A new multistage counter current extraction method of removing fluoride from defatted Antarctic krill powder

Abstract

This study aims to find an efficient acid extraction method to remove fluoride from defatted krill powder. Considering the effects of acid species, concentration, temperature, extraction time, solvent volume on the defluoridation efficiency, and final product yield, a new multistage counter current extraction method was developed. The optimum reaction condition was obtained by adding 10 ml of 0.3 M HCl to 1 g defatted krill powder and extracting for four stages, each stage was lasting for 60 min. After this process, fluoride content per dry weight of the final product was remarkably reduced to <5 mg/kg, defluoridation efficiency was 99.70%, and water consumption was minimized. Fourier transform infrared spectroscopy also indicated a decrease in the amount of fluorine, and basic chemical composition measurement indicated krill protein was not damaged during this process. Therefore, these results could be used as theoretical guidance for removing fluoride in practical application. Practical applications Defatted Antarctic krill powder is a cheap by‐product after krill oil extraction, but it contains both high‐quality protein and high concentration of fluoride. The toxicity of fluoride in krill powder makes it not be allowed as food resource. So, a new counter current extraction method was developed to defluorinate from defatted krill powder, which was an easy and cheap process, but high defluoridation efficiency with low water consumption. It has been successfully applied to the food pilot base, and it would help to obtain the safe defatted Antarctic krill powder in krill industry.

Comprehensive characterization and evaluation of the process chain and products from Euphausia superba exocuticles to chitosan

“…The protein‐to‐chitin ratio (Section 4.3.6 Equation ) of the krill exocuticle is calculated from the integral quotient by using mole fractions of arginine and tyrosine in the total protein content. These values could be calculated considering published protein compositions determined with the whole krill biomass 27,39 . The protein content of 35 ± 3% by weight is determined via multiplying the protein‐to‐chitin ratio by the chitin content (19.8%) via ADF‐ADL (see Section 4.3.3).…”

“…The protein content was quantified with the protein‐to‐chitin ratio by the following equation where, I C1 is the integral of the C1 carbon of chitin at 104 ppm, I AA is the integral of the ε‐/ξ‐carbon of the amino acids tyrosine and arginine at 157 ppm, n C1 is the number of chitin nuclei at 104 ppm, n AA is the number of amino acid nuclei at 157 ppm, w Chitin is the chitin content determined by the already mentioned ADF‐ADL method. X AA ( E. superba , whole krill: Tyr: 0.0359, Arg: 0.0506) 27,39 is the mole fraction of tyrosine and arginine calculated with the amino acid profile published by other authors. The mole fraction X AA was calculated by using the formula where, w Arg is the mass fraction of the arginine, w Tyr is the mass fractions of the tyrosine, M Arg is the residual molar mass of arginine (156.19 g/mol), M Tyr is the residual molecular mass of tyrosine (163.18 g/mol), and is the average residual molecular mass of the amino acids.…”

“…These values could be calculated considering published protein compositions determined with the whole krill biomass. 27,39 The protein content of 35 ± 3% by weight is determined via multiplying the protein-to-chitin ratio by the chitin content (19.8%) via ADF-ADL (see Section 4.3.3). Compared to the protein content derived from amino acid analysis of the exocuticle (Section 4.3.5, 39.8%) the proposed ss-NMR methods seem to give adequate results.…”

“…where, I C1 is the integral of the C1 carbon of chitin at 104 ppm, I AA is the integral of the ε-/ξ-carbon of the amino acids tyrosine and arginine at 157 ppm, n C1 is the number of chitin nuclei at 104 ppm, n AA is the number of amino acid nuclei at 157 ppm, w Chitin is the chitin content determined by the already mentioned ADF-ADL method. X AA (E. superba, whole krill: Tyr: 0.0359, Arg: 0.0506) 27,39 is the mole fraction of tyrosine and arginine calculated with the amino acid profile published by other authors. The mole fraction X AA was calculated by using the formula…”