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Stability
Stability Measuring InstrumentsStability Measuring Instruments743 Rancimat
Uwe LoyallMetrohm Ltd.CH-9100 HerisauSwitzerland
Stability
RancidityPrinciple of Rancimat methodEvaluationInfluences on the determinationTemperature ExtrapolationGLP - Validation of the instrumentThe 743 RancimatApplications Rancimat
OverviewOverview
Stability
RancidityRancidityhydrolytic rancidityoxidative rancidity
StabilityHydrolytic RancidityHydrolytic Rancidity
CH2
CH
CH2
O
OH
O
O
O
+ CH3(CH2)nCOOH
triglyceride
enzymes
CH2
CH
CH2
O
O
O
O
O
O+ H2O
diglyceride
fatty acid
StabilityHydrolytic RancidityHydrolytic Rancidityuse only dry air for Rancimat measurements
StabilityOxidative RancidityOxidative RancidityRadical chain reaction:Radical chain reaction:Initiation
RH R.
PropagationR. + O2 RO2
.
ROO. + RH R-OOH + R.
TerminationR. + R. R-RROO. + R. R-OO-R
StabilityOxidative RancidityOxidative RancidityPrimary reaction products:
Peroxides (R-OO-R)Hydroperoxides (R-OOH)unstable
Secondary reaction products:AldehydesAlcoholsCarbonic acids
StabilityFactors Accelerating OxidationFactors Accelerating OxidationOxygenHeavy metal ions (e.g. Fe, Cu)
catalyse chain initiationUV light
StabilityAntioxidantsAntioxidantsChain breaking substances
E.g. phenolic compoundsExamples
natural compoundssynthetic antioxidants: BHA, BHT, TBHQ, ...Tocopherol
Complexing agentscitric acid, phosphoric acid, ascorbic acid, ...
UV deactivatorsphenyl salicylate, hydroxybenzophenone
StabilityLimitations for Limitations for measurement of antioxidant activitymeasurement of antioxidant activityVolatile antioxidantsAntioxidants unstable at high temperatures
Stability
Principle of Principle of RancimatRancimat MethodMethod
StabilityQuality Assessment of Fats/OilsQuality Assessment of Fats/OilsRancimat test = accelerated oxidation test
at elevated temperatureunder exposure of air
faster autoxidation in a few hours instead of weeks/months
StabilityPrinciple of Principle of RancimatRancimat MethodMethod
fatty acids are oxidised by oxygen from air
low molecular organic acids are formed
organic acids stripped out of the oil by air flow
Stability
heating block (e.g. 120°C)
oil sample
reaction vessel
air inlet
measuring vessel
conductivity cell
absorption solution (water)
Principle of Principle of RancimatRancimat MethodMethod
StabilityRancimatRancimat CurveCurve
10.53
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
Induction period:•oxidation of fatty acids
peroxide formation•slow reaction•no formation of volatile carboxylic acids
•accelerated fast reaction•oxidation of fatty acids
formation of volatile carboxylic acids
Stability
EvaluationEvaluation
StabilityRancimatRancimat CurveCurve
10.53
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
induction time
10.53
stability time10.78
StabilityEvaluation of Induction TimeEvaluation of Induction Time
10.53
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
10.53
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
2nd derivative of measured curveshows maximum
= induction time
StabilityEvaluation of Stability TimeEvaluation of Stability Time
10.53
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
absolute increase in conductivity in the absorption solution
Δκ= 50 µS/cm
Stability
10.53
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
10.27
10.78
0
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8 9 10 11
µS/c
m
h
ReevaluationReevaluationAutomatic result can be modifiedTangent method (only manual)
StabilityInfluences on the determinationInfluences on the determinationTemperature ExtrapolationTemperature ExtrapolationTemperatureGas flowSample weight
StabilityInfluences on the resultsInfluences on the resultsTemperature:
10°C increase 50% induction time max. deviation of temperature: 0.3°Cstability of temperature <0.1°Cexact temperature adjustment important
Gas flow:small influenceno changes within ±10% flow change
Sample weight:small influencecooling effect depending on the sample weight
StabilityTemperature CalibrationTemperature CalibrationNecessary equipment:
GLP setwith certified temperature sensor
