Microbiological quality of milk from farms to milk powder manufacture: an industrial case study
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Accepted version
Date
2019-06-03
Authors
Paludetti, Lizandra F.
Kelly, Alan L.
O'Brien, Bernadette
Jordan, Kieran
Gleeson, David
Journal Title
Journal ISSN
Volume Title
Publisher
Cambridge University Press (CUP)
Published Version
Abstract
The experiments reported in this research paper aimed to track the microbiological load of milk throughout a low-heat skim milk powder (SMP) manufacturing process, from farm bulk tanks to final powder, during mid- and late-lactation (spring and winter, respectively). In the milk powder processing plant studied, low-heat SMP was produced using only the milk supplied by the farms involved in this study. Samples of milk were collected from farm bulk tanks (mid-lactation: 67 farms; late-lactation: 150 farms), collection tankers (CTs), whole milk silo (WMS), skim milk silo (SMS), cream silo (CS) and final SMP. During mid-lactation, the raw milk produced on-farm and transported by the CTs had better microbiological quality than the late-lactation raw milk (e.g., total bacterial count (TBC): 3.60 ± 0.55 and 4.37 ± 0.62 log 10 cfu/ml, respectively). After pasteurisation, reductions in TBC, psychrotrophic (PBC) and proteolytic (PROT) bacterial counts were of lower magnitude in late-lactation than in mid-lactation milk, while thermoduric (LPC—laboratory pasteurisation count) and thermophilic (THERM) bacterial counts were not reduced in both periods. The microbiological quality of the SMP produced was better when using mid-lactation than late-lactation milk (e.g., TBC: 2.36 ± 0.09 and 3.55 ± 0.13 cfu/g, respectively), as mid-lactation raw milk had better quality than late-lactation milk. The bacterial counts of some CTs and of the WMS samples were higher than the upper confidence limit predicted using the bacterial counts measured in the farm milk samples, indicating that the transport conditions or cleaning protocols could have influenced the microbiological load. Therefore, during the different production seasons, appropriate cow management and hygiene practices (on-farm and within the factory) are necessary to control the numbers of different bacterial groups in milk, as those can influence the effectiveness of thermal treatments and consequently affect final product quality.
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Keywords
Lactation period , Milk microbiological quality , Milk powder quality , Milk processing
Citation
Paludetti, L. F., Kelly, A. L., O'Brien, B., Jordan, K. and Gleeson, D. (2019) 'Microbiological quality of milk from farms to milk powder manufacture: an industrial case study', Journal of Dairy Research, 86(2), pp. 242-247. doi: 10.1017/S0022029919000347
Copyright
© Hannah Dairy Research Foundation 2019. Published by Cambridge University Press. This article has been published in a revised form in Journal of Dairy Research, http://dx.doi.org/10.1017/S0022029919000347 . This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works.