Baharin, B. S.

Che Man, Yaakob

M. H., Moh

Mirghani, Mohamed Elwathig Saeed

Selamat, Jinap

Setiowaty, Gabby

Universiti Putra Malaysia Institutional Repository

UPM Research Report 1998: Volume 2APPLICATION OF FOURIER TRANSFORMINFRARED SPECTROSCOPY FOR DETERMININGSOME PARAMETERS OF PALM OILY.B. Che Man, G. Setiowaty, S. Jinap, M.H. Moh,M.E.S. Mirghani and B.S. BaharinFaculty of Food Science and BiotechnologyUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: palm oil, FTIR spectroscopy, partial leastsquares regression, calibration, quality parameters.IntroductionMalaysia is the largest producer and exporter in palm oil in-dustry. Quality control system of palm oil and its fractionsturns out to be more and more important. However, manyanalytical methods based on AOCS and IUPAC to measuresome parameters of quality of palm oil are not very practical(AOCS, 1995). Fourier transform infrared spectroscopy hasbecome widely used for the determination of some parame-ters of edible oils and fats (van de Voort. 1992; van de Voort.1994). It has largely replaced manual analysis by analyticalmethods, improving efficiency, and reducing the requirementfor skilled labour and the use of hazardous chemicals withoutsacrificing accuracy (Stuart, 1996). Therefore the objectivesof this study were to determine the iodine value (IV) of palmoil and its products, the free fatty acid (FFA) in palm olein,the peroxide value (PV) of oxidised palm olein and the anis-idine value (AnV) of thermally oxidised palm olein.Materials and MethodsMaterials: RBD palm olein, superolein, palm oil, palmstearin, oleic acid. Methods: a few drops of each samplewere placed on the demountable cells. The cells weremounted in a cell holder in the FfIR spectroscopy and thescanning of each sample was carried out. These spectra wereratioed against background air spectrum. All standards werescanned in duplicate in region of 4000 to 400 cm". A partial-least-squares (PLS) analysis was chosen to develop a cali-bration model. Correlation spectra, which relate spectralchanges to the value of the variable of interest, were gener-ated and examined to identify spectral features that correlatewith the chemical data for samples. Calibration was derivedand optimised to generate a predictive model for determina-tion some parameters. The calibration routine includes avalidation procedure, which provides statistical parametersindicative of the predictive capability of the calibrationmodel. The accuracy of the validation step was assessed ac-cording to the standard error of prediction (SEP) and the co-efficient of determination (R2).218Results and DiscussionThe chemical results of some parameters obtained from theAOCS method and the spectral data obtained from scanningthe samples by FfIR spectroscopy were used together topredict the FfIR results. In IV determination, the spectral re-gion of a calibration set that covering a range of 27.9 to 65.3IV units between 3050 and 2984 cm", corresponding to theabsorption band of =C-H cis stretching vibration was used tobuild the PLS calibration model for the prediction of IV. Avalidation approach of this model yielded a good K of0.9995 and a SEP of 0.151. A set of palm olein samples thatcovers a wide range of FFA (0.08-1.04%) was used as thecalibration standard. A PLS calibration model for the predic-tion of FFA was developed based on the spectral range ofC=O stretching of FFA of 1728-1662 cm", The R2 and SEPyielded were 0.997 and 0.017% FFA units. For accuracy, themean difference gave a value of 0.00016, with FfIR methodgiving the higher prediction of FFA of palm olein thanchemical method. In determining PV of palm olein, thesamples, the samples having PV range of 3.52 to 9.86 wasused to construct the calibration model. For this calibrationset, the spectral region used in the calibration was set to in-clude all the data from 3082 to 3470 cm". The SEP obtainedwas 0.172 PV. The SEP obtained can be considered a meas-ure of the accuracy of the FfIR PV method because it relatespredicted PV to chemical PV. In terms of reproducibility, theduplicate FfIR analysis had a standard deviation of the dif-ference (SDD) of 0.02 PV, compared to an SDD of 0.05 PVfor duplicate chemical analyses. The SDD of the chemicalmethod was higher, indicating that the FfIR method is supe-rior in producing consistent results for anyone sample. In theAnV determination of palm olein, a FfIR calibration modelwas obtained, using the two wavelength regions (2747 to2619 cm" and 1715 to 1673 cm"). When the validation setpredicted with the calibration model, the SEP was 0.51, theR2 was 0.990 and the mean difference and standard deviationof difference for accuracy were 0.0864 and -0.0997, respec-tively. In terms of reproducibility, both the chemical andFfIR results have comparable mean differences and standarddeviations.ConclusionsIn this study, the determination of IV, FFA, PV, AnV ofpalm oil and its products by using a transmission cell ap-proachIFTIR spectroscopy and PLS analysis gave satisfac-.tory results comparing to the chemical method with good ac-curacy.ReferencesAOCS. 1995. "Official Methods and Recommended Practices of theAmerican Oil Chemists' Society" 4th edn, Champaign, IL.Stuart, B. 1996. "Modem infrared spectroscopy". John Wiley andSons, New York.van de Voort, F.R. 1992. "Fourier transform infrared spectroscopyapplied to food analysis". Food Res. Int. 25: 397-403.van de Voort, F.R. 1994. "FITR spectroscopy in edible oil analysis".INFORM.5: 1038-1042.Supported by IRPA Grant 03-02-04-0048

Application of fourier transform infrared spectroscopy for determining some parameters of palm oil

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Application of fourier transform infrared spectroscopy for determining some parameters of palm oil

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