title: Characterization of protease and effects of temperature and salinity on the biochemical changes during fermentation of Antarctic krill.
abstract: BACKGROUND
  Despite their abundance, Antarctic krill are underutilized because of numerous difficulties in their commercial processing. Ideally, fermentation technology can be applied to transform them into a popular condiment. In addition to the exploration of protease properties, the present study aimed to evaluate proteinase activity, pH, amino nitrogen, and histamine formation during fermentation at different temperatures and salt treatments.
  
  
  RESULTS
  Even though the activity of Antarctic krill protease reached a maximum at 40 °C and pH 7, it was stable at 30 °C and pH 7-9. Among the metal ions tested, Ca2+, Mg2+and K+increased protease activity, in contrast to Zn2+and Cu2+. Within each treatment, the highest protease activity and amino nitrogen content, as well as the lowest histamine level, were observed on day 12 of fermentation. Treatment at 35 °C with 180 g kg-1salt led to the production of maximum amino nitrogen (0.0352 g kg-1) and low histamine (≤0.0497 g kg-1).
  
  
  CONCLUSIONS
  Krill paste fermented for 12 days at 35 °C with 180 g kg-1salt exhibited the optimal quality and properties, suggesting an efficient method for fermentation of Antarctic krill and other aquatic resources. © 2017 Society of Chemical Industry.
authors.affiliation: College of Food Science and Engineering, Ocean University of China, Qingdao, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Fan
authors.affiliation: College of Food Science and Engineering, Ocean University of China, Qingdao, PR China.
authors.forename: Lili
authors.initials: L
authors.lastname: Tian
authors.affiliation: College of Food Science and Engineering, Ocean University of China, Qingdao, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xue
authors.affiliation: College of Food Science and Engineering, Ocean University of China, Qingdao, PR China.
authors.forename: Zhaojie
authors.initials: Z
authors.lastname: Li
authors.affiliation: College of Food Science and Engineering, Ocean University of China, Qingdao, PR China.
authors.forename: Hu
authors.initials: H
authors.lastname: Hou
authors.affiliation: College of Food Science and Engineering, Ocean University of China, Qingdao, PR China.
authors.forename: Changhu
authors.initials: C
authors.lastname: Xue
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D055162:Biocatalysis; D010450:Endopeptidases / Q000737:chemistry*; D033201:Euphausiacea / Q000737:chemistry* / Q000201:enzymology; D005285:Fermentation; D005396:Fish Products / Q000032:analysis*; D029941:Fish Proteins / Q000737:chemistry*; D005511:Food Handling / Q000379:methods*; D054712:Salinity; D013696:Temperature
chemical_list: D029941:Fish Proteins; D010450:Endopeptidases
keywords: Antarctic krill (Euphausia superba); fermentation; protease; salinity; temperature