Storage conditions of different edible seed oils: studying the effects of time and illumination during shelf-life by NIR and Visible spectroscopies.

Shelf-life storage conditions play a paramount role on the preservation of food quality [1]. Protection from temperature and light is of great importance to preserve the nutritional, sensory and organoleptic properties of food products [2]. In particular, foodstuff containing vegetable edible oils can be particularly susceptible to thermal- and photo-degradation if poorly stored, leading to a possible negative impact on the consumer’s expectations. In this perspective, the present study was focused on vegetable oils extracted from three different seeds: hemp, linseed and sunflower. The oils were freshly obtained from the corresponding seeds using an expeller (screw) press, put in 250 mL dark glass bottles and promptly stored under controlled conditions at 20°C. A shelf-life study was carried out over a period of 12 months, with the aim of simulating the everyday storage conditions of a common supermarket. During the considered period, the bottles were separated in two sets, which were exposed to different artificial light sources (neon and LED) but with the same light power and colour (6500K and 1500 lumen). Every second month, one bottle from each set was taken out from the storage warehouse and the oil directly analysed by means of near-infrared (NIR) and Visible (Vis) spectroscopy. Multivariate exploratory analysis tools such as Principal Component Analysis (PCA) and Multivariate Curve Resolution (MCR) highlighted that the different oil types can be easily distinguished by both NIR and Visible spectroscopy, and also that the effect of storage time can be detected. Colour intensity decreased over time for all the oil types, especially in the case of the hemp oil, which at the beginning was the most intensely coloured one but resulted also the most subjected to photodegradation of its pigments (mainly represented by chlorophylls). Moreover, differences between the type of illumination were observed, suggesting that neon lamps may prove more detrimental for the preservation of seed oils than the newer and more energy-efficient LED lamps.