Oxidative stability study of edible vegetable oils using near-infrared emission spectroscopy

Lipids are important constituents of food, and their oxidative stability is related to the time required to detect significant amounts of a degradation product (Induction Time - IT), such as hydroperoxides (HP). A new technique for determining IT is based on near-infrared emission spectroscopy (NIRES) to detect HP. Compared to the standard Rancimat method, the technique has advantages such as wide working temperature range, low sample volume and rapid analysis. In the present work a NIRES photometer was used to the study shelf life (SL) of soybean oil, submitted to domestic storage conditions. The determination of IT by NIRES was compared with the reference technique to detect conjugated dienes (CD). This work also proposed to study the correlation between the IT value for different types of edible oils and the concentration of pro-oxidative and antioxidant substances available in the literature. The possibility of estimating SL using Ahrrenius plot was also evaluated. The use of NIRES photometer in the soybean oil SL study was efficient since it was possible to quantify the effect of the different storage forms on the IT. Moreover, it was observed that there was a correlation with the results obtained by the CD analysis (Figure 1). The correlation between the IT of different types of oils and their respective chemical composition and also the estimation of SL based on the Arrhenius plot should be done carefully.