Effect of NaCl addition during diafiltration on the solubility, hydrophobicity, and disulfide bonds of 80% milk protein concentrate powder.
We investigated the surface hydrophobicity index based on different fluorescence probes [1-anilinonaphthalene-8-sulfonic acid (ANS) and 6-propionyl-2-(N,N-dimethylamino)-naphthalene (PRODAN)], free sulfhydryl and disulfide bond contents, and particle size of 80% milk protein concentrate (MPC80) powders prepared by adding various amounts of NaCl (0, 50, 100, and 150 mM) during the diafiltration process. The solubility of MPC80 powder was not strictly related to surface hydrophobicity. The MPC80 powder obtained by addition of 150 mM NaCl during diafiltration had the highest solubility but also the highest ANS-based surface hydrophobicity, the lowest PRODAN-based surface hydrophobicity, and the least aggregate formation. Intermolecular disulfide bonds caused by sulfhydryl-disulfide interchange reactions and hydrophobic interactions may be responsible for the lower solubility of the control MPC80 powder. The enhanced solubility of MPC80 powder with addition of NaCl during diafiltration may result from the modified surface hydrophobicity, the reduced intermolecular disulfide bonds, and the associated decrease in mean particle size. Addition of NaCl during the diafiltration process can modify the strength of hydrophobic interactions and sulfhydryl-disulfide interchange reactions and thereby affect protein aggregation and the solubility of MPC powders.
Key Laboratory of Functional Dairy of Beijing and Ministry of Education, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China.
X Y
XY
Mao
P S
PS
Tong
S
S
Gualco
S
S
Vink
D000818:Animals; D002417:Cattle; D003611:Dairy Products; D004220:Disulfides / Q000737:chemistry; D005374:Filtration / Q000379:methods; D005524:Food Technology; D057927:Hydrophobic and Hydrophilic Interactions / Q000187:drug effects; D008894:Milk Proteins / Q000737:chemistry*; D011208:Powders / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry / Q000494:pharmacology; D012995:Solubility / Q000187:drug effects
D004220:Disulfides; D008894:Milk Proteins; D011208:Powders; D012965:Sodium Chloride