Application of microfiltration in process cheese spread and whey protein concentrate manufacture.

摘要

Application of microfiltered (MF) milk for Process cheese spread (PCS) and whey protein concentrate (WPC) manufacture was investigated. Microfiltered milk retentate was used for PCS manufacture and permeate was utilized for WPC manufacture. Microfiltration of raw skim milk (0.2% fat) resulted in two fractions casein was concentrated in microfiltered milk retentate (MFR), and microfiltered milk permeate (MWP) which included whey proteins, was practically casein-free. The MFR was ultrafiltered (UF) to approximately 1.3X and the resulting concentrate (MFC) was used for Process cheese manufacture. To develop cheese base with 'Swiss cheese like' flavor, MFC was fermented with thermophilic lactic acid bacteria (Lb. bulgaricus and St. thermophilus) along with propionic acid bacteria (P. shermanii). 'Swiss cheese like' flavor was perceptible in the fermentate after 5 days of incubation, but the flavor was very mild to be perceived in Process cheese. Process cheese spread were therefore formulated with flavor concentrates. Milk protein concentrate (MPC) 70, because of its higher protein and lower lactose, was used to fortify solids in PCS formulations with higher MFC. Three treatments and a control (C) were formulated such that the ratio of natural Swiss cheese:MFC was 2:3 (T1), 1:3 (T2), no natural cheese (T3), and C from only natural cheese (3 replicates). With an increase in the amount of MFC, mineral content increased while protein content and spreadability decreased. Spreadability of C and T1 was significantly higher than that of T2 and T3 after 2.5 and 5 min. There was a decrease in viscosity with an increase in the amount of MFC in the formulation possibly because of overcreaming in PCS with natural cheese. Viscosity of C, T1, T2, and T3 was 0.73, 0.68, 0.67, and 0.63 Pa s, respectively. Relatively lower dependence of viscoelastic moduli on frequency of T1 and T2 than that of C and T3 suggested a poor interaction between the protein from natural cheese and MFC. Partial replacement of natural Swiss cheese with MFC improved sensory properties of PCS. Overall flavor, body and texture, appearance, and acceptability scores of T1 (7.2, 7.4, 7.8, and 7.4, respectively) were higher than those of the control (6.2, 6.3, 7.5, and 6.2, respectively). Scores of control and T2 were not significantly different. All the scores of T3 were significantly lower than those of other treatments. In a separate study, MWP was UF and then spray dried to milk whey protein concentrate (MWPC). Clarified and pasteurized Cheddar cheese whey was either directly UF or first MF and then UF before spray drying to produce conventional whey protein concentrate (CWPC) or microfiltered conventional whey protein concentrate (DWPC), respectively. None of the streams for MWPC manufacture were ever pasteurized. The UF concentration factor was 10X for MWPC (4 replicates) and 8X for CWPC and DWPC (3 replicates). The MWPC products therefore had higher protein content (48.7%) than CWPC and DWPC (34.8 and 37.2%, respectively). All three products were compared for native protein and functional properties (gelation, emulsion stability, and foam overrun and foam stability). Native protein measured as protein precipitable at pH 4.6 was lower in MWPC (82.5%) than in CWPC (92.8%) and DWPC (95.6%). Gelation, measured as least concentration endpoint (LCE), was affected by the source of whey. Gel formation in CWPC and DWPC occurred at 6.3 and 6.2% protein, respectively, which was significantly lower than that of MPWC (7.1%). Emulsion stability (ES) of product produced with MF (MWPC and DWPC) was lower (1.6 and 1.3%, respectively) than that produced without MF (CWPC), 5.4%. Microfiltration of whey source resulted in 'turbidity-free' WPC solution. Foam overrun of DWPC was greater than that of MWPC (1059.7 and 952.7%, respectively) but the foam stability of MWPC was higher than that of DWPC. Thus, WPC resulting from MF of whey source exhibits functional properties that are very different from those produced by the conventional method. Microfiltration therefore can be successfully employed for developing new dairy ingredients and expanding their use in the food industry.