超声场耦合亚临界水分离黄鲛鱼内脏油脂的工艺优化

为研究鱼内脏高值化利用提供绿色环保、高效可行的新方法，本文对超声耦合亚临界水技术分离黄鲛鱼内脏油脂的效果和机理进行了研究，并与酶法、超声辅助溶剂法、超临界二氧化碳法的萃取效果进行了比较。利用气相色谱-质谱法（GC-MS）分析超声耦合亚临界水萃取鱼油的脂肪酸组成。通过测定黄鲛鱼内脏基质蛋白的水热液化反应的转化率揭示亚临界水高效分离鱼内脏油脂的化学机制。对鱼内脏冻干细颗粒物做扫描电镜，观察超声场物理效应联合亚临界水水热液化效应对鱼内脏基质蛋白网状结构的破坏性。试验结果显示:超声耦合亚临界水萃取鱼油的最佳工艺条件与黄鲛鱼内脏基质蛋白质发生水热液化反应的最佳条件一致，即在250 W/L，20 kHz的超声场耦合260 ℃、10 MPa的亚临界水媒介中萃取/反应60 min时，鱼油萃取率最高是59.87%±2.86%，反应转化率最高是92.37%±3.12%。与其他三种萃取方法相比，超声耦合亚临界水法的鱼油萃取率最高，不仅如此，鱼油中的二十碳五烯酸（eicosapentaenoic acid，EPA）和二十二碳六烯酸（docosahexaenoic acid，DHA）的含量也最高，分别是（46.01±0.31）mg/g和（116.78±0.91）mg/g。超临界二氧化碳法萃取鱼油的酸价、过氧化值和羰基价最小，分别是（7.15±0.33）mg KOH/g、（1.83±0.13）mmol/kg和（2.01±0.21）mEq/kg。超声耦合亚临界水技术能够高效破坏鱼内脏基质蛋白的网状结构，充分释放网孔中包裹的鱼油，具有绿色环保、萃取时间短、鱼油萃取率高和鱼油中EPA、DHA含量高的优势。超临界二氧化碳萃取的鱼油氧化稳定性最佳，但萃取时间较长，萃取率较低。本研究阐明了超声耦合亚临界水萃取黄鲛鱼内脏油脂的作用机制，为精准利用该技术提供了试验和理论依据。

Optimization of Oil Separation from Spanish Mackerel Viscera by Ultrasonic Field Coupled with Subcritical Water

To explore an effective solution for high-value utilization of fish viscera, ultrasound coupled with subcritical water extraction (USCWE) was used to separate fish oil from Spanish mackerel viscera. The results were compared with those from enzymatic extraction (EE), ultrasonic-assisted organic solvent extraction (UOSE), and supercritical carbon dioxide extraction (SCE). Gas chromatography-mass spectrometry (GC-MS) was applied to analyze the fatty acid composition of the fish oil. The conversion rate of hydrothermal liquefaction (CRHL) of Spanish mackerel visceral stroma protein (SMVSP) was determined to explore the chemical mechanism of USCWE. Scanning electron microscope (SEM) was applied to observe the destructive action of ultrasonic physical effect coupled with subcritical water hydrothermal liquefaction on the network structure composed of stroma protein. The optimal conditions for USCWE of fish oil were consistent with that for the CRHL of SMVSP. The maximum extraction yield (EY, 59.87%±2.86%) of fish oil and CRHL of SMVSP (92.37%±3.12%) were obtained at 260 ℃ and 10 MPa with ultrasound enhancement (250 W/L, 20 kHz) for 60 min. Compared with the other three extraction methods, the EY of fish oil by USCWE was the highest. Moreover, the contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil were also the highest, which were (46.01±0.31) mg/g and (116.78±0.91) mg/g, respectively. The fish oil obtained by SCE showed the lowest acid value (AV, (7.15±0.33) mg KOH/g), peroxide value (POV, (1.83±0.13) mmol/kg), and carbonyl group value (CGV, (2.01±0.21) mEq/kg). USCWE could effectively destruct the network structure composed of stroma protein and fully released the fish oil wrapped in the mesh which had the advantages of environmental protection, short extraction time, high extraction yield and high content of EPA or DHA. The oxidation stability of fish oil by SCE was the highest, but the extraction time of SCE was longer and the EY was lower. This study elucidated the mechanism of USCWE of fish oil from Spanish mackerel viscera and provided experimental and theoretical basis for the precise use of this technology.