The effects of microfluidization on the physical, microbial, chemical, and coagulation properties of milk

Abstract

This work examines the use of mild heat treatments in conjunction with 2-pass microfluidization to generate cheese milk for potential use in soft cheeses, such as Queso Fresco. Raw, thermized, and high temperature, short time pasteurized milk samples, standardized to the 3% (wt/wt) fat content used in cheesemaking, were processed at 4 inlet temperature and pressure conditions: 42°C/75 MPa, 42°C/125 MPa, 54°C/125 MPa, and 54°C/170 MPa. Processing-induced changes in the physical, chemical, and microbial properties resulting from the intense pressure, shear, and cavitation that milk experiences as it is microfluidized were compared with nonmicrofluidized controls. A pressure-dependent increase in exit temperature was observed for all microfluidized samples, with inactivation of alkaline phosphatase in raw and thermized samples at 125 and 170 MPa. Microfluidization of all samples under the 4 inlet temperature and processing pressure conditions resulted in a stable emulsion of fat droplets ranging from 0.390 to 0.501 μm, compared with 7.921 (control) and 4.127 (homogenized control) μm. Confocal imaging showed coalescence of scattered fat agglomerates 1 to 3 μm in size during the first 24 h. We found no changes in fat, lactose, ash content or pH, indicating the major components of milk remained unaffected by microfluidization. However, the apparent protein content was reduced from 3.1 to 2.2%, likely a result of near infrared spectroscopy improperly identifying the micellar fragments embedded into the fat droplets. Microbiology results indicated a decrease in mesophilic aerobic and psychrophilic milk microflora with increasing temperature and pressure, suggesting that microfluidization may eliminate bacteria. The viscosities of milk samples were similar but tended to be higher after treatment at 54°C and 125 or 170 MPa. These samples exhibited the longest coagulation times and the weakest gel firmness, indicating that formation of the casein matrix, a critical step in the production of cheese, was affected. Low temperature and pressure (42°C/75 MPa) exhibited similar coagulation properties to controls. The results suggest that microfluidization at lower pressures may be used to manufacture high-moisture cheese with altered texture whereas higher pressures may result in novel dairy ingredients.

Microstructure of a Model Fresh Cheese and Bioaccessibility of Vitamin D3 Using In Vitro Digestion

“…Although no statistical significance was found, there were visible differences between samples’ curd formation at lowest and highest homogenization pressures. When processed at higher pressures (150 MPa), a shattered curd was observed as described in other studies where weak milk gels have been formed when using microfluidization at 170 MPa [27], however further processing factors such as pressing might have minimized the effect of homogenization pressure on textural properties.…”

Effect of high‐energy emulsification on properties of commercial low‐temperature pasteurised milk

“…Bucci et al . () reported that microfluidisation (125 and 170 MPa) effectively decreases fat droplet size below 0.5 μm compared to control droplets (7.921 μm) in a pressure‐dependent manner. Jafari et al .…”

“…It appears that high-pressure homogenisation was effective at improving particle uniformly and especially at decreasing fat globule size. Bucci et al (2018) reported that microfluidisation (125 and 170 MPa) effectively decreases fat droplet size below 0.5 lm compared to control droplets (7.921 lm) in a pressure-dependent manner. Jafari et al (2007) reported that microfluidisation treatment creates the smallest particles and results in a mono-distribution compared to particle size distributions for general homogenisation, ultrasonication and microfluidisation treatments; the results presented in Figure 2 show similar behaviour.…”

Applications of Microfluidization and High Pressure Processing in Food Industry and the Effect of Them on Food Products

“…But, when the temperature of the heat treatment increases, changes may occur in the dairy product quality related to color, flavor, and protein stability [24]. Therefore, High pressure processing could be considered as an alternative mechanism to produce high-quality, safe, dairy products by eliminating pathogens and reducing spoilage micro flora [25]. High-pressure processing can be operated as a batch or continuous process.…”