Basics Of Milk Cooling Technology You Need to Know 🧊

Introduction

The dairy industry plays a vital role in providing essential and nutritious milk and milk products to consumers worldwide. To ensure the freshness, quality, and safety of these products, it is of utmost importance to maintain proper temperature throughout the dairy value chain starting from milk collection to production, storage, and distribution processes. This is where milk cooling technology emerges as a vital component of the dairy industry’s infrastructure.

When milk is harvested from dairy animals, it is at its body temperature. This provides an ideal environment for bacteria to multiply exponentially. Without efficient and effective cooling, these bacteria can proliferate and lead to spoilage, compromising the integrity of the milk. Additionally, certain harmful bacteria can pose serious health risks if consumed, emphasizing the criticality of preventing their growth.

It is essential to maintain the proper temperature of milk to preserve its freshness, nutritional value, and overall quality. It also helps in the reduction of spoilage of milk and restricts the growth of bacteria. This is where milk cooling technology comes into play, serving as the backbone of the dairy industry’s quality assurance process.

The significance of maintaining proper milk temperature cannot be overstated. Even a minor delay in cooling can have a detrimental impact on milk quality, leading to bacterial growth, flavor degradation, and decreased nutritional value. Inadequate milk cooling can compromise the safety of dairy products and result in financial losses for farmers and processors.

Quality and safety are not the only factors influenced by milk cooling technology. Compliance with regulations is also a crucial aspect. Many countries have established standards and guidelines regarding milk temperature and cooling procedures to ensure consumer protection. Failure to adhere to these regulations can have legal consequences and jeopardize the reputation of dairy producers.

In this blog post, we will discuss the basics of milk cooling technology, exploring its underlying principles, key components, and best practices. Whether you are a dairy farmer, processor, or refrigeration engineer specializing in dairy applications, understanding the fundamentals of milk cooling technology is essential to ensure the preservation of milk quality and the continued success of the dairy industry.

Why Milk Cooling is Important?

Milk is a highly perishable commodity. It has a shelf-life of 3-4 hours after milking depending on the cleanliness and hygiene maintained at the farm level. Normal ambient temperature is suitable for the rapid growth of bacteria in milk. So, Milk Cooling plays an important role in maintaining the freshness and quality of milk. In this blog section, we will explore the reasons why milk cooling is of utmost importance, highlighting its impact on both the dairy industry and consumers.

Preservation of Freshness

Milk is a highly perishable product and susceptible to bacterial growth and spoilage. The temperature of milk coming out from the udder of the animal is almost at the body temperature of the animal. This temperature provides an ideal environment for the exponential growth of bacteria. Effective and rapid cooling will bring down the temperature of milk thus slowing down the growth of bacteria and preserving its freshness. It is recommended to cool down the milk to 4°C (39°F) to extend its self-life and maintain its quality. Cooling and storing milk at this temperature also maintains its sensory qualities, such as taste, aroma, and texture.

Prevention of Microbial Growth

Milk contains bacteria even when it is extracted from the animal, further external factors such as the milking container, environment, and milker add further bacteria in the process of milking. These bacteria grow exponentially leading to spoilage and potential health risk. Cooling of milk to 4°C (39°F) inhibits the growth of bacteria including harmful pathogens such as Salmonells, E. coli, etc. Proper milk cooling practices are vital to ensure that the milk remains safe for consumption.

Preservation Nutritional Value

Milk is known for its nutritional content, including proteins, vitamins, and minerals. When milk is kept at ambient temperature the enzymes naturally present in the milk change its composition leading to degradation of these vital nutrients. This also results in the development of undesirable flavors and odors. By efficiently cooling milk, these enzymatic reactions are slowed down, preserving the milk’s natural taste and nutritional integrity. Storing milk between 4°C – 6°C also helps retain the vitamins, minerals, and proteins present in milk, ensuring that consumers get the maximum benefits.

