Study On Defluoridation And Preparation Of High Value Products From Antarctic Krill

Antarctic krill is full of nutrition,which is a development prospect of ocean resources.Because of the highest protein content,usage of Antarctic Krill mainly focus on its protein,including protease,active peptide and amino acid etc.But,High fluoride concentration in the Antarctic krill restricts its application in the field of food.At present study on defluorization method of Antarctic krill mainly focus on adsorption method,which has some advantages,such as high material diversity and high fluoride removal rate.As a kind of natural adsorbent,bamboo charcoal is a kind of agricultural by-products.It has structure of porous,lead to excellent adsorption performance.In order to improve the specificity to fluorine,many research modified adsorbent with loading ion.As a result of the existence of empty d orbitals,the transition metal easily form coordination with fluoride ions to improve the adsorption of fluoride specificity.Studies have shown that seafood processing by-products accounted for 50% ~ 70% of raw materials.Crustaceans material are main content of the seafood by-products,which are all effective ingredients of chitin and chitosan.The effective utilization of these by-products can reduce environmental pollution to explore the waste-free comprehensive utilization.So this study treat the effective development and utilization of Antarctic krill as a key point to find the efficient method to remove fluorid.The study also focus on technical point of the by-products,for further high value and providing technical basis.The experiment loaded iron ions on bamboo charcoal to remove fluoride from Antarctic krill enzymolysis liquid,then explored the efficiency and applicability of the absorbent.In order to improve the added value of the Antarctic krill enzymolysis liquid,the experiment also used enzymatic hydrolysis residue to prepare chitin,chitosan and chitosan oligosaccharide for improving value of Antarctic krill enzymolysis liquid,the results showed that:1)Experiments explored the necessity of removing fluorine,used modified bamboo charcoal as absorbent to remove fluoride in supernatant,obtained the best adsorption conditions as below: adsorbent quantity = 0.01 g/m L,adsorption temperature = 40 ℃,the adsorption time = 1 h,particle size of adsorbent =40-60 mu.In this condition,fluoride remove rate reach to 73%,higher than the unmodified absorbent,fluoride concentration in the supernatant fluid can be reduce to safe standard.2).Based on the adsorption process model and mathematical analysis,found that the adsorption process is conformed to be suitable for the Langmuir isotherm equation,and to be favorable adsorption.The adsorption processes is spontaneous,and accompanied by the endothermic reaction.The fluoride process is conformed to be suitable for the secondary dynamics model and controlled by more than one speed step.By comparing the BC,Fe-BC and F-Fe-BC of the infrared absorption spectrum,combined with the mathematical model,parameter and infrared spectrum,study made analyzes of the mechanism of fluoride using modified bamboo charcoal.3).The study used enzymatic hydrolysis residue as raw material,after degreasing,explored the best decalcified conditions using citric acid.The best condition as below:citric acid concentration of 13 g/L,and solid-liquid ratio 1:3,the reaction time10 h.Compared with the decalcified effect of hydrochloric acid,citric acid have high advantage to take off the calcium citrate.Through the orthogonal experiment,the study find the best condition of alkaline protease enzyme to remove protein from hydrolysis residue : temperature 60 ℃,time of 4h,with enzyme quantity is 900 u/g.In the contrast of alkaline deprotein effect,alkaline protease is the best choice for protein remover.The study used samples of chitin as raw material,using alkaline removal acetyl,find the best the deacelation system conditions determining through orthogonal test as follows:temperature 100 ℃,time of 12 h,50% Na OH solution concentration.In this condition,the degree of deacetylation reach to 83.22%.After decolorizing,according to the national standard testing,the indicators for the residue from the Antarctic krill enzyme solution of chitin and chitosan are food grade standard.4)The study used chitosan samples as raw materials to product oligosaccharides with specific enzymes(chitosan enzyme)and non-specificity enzyme(cellulose enzyme)respectively.The study determined the optimum digestion conditions of two enzymes through the orthogonal experiment.The optimum condition for enzymatic hydrolysis of chitosan enzyme as below,the digestion time 250 min,enzyme quantity 15 u/g,the substrate concentration 3%,the temperature 45 ℃,p H5.8,and cellulase enzyme optimal condition as below,enzymolysis time is 12 h,enzyme quantity is 6 u/g,the substrate concentration was 3%,the temperature is 50 ℃,p H5.0.Under these best conditions of enzymatic hydrolysis,the product yield were higher than 60%.The study made analysis of enzymolysis products using thin layer chromatographic respectively,found that different digestion time can product different degree of polymerization,which can demostrate two kinds of acting sites to chitosan.So in order to get the required degree of polymerization,experiments can controlled enzymatic hydrolysis time or enzyme.