Comparison of nanofiltration and evaporation technologies on the storage stability of milk protein concentrates

Abstract

Milk protein concentrates (MPCs) are highly nutritional and functional products manufactured from skim milk with low lactose levels. But, solubility of MPC decreases with time and temperature of storage, which often limits their application in food industries. The aim of present study is to compare the effect of nanofiltration and evaporation technologies on the rehydration stability of milk protein concentrates during storage. The MPCs produced by evaporation and nanofilteration were stored at different temperatures (25, 35, and 45°C) for a period of 24 weeks to observe any changes in the storage stability. The results showed that at a given storage temperature, the rehydration properties, such as solubility, viscosity, turbidity, and particle size of the nanofiltered milk protein concentrate (NF-MPC) were better compared to the same properties of the evaporated milk protein concentrate (EP-MPC). In addition, the contents of soluble protein, calcium, phosphorus, and magnesium of NF-MPC were higher than that of EP-MPC. However, no significant differences were observed in the contents of soluble lactose, sodium, and potassium of EP-MPC and NF-MPC during storage. The insoluble materials of MPC were mainly Dairy Sci. & Technol. (2016)

Effect of gelling temperature and calcium chloride concentration on rheological and microstructural properties of acid‐induced gels of milk protein concentrates

“…In addition, denatured whey proteins can be bridges between casein micelles, thus increasing the number of protein‐protein interactions. The effect of ionic content on the difference in gel properties is negligible because soluble protein, calcium, phosphorus, and magnesium are present in equal amounts in NF‐MPC and EP‐MPC (Table ) (Cao et al, ). After EP‐MPC and NF‐MPC reached the gel point, the tan δ values first increased and then decreased; the maximum tan δ was observed when MPCs were gelled at different temperatures, at which point protein–protein bonds and strands in the gel were apt to relax, resulting in a greater rearrangement of both inter‐ and intramolecular forces in the gel.…”

“…Larger micelles cause an increased number of bonds and junction zones between the casein particles. In addition, denatured whey proteins can be bridges between casein micelles, thus increasing the number of (Cao et al, 2016). After EP-MPC and NF-MPC reached the gel point, the tan δ values first increased and then decreased; the maximum tan δ was observed when MPCs were gelled at different temperatures, at which point protein-protein bonds and strands in the gel were apt to relax, resulting in a greater rearrangement of both inter-and intramolecular forces in the gel.…”

“…Evaporation is the traditional process of concentrating MPC, however, the downside of this process is that it could cause an undesired denaturation of milk proteins due to the high temperatures that are required. In order to minimize this adverse effect, MPC has more recently been produced using an alternative process called nanofiltration, which ensures less denaturation and enhanced solubility of proteins (Cao, Wang, et al, ; Cao, Zhang, et al, ). Nanofiltration is an innovative membrane separation technique that is now commonly applied to milk concentrations in the dairy industry.…”

“…A pressure‐driven membrane technology, the process is intermediate between ultrafiltration and reverse osmosis, and is known to be highly efficient in retarding organic compounds with a high molecular weight, such as lactose or protein (Pan, Song, Wang, & Cao, ). Recent reports have noted that nanofiltration improves the solubility and even the storage stability of MPC products (Cao et al, ; Cao, Zhang, et al, ), because compared with skim milk, casein micelles aggregated compactly after evaporation, while surface hydrophobicity increased and free sulfhydryl content decreased in evaporated milk. However, the microstructure of the casein micelles was relatively undisturbed after nanofiltration, with surface hydrophobicity and free sulfhydryl content reduced.…”

Milk protein concentrates: opportunities and challenges

“…Rajagopalan and Cheryan (1991) suggested the use of microfiltration process for the complete removal of milk fat to produce MPCs and MPIs with excellent functional properties. Cao et al (2016) reported use of pasteurized skim milk (85°C/15 s) followed by UF and conventional evaporation. Li and Corredig (2014) heated the UF/DF retentates up to 80°C/ 15 min for the first time to study the effect of pH as well as heat treatment on calcium release during acidification process and buffering capacity.…”