Meeting Regulatory Compliance

Many countries have specific regulations and standards in place to ensure the safety and quality of milk and dairy products. In India FSSAI (Food Safety and Standards Authority of India) is in place to protect consumers and maintain high-quality standards in the dairy industry. Proper milk cooling is a mandatory requirement stipulated by regulatory bodies. By adhering to these guidelines, dairy farmers and milk processors not only ensure the safety of their products but also demonstrate their commitment to maintaining industry standards.

Energy Efficiency and Cost Savings

Implementing proper milk cooling not only ensures product quality but also contributes to energy efficiency and cost savings. Dairy farms and processing facilities require substantial amounts of energy to cool milk. Energy-efficient cooling technologies, such as insulated storage tanks and heat recovery systems, can significantly reduce energy consumption and operating costs. By optimizing cooling systems, investing in energy-efficient equipment, and adopting best practices, dairy operations can minimize their environmental impact, conserve resources, and contribute to a greener future.

Optimizing Milk Processing

Milk cooling plays a critical role in the larger dairy supply chain, particularly during milk processing. When milk is promptly and efficiently cooled, it arrives at processing facilities in optimal condition. This allows for effective separation, homogenization, and pasteurization processes, resulting in superior dairy products such as milk, cheese, yogurt, and butter.

Milk cooling is a critical step in ensuring the freshness, safety, and quality of milk and is an integral part of the dairy industry that cannot be underestimated. By recognizing its importance and implementing proper cooling practices, we can preserve the freshness, safety, and nutritional value of milk, while also complying with regulations and optimizing milk processing. Let us remember that behind every glass of milk lies a well-maintained cooling system that ensures the quality and satisfaction of consumers worldwide.

Keeping it Cool, But Not Too Cool: The 4°C Rule

 Milk cooling is essential for preserving its quality and safety. It is generally recommended not to cool milk below 4°C (39.2°F) for specific reasons. It’s important to understand why milk should not be cooled below 4°C. In this section, we will discuss the reasons behind this recommendation and explore the potential consequences of extreme cooling.

Risk of Freezing

Milk is primarily composed of water, proteins, fats, and various dissolved solids. When milk is cooled below 4°C, the water content starts to freeze, leading to the formation of ice crystals. Freezing can cause structural damage to the milk, resulting in changes to its texture and quality. Additionally, the expansion of water due to freezing can cause spillage of milk and damage to the container, leading to potential product loss and safety hazards.

Ice Crystal Formation

When milk is cooled below 4°C, there is a risk of ice crystal formation. When water in milk freezes, it expands and can damage the milk’s structure. Ice crystals can cause changes in texture, affecting the milk’s ability to emulsify and blend properly. This can impact the quality and performance of milk in various dairy products.

Protein Denaturation

Extreme cooling can lead to protein denaturation, which is the alteration of the milk proteins’ natural structure. Proteins play a vital role in the functionality and nutritional value of milk. Denaturation disrupts their structure, resulting in reduced solubility, impaired emulsifying properties, and potential loss of essential amino acids. This can negatively impact the quality and processing characteristics of the milk and its derived products.

Fat Stability

Milk contains fats that can be affected by very low temperatures. When milk is cooled below 4°C, the fat may solidify and separate which affects the taste, texture, and quality of the milk. These changes can result in milk separation or the development of off-flavors.

Quality Deterioration

Colder temperatures can intensify the absorption of off-flavors and odors from the environment into the milk. When milk is stored below 4°C, it becomes more susceptible to absorbing undesirable tastes and aromas present in the refrigeration unit, affecting its overall quality. This can be particularly problematic in cases where milk is stored alongside strong-smelling substances or spoiled food items.

Energy Consumption

Cooling milk below 4°C requires additional energy and resources. Dairy farms and processing facilities need to maintain a balance between efficient cooling and energy consumption. Cooling milk to a slightly higher temperature, such as 4°C, allows for energy conservation while still ensuring proper cooling and preservation. Avoiding extreme cooling can help reduce energy consumption and operational costs, making milk production more sustainable in the long run.

It’s worth noting that different countries and regions might have specific guidelines and regulations regarding milk cooling temperatures. These recommendations are typically based on scientific research and best practices in the dairy industry.