Control of the accuracy of the heating blockDetermination of the temperature correction
for each temperaturefor each heating blockeach gas flow
StabilityTemperature DependencyTemperature Dependencysample at different temperatures
StabilityTemperature ExtrapolationTemperature Extrapolationevaluation of dependency: temperature vs. induction time
tem
pera
ture
log (induction time)
T = f(t)
)( TBeAt ⋅⋅=
StabilityExtrapolationExtrapolationStandard factor = temperature coefficient:change of induction time per 10°C
theoretical value = 2
estimated shelf life time
Stability
The 743 RancimatThe 743 Rancimat
StabilityThe new PC controlled The new PC controlled RancimatRancimat8 samples2 temperaturesup to 4 Rancimats/Thermomats per PC
StabilitySingle Button Single Button -- Single ConnectionSingle Connectionoptional: calibrated external Temperature Sensor
connection to PC
StabilityInternal or external Air SupplyInternal or external Air Supplyonly Rancimat
StabilityOperationOperationDisposable reaction vessels and gas inlet tubes
no time-consuming cleaningno fragile and expensive glasswareOne-piece measuring vessel cover and conductivity cell
StabilityConductivity CellConductivity CellCell constant:
1.1 cm-1 (± 0.1)
StabilityFeaturesFeatures743 Rancimat is controlled by PC
(WindowsTM 95/98/NT/2000/XP)8 samples per Rancimat in 2 independent heating blocks (2
temperatures per Rancimat)up to 4 Rancimat units may be attached to 1 PC (32 Samples)every channel may be handled independentlyTemperature range: 50 ... 220 °CStability of temperature: < 0.1 °C
StabilityFeaturesFeaturesLive curveAutomatic determination of results acc. to
AOCS Cd 12b-92, AOM or other standard formats
Database functionsReprocessing of single runsDetermination of the temperature coefficientDisposable glasswareHardware validation / GLP Function --> improved result
accuracy.
Stability
Instrument OperationInstrument Operation
StabilityMain ScreenMain Screen
Start/Stopheating
Start/Stop determination
Live display
Method settings
StabilityParametersParameters
For oils and fats100 – 140°C
Tabled value (see manual)
Determine with external temperature sensor
See tab Evaluation
StabilityEvaluationEvaluation
1.45
0
5
10
15
20
25
30
35
40
45
50
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75
µS/c
m
h
Induction time =
maximum of 2nd derivative
Δκabsolute increasein conductivity
StabilityFormulasFormulas
StabilityStandardsStandards
Extrapolation functionTheoretical factor 2
FreeFixed to 110°C (AOCS)
97.8°C (AOM)
StabilityPreparing determinationPreparing determinationSelect method and modify parameters if necessaryStart heating
45 min to 120°C60 min to 220°C
Prepare measuring vesselLow conductivity of the distilled water (< 5 µS/cm)Check conductivity cells (cell constant 1.0 – 1.2)Replace plastic beakers (10 – 20 determinations)
Prepare reaction vesselRemove particles (cardboard box, cullet, ...)Position of the air inlet tube
StabilityWhen temperature is reachedWhen temperature is reachedPlace measuring vesselConnect tubingsInsert reaction vessel Start determination immediately
StabilityResultsResults
StabilityGLPGLPValidation of the instrumentValidation of the instrument
StabilityGLP GLP –– Hardware ValidationHardware ValidationAutomatic Monitoring:
TemperatureConductivityGas flow
GLP Properties
GLP Status Information
StabilityGLP Test TemperatureGLP Test Temperature
StabilityGLP Test ConductivityGLP Test Conductivity
Stability
Applications Applications RancimatRancimat
StabilityApplications Applications RancimatRancimatOxidative stability of pure edible fats and oils from plants or
animalsOxidative stability of natural fats and oils from food or
cosmetics after extraction with petrol etherAntioxidant researchOxidative stability of FAME (fatty acid methyl ester, biodiesel)Oxidation stability of light heating oil with Cu catalyst
StabilityRancimat Applications 1Rancimat Applications 1Oxidation Stability of Edible Fats and OilsOxidation Stability of Edible Fats and OilsAnimal fats/oils:
Butter, fish oil, lard, etc.Vegetable fats/oils:
soybean, sunflower,coconut, peanut, palmFat/oil containing products
direct measurements: margarineafter extraction of the fat: meat, nuts, etc.
