Generally speaking, the fat content in fish viscera is higher, the fat content in saury viscera is 25.1%, and the lecithin content is also richer.
Lecithin is mainly found in egg yolks, soybeans, animal and plant tissues.
The current sources of lecithin products are soybeans and egg yolks. Zhang Limin uses supercritical carbon dioxide to extract lecithin from soybeans; Chang Haotuan extracts lecithin from egg yolks and analyzes its oxidative stability.
Soy lecithin is rich in saturated fatty acids and low in unsaturated fatty acids. The fatty acid composition of the phospholipids in the egg yolk is not ideal, and the cholesterol level is relatively high.
Lecithin (marine lecithin) from marine organisms is rich in n-3 polyunsaturated fatty acids, which can be better absorbed by tissues, which has attracted widespread attention.
In addition, it can reduce the incidence of coronary heart disease, hypertension and Alzheimer’s disease, and improve the brain and vision functions of infants and young children.
Supercritical fluid technology
Supercritical fluid technology is an emerging extraction technology, which is non-toxic, low in price, and mild in use conditions. Compared with other extraction techniques, its extraction effect is better.
In this experiment, saury viscera was selected as the research object, and saury oil was extracted once by supercritical CO2 extraction technology.
Lecithin contains a certain polarity, and the lecithin is extracted twice with absolute ethanol as an entrainer.
Response surface analysis was used to optimize the process parameters and determine the fatty acid composition of saury oil and lecithin, providing technical reference for the deep processing of saury oil and lecithin.
For supercritical CO2 extraction of fish oil and lecithin, both the yield and properties of fish oil and lecithin must be considered, as well as factors such as extraction cost. Therefore, the process parameters to be investigated for the extraction of fish oil and lecithin are 3 and 4 respectively: Extraction pressure, extraction temperature and extraction time; extraction pressure, extraction temperature, entrainer (absolute ethanol) flow rate and extraction time.
Carry out single factor experiments separately to determine the optimal extraction conditions and factor levels. Due to the limitation of the test equipment, the maximum extraction pressure cannot exceed 45MPa, so the fixed factor conditions for the fish oil extraction single factor test are the extraction pressure 40MPa, the extraction temperature 45°C, and the extraction time 2.5h; the fixed factor conditions for the lecithin extraction single factor test The extraction pressure is 40MPa, the extraction temperature is 50°C, the entrainer flow rate is 1.5mL/min, and the extraction time is 2h. Change any of these factors to perform the experiment.
On the basis of single factor experiments, response surface analysis was used to optimize the optimal process parameters for supercritical extraction of fish oil and lecithin.
Supercritical CO2 extraction of Cololabis saury oil Weigh about 30g of raw material wet sample into a 50mL extraction kettle, check the air tightness of the equipment, set the extraction temperature and outlet valve temperature. Open the CO2, N2 gas storage tank valve, set the required extraction pressure, and open the outlet valve to collect the extract.
Accurately weigh the quality of the saury visceral oil and calculate the yield.
Yield (%) = saury oil quality / raw material quality xl00.
Supercritical CO2 extraction of saury lecithin The de-oiled saury viscera is extracted with anhydrous ethanol as a co-solvent for secondary extraction with supercritical CO2. The obtained lecithin ethanol solution is separated by vacuum distillation, and the lecithin is vacuum dried.
Yield (%) = saury lecithin quality / raw material quality xl00.
The extraction pressure is 45.0MPa, the extraction temperature is 50°C, the extraction time is 2.5h, and the cosolvent flow rate is 1.9mL/min.
Under these conditions, the lecithin yield predicted by the response surface model was 9.2g/100g.
In the actual operation process, both feasibility factors and optimal results must be considered. Therefore, the actual extraction process conditions are determined as: extraction pressure 45MPa, extraction temperature 50°C, extraction time 2.5h, and entrainer flow rate 2.0mL/ min. In order to verify the reliability of the test results, the actual extraction process conditions were used to carry out the verification test, and the actual yield of lecithin was 9.2g/100g, which was basically consistent with the theoretical prediction value.
Therefore, the lecithin extraction process parameters obtained by response surface analysis are true and credible and have practical value.
Fatty acid composition of saury oil
In the fatty acid composition of saury visceral lecithin, the content of polyunsaturated fatty acids accounted for the most, reaching 27.7%, and the most important EPA and DHA reached 5.6% and 27.4%, respectively. The content of DHA was the highest of all fatty acids.
The content of erucic acid is the most in monounsaturated fatty acids, and palmitic acid is the most in saturated fatty acids. The DHA/EPA ratio of saury viscera lecithin was 4.9, while the DHA/EPA ratios of squid and anchovies were 1.4 and 2.8, respectively.
The optimal process conditions for supercritical CO2 extraction of Cololabis saury oil and lecithin are: extraction pressure 45MPa, extraction temperature 55, extraction time 3h; extraction pressure 45MPa, extraction temperature 50°C, extraction time 2.5h, and entrainer flow rate 2.0mL/min .
The order of the factors affecting the yield of fish oil is: extraction pressure>extraction time>extraction temperature.
Under the optimal process conditions, the yields of fish oil and lecithin reached 22.0g/100g (wet sample) and 9.2g/100g (wet sample), respectively. The obtained fish oil and lecithin are rich in unsaturated fatty acids. The fish oil contains the most monounsaturated fatty acids, and the lecithin contains the most polyunsaturated fatty acids, especially DHA, which has good quality.
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