title: Calcium hydroxide as a processing base in alkali-aided pH-shift protein recovery process.
abstract: BACKGROUND
  Protein may be recovered by using pH shifts to solubilize and precipitate protein. Typically, sodium hydroxide is used as the processing base; however, this has been shown to significantly increase sodium in the final recovered protein.
  
  
  RESULTS
  Protein was extracted from black bullhead catfish (Ameiurus melas) using a pH-shift method. Protein was solubilized using either sodium hydroxide (NaOH) or calcium hydroxide (Ca(OH)2) and precipitated at pH 5.5 using hydrochloric acid (HCl). Protein solubility was greater when Ca(OH)2was used compared to NaOH during this process. Using Ca(OH)2as the processing base yielded the greatest lipid recovery (P < 0.05) at 77 g 100 g-1, whereas the greatest (P < 0.05) protein recovery yield was recorded as 53 g 100 g-1protein using NaOH. Protein solubilized with Ca(OH)2had more (P < 0.05) calcium in the protein fraction, whereas using NaOH increased (P < 0.05) sodium content.
  
  
  CONCLUSIONS
  Results of our study showed that protein solubility was increased and the recovered protein had significantly more calcium when Ca(OH)2was used as the processing base. Results showed both NaOH and Ca(OH)2to be an effective processing base for pH-shift protein recovery processes. © 2016 Society of Chemical Industry.
authors.affiliation: Food Engineering Department, Yeditepe University, Kayisdagi, Istanbul, Turkey.
authors.forename: Ilgin
authors.initials: I
authors.lastname: Paker
authors.affiliation: Animal and Nutritional Sciences, West Virginia University, Morgantown, WV, 26506-6108, USA.
authors.forename: Jacek
authors.initials: J
authors.lastname: Jaczynski
authors.affiliation: Animal and Nutritional Sciences, West Virginia University, Morgantown, WV, 26506-6108, USA.
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Matak
mesh_terms: D000818:Animals; D002126:Calcium Hydroxide / Q000737:chemistry*; D002136:Calcium, Dietary / Q000032:analysis; D011232:Chemical Precipitation; D004041:Dietary Fats / Q000032:analysis; D004044:Dietary Proteins / Q000737:chemistry / Q000302:isolation & purification*; D005396:Fish Products / Q000032:analysis*; D029941:Fish Proteins / Q000737:chemistry / Q000302:isolation & purification*; D005398:Fisheries; D005503:Food Additives / Q000737:chemistry*; D005511:Food Handling; D018857:Food Packaging; D061353:Food Storage; D006801:Humans; D006851:Hydrochloric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007059:Ictaluridae; D009753:Nutritive Value; D012972:Sodium Hydroxide / Q000737:chemistry; D012995:Solubility; D014618:Vacuum; D014903:West Virginia
chemical_list: D002136:Calcium, Dietary; D004041:Dietary Fats; D004044:Dietary Proteins; D029941:Fish Proteins; D005503:Food Additives; D012972:Sodium Hydroxide; D002126:Calcium Hydroxide; D006851:Hydrochloric Acid
keywords: calcium hydroxide; pH shift; protein recovery; protein solubility; sodium