By adhering to specific temperature guidelines provided by regulatory authorities and industry standards., dairy producers can maintain the quality, safety, and freshness of milk throughout the supply chain, ultimately delivering a superior product to consumers.

Milk Cooling Methods

Proper milk cooling is crucial for maintaining the freshness and quality of dairy products. In the dairy industry, several milk cooling methods are commonly employed. The three widely used cooling methods used in dairy industries are,

1. Direct Expansion (DX) Cooling,
2. Ice Bank (IBT) Cooling
3. Plate Heat Exchanger (PHE) Cooling

In this blog section, we will discuss the three widely used milk cooling methods, we will look into their working principles and highlight the benefits of each method, including their energy efficiency and cooling capacity.

01. Direct Expansion (DX) Cooling

Direct Expansion cooling is the most popular method of cooling used in the dairy industry.

This method uses a refrigeration system to provide cooling by directly cooling the milk without the need for a secondary medium. The circulation of refrigerant removes heat from the milk.

The refrigerant is a chemical substance with a low boiling point and high heat absorption capacity and plays a central role. The process starts with the refrigerant in a gaseous state inside the evaporator coil, which is typically located inside the milk tank. As warm milk meets the evaporator, the refrigerant absorbs heat from the milk and evaporates, transforming it into a gas.

The gaseous refrigerant then travels to the compressor, which increases its pressure and temperature. This compressed refrigerant gas then moves to the condenser coil, where it releases heat to the surrounding environment. As the refrigerant cools down, it condenses back into a liquid state.

The liquid refrigerant then passes through an expansion valve or metering device, which reduces its pressure. This pressure reduction causes the refrigerant to cool further, preparing it to enter the evaporator once again to repeat the cycle.

The Bulk Milk Cooler (BMC) uses this method of cooling and is made of stainless steel which stores the milk. The bottom of the tank forms the evaporator in which the refrigerant expands and absorbs heat from the milk. An agitator inside the tank agitates the milk at a speed of 25-30 RPM, enabling it to mix the milk properly to ensure uniform temperature across the milk.

Advantages of DX Cooling System in Bulk Milk Coolers

1. Energy Efficiency:  DX cooling systems are known for their ease of operation and high energy efficiency. This eliminates the need for any secondary medium for heat transfer. This provides direct cooling, reducing energy consumption.
2. Precise Temperature Control: DX cooling allows for precise temperature control as the operation of the compressor is controlled in relation to the desired milk temperature. This enables dairy farmers to maintain optimal storage conditions and comply with regulatory standards.
3. Easy Installation: DX cooling systems are relatively simple to install compared to other cooling methods. They require fewer components and can be tailored to suit the specific requirements of the BMC.
4. Cost-effectiveness: The simplicity of DX systems makes them cost-effective to install and maintain, particularly in small to medium-sized applications.

Disadvantages of DX Cooling System in Bulk Milk Coolers

1. Limited Cooling Capacity: DX cooling systems may have limitations in terms of their cooling capacity. Larger-scale milk cooling applications may require multiple DX systems or alternative cooling methods to meet the demand.
2. Maintenance and Repair: Like any cooling system, DX systems in BMCs require regular maintenance and occasional repairs to ensure proper functioning. Maintenance activities, such as cleaning the evaporator and condenser coils, should be carried out as per the manufacturer’s guidelines.
3. Initial Cost: The initial investment cost for installing a DX cooling system in a Bulk Milk Cooler may be higher compared to other cooling methods. However, long-term energy savings and efficient milk cooling may help offset this initial investment.
4. Refrigerant Considerations: The choice of refrigerant for the DX system should consider environmental considerations and safety regulations. Opting for refrigerants with lower environmental impact, such as those with low global warming potential (GWP), is advisable.

The DX cooling system used in Bulk Milk Coolers provides efficient and reliable cooling for preserving milk quality. While it offers advantages such as energy efficiency, rapid cooling, and precise temperature control, it is essential to consider factors such as cooling capacity, maintenance requirements, initial costs, and refrigerant selection. Proper installation, regular maintenance, and monitoring are crucial for optimal performance and milk preservation in BMCs.

