UTILIZATION OF NEW METHODS TO CONTROL THE QUALITY OF SOME ESSENTIAL OILS ADDED TO FOOD PRODUCTS DURING PROCESSING

Abstract

The main objectives of the present study were to develop a technique based on volatile compounds profile comparison using multivariate analysis (MVA) including principal component analysis (PCA) for detecting of adulteration or assessment of the authenticity of essential oils. Also, to evaluate the stability of essential oils used in flavouring biscuits, during baking and storage. Seven model samples of Menthapiperita (M. piperita) adulterated with (5- 50% v/v) Menthaspicata (M. spicata) were prepared and subjected to Gas Chromatography – Mass Spectrophotometry GC-MS / PCA. The results of GC-MS analysis revealed a gradual decrease in menthol and menthone, the most potent odorants of M. piperita oil, whereas the characteristic volatiles of M. spicata were detected in the adulterated M. piperita oil model samples at variable levels of adulteration. The decrease in the odour sensory quality of the adulterated samples was coincident with the decrease in the relative concentration of menthol and menthone. However, this decrease showed dramatic trend at high levels of adulteration (30 -50% v/v). The PCA and cluster analysis of the GC-MS data revealed an accurate detection of M. piperita oil adulteration with different levels (from 5 to 50% v/v) of M. spicata oil. Fourier transform infrared spectroscopy (FTIR) combined with multivariate calibration using partial least square (PLS) was used for analyzing of the seven adulterated M. piperita samples. The results revealed the effectiveness of this technique as a direct and simple method alternative to GC-MS analysis. The quality of essential oils of five cumin samples, obtained from local market, was evaluated in comparison with authentic sample by using GC-MS / PCA. All investigated samples showed a remarkable decrease in the total yields of the more volatile compounds and a significant increase in cuminaldehydes. This result may be correlated to the temperature and time of storage.