title: Tuning the pH-shift protein-isolation method for maximum hemoglobin-removal from blood rich fish muscle.
abstract: A main challenge preventing optimal use of protein isolated from unconventional raw materials (e.g., small pelagic fish and fish by-products) using the pH-shift method is the difficulty to remove enough heme-pigments. Here, the distribution of hemoglobin (Hb) in the different fractions formed during pH-shift processing was studied using Hb-fortified cod mince. Process modifications, additives and prewashing were then investigated to further facilitate Hb-removal. The alkaline pH-shift process version could remove considerably more Hb (77%) compared to the acidic version (37%) when proteins were precipitated at pH 5.5; most Hb was removed during dewatering. Protein precipitation at pH 6.5 improved total Hb removal up to 91% and 74% during alkaline and acid processing, respectively. Adding phytic acid to the first supernatant of the alkaline process version yielded 93% Hb removal. Combining one prewash with phytic acid at pH 5.5 followed by alkaline/acid pH-shift processing increased Hb removal up to 96/92%.
authors.affiliation: Department of Biology and Biological Engineering-Food and Nutrition Science, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; Department of Seafood processing, Faculty of Marine Sciences, Tarbiat Modares University, P.O. Box 46414-356, Noor, Iran. Electronic address: abdollahi.mkh@gmail.com.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Abdollahi
authors.affiliation: Department of Biology and Biological Engineering-Food and Nutrition Science, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; Department of Plant Breeding, Swedish University of Agriculture, P.O. Box 101, SE 230 53 Alnarp, Sweden.
authors.forename: Sofia
authors.initials: S
authors.lastname: Marmon
authors.affiliation: Department of Biology and Biological Engineering-Food and Nutrition Science, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden; Department of Agro-Industry, School of Agricultural Technology, Walailak University, Thasala, Nakhon Si Thammarat 80161, Thailand.
authors.forename: Manat
authors.initials: M
authors.lastname: Chaijan
authors.affiliation: Department of Biology and Biological Engineering-Food and Nutrition Science, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Undeland
mesh_terms: D000818:Animals; D005396:Fish Products / Q000032:analysis*; D005399:Fishes / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009132:Muscles / Q000378:metabolism*
chemical_list: D006454:Hemoglobins
keywords: Acid; Alkaline; Fish; Heme proteins; Hemoglobin; pH-shift