Monitoring of Hazelnut oil quality during thermal processing in comparison with extra virgin olive oil by using ATR-FTIR spectroscopy combined with chemometrics

Hazelnut oil (HO), which is not widely used because its healthy properties are not fully known yet, is an excellent nutrient due to its high content of monounsaturated fatty acids and antioxidants. In this study, the effects of thermal processing on the quality of HO in comparison to extra virgin olive oil (EVOO), which is one of the healthiest and heat-resistant oils, were investigated using Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Oil samples were heated at a frying temperature (180 degrees C) for 24 h in periods of 8 h per day and alterations in the spectra of these oils sampled every 2 h were evaluated. The heating process caused decreases in the areas of the bands at 3007 and 722 cm(-1) and the area ratios of 3007/2854 and 722/2854 cm(-1) and increases in the areas of the bands at 987 and 965 cm(-1) and the area ratio of 965/2854 cm(-1) in both oils suggesting the conjugation and cis-trans isomerization of unsaturated fatty acids. In addition, heating caused increases in the areas of the bands at 3475 and 1744 cm(-1) and the ratios of 3475/2854 cm(-1) and 1744/2854 cm(-1), a shift to a lower value in the wavenumber and a broadening of the 1744 cm(-1) band indicating the formation of primary and secondary oxidation products in the heated oils, which were also supported by chemical studies. Most of these changes began earlier in EVOO and all occurred to a higher extent, revealing that HO has a higher thermal stability than EVOO. Principal component analysis and hierarchical cluster analysis confirmed that HO is more resistant to heat than EVOO. These results showed that HO is superior to EVOO and it could be used for frying as a healthier and cheaper oil alternative. This study also indicated that oil oxidation could be monitored easily and rapidly via ATR-FTIR spectroscopy. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that hazelnut oil (HO) has higher thermal stability compared to extra virgin olive oil (EVOO), making it a healthier and cheaper alternative for frying. This suggests that HO could be a superior choice for culinary applications.