Evaluation of seed oil quality in Iris lactea by attenuated total reflection-Fourier transform infrared spectroscopy coupled with chemometrics

Abstract

Iris lactea Pall. var. chinensis (Fisch.) Koidz. Seed oil has high medicinal value, including antibacterial, anti-inflammatory, and prevention and treatment effects on hypertension. In this study, the oil from nine different geographical locations of I. lactea seeds was extracted, and then the total polyphenol content, the ratio of major unsaturated and saturated fatty acids, and the antioxidant capacity of the oil were examined separately. Combining attenuated total reflection-Fourier transform infrared spectroscopy and chemometric methods, analysis models of the total polyphenol content, the ratio of major unsaturated fatty acids and saturated fatty acids, and the antioxidant capacity of I. lactea seeds oil were developed. The results showed that the total polyphenol content of I. lactea seeds oil ranged from 14.46 to 104.91 mg/kg gallic acid equivalents, the ratios of unsaturated to saturated fatty acids were between 5.00 and 12.50, and the half-maximal inhibitory concentration of scavenging 2,2-Diphenyl-1-picrylhydrazyl free radicals was between 3.53 and 7.23 mg/mL. The proposed model for the ratio of unsaturated to saturated fatty acids showed good robustness with the root mean square error being adequate for the intended demand (<1), the correlation coefficients greater than 0.95, and the ratio of prediction to deviation greater than 3. The correlation coefficient of the total polyphenol content and antioxidant activity models were greater than 0.9 and the ratio of prediction to deviation was both greater than 2, showing a good correlation. In conclusion, all results indicated that I. lactea seeds oil was a healthy oil with development value, and attenuated total reflection-Fourier transform infrared spectroscopy was a simple and reliable method to evaluate the quality of I. lactea seeds oil as an alternative to wet chemical methods.