Oil from the wild almond Amygdalus scoparia obtained by green processes. Comparative lipidomic profiling

Abstract

In the present work two kind of extraction methods have been compared to obtain oil from wild almonds. Both methods can be considered greener than traditional alternatives. Almonds, which belong to the Rosaceae family, are among the most popular tree nuts worldwide. Iran is located in a half-dry, dry region of the world. Almond is considered as one of the oldest fruit trees in Iran. Amygdalus scoparia is a wild species of almond and occupies large areas in many parts of Iran and its neighbouring countries. Regarding the beneficial effects of almonds, the extraction and use of the oil from the A. scoparia kernel could be of interest due to their fatty acids composition. Their composition can be compared with those of olive oil as nutritionally healthful edible oil, and also as relatively stable oil because of the high levels of monounsaturated fatty acids and presence of natural antioxidants. On one hand, Supercritical Fluid Extraction (SFE) was tested. In these extractions CO2 was used as solvent, the studied factors were pressure (200, 300 and 400 atm) and temperature (40, 60 and 80 ºC); moreover, two amounts of ethanol (5 and 10 % v/v) were tested in the conditions that provided the higher yield. On the other hand Pressurized Liquid Extraction (PLE) was tested. In this case the solvents tested were ethanol, acetone and hexane at three different temperatures (50, 100 and 150 ºC) and extraction times (5, 10 and 15 min). In both cases optimization was performed by means of experimental design based in Response Surface Methodologies. The obtained oils obtained by using the different technologies were analysed by two different methods, namely GC-MS after derivatization to measure the different fatty acids present in the samples and HPLC-ELSD to measure the different lipid classes extracted. The main lipid class extracted were tryglycerides (above 98%), being oleic acid, C18:1, their main fatty acid (around 58% in PLE and 70 % in SFE), followed by palmitic acid, C16. In terms of yield the highest oil recovery was found using PLE with ethanol at 100 ºC (50% w/w) while in the supercritical fluid extractions the higher yield was obtained using CO2+10% ethanol at 400 atm and 40 ºC (42.3 % w/w).