Meike Samtlebe

Review: elimination of bacteriophages in whey and whey products

Asthecheesemarketfacesstronginternationalcompetition,theoptimizationofproductionprocesses becomes more important for the economic success of dairy companies. Indairy productions, whey from former cheese batches is frequently re-used to increasethe yield, to improve the texture and to increase the nutrient value of the final product.Recycling of whey cream and particulated whey proteins is also routinely performed.Most bacteriophages, however, survive pasteurization and may re-enter the cheesemanufacturing process. There is a risk that phages multiply to high numbers during theproduction. Contamination of whey samples with bacteriophages may cause problems incheese factories because whey separation often leads to aerosol-borne phages and thuscontamination of the factory environment. Furthermore, whey cream or whey proteinsused for recycling into cheese matrices may contain thermo-resistant phages. Drainedcheese whey can be contaminated with phages as high as 10

Whey powders are a rich source and excellent storage matrix for dairy bacteriophages

Thirteen whey powders and 5 whey powder formulations were screened for the presence of dairy bacteriophages using a representative set of 8 acid-producing Lactococcus lactis and 5 Streptococcus thermophilus, and 8 flavour-producing Leuconostoc pseudomesenteroides and Leuconostoc mesenteroides strains. Lytic L. lactis phages were detected in all samples, while S. thermophilus and Leuconostoc phages were present in 50% or 40% of the samples, respectively. Maximal phage titers were 6×107 plaque-forming units (pfu)/g of whey powder for L. lactis phages, 1×107pfu/g for Leuconostoc phages and 1×105pfu/g for S. thermophilus phages. In total, 55 phages were isolated and characterized. Thirty one of the 33 lactococcal phages tested belonged to the wide-spread 936 phage group. In the course of this study, a PCR detection method for Leuconostoc phages (Ali et al., 2013) was adapted to new phage isolates. Furthermore, a remarkably high stability of phages in whey powder samples was documented during a long-term storage period of 4 years.