Effects of UV Irradiation in a Continuous Turbulent Flow UV Reactor on Microbiological and Sensory Characteristics of Cow's Milk

Abstract

The dairy industry under current pasteurization conditions (15 s at 72°C) and sanitary standards achieves a safe product with excellent quality. In an ever-competitive market there is still a need to improve product quality and extend shelf life of dairy products to increase competitiveness and open up new markets. In an attempt to test the effect of UV irradiation on microbiota of fluid milk, a continuous flow UV system at 254 nm was used to treat 3.5 and 2% fat milk at two UV doses (880 and 1,760 J liter(-1)). Milk was obtained from three processors, and two lots from each processor were assessed. To assess the impact on the most descriptive native microbiota in pasteurized milk after UV illumination, the product was held at two storage temperatures (4 and 7°C) and tested weekly for 5 weeks for aerobic plate counts (psychrotrophic and mesophilic bacteria), laboratory pasteurization counts, aerobic sporeformers, coliform organisms, and titratable acidity. Microbial counts for all tested microorganisms were lower in UV-treated milk when compared with control throughout storage at 4 and 7°C in both 3.5 and 2% fat milk. Sensory analysis indicated that there is a sensory defect associated with UV treatment at the wavelength used.

Efficacy of Ultraviolet (UV-C) Light in a Thin-Film Turbulent Flow for the Reduction of Milkborne Pathogens

“…Fatty acid hydrolysis leads to rancidity. Sensory analysis in Rossitto et al (2012) demonstrated that UV-C treatment of pasteurized cow's milk at 880 and 1760 J/L could be distinguished from untreated milk in a triangle test for difference. Matak et al (2007) reported some panelists used aroma descriptors of ''barnyard'' and ''goaty'' for raw goat milk treated with 16 J/cm 2 for 18 s. Cilliers et al (2014) reported a ''tallowy'' descriptor of aroma and flavor of raw cow's milk treated with a UV-C dose of 1045 J/L.…”

“…UV treatment of milk, in its initial phases of industrial implementation, could be used as an adjunct to thermal pasteurization at the point of bottling to eliminate any microorganisms that survived heat treatment and postpasteurization growth that might occur. UV-C treatment postpasteurization has been shown to increase shelf life of fluid 2%-fat and 4%-fat milk from 7 to 35 days (Rossitto et al, 2012). Utilization of UV treatment as a replacement to thermal pasteurization still has many regulatory steps to address regarding its application, but if utilized would be a green technology with significant energy savings.…”

“…Thermal pasteurization used to make milk safe for consumption has associated with it high energy costs, can denature proteins, and has associated issues with flavor degradation. Many nonthermal technologies, such as the germicidal portion of ultraviolet light (UV-C) ranging from 200 to 280 nm, are now being investigated as an alternative to thermal treatment of milk to inactivate pathogens and improve shelf life (Bintsis et al, 2000;Sastry et al, 2000;Smith et al, 2002;Sudhirk, 2004;Matak et al, 2005;Krishnamurthy et al, 2007;van Wyk and Gouws, 2011;Rossitto et al, 2012). UV technology has the advantage of being chemical free, producing less waste, and being more energy efficient than the traditional thermal pasteurization process.…”

Chemical characterization of milk after treatment with thermal (HTST and UHT) and nonthermal (turbulent flow ultraviolet) processing technologies

“…Recent technology developments involving continuous turbulent flow UV processing have enabled UV to be used in conjunction with pasteurization as a posttreatment method for milk, with the result that the shelf life of milk could be increased by at least 30% (Rossitto et al, 2012;Koutchma and Barnes, 2013). In laboratory studies conducted at the University of California-Davis (Rossitto et al, 2012) on milk with 3.5 and 2% fat at UV doses of 880 and 1,760 J/L, continuous turbulent flow UV processing has been shown to be effective against milk microflora and capable increasing milk shelf life to 28 to 35 d. Microbial counts for all tested microorganisms were lower in UV-treated milk compared with control milk throughout storage at 4 and 7°C in both 3.5 and 2% fat milk (Rossitto et al, 2012). A reduction in pathogenic organisms such as E. coli O157:H7, Listeria monocytogenes, Salmonella senftenberg, Yersinia enterocolitica, and Staphylococcus aureus has been achieved and help to ensure the safety of milk using UV processing (Cullor, 2011, Crook et al, 2015.…”

Ultraviolet-C Irradiation: A Novel Pasteurization Method for Donor Human Milk

“…Milk is difficult to treat with UV-C due to its high absorption coefficient of 300 cm −1 at a wavelength of 254 nm compared to the absorption coefficients of drinking water and beer with 0.1 and 20 cm −1 , respectively [21]. Previous studies showed that UV-C irradiation can be used to successfully reduce the microbial load of opaque liquids such as bovine milk and various fruit juices without affecting sensory quality, however no measurement was made on the bioactivity of milk [25]–[27]. A turbulent flow around a UV-C source was created and this therefore exposed the micro-organisms to photons at the interface between the opaque liquid and the photon source.…”