antioxidants application 2
TRANSCRIPT
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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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1. OIL DETERIORATION
i. Oil deterioration
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1. OIL DETERIORATION
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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2. OXIDATION & ANTIOXIDATIONi. Oxidation (also autoxidation)
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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2. OXIDATION & ANTIOXIDATIONi. Oxidation (also autoxidation)
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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3. ANTIOXIDANTSii. Antioxidants categories
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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3. ANTIOXIDANTSii. Antioxidants categories
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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3. ANTIOXIDANTSii. Antioxidants categories
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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3. ANTIOXIDANTSii. Antioxidants categories
By origin
Natural oxidants
Rosmarinic AcidCarnosol
Caffeic acidFerulic acid
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3. ANTIOXIDANTSii. Antioxidants categories
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