Some physicochemical properties, fatty acid composition and antimicrobial characteristics of different cold-pressed oils

Abstract

Since the demand for organic food in the field of vegetable oils is increasing, consumers tend to look for products that haven't been produced by extracting oils from seeds by using solvents such as hexane, or having undergone chemical refining processes. To consumers looking for oils that can enhance human health and prevent certain diseases, cold-pressed oils are the alternative product, The interest in cold-pressed oils is constantly growing. Moreover, some cold-pressed vegetable oils may present antimicrobial activities and might thus provide a natural way to reduce pathogens on fresh products. This study aims to determine the physicochemical properties, fatty acid compositions and antimicrobial characteristics of cold-pressed argan, pomegranate, date, flax, safflower, golden berry, walnut, and grape seed oils. The cold-pressed date and flax seed oils analyzed showed the lowest acid value (0.30 mg KOH/g) and peroxide value (1.4 meqO(2)/kg) respectively. Gas Chromatography analysis of fatty acid methyl esters indicated that the dominant fatty acid of argan, golden berry and flax seed oils were oleic (53.41%), linoleic (74.92%) and linolenic acids (56.25%) respectively (p<0.001). Cold-pressed pomegranate seed oil contained approximately 85.89% conjugated linolenic acid (CLnA) and had the lowest total saturated fatty acids. Furthermore, cold-pressed oils showed a different spectral activity against the tested pathogenic bacteria and aflatoxigenic molds. The antimicrobial activity of cold-pressed oils against pathogens and molds was improved by an increase in the concentration of oils. The most effective inhibitors among the tested cold-pressed oils are the pomegranate and argan oils, followed by walnut oil. In this study, safflower oil on S. enteridis ATCC 13076 and pomegranate oil on L. monocytogenes ATCC 7644 have had the largest inhibition zones, with diameters in excess of 26.4 and 25.5 mm, respectively. Grape oil, however, was found to be the most inhibitory to both molds, namely Aspergillus parasiticus NRRL 2999 and Aspergillus parasiticus NRRL 465, exhibiting maximum zones of inhibition of up to 20 mm.