Effect of partial whey protein depletion during membrane filtration on thermal stability of milk concentrates

Abstract

Membrane filtration technologies are widespread unit operations in the dairy industry, often employed to obtain ingredients with tailored processing functionalities. The objective of this work was to better understand the effect of partial removal of whey proteins by microfiltration (MF) on the heat stability of the fresh concentrates. The micellar casein concentrates were compared with control concentrates obtained using ultrafiltration (UF). Pasteurized milk was microfiltered (80 kDa polysulfone membrane) or ultrafiltered (30 kDa cellulose membrane) without diafiltration (i.e., no addition of water) to 2× and 4× concentration, based on volume reduction. The final concentrates showed no differences in pH, casein micelle size, or mineral concentration in the serum phase. The micellar casein retentates (obtained by MF) showed a 20 and 40% decrease in whey protein concentration compared with the corresponding UF milk protein concentrates for 2× and 4× concentration, respectively. The heat coagulation time decreased with increasing protein concentration, regardless of the treatment; however, MF retentates showed a higher thermal stability than the corresponding UF controls. The average diameter for casein micelles increased after heating in UF but not MF concentrates. The turbidity (measured by light scattering) increased after heating, but to a higher extent for UF retentates than for MF retentates at the same protein concentration. It was concluded that the reduced amount of whey protein in the MF retentates caused a significant increase in the heat stability compared with the corresponding UF retentates. This difference was not due to ionic composition differences or pH, but to the type and amount of complexes formed in the serum phase.

A comparison of the heat stability of fresh milk protein concentrates obtained by microfiltration, ultrafiltration and diafiltration

“…Recent studies demonstrated that there are profound differences in heat stability between MF and UF concentrates, the latter containing a higher concentration of whey proteins (Renhe and Corredig, 2018). The removal of whey proteins increases the heat stability, when the concentrates are compared at the same concentration factor and under comparable serum composition (Renhe and Corredig, 2018). The processing history of the retentates is therefore critical to their stability.…”

Diafiltration affects the gelation properties of concentrated casein micelle suspensions obtained by filtration

“…The protein composition of the serum phase was determined using RP-HPLC (Renhe and Corredig, 2018). Centrifugal supernatant (400 μl) was dissolved in 1600 μl guanidine buffer, which contains 21.5 m m sodium citrate, 6 m guanidine hydrochloride, 19.5 m m dithiothreitol, and 0.1 m BisTris buffer (pH 7.0) (Bonfatti et al ., 2008).…”

Integrated Continuous Bioprocess Development for ACE-Inhibitory Peptide Production by Lactobacillus helveticus Strains in Membrane Bioreactor

“…This clearly indicates a phenomenon of peptide retention by the microfiltration membrane during the process. Retention of non-casein nitrogen during milk microfiltration was observed previously (Boiani et al, 2017;Renhe and Corredig, 2018) probably due to interactions with caseins and calciumphosphate clusters (Cross et al, 2005). Peptide productivities of the different processes (batch, continuous in CBR and in MBR) used in this study were compared ( Table 3).…”