02. Ice Bank (IBT) Cooling

 Ice Bank (IBT) Cooling is a milk cooling method that utilizes the concept of building ice to cool the milk. The system consists of an Insulated Tank filled with water and a set of evaporative coils. The evaporative coil is a part of the refrigeration system. When refrigerant expands inside the evaporative coil ice starts forming over the coil which keeps the water in the tank to desired temperature. This chilled water is then used to cool the milk when required.

An Ice Bank Type Bulk Milk Cooler is a specific type of milk cooling system that utilizes the concept of an ice bank to cool bulk quantities of milk. The IBT Bulk Milk Cooler consists of a semi-cylindrical tank with an integrated insulated ice bank. The IBT contains a large amount of water and the evaporative coil on which Ice is formed and thus brings the water temperature to almost between Zero to One Degree Celsius.

The system also has a chilled water circulation pump that sprays the water at the outer surface of the milk tank with a suitable pipe arrangement so that the water glides all along the surface of the tank. The chilled water while gliding over the surface absorbs heat from the milk dumped in the milk tank.

An agitator inside the tank agitates the milk at a speed of 25-30 RPM, enabling the mixing of the milk properly to ensure uniform temperature across the milk. The heat from the milk is transferred to the ice bank, causing the ice to melt gradually.

Advantages of IBT Cooling System in Bulk Milk Coolers

1. Rapid Cooling: IBT Bulk Milk Coolers are designed to provide rapid and efficient cooling of milk. The ice bank enables quick heat transfer, resulting in faster cooling times and better preservation of milk quality.
2. Energy Efficiency: These coolers take advantage of off-peak electricity rates to form the ice bank during low-demand periods. The stored ice acts as a thermal energy reservoir, reducing the need for electricity consumption during peak hours. This energy-efficient operation helps to lower electricity costs.
3. Flexibility in Milk Cooling: IBT Bulk Milk Coolers offer flexibility in milk cooling operations. The ice bank provides additional cooling capacity, acting as a buffer to handle variations in milk production and peak load demands effectively. This flexibility is particularly beneficial in regions with fluctuating milk volumes or irregular milk production patterns.
4. Space Efficiency: The integrated ice bank eliminates the need for separate ice storage, reducing the overall space requirements for milk cooling operations. This is especially advantageous in locations with limited space availability.

Disadvantages of IBT Cooling System in Bulk Milk Coolers

1.  Maintenance and Cleaning: Regular maintenance and cleaning are necessary for Ice Bank Cooling systems to ensure efficient operation. The ice bank storage tank needs to be periodically defrosted and cleaned to maintain proper hygiene standards.
2. Limited Cooling Capacity: The cooling capacity of an Ice Bank Cooling system is limited to the amount of ice stored. If the ice bank is not properly sized or there is a sudden increase in milk production, it may not be able to meet the cooling requirements during peak periods.

03. Plate Heat Exchanger (PHE) Cooling

Plate heat exchangers (PHEs) play a crucial role in the cooling process within the dairy industry. They are efficient and reliable devices used to transfer heat from one medium to another, such as from milk to chilled water, to maintain proper temperature control and ensure product quality.

The system used Plate Heat Exchanger Cooling method popularly known as Instant Milk Chilling Unit (IMCU). An Instant Milk Cooling Unit (IMCU) is a device used in the dairy industry to rapidly cool raw milk to preserve its freshness and quality.

The IMCU typically consists of a refrigeration unit, a heat exchange system, and a milk storage tank. The milk is processed in IMCU, where it passes through the heat exchange system. The heat exchangers or Plate Heat Exchangers (PHE) utilize a series of stainless-steel plates that are assembled to create a heat exchange surface. The milk flows through alternate channels, while a cooling medium, usually chilled water or a refrigerant, flows through the remaining channels, enabling heat transfer and cooling the milk rapidly. This process brings down the temperature of the milk to the desired level, typically around 4°C (39°F).

