The dairy industry faces an invisible but powerful challenge: bacteriophages, viruses that attack the lactic bacteria used in milk fermentation to produce yoghurt and cheese. These viruses can severely disrupt the acidification process of milk and curd, which is fundamental to creating high-quality dairy products.
Bacteriophages, or simply phages, are viruses that specifically infect lactic bacteria, transforming host cells and releasing new viral particles ready to infect other cells. This infection cycle interrupts the fermentation process, leading to insufficient acidification of the milk. The consequences include not only the risk of poor-quality products but also the proliferation of pathogenic microorganisms, compromising food safety.
How Bacteriophages Enter the Production Process
Bacteriophages can infiltrate dairy production through various sources:
- Raw Materials: Raw milk can be a primary source of phages if not adequately treated.
- Processing Environment: Unsanitised equipment and surfaces can harbour and spread phages.
- Starter Cultures: Starter cultures themselves can be attacked and contaminated by phages, especially if they are not rotated or if they include phage-sensitive strains.
Prevention and Control of Bacteriophage Infections
Preventing and controlling bacteriophage infections require rigorous, integrated measures:
- Strict Hygiene: Maintaining strict hygiene throughout the production process is crucial. Equipment, production lines, and the surrounding environment must be regularly sanitised to reduce the presence of phages.
- Heat Treatment: Heating the milk can inactivate many types of bacteriophages. However, some phages exhibit heat resistance, requiring the use of chemical biocides alongside heat to ensure their inactivation.
- Starter Culture Rotation: Regularly changing the starter cultures used in fermentation helps prevent phage adaptation and proliferation. This empirical method effectively reduces the incidence of phage infections.
- Phage-Resistant Strains: Modern molecular biology techniques enable the development of bacteriophage-resistant bacterial strains. These strains possess multiple resistances, although phages may eventually evolve to overcome these defences.
- Natural Whey Starters: In cheese production, such as Grana Padano, natural whey starters can mitigate the negative effects of bacteriophage infections. The spontaneous selection of resistant strains within the whey starter can maintain fermentative activity without significant impacts on production.
Impacts of Bacteriophage Infections on Dairy Products
Bacteriophages can lead to significant defects in dairy products, including:
- Texture and Consistency Defects: Insufficient acidification can result in cheeses with unsuitable textures and inconsistencies.
- Off-Flavours: The proliferation of undesirable bacteria can introduce unwanted flavours, compromising the cheese’s organoleptic profile.
By implementing effective preventative measures and leveraging advances in science, the dairy industry can mitigate the risks posed by bacteriophages and ensure the production of high-quality, safe products.
