

Vacuum packing or N2 flush Oxygen scavengers Low permeable film Antioxidants

Temperature

According to the formula: C=Co+kt ()Where C: value of index after time t of fryingCo: initial value in fresh oil before fryingk: rate constant of reaction

Temperature Oxidation index k (h-1)

Conjungateddienes

Conjungatedtrienes

P-Anisidine value % Polar compounds

155 0.058 0.012 10.784 1.476

165 0.066 0.013 11.576 1.540

175 0.085 0.009 12.033 1.670

185 0.094 0.009 12.689 1.765

195 0.111 0.012 13.650 1.971


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2. OXIDATION & ANTIOXIDATIONii. Antioxidation

Water activity

Rate of oxidation decreases as the water activity islowered towards the monolayer

Moisture released from food acts as protective shield

preventing oxygens contact to surface Metal ions

Restricting free metals will slow down lipid oxidation

Using chelators

Light Packaging

Antioxidants


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3. ANTIOXIDANTS

i. Definition

ii. Antioxidant categories

iii. Ideal antioxidants

iv. Consideration of choosing antioxidants

v. Specific antioxidants


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3. ANTIOXIDANTSi. Deffinition:

Subtance delay autoxidation by:

Inhibiting formation of free radicals in initial step

Interrupting the propagation of free radical chain

AH (antioxidant): free radical acceptor or hydrogen donor

react primarily with RO2 not with R.

RO2. + AH ROOH + A.

RO2. + AH2 ROOOH + HA

.

HA. + HA. A + AH2

The most common types od lipid soluble antioxidantsare mono or polyhydric phenols with ring substituents


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3. ANTIOXIDANTSii. Antioxidants categories

By mechanism

Chain-breaking antioxidants

Preventive inhibitors

Synergism

By origins

Synthetic Antioxidants

Natural Antioxidants


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By mechanism Chain-breaking antioxidants

Able to compete with the substrate for chain-carryingspecies

Produce a lag period ( induction period IP) due to

antioxidants concentration until about 90% of which isdestroyed

Effectiveness represents the possibility of blocking the radicalchain process by reaction with peroxyl radicals

Preventive inhibitors

Inhibit oxidation by induced decomposition ofhydroperoxides by forming stable alcohols or inactiveproducts by non-radical processes

Include elemental sulphur, thiols, sulphides, disulphides,metal chelating agents


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By mechanism Synergism:

mixture of antioxidants produce a more activity than sum ofactivities of the individual ones used separately

2 categories of synergism Involving action of mixed free radical acceptors Involving the combined action of free radical acceptor and a metal

chelating agent


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By mechanism Synergism

Synergism mechanisms: 2 hypothesis

2 mixed free radical acceptors: AH & BH

Dissociation energy of AH > that of BH BH reacts more slowly than AH due to steric hindrance

Reactions: RO2

. + AH ROOH + A. A. + BH B. + AH

Result in regeneration of the primary antioxidant

Metal complexing agents Deactivate trace metal

Often present as salt of fatty acids

Ex.: citric acid, phosphoric acid, polyphosphate, acid ascorbic


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3. ANTIOXIDANTSii.Antioxidants categories

By origins

Synthetic antioxidants:


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By origin

Natural oxidants

Rosmarinic AcidCarnosol

Caffeic acidFerulic acid


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By origin

Synthetic antioxidants

BHA (ButylatedHydroxyanisole)

BHT (Butylated HydroxyToluene)

Propyl gallate (PG)


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3. ANTIOXIDANTSiii. Ideal antioxidants

No harmful physiological effects

No contribute off-flavor, odor, color to the food

Effective in low concentration

Fat solubleCarry through effect no destruction during

process

Readilyavailable

Economical

Not absorbable by the body


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3. ANTIOXIDANTSiv. Consideration of choosing antioxidants

Safety

Anti-oxidation effectiveness

Off-odor

Off-color

Convenience of antioxidant incorporation to foods

Carry though effect

Stability to pH & food processing

Availability

Cost

Non-absorbable


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3. ANTIOXIDANTSv. Specific antioxidants

Tocopherol


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4. APPLYING AND TESTING METHODS

i. Actual condition of manufacturingapplication

ii. Applying methods

iii. Testing methods

iv. Consideration of choosing applying andtesting method

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Antioxidants Application 2

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