Ultrafiltration Treatment Tilapia Meat Enzymatic Hydrolysate And The Effect On Flavor Substances

The tilapia meat enzymatic hydrolysate rich in peptides、amino acids andminerals can be used as functional food additives, but due to the appearance ofturbidity, heavier bitterness and fishy smell and poor sensory quality, its developmentand utilization are limited. In this study, tilapia meat enzymatic hydrolysate as rawmaterial, enzymatic hydrolysate was pretreatmented by filter aids,thenultrafiltrationUltrafiltration step by step, using MWCO10kDa、5kDa、3kDa、1kDaultrafiltration membrane for ultrafiltration step by step and made molecular weightdistribution <10kDa,<5kDa,<3kDa,<1kDa UF. This experiment mainly studyoptimum technological parameters of ultrafiltration pretreatment methods, optimumtechnological parameters of ultrafiltration step by step, basic properties and flavorsubstance of ultrafiltration at all levels etc, in order to produce good sense, betterfavor and nutrient rich enzymatic hydrolysate, to improve added value of the tilapiaand the development and utilization of new protein resources to provide theoreticalsupport. This experiment mainly study results are as follows:1. The degree of hydrolysis (DH) of enzymatic hydrolysate is26.97%;thecontent of amino nitrogen is2.69mg/mL; protein content is36.5mg/mL;colorvalues(A420nm) and clarify degrees(A680nm) are respectively0.683、39.5%;thesensory evaluation score of bitterness and fishy smell is1.3;the components ofmolecular weight more than10kDa in enzymatic hydrolysate accounted for about0.65,while the components of molecular weight less than5kDa accounted for86.10%.2. It was discussed that the effect of perlite,500#and700#diatomite,0.22μm and0.45μm microfiltration membranes on enzymatic hydrolysate, and determine the bestdosage of filter aid: pearlite is9g/100mL,500#diatomite is25g/100mL,700#diatomite is25g/100mL, and the effect of filter aid and microfiltration membrane aresimilar. The sensory evaluation protein recovery and TAV value as index, the effectof the different pretreatment on enzymatic hydrolysate are compared: the loss of theamino acids in0.22μm microfiltration membrane treatment fluid is least, the loss ofthe amino acids in perlite filtrate is less, the loss of the amino acids in500#diatomite filtrate is little; the less degree of freshness in enzymatic hydrolysate is less thandiatomite, the microfiltration membrane and filter aid both make the enzymatichydrolysate bitter less, but the effect of perlite is better than the0.22μmmicrofiltration membrane; the microfiltration membrane and filter aid both make theenzymatic hydrolysate sweet less,but the effect of perlite is less than diatomite.3. Membrane flux as Indicators, enzymatic hydrolysate pretreatmented by perlite9g/100mL as sample solution before ultrafiltrate, it determined the optimumtechnological condition combination ultrafiltration operation cycle is25min,operating pressure is12psi, material liquid pH value is natural pH.4. It was studied the effect of ultrafiltration treatment on molecular weightdistribution, clarify degree, color vaule and thermal stability of the enzymatichydrolysate. Compared with enzymatic hydrolysate, the proportion of componentwith3k<M<5kDa,1k<M<3kDa in ultrafiltration permeate both increased; theproportion of component with M<1kDa were both reduced; the proportion ofcomponent with M<1kDa in permeate of MWCO1kDa was27.19%;the color of thetrapped fluid was deeper, and its clarity diminished; the color of the permeate ofMWCO10kDa,5kDa,3kDa,1kDa and the trapped fluid of MWCO3kDa,1kDa weredeeper, clarify degree increased and the difference is not obvious; the thermal stabilityof10kDa permeate and5kDa trapped fluid are poorer, the thermal stability of3kDaand1kDa trapped fluid are good, the thermal stability of3kDa and1kDa permeate arebest;10kDa5kDa UF can effectively intercept substances, which influence thestability of enzymatic hydrolysate thermal stability,at the same time the content ofprecipitation and the change of color value and clarify can be associated withultrafiltration intercept limited.5. It has been studied the effect of ultrafiltration step by step on flavorsubstances of enzymatic hydrolysate: different molecular weight range of ultrafiltratehave different flavor characteristics: the freshness of3kDa and1kDa permeate aremore prominent, the sweetness of1kDa permeate is more outstanding, the bitternessof5kDa permeate is evident.Except Zn2+, the content of K+, Na+, Mg2+, Ca2+ionswere lower in the ultrafiltrates. The volatile components of enzymatic hydrolysatebefore and after ultrafiltrate are detected by HS-SPME-GC-MS, the result showed thetypes and component part of the volatile components in enzymatic hydrolysate withdifferent molecular weight distribution are different; the type and component part ofthe volatile components in enzymatic hydrolysate and10kDa permeate are70、69 species respectively，the type of the permeate of MWCO5kDa,3kDa and1kDarespectively are75,84and82species; compared with enzymatic hydrolysate, thepercentage of acids, ketones, nitrogenous compounds and sulfocompound inultrafiltration permeate all increased, the change of acids and nitrogenous compoundsare largest, the proportion of aldehydes, alcohols, esters and furan compounds inultrafiltration permeate were both reduced, the changes of esters and aldehydes werelargest.