3/19/14 UCDAVIS Methods to Determine Oxidation Extra Virgin Olive Oil Sensory Methods ·Free Fatty Acids ·Peroxide Value ·Conjugated Dienes ·Carbonyl Compounds .TBA Value Gas Chromatographic Methods Fluorescence Methods The International Olive Committee's PERCENTAGE OF SAMPLES FAILING SENSORY PANELS THAT WERE CONFIRMED BY CHEMICAL TESTS (IOC)olive oil standards 15 0. 07 33 Peraxide Values It should shown a value no greater thatn 20 meq/kg. STAR 64 BERTOLLI 0 0 0 8 62 COLAVITA 0 17 0 00 35 100 UV absorbance,the standards call for K232 absorbance values below 2.5. 680001265 1
3/19/14& 1& Extra Virgin Olive Oil . • Sensory Methods • Free Fatty Acids • Peroxide Value • Conjugated Dienes • Carbonyl Compounds • TBA Value • Gas Chromatographic Methods • Fluorescence Methods Methods to Determine Oxidation The International Olive Committee’s (IOC) olive oil standards Free$fa'y$acidity$values provide&an&indica1on&of&how&the&fruit&was& handled&prior&to&processing&and&the&length&of&1me&from&harvest&to&milling.& Free&acidity&is&also&an&early&indicator&of&the&poten1al&longevity&of&the&oil.&& It&may&be&no&higher&than&0.35%&in&extra&virgin&olive&oils&(EVOO).&& Peroxide$Values$It&should&shown&a&value&no&greater&thatn&20&meq/kg.& Experience&indicates&that&highLquality,&recently&milled&oils&exhibit&peroxide& values&below&12&meq/kg.&Truly&excellent&oils&may&have&PV&as&low&as&7&meq/kg& (9&meq/kg&for&organic&oil).&& UV$absorbance,&the&standards&call&for&K232&absorbance&values&below&2.5.& Low&values&correlate&with&highLquality&oil,&as&UV&absorbance&detects&early&and& later&states&of&oxida1on.& PERCENTAGE$OF$SAMPLES$FAILING$SENSORY$ PANELS$THAT$WERE$CONFIRMED$BY$CHEMICAL$TESTS BRAND$ #$OF$ SAMPLES$ FAILING$ SENSORY$ PANELS$ Free$ Fa'y$ Acids$ Fa'y$ acid$$ Profile$ Peroxide$ Value$ UV$ K232$ DAGs$ LUCINI& 2& 0& 0& 0& 0& 0& FILIPPO&BERIO& 15& 0& 0& 0& 7& 33& STAR& 11& 0& 0& 0& 0& 64& BERTOLLI& 13& 0& 0& 0& 8& 62& COLAVITA& 10& 0& 0& 0& 0& 70& POMPEIAN& 17& 0& 0& 0& 35& 100& AVE,&ALL& BRANDS& 68& 0& 0& 0& 12& 65&
3/19/14 Methods of Olive Oil Analysis Acidity from Lipolysis ·Acidity -Free Fatty Acids -Acidity Value Factors -060-9 HC-DH ·Oxidation +e-0m -Microbial -Peroxide Value EC0-R N H ME-Or -Enzymes -Temperature -UV Absorption -Moisture Composition of Fatty Acids -Preparation of Methyl Esters Determination by Capillary GLC Kintsakk,1998 Acidity Limits(IOOC) I.Free Fatty Acids Free Fatty Acids () Percentage by weight of a specified fatty acid (e.g.,oleic acid) Applicable to all crude and refined vegetable oils,marine oils,and animal fats c Oi AOCS Offclal Method Ca 5a-40
3/19/14& 2& Methods&of&Olive&Oil&Analysis& • Acidity& – Free&Fa^y&Acids& – Acidity&Value& • Oxida1on& – Peroxide&Value& – UV&Absorp1on& • Composi1on&of&Fa^y&Acids& – Prepara1on&of&Methyl&Esters& – Determina1on&by&Capillary&GLC& Acidity&from&Lipolysis& • Factors& – Microbial& – Enzymes& – Temperature& – Moisture& Kiritsakis,&1998& Acidity&Limits&(IOOC)& Category$ Free$Fa'y$Acids$(%$oleic$acid)$ Extra&Virgin&Olive&Oil& <0.9& Virgin&Olive&Oil& <2.1& Ordinary&Virgin&Olive&Oil& <3.4& Lampante&Oil& >3.3& Refined&Oil& <0.4& Olive&Oil& <1.1& Crude&Olive&Residue&Oil& No&Limit& Refined&Olive&Residue&Oil& <0.4& Olive&Residue&Oil& <1.1& Kiritsakis,&1998& I.&&&Free&Fa^y&Acids& • Percentage&by&weight&of&a&specified&fa^y&acid& (e.g.,&%&oleic&acid)& • Applicable&to&all&crude&and&refined&vegetable& oils,&marine&oils,&and&animal&fats& AOCS&Official&Method&Ca&5aL40&
