Extending the shelf-life of dairy products by controlling spoilage microorganisms from farm to fork

The dairy industry is facing a quality problem due to the presence of certain bacteria capable of surviving the pasteurization process. This group of bacteria is called “sporeformers”, and they have the ability to affect the quality of dairy products during storage (i.e. fluid milk, cheeses) and limit their potential markets (i.e. milk powder). Since no current technology or interventions are readily available to control this group of bacteria, especially at farm level, the identification of their contamination routes is essential information to design potential interventions in order to control them.

 To address this issue, Dr. Andreia Bianchini and her research group¹ at The Food Processing Center/ Food Science and Technology Department at UNL, are trying to understand where these bacteria can be found around the farm and where they potentially enter the milk production chain. This research started five years ago, with three consecutive phases and one main objective of “improving the quality of dairy products”. Samples were collected from one farm at different sampling points including animal feed, manure, bedding material, drinking water, raw milk and cow teats, among others. After bacterial isolates were collected, identification was performed to determine the main sources of each type of bacteria using molecular approaches.

 To have a complete study “from farm to fork”, her group was also able to evaluate a fluid milk processing facility in Nebraska. They identified potential “problematic” bacteria (named Paenibacillus spp.) with the ability to grow under refrigeration conditions, producing quality defects in fluid milk and reducing its shelf-life. They also found the same bacterium type in raw milk, which indicated that the raw milk was actually one of the sources of this bacteria. Even though this bacteria is usually present in low numbers in raw milk, they are certainly part of the problem related to early spoilage of fluid milk. By controlling this bacteria, the shelf-life of fluid milk could be extended to 21 days, which could help the industry not only achieve longer distribution distances but also provide a better quality of fluid milk to consumers.

 However, after thoroughly evaluating this small size milk chain in Nebraska (one farm and one processing facility), Dr. Bianchini’s group was interested in learning more about the issue by exploring other farms and other processing facilities. Therefore, the scope of the study was expanded to include three additional dairy farms in Nebraska and one additional dairy processing facility (condensed milk plant). In this second phase, the main objectives were to evaluate the sporeforming bacteria population at different farms throughout the different seasons, and any variation due to different facilities. In this larger study the researchers focused on understanding those strains with the ability to either cause issues to the fluid milk industry (psychrotrophic strain) or those that could be carried through the milk powder production chain (all types of sporeformers). High levels of sporeformers in milk powder can definitely limit the market for this valuable dairy product. Better understanding these different groups of bacteria could help to design interventions to control them at early stages. This would allow the milk and dairy processors to better fulfill the required standards both locally and in the global market. This goal would benefit the whole dairy industry.

 This second phase of the research was just concluded this past May. The findings indicate that the environment around the milking parlor, more specifically the milking equipment and cow teats are the main sources of “problematic” strains. They also found that the bacteria population in the different farmers in Nebraska was quite similar to those described in other regions of the US. Thus, potential interventions may be effective across different regions of the United States. Based on all the information gained throughout the past years, Dr. Bianchini’s group is now evaluating potential interventions (i.e. different sanitation practices and bedding material) at the farm level to reduce the presence of sporeformers in the milk chain. The effectiveness of the proposed interventions will be tested starting summer 2016 through summer 2017. Multiple farms will be included in the project to provide reliable information, and part of this project will include a survey of current on farm practices applied in Nebraska. The ultimate goal of this current project is to provide guidelines for better practices at farm level to ensure low sporeformers counts in raw milk. Long term, Dr. Bianchini’s group expects that the results obtained from all this research will provide effective solutions for the food industry to ensure quality of their dairy products.

 ¹Research Team

Andreia Bianchini, PhD

Jayne Stratton, PhD (Co-Pi in the research projects)

Bismarck Martinez, PhD (post-doc)

Rhaisa Crespo, PhD Student working on the farm interventions