Research On Preparation And Activity Of Glyceryl Ester Fish Oil

The n-3 PUFA such as EPA and DHA, which are abundant in fish oil, have significant physiological activity such as prevention of cardiovascular and cerebrovascular diseases, enhancing the visual system and nervous system function, anti-cancer function and anti-inflammatory function. Triglyceride-type and phospholipid-type fish oils are preferred because they exist in nature. However, n-3 PUFA content is very low in natural triglycerides, besides, source of phospholipid-type fish oils is limited. For this reason, many researchers focus on incorporating EPA and DHA to triglycerides and phospholipids.As for the activity, studies have shown that triglyceride-type fish oils are superior to the ethyl ester-type products in the digestion, absorption and bioavailability, but no comparison of triglyceride (TG), free fatty acid (FFA), ethyl ester (EE) and phospholipid (PL) type fish oil in the same experimental system is found. Besides, nearly all researchers focus on high EPA and DHA feeding(1% to 5% of the diet), and no report about lower EPA and DHA feeding is found. In this thesis, TG and PL type of fish oils rich in EPA and DHA are prepared with enzyme reaction, after that, the activity of different types of EPA and DHA lipids (TG, FFA, EE, PL)is studied in the low EPA and DHA feeding condition.First, in this thesis a series of lipases are used in interesterification (transesterification) reaction with TG and EE as the substrates, the EPA and DHA content are detected, and then an effective lipase (K lipase) is chosed. Acidolysis reaction is carried up between TG poor in PUFA and PUFA exposed to K lipase, with packed-bed reactor as reaction containers. The effect of wriggle pump position, liquid storing pool temperature, reaction liquid velocity, substrate mole ratio and reaction time, amounts of lipase, reaction temperature is studied by single factor experiment. The optimum conditions are: Peristaltic pump in the downstreamer of packed bed, liquid pools temperature agreed with reaction temperature, reaction liquid velocity 1ml/min, substrate mole ratio 2:1(FA/TG), reaction time 72h, amounts of lipase 6%(lipase/triglyceride,m/m), reaction temperature 55℃.Subsequently, a series of lipases is used in interesterification (alcoholysis) with soyabean lecithin and PUFA as the substrate, the EPA and DHA content are detected, and then an effective lipase (lecitase ultra) is available. With lecitase ultra as catalyst, the effect of different factors is studied by single factor experiment. The optimum conditions are: In organic solvent(hexane) system, reaction temperature 45℃, substrate concentration 40%(phospholipid/hexane , g/ml), lipase concentration 200%(enzyme/phospholipid,m/m), amounts of water 50%(water/phospholipid,ml/g), substrate mole ratio(FA/PL) 8, reaction time 48h.In the end, different type(TG, FFA, EE and PL)of fish oils with same EPA/DHA ratio are prepared. Effects on mice lipid metabolism and DHA composition are studied when dieting different fish oils in the long term and in the short term, besides, the difference between low-fat feeding and high-fat feeding is studied. The results are: Weight loss is not only affected by total fat in the diet, but also the structure, especially phospholipid is better than triglyceride. Reduction of blood fat is affected by total fat in the diet when dieting different fish oils in low doses, and it needs longer time to reduce blood fat when dieting high-fat diet. DHA composition of hepatic lipids significantly increases when dieting different type of fish oils in the short term in low doses, while the change of brain DHA composition is significantly affected by total fat in the diet.