Feasibility of oil extraction from seeds of Fraxinus excelsior.L and evaluation of its qualitative properties during storage

Abstract

Background: Oils and fats are important components of food formulation so that the stability of oils during storage and heating is an important criterion in evaluating oils quality. Today, attention to the use of vegetable oils has increased due to its potential health benefits and high oxidative stability. Due to the prevalence of Fraxinus excelsior tree in the region and its widespread use of seeds and fruits in medicine and lack of information on its oil and the effect of microwavepretreatment on Fraxinus excelsior seed oil, in this study we tried to identify Fraxinus excelsior oil and use Microwave pre-treatment to improve the quality of Fraxinus excelsior oil. Materials and Methods: After preparing the oil seeds to find the optimal moisture to increase the oil extraction efficiency, the Fraxinus excelsior seeds were divided into five parts and their moisture content was adjusted to 1, 2.5, 5, 7.5 and 10%, respectively, and then under extraction. They were placed with a cold press. The grains were then divided into four equal parts and subjected to microwave pretreatment for 4 time periods (0 (control sample), 1, 2 and 3 minutes) and frequency 2450 MHz, and after adjusting the humidity to the optimal amount by extraction method. The oil was extracted by cold pressing and then the samples were stored at room temperature (25°C) for 3 months and its quality characteristics (acid value, peroxide value, fatty acid content, oxidative stability by rancimet test, Saponification value, iodine value, refractive index, total phenolic compounds, phytosterol and tocopherol content and triacylglycerol) were evaluated.Results & Conclusion: The results showed that the highest percentage of extraction was related to moisture content of 1% (14.59%) and pretreatment time of 3 minutes (18.18%). Microwave pretreatment also increased acid value, peroxide value, total phenolic compounds, alpha and gamma tocopherols and oxidative stability and had no significant effect on fatty acids and phytosterol composition. Also, the results of 90 days of oil storage showed that increasing the storage time increased the acid value, peroxide value, beta and gamma tocopherols and decreased alpha tocopherol. Also, storage of Fraxinus excelsior oil had no overall effect on total phenolic compounds, fatty acids and phytosterol levels.

Keywords: Fraxinus excelsior, Microwave pretreatment, Cold press, Fatty acids, Oxidative stability