Biologicale Valuation And Inhibition Of Lipid Oxidation In Fish Oil Of Enzymatic Hydrolysate Of Polysaccharides From Enteromorpha Prolifra

Enteromorpha prolifera,distributed worldwide from the intertidal to the upper subtidal zones of China,is one of the most common green algae.It possesses high nutrient value and can be edible.Futhermore it also has a wide range of pharmacological properties,such as antitumor,antioxidant and immunoregulatory properties.This alga is a kind of economic type macroscopic green alga because of its strong propagation capability and low cost.Therefore,studies on the polysaccharides from Enteromorpha prolifra,can not only improve the utilization rate of Enteromorpha prolifra,but also lay the foundation for its deep processing into functional food.In recent years,low-molecular-weight algal polysaccharides have received widespread attention because of their higher biological activity,lower viscosity,and better solubility.It is hypothesized that low-molecular-weight EP may also have a higher activity and more potential applications.In the present study,the water soluble polysaccharide from Enteromorpha prolifera was hydrolyzed by pectinase in combination with glucoamylase.The hydrolysalte(EEP)was investigated for the antioxidant activity,anti-tyrosinase activity and its ability to inhibit lipid oxidation in fish oil emulsion.The main results that we have obtained are as follows:1.Crude polysaccharide(EP)was extracted from E.prolifera with hot water.EP was enzymatic hydrolyzed by pectinase and glucoamylase.The degradation conditions were optimized using a Box-Behnken response surface design(BBRS).The optimum conditions were established as:degradation temperature 45.2?,enzyme concentration 48.50 U/mL,and the activity ratio of pectinase to glucoamylase 3.40:1.Under these conditions,hydrolysis was carried out for 3 h,degradation rate of polysaccharide was determined to be 12.10%and the resulting hydrolysaltes was named as EEP.2.The contents of chemical component of EP and EEP are different.After enzymatic hydrolysis,the content of total sugar increased,and that of sulfate decreased,while the content of uronic acid and protein remained almost unchanged.UV-VIS absorption spectra and FT-IR spectra of EEP had no significant different with those of EP.The molecular weight of EP and EEP were determined to be 1257 and 309 kDa by High performance Gel Permeation Chromatography(HPGPC).GC-MS was employed to analyze the monosaccharide composition,which indicated that EP and EEP were mainly made up of rhamnose,glucose and xylose,as well as small portions of mannose and galactose.The in vitro antioxidant activities of EP and EEP were evaluated by determining their ferric iron reducing power,iron(?)chelating activity and radical(DPPH,hydroxyl and superoxide anion radicals)-scavenging abilities.It was found that the antioxidant activity of EEP was greatly increased when compared to those of EP.The inhibitory effect on tyrosinase of EP and EEP was also evaluated.The result indicated that EEP has superior anti-tyrosinase activity to that of the EP.EEP has been demonstrated to be a competitive-uncompetitive mixed type inhibitor.In the investigation on the fluorescence spectrum of tyrosinase,it was found that EEP had a quenching effect on the intrinsic fluorescence spectra of tyrosinase.We further monitored the changes in tyrosinase hydrophobicity in the presence of EEP.The result suggested that EEP affect the tertiary structure of tyrosinase.3.The effect of emulsifier(Tween 80,gum Arabic,Lecithin)and EPP concentration(0.25-3%wt./wt.)on the physical characteristics of fish oil emulsions was investigated.The results showed that Tween 80 exhibited the best emulsifying properties and improved physical stabilities of fish oil emulsions,and 1%(wt./wt.)EEP was the optimum concentration for the preparation of fish oil emulsions.The influences of extreme environment on the stability of the fish oil emulsion were investigated.The results showed the stability of fish oil emulsion in the presence of EEP has been improved when compared to that in absence of EEP.The influence of EEP addition on the oxidative stability and physical stability of fish oil emulsion was investigated.EEP was added to fish oil emulsion as antioxidant while VE and TBHQ were used as positive controls,and fish oil emulsion(T80)without the addition of antioxidant as the blank control.Samples were investigated for the physical properties,lipid hydroperoxide formation,secondary reaction products(TBARS)formation,pH and long chain polyunsaturated omega-3 fatty acid content during the storage at 45?.The results indicated that the physical stability of the samples containing the different antioxidants(EEP,VE,TBHQ)followed the order:EEP>VE>TBHQ.The oxidative stability of fish oil emulsions:VE>EEP>TBHQ.Therefore,EEP effectively improved the oxidative stability and physical stability of fish oil emulsion.