Ensuring Milk Safety: From Farm to Plant Hygiene

Ensuring the cleanliness and safety of milk from farm to processing plant involves meticulous procedures to minimize bacterial contamination. While some bacteria reside naturally in a cow's udder, they typically do not pose a significant risk unless the udder is infected. The main sources of microbial contamination in milk production extend beyond the udder to include the cow's body, milking equipment, barn air, and even the personnel involved in milking.

To mitigate bacterial presence in raw milk, stringent measures are crucial. Prior to milking, cows undergo thorough washing and sanitization of their flanks, udders, and teats. Large dairy farms often employ dedicated wash pens for this purpose. Milking equipment and utensils must be meticulously cleaned and disinfected using methods such as steam or chlorine solutions, ensuring a chlorine concentration of approximately 200 ppm for effective sanitation.

Upon collection, bulk milk tanks are subjected to rigorous cleaning processes. Manual cleaning involves washing with hot water and detergent, followed by sanitization using chlorine solutions. Alternatively, mechanical cleaning at higher temperatures enhances effectiveness, followed by the same chlorine sanitation protocol. Manual cleaning of tank outlets and exteriors is also essential to prevent external contamination.

Advanced cleaning techniques like Cleaning in Place (CIP) further streamline hygiene procedures. CIP systems utilize vacuum or pressure to automate cleaning, sanitizing, and rinsing of pipelines and bulk milk tanks, ensuring thorough sanitation without disassembly.

In summary, safeguarding milk quality hinges on comprehensive hygiene practices throughout the milk production and processing chain. By addressing potential sources of microbial contamination—from the cow's udder to milking equipment and storage tanks—producers uphold stringent standards that preserve the safety and integrity of milk destined for consumer consumption. These protocols not only adhere to regulatory requirements but also uphold consumer confidence in the quality and safety of dairy products.
Ensuring Milk Safety: From Farm to Plant Hygiene

The Impact of Thermoduric Bacteria on Milk Quality

Thermoduric bacteria play a crucial role in determining the hygiene quality of milk due to their ability to withstand pasteurization temperatures. These heat-resistant organisms, including spore-forming Bacillus cereus, survive the dairy farming environment and enter milk primarily during the milking process, often through cow teats tainted with soil, bedding, or feces.

Their survival through pasteurization can significantly impact milk quality. Despite common knowledge of spore-forming bacteria like Bacillus cereus, newer studies highlight non-spore-forming strains such as Streptococcus spp., Enterococcus spp., and Lactobacillus spp., with surprisingly high heat tolerance of up to 60–80 °C. This resilience leads to increased concerns during milk processing, where compromised milk residues or poorly managed silage inadvertently encourage thermoduric growth.

The challenge escalates as these bacteria contribute significantly to the aerobic plate count (APC) in pasteurized milk. Product manufacture can face hindrances due to these resilient organisms, potentially leading to product quality issues in the final dairy products.

Even more concerning is the adaptability of certain thermoduric strains to grow at refrigeration temperatures, posing additional obstacles to dairy farmers and processors. The proliferation of these bacteria isn't solely a concern for food safety and processing; it also ties into broader agricultural practices, such as rubberware management and silage quality control.

To mitigate the risks posed by thermoduric bacteria, it's crucial for dairy farms and processors to implement rigorous hygiene protocols, focusing on preventative measures like equipment sterilization, effective waste management, and ensuring optimal silage conditions. By prioritizing these strategies, the dairy industry can safeguard milk quality and maintain consumer confidence in dairy products.
The Impact of Thermoduric Bacteria on Milk Quality

Bacterial contamination of raw milk: Sources and factors

The dairy products industry is going toward safe milk and its products in the food market. Milk quality and food safety concern in the consumers’ health and nutrition in public health surveillance prevent food-borne diseases, food poisoning, and zoonosis risk by raw milk and fresh dairy products. The consumption of pathogen containing products may cause illnesses ranging from upset stomach to more serious symptoms (e.g., diarrhea, fever, vomiting, and so on.

Researches showed that, the number and types of microorganisms in milk immediately after milking are affected from different factors which include:
*poor hygienic condition of the milking environment,
*absence of cooling system,
*poor sanitary condition of the milk containers,
*poor udder and teats cleaning practice,
*failure of washing and drying cow’s udder,
*the absence of usage of detergent for cleaning vending environments, and
*the poor personal hygiene of the milkers.

Additionally, condition of storage, manner of transport, use of plastic containers for milk collection, mixing of milk obtained from different cows and the presence of further contamination at the milk selling sites.

Raw milk can often be contaminated with pathogens, either directly through organisms shed as a result of udder infection or indirectly. Indirect contamination may arise from:
*a cow’s own faecal matter contaminating the udder and teats,
*faecal matter of other cows contaminating the udder
*milking clusters contacting surfaces with faecal contamination, and
*post-harvest environmental contamination.

Bacterial contamination of raw milk can originate from distinct or different sources: air, milking system, feed, soil and, skin or hair of the animals or utensils.

