Extraction and functional properties of ultrasonicated chitin and chitosan from crustacean byproducts.

摘要

The influence of high intensity ultrasound during extraction of chitin from North Atlantic Shrimp (Pandalus Borealis) and Fresh Water Prawn (Macrobrachium Rosenbergii) on yield, purity, and crystallinity was investigated. As a subsequent step, effect of ultrasound under different conditions (time, power intensity and temperature) as a pretreatment for deacetylation of chitin from North Atlantic shrimp on yield, purity, time and degree of deacetylation was studied. Yield, mineral and protein content were determined after each processing step. Purity of extracted chitin was assessed as total amount of glucosamine in samples. The crystallinity Index was determined using wide angle X-ray scattering. Analysis of scanning electron microscope images confirmed morphological changes in samples. Degree of acetylation was determined by both Fourier Transform Infrared Spectrometry, (FTIR) and direct titration. Yield of chitin from NAS decreased from 17.02+/-0.66% to 11.09+/-1.46% of initial mass with extensive sonication, for FWP the yield decreased from 8.28+/-1.27 to 5.02+/-0.64 of initial mass, which was attributed to increased concentrations of depolymerized materials in the wash water. Removal of minerals was not affected by sonication. Application of ultrasound enhanced removal of proteins for NAS from 0.58+/-0.08% to 0.32+/-0.03% dry weight and for FWP 0.028+/-0.06 to 0.013+/-0.001 dry weight. High Intensity Ultrasound as a pretreatment resulted in accelerated removal of the acetyl-groups under industrial conditions. For samples sonicated for 60 minutes resulted in 90% deacetylated chitosan after 100 minutes of treatment. Application of ultrasound for 15 minutes at 65 and 43 Wcm-2 resulted in DDA of 84.03 and 63.60%, respectively. Samples sonicated at 30°C 65 Wcm-2 for 15 and 30 minutes resulted in 74 and 78% deacetylation of samples. Results were attributed to the chemical and mechanical effect of ultrasound. High intensity ultrasound as a pre-treatment promotes conversion of chitin to chitosan through changes in the chitin structure and by enhancing accessibility of the solvents to its reactive sites. Increased surface area and higher homogeneity of sonicated chitin particles may also be responsible for its increased reactivity. This may results in benefits such as lower production cost, less time and better control of the deacetylation process.