Effect of sodium chloride addition during diafiltration on the solubility of milk protein concentrate

Abstract

There is considerable interest among food manufacturers to incorporate protein into food products in both developed and developing countries. Dairy proteins are excellent choices for many different applications, as they are known to have several nutritional and functional benefits. Membrane filtration techniques are often utilized as the preferred method of fractionation, due to the high throughput and continuous nature of the process. One such product produced from membrane filtration of skim milk is called milk protein concentrate. This product is valued for its high protein content, but it has historically exhibited poor solubility when reconstituted into water, which severely restricts the food applications for which it is suitable. There is some existing evidence that milk protein concentrates which contain elevated levels of sodium exhibit higher solubility upon reconstitution into water. The main objective of this thesis project was to demonstrate the effect of sodium chloride, added to diafiltration water utilized during the manufacturing process, on the solubility of milk protein concentrate.It was observed that the addition of sodium chloride into diafiltration water at levels of 50 mM, 100 mM, and 150 mM had a beneficial effect on the solubility of milk protein concentrate across a variety of reconstitution conditions. For example, when milk protein concentrate was mixed for 1 h on a stage mixer at 23 °C ± 1 °C, a significant increase (p < 0.001) in mean solubility was observed when at least 50 mM NaCl had been incorporated into DF water. The incorporation of 50 mM NaCl into DF water v significantly increased (p < 0.001) the mean solubility of milk protein concentrate from 59.81 % to between 64.34 % and 71.78 %. The addition of 100 mM NaCl significantly increased (p < 0.001) the solubility to between 88.80 % and 96.24 %, and the addition of 150 mM NaCl significantly increased (p = 0.005) the solubility to between 92.79 % and 100 %.Minerals analysis of dry powders revealed a significant increase (p < 0.001) in levels of sodium. The addition of 50 mM NaCl into DF water was associated with a significant increase (p < 0.001) in powder Na content to between 2.48 mg/g and 7.44 mg/g. The addition of 100 mM NaCl into DF water was associated with a significant increase (p = 0.002) in powder Na content to between 5.80 mg /g and 10.75 mg/g, and the addition of 150 mM NaCl into DF water was associated with a significant increase (p = 0.001) in powder Na content to between 9.57 mg/g and 14.53 mg/g. A significant difference (p < 0.001) in magnesium level was also detected. Differences in calcium content were not found to be statistically significant (p = 0.016) at α = 0.01.Preliminary observations of milk protein concentrate upon reconstitution were made using a confocal laser scanning microscopy method. This method showed evidence of possible differences in powder particle rehydration and affinity for lipid association between powder particles manufactured at different treatment levels. As the level of NaCl incorp...

Functional Characteristics of Milk Protein Concentrates and Their Modification

“…It would therefore appear that minerals affect the protein aggregation and hence the solubility. This was also in agreement to other findings by Gualco (2010) and Havea (2006). Even after production, salts addition would definitely affect solubility as Hussein et al (2011) found out that total rehydration time in native micellar casein was reduced from 467 min to about 217 min and 187 min when NaCl (12% concentration) and CaCl 2 (2.25% concentration) were added, respectively.…”

Effect of adding salt during the diafiltration step of milk protein concentrate powder manufacture on mineral and soluble protein composition

“…MPC80 powders were manufactured as described by Gualco (2010). Pasteurized skim milk (140 kg) was ultrafiltered by using a model R12 cross flow membrane recirculatory pilot plant unit (Niro Inc, Hudson, WI, USA) equipped with dual 10 kDa cut-off spiral-wound polyethersulfone membranes (Snyder Filtration, Vacaville, CA, USA).…”

Effect of NaCl addition during diafiltration on the solubility, hydrophobicity, and disulfide bonds of 80% milk protein concentrate powder

“…Replacement of approximately 30% of the calcium of the ultrafiltered skim milk retentate by sodium ions can result in a MPC80 powder with little insoluble material, because removal of calcium ions increases the electrostatic repulsive forces between the casein micelles, to improve hydration properties of MPC80 powder (Havea, 2006). Compared with that of MPC80 powder made without addition of NaCl, the solubility of MPC80 powder produced with NaCl addition during diafiltration increases significantly (Gualco, 2010). The mechanism behind this effect needs further elaboration.…”