| Summary: | The aims of this research project were to identify a functional protease and optimize hydrolysis conditions for this enzyme to facilitate efficient alcohol extraction of phospholipid (PL)-rich oil from Antarctic krill, Euphausia superba. The following hydrolysis conditions tested were: frozen krill and water ratio (KWR), hydrolysis temperature (HTe), pH, enzyme dosage (ED), and hydrolysis time (HTi). These conditions were studied by single factor and orthogonal experiments. Finally, the efficiency of various solvents used for extracting the krill oil was compared. Alcalase was identified as the most suitable enzyme for enzymolysis of Antarctic krill among 5 commonly used enzymes based on the degree of hydrolysis (DH). The optimal conditions for enzymolysis Antarctic krill with alcalase were: KWR = 2:1, HTe = 55~60ºC, pH = 8.0, ED = 3000 U/g and HTi = 4 h (end pH = 6.5~6.7). Range analysis in orthogonal experiments gave the following ranking of influencing factors: KWR (R = 6.2) > ED (R = 2.3) > pH (R = 0.3) > HTi (R = 0.2). Under the optimal conditions, the DH was 31.1 %. Meanwhile, peptides with an average length of 3.2 and a molecular mass of 352 were obtained. Extraction was performed from “PEF”, defined as freeze dried lipid phase after 75~80℃ for 5 min after hydrolysis, and 600xG centrifugation for 5min. Compared with 5 commonly used solvents, 99.5% ethanol gave the most complete extraction of PL rich krill oil (KO). Under the conditions of extraction temperature (ETe) = 45 ºC, PEF and 99.5% ethanol ratio (PER) = 1:10 and extraction time (ETi) = 3h, highest KO extractability (m (KO) / m (PEF)) was 74%; PL concentration (m (PL) / m (KO)) was 32.1%; total KO extractability (m (KO) / m (total lipid in PEF)) was 99.4%; total PL extractability (m (PL) / m (total PL in PEF)) was 102.8%. Under the conditions of ETe = 25ºC, PER = 1:6, ETi = 1h, highest PL concentration was 33.9%; KO extractability was 61%; total PL extractability was 89.5%; total KO extractability was 82.0%. Under the conditions of ETe = ...
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