Calcium hydroxide as a processing base in alkali‐aided pH ‐shift protein recovery process

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 ) 2 was used compared to NaOH during this process. Using Ca( OH ) 2 as 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 −1 protein using NaOH . Protein solubilized with Ca( OH ) 2 had more ( P < 0.05) calcium in the protein fraction, whereas using NaOH increased ( P < 0.05) sodium content. CONCLUSION Results of our study showed that protein solubility was increased and the recovered protein had significantly more calcium when Ca( OH ) 2 was used as the processing base. Results showed both NaOH and Ca( OH ) 2 to be an effective processing base for pH ‐shift protein recovery processes. © 2016 Society of Chemical Industry