| Antarctic krill (Euphausia superba) has the largest biomass in fishery on earth, which isurgently in need of exploitation. It provides untapped potential food source for humans due tothe high nutrition. As an abundant fishery resource, the utilization of Antarctic krill is veryimportant for our country. Amount of by-products produced in processing, including shrimphead, shell, etc., are rich in protein, oil, astaxanthin and chitin. The added value will beincreased by taking full advantage of processing by-products. Based on the nutrientcompositions and properties, the dissertation were focused on the utilization of Antarctic krillprocessing by-produsts by enzymatic hydrolysis with the high activity of endogenousenzymes to improve the protein recovery and quality. The writing also studied the dryingprocess and characteristic of the products. A feasible way was proposed to utilize theprocessing of by-products of Antarctic krill.The chemical components of the Antarctic krill and the protein fractionation of krillmuscle were determined. The nutrient compositions and properties of the by-products wererevealed by being compared to those of Antarctic krill muscle and economically importantspecies freshwater prawns (Macrobrachium nipponense) and penaeid shrimps (Metapenaeusensis). The processing by-products of Antarctic krill contributed67.5%to the total weight.The crude protein contents in the by-products of krill was10.0g/100g, which had37%ofessential amino acids (EAAs). The myosin heavy chain (MHC) and actin were the majorproteins in muscle.The krill processing by-products contained high level of total lipid (3.3%)and polyunsaturated fatty acids constituted34%of fatty acids with high levels of EPA(19.08%) and DHA (10.02%). Krill also provided considerable iron, zinc, calcium andselenium. Therefore, the Antarctic krill by-product is worthy of utilization.The proteolytic activity of Antarctic krill endogenous enzymes in different pH weredetermined. The effect of temperature and time on hydrolysis and the protein fractionation ofhydrolysate were analysed. The result showed that: the activity of Antarctic krill endogenousenzymes had two obvious peaks at pH5.5and pH8.0respectively, which was effective for theprotein recovery of Antarctic krill processing by-products. The protein recovery of krillby-products and astaxanthin content in sediment were highest at50oC for2h. Under thisconditions, the molecule weight of dydrolysate was mainly distributed less than2000, whichcontained37.88%in180~1000and40.47%below180. Actin was the major protein insediment.The enzymatic hydrolysis process and conditions were studied to recovery the protein inAntarctic krill by-products thoroughly. The result showed that: the processing by-products ofAntarctic krill were hydrolysed by endogenous enzymes and Alcalase step by step. Under theoptimum conditions of Alcalase, which were pH8.5, temperature50oC, time2h and enzymedosage3750u/g·pro, the protein recovery was up to86.1%.Eeffects of drying conditions on the quality of protein powder were investigated tooptimize the drying process, and the compositions and total amino acid of production werefurther determined. The results showed that the optimum conditions of spray drying were asfollows: inlet air temperature was180oC, the feed temperature was50oC, the feed speed was 25~30mL/min, and the feed concentrations of the sample hydrolysed by endogenous enaymeand Alcalse were30%and32%respectively. Both powders had high quality and goodinstantly solubility. Additionally, the protein contents in the two kinds of protein powder were70.5g/100g and78.6g/100g, respectively. And the amino acid compositions of them were similarto that of raw material. Hence, the two kinds of the protein powders were highly qualified andsuitable as the protein additive and food resource. The sediment was rich in astaxanthin(843.59mg/kg), which can be a good souce of astacanthin and also applid as the special feed. |
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