ATTENUATED TOTAL REFLECTANCE-FOURIER TRANSFORM INFRARED SPECTROSCOPY COUPLED WITH CHEMOMETRICS TO DETECT SELECTED ANIMAL BODY FATS, VEGETABLE OILS AND THEIR ADMIXTURE IN GHEE
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Date
2022
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ICAR-NDRI, KARNAL
Abstract
Ghee is a popular traditional dairy product of India. Due to its high demand and insufficient supply during lean season, it becomes prone to adulteration by unscrupulous traders in the market. The present study was conducted to develop suitable models using ATR-FTIR coupled with chemometrics for detection of selected animal body fats, vegetable oils and their admixture in ghee. Milk samples were procured and ghee samples were prepared using creamery butter method. Vegetable oils from five reputable brands and animal body adipose tissues were purchased from local market of Karnal. Animal body fats were extracted from the respective adipose tissues of the animal using dry rendering process. GC-analysis revealed that the short chain fatty acids were only present in pure ghee and not in adulterants targeted in the study. Linoleic acid concentration was significantly higher in soybean oil as compared to that in other oils and fat studied. Palmitic acid was the major fatty acid in vanaspati and trans fatty acids (eladic acid) was only present in vanaspati. Goat body fat contained higher amount of stearic acid as compared to that in other oils/ fats studied. Oleic acid concentration was higher in palmolein oil and pig body fat as compared to that in other oils and fats studied. Prepared cow and buffalo ghee were mixed in equal proportions to obtained pure mixed ghee (PMG). Adulterants, viz. soybean oil (SO), vanaspati (VG), palmolein oil (PO), goat body fat (GBF), pig body fat (PBF), sheep body fat (SBF) were added individually at 1, 3, 5, 10, 15 and 20 as well as in combinations, viz. SO+GBF, VG+GBF, PO+GBF, SO+PBF, VG+PBF, PO+PBF, SO+SBF, VG+SBF and PO+SBF in PMG in the ratios of 1:2.3, 2:4.6, 3:7, 4:9.3 and 5:11.6, respectively. FTIR spectra analysis of all the samples were performed and the data obtained was subjected to chemometric analysis. Functional group regions of the mixed ghee and adulterants were almost similar while slight differences in their finger print regions were observed. Wavenumber regions which were found useful for detecting adulteration of ghee with SO, VG, PO, GBF, PBF and SBF were 727-702, 1120-1080 and 985-955, 1167-1137, 1760-1730, 1190-1140 and 1100-970, 1190-1140 and 1120-970 and 732-710 cm-1, respectively. Wavenumber regions which were found useful for detecting adulteration of ghee with admixture of SO+GBF, VG+GBF, PO+GBF, SO+PBF, VG+PBF, PO+PBF, SO+SBF, VG+SBF and PO+SBF were 1180-1140 and 1120-1098, 1170-1145 and 1120-1087, 1175-1135 and 1125-1080, 1170-1140 and 1130-1090, 1180-1140 and 1120-1090, 1200-1130 and 1123-1093, 730-710, 1125-1085 and 740-700 cm-1, respectively. PCA applied in the selected regions showed separate clusters from PMG even for the lowest level of spiking of each adulterant and their admixture and as the level of spiking of adulterants increased, clusters shifted towards pure adulterants. PLS and PCR models applied in the selected regions of the FTIR spectra were equally efficient in detecting the selected adulterants in ghee as indicated from the R2, RMSEC, RMSEV and Bias values. Calibration curves between the actual and predicted levels of all the individual adulterants and their admixture in ghee were linear with a slope of 45° and no x or y intercepts indicating the suitability of the models in detecting them in ghee. SIMCA approach in conjunction with the established PLS models applied in the selected wavenumber regions showed the classification efficiency for pure mixed ghee, pure body fats and pure vegetable oils as 100% indicating that models were effectively developed for their detection in ghee. Classification efficiencies for ghee samples containing individual adulterants and their admixture at all the levels studied were never fell down below 85 and 73%, respectively. Using ATR-FTIR, we can detect up to 1% level of selected individual adulterants and 3.3% level of admixture of animal body fat and vegetable oil in ghee. Rapid, non-destructive, low cost and accurate analytical protocol involving a combined use of FTIR spectroscopy and chemometrics for rapid and accurate determination of soybean oil, vanaspati, palmolein oil, goat, pig, sheep body fat and admixture of SO+GBF, VG+GBF, PO+GBF, SO+PBF, VG+PBF, PO+PBF, SO+SBF, VG+SBF and PO+SBF in ghee is now available which the industries can adopt for regular testing of their samples.