A 100-Year Review: Microbiology and safety of milk handling

Abstract

Microbes that may be present in milk can include pathogens, spoilage organisms, organisms that may be conditionally beneficial (e.g., lactic acid bacteria), and those that have not been linked to either beneficial or detrimental effects on product quality or human health. Although milk can contain a full range of organisms classified as microbes (i.e., bacteria, viruses, fungi, and protozoans), with few exceptions (e.g., phages that affect fermentations, fungal spoilage organisms, and, to a lesser extent, the protozoan pathogens Cryptosporidium and Giardia) dairy microbiology to date has focused predominantly on bacteria. Between 1917 and 2017, our understanding of the microbes present in milk and the tools available for studying those microbes have changed dramatically. Improved microbiological tools have enabled enhanced detection of known microbes in milk and dairy products and have facilitated better identification of pathogens and spoilage organisms that were not known or well recognized in the early 20th century. Starting before 1917, gradual introduction and refinement of pasteurization methods throughout the United States and many other parts of the world have improved the safety and quality of milk and dairy products. In parallel to pasteurization, others strategies for reducing microbial contamination throughout the dairy chain (e.g., improved dairy herd health, raw milk tests, clean-in-place technologies) also played an important role in improving microbial milk quality and safety. Despite tremendous advances in reducing microbial food safety hazards and spoilage issues, the dairy industry still faces important challenges, including but not limited to the need for improved science-based strategies for safety of raw milk cheeses, control of postprocessing contamination, and control of sporeforming pathogens and spoilage organisms.

Role of Bacillus species in biofilm persistence and emerging antibiofilm strategies in the dairy industry

“…Despite advances in food preservation techniques, bacterial spoilage remains a leading cause of global food loss . Nearly one‐third of all food produced worldwide is estimated to be lost postharvest, and much of this loss can be attributed to microbial spoilage .…”

“…The microbial quality of raw milk is crucial for the production of quality dairy products . Bacterial contamination can affect the quality, functionality, and safety of milk and its derivatives adversely . Globally, the dairy industry produces a wide range of perishable (milk and cream) and semi‐perishable foods (cheese, butter, and yogurt) as well as food ingredients (milk powders, whey protein concentrates and caseinates) .…”

“…The environmental conditions in the modern dairy industry represent a perplexing challenge for the survival of bacterial species, due, for instance, to milk pasteurization, refrigerated storage temperatures, and aggressive cleaning procedures . Nevertheless, as mentioned above, a high prevalence of Bacillus species in the form of biofilms is reported for the dairy environment .…”

“…Bacteria in milk can lead to spoilage and / or health risks, so milk manufacturing is subject to extremely stringent regulations . Moreover, as the removal of biofilm cells from surfaces can be very challenging, the best strategy to eradicate bacterial biofilms from dairy‐related environments would be preventing their formation.…”

“…Despite advances in food preservation techniques, bacterial spoilage remains a leading cause of global food loss. 22,23 Nearly onethird of all food produced worldwide is estimated to be lost postharvest, and much of this loss can be attributed to microbial spoilage. 24 Dairy products constitute one of the leading sectors affected by food loss, as nearly 20% of conventionally pasteurized fluid milk is discarded before consumption each year.…”