Antioxidant research
Stability
InduktionszeitStabilitätszeit
0
5
10
15
20
25
30
35
40
45
50
0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5
µS/c
m
h
sesam oil / sesam oil / sesam oil / sesam oil /
sesam oil / sesam oil / sesam oil / sesam oil /
Sesame OilSesame Oil4 temperatures: 100°C, 110°C, 120°C, 130°C
Stability
10
20
30
40
50
60
70
80
90
100
110
120
130
140
101 102 103 104
°C
h
estimated life time at 20°C: 1.2 years
Sesame OilSesame Oil4 temperatures: 100°C, 110°C, 120°C, 130°C
Stability
Induction timeStability time
0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5
64.1
µS/
cm
h
Olivenoel / Olivenoel / Olivenoel / olive oil /
Olive OilOlive Oil4 temperatures: 100°C, 110°C, 120°C, 130°C
Stability
10
20
30
40
50
60
70
80
90
100
110
120
130
140
101 102 103
°C
h
Olive OilOlive Oil4 temperatures: 100°C, 110°C, 120°C, 130°C
estimated life time at 20°C: 0.7 years
StabilityStandardsStandardsISO 6886
Animal and vegetable fats and oils – Determination of oxidation stability
AOCS Cd 12b-92Sampling and analysis of commercial fats and oils: Oil Stability Index
AOM - Active oxygen method2.4.28.4-93
Fat stability test on Autoxidation. CDM, Japan
StabilityInformation on ApplicationsInformation on ApplicationsApplication Bulletins
204, 141, 232, 237Application Notes
R-1, R-3, R-4, R-5, R-6, R-7Reprint
A modern method of determining the oxidative stability of fats and oils (679)Comparison AOM - Rancimat
StabilityAOM AOM –– RancimatRancimat methodmethod
Comparison Rancimat - AOM
0
5
10
15
20
25
30
35
0 5 10 15 20 25 30 35
Induction time Rancimat [h]
Indu
ctio
n tim
e A
OM
[h]
StabilityReprint: AntioxidantsReprint: Antioxidants
Published inPublished inFood Marketing Food Marketing & Technology& TechnologyAugust 2002August 2002
StabilityRancimat Applications 2Rancimat Applications 2Oxidation Stability of FAME / BiodieselOxidation Stability of FAME / BiodieselFAME = fatty acid methyl esterreplaces mineral oil based fuels (i.e. diesel)produced
from vegetable oils (e.g. canola oil, soybean oil)by transesterification
subsidized by government in some countriesquality control (oxidative stability) by Rancimat method
EN 14112
StabilityProduction of FAMEProduction of FAME
CH2
CH
CH2
OH
OH
OH
CH3 OO
+ 3
triglyceride
catalyst
CH2
CH
CH2
O
O
O
O
O
O+ 3 CH3OH
glycerol fatty acid methyl ester (FAME)fatty acid methyl ester (FAME)
methanol
StabilityFAME: Temperature DependencyFAME: Temperature Dependencytemperatures from 60° - 130°C
0
10
20
30
40
50
60
70
80
90
100
50 100 150 200 250 300
µS/c
m
h
RME+AO,RA-73-1 / 60°C RME+AO,RA-73-1 / 60°C RME+AO,RA-73-1 / 70°C RME+AO,RA-73-1 / 70°C RME+AO,RA-73-1 / 80 °C RME+AO,RA-73-1 / 80 °C RME+AO,RA-73-1 / 90°C
RME+AO,RA-73-1 / 90°C RME+AO,RA-73-1 / 100°C RME+AO,RA-73-1 / 100°C RME+AO,RA-73-1 / 110°C RME+AO,RA-73-1 / 110°C RME+AO,RA-73-1 / 120°C RME+AO,RA-73-1 / 120°C
StabilityFAME: Temperature DependencyFAME: Temperature Dependency
StabilityInformation on ApplicationsInformation on ApplicationsApplication Note R-9Standard EN 14112
Fatty Acid Methyl Esters (FAME) – Determination of oxidation stability (Accelerated oxidation test)
StabilityRancimatRancimat Applications 3Applications 3Oxidative stability of light heating oilOxidative stability of light heating oilwith Cu catalystHeating oil and heating oil with additive
0
1
2
3
4
5
6
7
8
9
10
0,0 2,5 5,0 7,5 10,0 12,5 15,0
µS/c
m
h
Heizöl EL + Additiv, RA-74-2 / 135°C Heizöl EL + Additiv, RA-74-2 + Sperre / 135°C
Heizöl EL, RA74-1 / 135°C Heizöl EL, RA74-1 + Sperre / 135°C
StabilityApplication InformationApplication InformationApplication Works
D7-078-0700 D7-082-0201
