| Fish oil and the antioxidant activity hydrolysate was respectively extracted fromgrass carp viscera using hot water autolytic hydrolysis. On the basis of the singlefactor, the hydrolysis conditions were optimized by response surface methodology(RSM) and the antioxidant activity of hydrolysate were investigated. The optimisedhydrolysis conditions were temperature59℃, heat time74min and addition water56mL/100g sample. Under above conditions, the oil extraction rate was68.34±0.89%,which was in accordance with the predicted value of71.60%. Compared onantioxidant activity of homogenate that was not hydrolyzed by hot water autolyticmethod, the hydrolysate of each10miligram dry material exhibited a strongerscavenging activities up to (18.68±1.80)%for hydroxyl radical.1884g ctenopharyngodon idellus offal was hydrolyzed using above optimisingtechnological parameter,448g fish oil,138g residue, and2017mL hydrolysate (solidcontent was10.86%) was prepared. After residue was extracted by petroleum ether, itsfat content declined to17%.Hydrolysate concentrated was dehydrated by employing hot air drying and spraydrying. Entire hot air drying process mainly was falling rate period controlled byinternal diffusion. The mathematical model was in accord with Page equation:MR=exp(-(0.01371+0.0003234T-0.02672h)t0.7599), the experiment indicated that testvalue was agreed with simulated value. Parameter of spray drying was as followed:Inlet air temperature was170~190℃, outlet air temperature was80~90℃, solidcontent was25%~35%and the rate of material entrance was15~20mL/min.Antioxidant activity of polypeptide powder obtained from hot air drying andspray drying was discussed respectively. The reducing power of the polypeptidepowder got from hot air drying was (0.958+0.014)/1.0mg/mL, the rate hydroxylfree radical scavenging rate was (54.48+0.69)%/40mg/mL. while the reducingpower of the polypeptide powder got from spray drying was (0.360+0.013)/1.0mg/mL, which is lower than that got from hot air drying. the hydroxyl free radicalscavenging rate was (52.07+1.33)%/40mg/mL, which was also lower than that gotfrom the hot air drying. Compared with the national standard for fish meal, the fatcontent of both types was below10%and protein content of both was above60%,which completely conformed to the national standard (GB/T19164-2003) of the firstlevel of fishmeal. When using color difference meter to analyse the color difference of the polypeptide powder, we got the following results: for the polypeptide powder gotfrom hot air drying, value L*was21.43and value b*was2.12, rendering as darkbrown; as for the polypeptide powder got from spray drying, value L*was59.53andvalue b*was23.96, rendering as light yellow. In general, the polypeptide powder ofspray drying is much better in the color and luster.The adsorption property of polypeptide podwers after freezing-drying wasinvestigated by different macroreticular resins, among which D201-Cmacroreticularresin was apparently superior to D101and D4020considering different amounts anddesorption efficiencies of adsorbed substance and its property such as content ofamino acid nitrogen, reducing ability and scavenging capability for hydroxyl radical.Static adsorption kinetics of D201-C macroreticular resin was investigated and it wasfound that at the begining of the adsorption, the amount of adsorbed substance was27.25mg/g after1hour and subsequently the desorption efficiency became lower.The amount of amino acids dropped from0.702mg/mL to0.619mg/mL in the first2hours and subsequently no apparent changes can be monitored, namely adsorptionequilibrium was reached within2hours. |
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