3/19/14 Free Fatty Acids Procedure ll.Acid Value Weigh the designated sample size into an oil sample Amount of KOH(mg)needed to neutralize the bottle or Erlenmeyer flask.(Cap bottle and shake vigorously for 1 min if oil has been blanketed with free fatty acids in 1g of sample carbon dioxide gas.) Applicable to crude and refined animal, Add the specified amount of hot neutralized alcohol and 2 mL of indicator. vegetable,and marine fats and oils,and various products derived from them Titrate with standard sodium hydroxide,shaking vigorously until the appearance of the first permanent pink color of the same intensity as that of the neutralized alcohol before the addition of the sample. The color must persist for 30 seconds. AOC5 Offidal Method Ca 5a-40 I.UV Absorbance K232:Measure conjugated dienes ated hydroperoxides formed as primary AR-Raesgs) Low absorbance values correspond to good quality olive oil. AOAC Offcial Method Ch5-91
3/19/14& 3& Free&Fa^y&Acids&Procedure& • Weigh&the&designated&sample&size&into&an&oil&sample& bo^le&or&Erlenmeyer&flask.&(Cap&bo^le&and&shake& vigorously&for&1&min&if&oil&has&been&blanketed&with& carbon&dioxide&gas.)& • Add&the&specified&amount&of&hot&neutralized&alcohol& and&2&mL&of&indicator.& • Titrate&with&standard&sodium&hydroxide,&shaking& vigorously&un1l&the&appearance&of&the&first&permanent& pink&color&of&the&same&intensity&as&that&of&the& neutralized&alcohol&before&the&addi1on&of&the&sample.&& The&color&must&persist&for&30&seconds.&& AOCS&Official&Method&Ca&5aL40& II.&&&&Acid&Value& • Amount&of&KOH&(mg)&needed&to&neutralize&the& free&fa^y&acids&in&1&g&of&sample& • Applicable&to&crude&and&refined&animal,& vegetable,&and&marine&fats&and&oils,&and& various&products&derived&from&them& AOCS&Official&Method&Cd&3dL63& • K232:&&Measure&conjugated&dienes& • Determines&conjugated&hydroperoxides&formed&as&primary& oxida1on&products& I.&UV&Absorbance& AOAC&Official&Method&Ch&5L91& • K270:&&Measure&conjugated&trienes& • Detects&substances&formed&during&earth&treatment&in&refining& process& – Kmax&is&the&specific&ex1nc1on&at&wavelength&with& maximum&absorbance&(270&nm).&& • Low&absorbance&values&correspond&to&good& quality&olive&oil.&
3/19/14 Ultraviolet Absorption Calculations: ·Beer'sLaw ·A=ebc bxc A 、A=absorbance Record Abs 232nm.268nm,262nm,272nm S=thickness of the cuvette, ntration of the solution (g/100mL) ·K=Abs/Conc. AQAC Official Method Ch5-91 ll.Peroxide Value Procedures-Back Titration ·Extent of oxidation Primarv product-Earlv stage of oxidation 人人 0.1M Na,S.O 0.Sm Sat.Kl Yellow Dsappeared 30ml Distilled H.O AOAC Official Method Cd 8b-90
3/19/14& 4& Ultraviolet&Absorp1on& 0.25g&Oil&&+&&& Pure&isooctane/& Pure&cyclohexane& Record&Abs&@&232nm,&268nm,&262nm,&272nm& 25ml& AOAC&Official&Method&Ch&5L91& • Kλ&=&specific&ex1nc1on&at&λ • E&λ&=&ex1nc1on&measured&at&λ • S&=&thickness&of&the&cuve^e,& (cm)& • C&=concentra1on&of&the& solu1on&(g/100mL)&& • K=Abs/Conc.$ Calcula1ons:& • Beers&Law&:& • A&=ebc& • A&=absorbance&& • e&=molar&absorb1vity&(molL1&cmL1)& • b&=path&length&(cm)& • c&=concentra1on&of&the&compound& in&solu1on&(mol&LL1)& AOAC&Official&Method&Ch&5L91& II.&Peroxide&Value& • Extent&of&oxida1on& • Primary&product&–&Early&stage&of&oxida1on& ProceduresL&Back&Titra1on& Oil&sample& 50ml&3:2&ace1c&acid&+&isooctane&solu1on& 0.5ml&Sat.&KI& Sit&for&1&min& (keep&shaking)& 30ml&Dis1lled&H2O& 0.1M&Na2S2O3& 0.5ml&10%&SDS& 0.5ml&starch&indicator& Yellow&Disappeared& Blue&Disappeared& 250ml& AOAC&Official&Method&Cd&8bL90&
3/19/14 Gas Chromatography GC ethods Hanjiang Zhu Column oven ased on P. Capillary columns
3/19/14& 5& GC Methods Hanjiang Zhu Gas$Chromatography$ Typically&T& programming&is& required,&which& provides&a&basis&for& the&separa1on&of& sample&components& based&on&BP.& Capillary$columns$