Once it is secreted from the udder, milk can easily be contaminated by spoilage microorganisms and food-borne pathogens from various sources including animal faeces, soil, air, feed, water, equipment, animal hides and people. Thus, the prevalence of pathogenic and spoilage microorganisms in milk and dairy products is influenced by a high number of factors and their combinations.

The mammary gland participates in the excretion of numerous xenobiotic substances from veterinary drug milk residues and contaminants originated from milk and other chemical residues to environmental pollutants on the grasslands, animal feedstuffs, and the field crops. The presence of residual concentrations of milk contaminants and pathogens is an indicator of milk quality in cow dairy farms.
Bacterial contamination of raw milk: Sources and factors

Raw milk associated with Campylobacter jejuni

Raw milk is a common source of infections. The bacterial are often carried by healthy cattle and by flies on farms. Non-chlorinated water may also be a source of infections. However, properly cooking chicken, pasteurising milk, and chlorinating drinking water will kill the bacteria.

Raw milk may become contaminated with C. jejuni in one of two ways. It may excreted directly by a mastitis udder or feces may contaminated the product. Contamination of milk from C. jejuni mastitis is thought to be rare, but direct milk excretion leading to human cases has been reported.

Milkborne campylobacteriossis outbreaks have even almost invariably associated with consumption of raw or inadequately pasteurised cow’s milk. However, a few cases of C. jejuni and C. coli enteritis have been trace to ingestion of raw goats milk in United States, Great Britain and Australia, with the epidemic strain identified in fecal samples from incriminated goats.
Raw milk associated with Campylobacter jejuni

Grade A raw milk standard for pasteurization

Chemical, bacteriological and temperature standards have been established for grade A raw milk products intended for pasteurization, as well as for grade A pasteurized and bulk shipped heat-treated milk products.

In case raw milk for pasteurization the standard are as follows:

Temperature: cool to 50 F or less and maintained there at until process.

Bacterial limit: individual producer milk not to exceed 100,000 per ml prior to comingling with other producer milk.

Not exceeding 300,000 per ml as comingled mil prior to pasteurization.

Antibiotics: not detectable zone with the Baccilus subtilis method of equivalent.
Grade A raw milk standard for pasteurization

Bacterial contamination in milk

Milk drawn from healthy cows under hygienic milking conditions is relatively clean and free from bacteria.

However many factors increase bacterial count substantially such as atmosphere, dirty and poor health udder, unclean utensils or unhealthy cows.

Nevertheless, contamination from soil, faces or bedding is also a potential source of food poisoning bacteria.

In order to reduce or eliminate contamination by spoilage and pathogenic organisms from farm to the dairy plant, the cow’s teat and surrounding udder area and all utensils and equipment used during milking and processing should be properly cleaned and sanitized.

Milk residue left on equipment contact surfaces support the growth of a variety of bacteria such as Micrococcus, Streptococcus and Bacillus spp.

Having limited bacterial contamination during milking, it is essential that contamination from equipment situated between the cow and the refrigerated storage tank is kept to a minimum.

Cooling the milk also one of the measures to reduce the bacterial contamination. Bacteria grow and multiply rapidly in warm milk. Cool milk to 16 C within 20 minutes and to 4 C within 90 minutes after it is drawn from the cow will preventing bacterial growth in milk.

A variety of sources of contamination also exist in the processing plant. Personnel and air probably contribute little to the contamination of pasteurized milks.

One of the worst bacterial contamination involved Snow Brand Milk Products Company in Japan, which infected more than thirteen thousand people and led to closure of thirty factories across the nation.

Bacterial contamination in milk

Source of Bacteria in Milk

Source of Bacteria in Milk
Some bacteria are normally present in the udder of the cow, and these may contribute to the bacterial flora of the milk. However, unless the udder is infected, it is not considered to be an important source of such microorganisms. 

Other sources of microbial contaminations of milk are the body of the cow, milking machines and other equipment and utensils, the air in the milking barn, and the hands, nose, and throat of those attending to the milking process. In the handling of milk upon delivery to the processing plant or dairy, further sources of contamination may be encountered.

In order to limit the number of bacteria present in raw milk, certain precautionary procedures are ordinarily applied. The flanks, udder, and teats of the cow should be washed, treated with a sanitizing solution, and dried before milk is drawn. 

Large dairy farms often have a special wash pen for cows to be milk. Utensils, including the milking machine, should be cleansed and disinfected either with live steam or with a solution of chlorine (about 200 ppm of available chlorine). 

Bulk milk tanks may be cleaned manually with detergent and water at about 130 F , the sanitized with chlorine solution, or cleaned mechanically with detergent and water at 150 F, and finally sanitized with chlorine solution. Outlet valves and the outside of the tanks must be cleaned and sanitized manually. Cleaning in place (CIP) may be used to clean, sanitized, and rinse the pipe line and the bulk milk line tank of a vacuum or pressure system is available.
Source of Bacteria in Milk