Effects of Ultra-High Pressure Homogenization on Microbial and Physicochemical Shelf Life of Milk

Abstract

The effect of ultra-high pressure homogenization (UHPH) on microbial and physicochemical shelf life of milk during storage at 4 degrees C was studied and compared with a conventional heat preservation technology used in industry. Milk was standardized at 3.5% fat and was processed using a Stansted high-pressure homogenizer. High-pressure treatments applied were 100, 200, and 300 MPa (single stage) with a milk inlet temperature of 40 degrees C, and 200 and 300 MPa (single stage) with a milk inlet temperature of 30 degrees C. The UHPH-treated milks were compared with high-pasteurized milk (PA; 90 degrees C for 15 s). The microbiological quality was studied by enumerating total counts, psychrotropic bacteria, lactococci, lactobacilli, enterococci, coliforms, spores, and Pseudomonas. Physicochemical parameters assessed in milks were viscosity, color, pH, acidity, rate of creaming, particle size, and residual peroxidase and phosphatase activities. Immediately after treatment, UHPH was as efficient (99.99%) in reducing psychrotrophic, lactococci, and total bacteria as was the PA treatment, reaching reductions of 3.5 log cfu/mL. Coliforms, lactobacilli, and enterococci were eliminated. Microbial results of treated milks during storage at 4 degrees C showed that UHPH treatment produced milk with a microbial shelf life between 14 and 18 d, similar to that achieved for PA milk. The UHPH treatments reduced the L* value of treated milks and induced a reduction in viscosity values of milks treated at 200 MPa compared with PA milks; however, these differences would not be appreciated by consumers. In spite of the fat aggregates detected in milks treated at 300 MPa, no creaming was observed in any UHPH-treated milk. Hence, alternative methods such as UHPH may give new opportunities to develop fluid milk with an equivalent shelf life to that of PA milk in terms of microbial and physicochemical characteristics.

Characterization of Whey Protein Oil-In-Water Emulsions with Different Oil Concentrations Stabilized by Ultra-High Pressure Homogenization

“…Similar results have been obtained when applying the same homogenization pressures to soymilk or cow milk [27,30]. A previous study of the present authors showed that although pressures of up to 200 MPa were effective in decreasing the droplet size of emulsions with 4 g WPI/100 g (w/v) and 20 g/100 g of oil content, increasing the pressure to 300 MPa tended to increase the droplet size [23].…”

Vegetable milks and their fermented derivative products

“…3A) are aggregated, while in that which has been UHPH-treated (Fig 3A), not only are the fat globules non-aggregated but they are also distributed, forming a kind of network that enhances physical stability. Sometimes homogenization pressures are also capable of reducing the microbial load of the product prior to the thermal treatment, if they are greater than 200 MPa (N. Cruz et al, 2007;Pereda, Ferragut, Quevedo, Guamis, & Trujillo, 2007;ValenciaFlores et al, 2013). Despite the advantages, this emergent technology is being only used in a laboratory and pilot-scale due to the high investment costs.…”

High hydrostatic pressure technology in dairy processing: a review

“…Vegetative forms of yeasts and moulds are most pressure sensitive compared to their spores (Smelt 1998) and results in 99.99% of reduced activity of psychrotrophics, lactococci and total bacterial count (Pereda et al 2007) alongwith reduction in yeast and mould growth (Daryaei et al 2006). Vachon et al (2002) revealed that dynamic high pressure treatment inactivates 3 major food pathogens (Listeria monocytogenes LSD 105-1, Escherichia coli O157:H7 ATCC 35150 and Salmonella enteritidis ATCC 13047) present in milk.…”