Effect of Ultrasonication Time on Physical and Chemical Properties of Kilka Fish Oil, Corn Oil and Soybean Oil

Abstract

Introduction Edible oils constitutes a chief component of human diets in our daily life to supply essential fatty acids, energy, and nutrients to human. The nutritional value of edible oils varies depending on the type of oil, processing methods, extraction techniques, and storage conditions. Generally, edible oils are high in triacylglycerols with minor compositions. The presence of high amount of unsaturated fatty acids in the structure of triacylglycerol leads to a reduced shelf life of oils. This is associated to the undesired lipid oxidation that occurs when unsaturated fatty acids are exposed to light, oxygen, and heat. This is a major concern in food industry as it might result in undesired food quality deterioration involving reduction of nutritional components and off-flavors. The demand for nutritious and healthy animal and vegetable oils has been increased with a growth in population and economic progress. Therefore, researches for functional and nutritious edible oils has gained world attention on the technology to process edible oils. The use of ultrasound as a new technology in food processes is increasing due to its potential for changing materials and processing speed. This technique displays several advantages over conventional techniques in terms of time, energy consumption, and higher output. Ultrasonic processing is used in the food industry for numerous processes on high lipid containing food products in cutting, cooking, homogenization/emulsification, and microbial inactivation. The aim of this study was to investigate the effect of ultrasound time (0, 20, 40 and 60 min) on physicochemical properties of corn oil, soybean oil and kilka fish oil. Materials and Methods Commercial kilka fish oil, corn oil and soybean oilwere purchased from local market. All of the chemicals and reagents used were analytical reagent grade. Each oil was poured at 250 ml Beaker and then treated with an ultrasonic probe at a frequency of 20 kHz for a specified period of time. Oil chemical and physical properties such as acid value (mg/g), peroxide value (meq O2/kg), oxidative stability index (h), thiobarbituric acid value (mg/kg), conjugated diene value (%), fatty acid composition, fourier transform infrared (FTIR) spectroscopy and color parameters (L*, a*, b* and ∆E) were determined. Data analysis was done using SPSS software and completely random design. Results and Discussion The results of this study showed that with increasing the duration of ultrasound, acid value, peroxide value, TBA value and conjugate diene value, increased and the induction period decreased. On the other hand, ultrasound treatment led to increase palmitic acid, stearic acid, oleic acid, saturated fatty acids (SFA) and monounsaturated fatty acid (MUFA), and decrease linoleic acid, linoleic acid (and palmitoleic acid, eicosapentaenoic acid and docosahexaenoic acid in kilka fish oil), polyunsaturated fatty acid (PUFA), polyunsaturated fatty acid/saturated fatty acids (PUSFA/SFA), unsaturated fatty acid/saturated fatty acids (USFA/SFA), Cox value in corn, soybean, and kilka fish oils. Ultrasound did not change the fourier transform infrared spectroscopy but did change some color parameters. Sonication caused an increase in L* (more lightness) of corn oil, a decrease in a* (more greenness) of soybean oil, an increase in b* (more yellowness) of corn and soybean oils, and a decrease in ∆E compared to control samples. Probably, ultrasound causes destruction and isomerization of the double bands of pigments and as a result changes in color indices. According to the results of this study, ultrasound treatment accelerated the oxidation and degradation of oils and as a result, changed some of the physicochemical properties of the oil, which varied according to the type of oil.

Keywords

• corn
• fish
• oil
• soybean
• ultrasound