The capacity of the plate heat exchanger (PHE) is designed based on Milk Flow Rate, Milk Input Temperature, and desired Milk output temperature.

Advantages of Plate Heat Exchanger (PHE) Cooling

1. Instant Cooling: Plate Heat Exchangers provide instant cooling of milk due to the large heat transfer surface area. The design allows for efficient heat transfer between the milk and the cooling medium, enabling quick cooling and minimizing the growth of bacteria.
2. Energy Efficiency: IMCU Cooling systems are known for their energy efficiency. The close temperature approach between the milk and the cooling medium reduces the energy required for cooling. Additionally, the use of efficient heat exchange materials, such as stainless-steel plates, enhances energy transfer efficiency.
3. Compact Design: Plate Heat Exchangers have a compact and space-saving design. The stacked plate configuration results in a smaller footprint compared to other cooling methods, making them suitable for locations with limited space.
4. Flexibility and Scalability: PHEs can be easily expanded or modified to accommodate varying milk flow rates and cooling requirements.

Disadvantages of Plate Heat Exchanger (PHE) Cooling

1. Cost: Plate Heat Exchangers can have a higher initial cost compared to some other milk cooling methods. The equipment and installation expenses associated with the system may be relatively high, which could pose a financial challenge for smaller dairy farms or facilities with budget constraints.
2. Sensitivity to Fouling: Plate Heat Exchangers are sensitive to fouling, which refers to the accumulation of deposits or impurities on the heat exchange surface. If the milk contains particulates or is not properly filtered, fouling can occur, reducing the heat transfer efficiency and necessitating more frequent cleaning and maintenance.
3. Maintenance and Repairs: While the maintenance of Plate Heat Exchangers is generally straightforward, any damage or failure of the plates can require specialized expertise for repair or replacement. In such cases, the downtime for repairs and the associated costs can be potential disadvantages.
4. Cleaning: Regular cleaning is essential to ensure the optimal performance of PHEs.

The design of PHEs facilitates easy disassembly, allowing for thorough cleaning and inspection of plates to prevent fouling and contamination. Effective cleaning protocols, such as CIP (cleaning-in-place) systems must be followed for effective performance and hygiene to prevent bacterial growth.

Milk cooling methods are crucial for maintaining the quality and safety of dairy products. The whole objective of adopting a suitable milk cooling method is to prevent bacterial growth, preserve the nutritional value of milk, and extend its shelf life. Proper temperature control during milk cooling is essential to meet industry standards and regulatory requirements.

Best Practices for Milk Cooling

 Proper milk cooling is essential for maintaining milk quality and ensuring the production of longer self-life and high-quality dairy products. By implementing best practices, dairy farmers and processors can optimize milk cooling processes and enhance milk preservation. In this section, we will discuss practical tips and recommendations for optimal milk cooling and highlight their impact on milk quality.

Cooling Milk at Source

Cooling milk immediately after milking is an effective practice. It is always therefore recommended to have milk chilling infrastructure at the Village Level Milk Collection Centers. This approach aims to preserve the quality and freshness of the milk by inhibiting bacterial growth and minimizing the risk of spoilage. Proper milk cooling at the source is essential for maintaining milk quality from farm to dairy processing facilities, contributing to the production of safe and high-quality dairy products for consumers.

Pre-Cooling Milk

To achieve optimal milk cooling, it is recommended to pre-cool the milk before storage. Pre-cooling involves rapidly reducing the milk’s temperature to below 10°C (50°F) within a short time after milking. This step minimizes the growth of bacteria and helps maintain milk quality. Pre-cooling helps reduce the bacterial count in milk, slowing down microbial growth, preserving milk freshness, and minimizing the risk of undesirable chemical reactions that can negatively affect product quality.

Agitator Usage

Agitators are essential components of milk storage tanks and play a crucial role in maintaining milk quality. This enables us to maintain a uniform temperature and breaks the temperature gradient. Ensure the Agitator blade and shaft are cleaned properly. The agitator must run continuously during the milk cooling process. Once the milk reached 04°C the operation of the agitator must shift to cyclic mode. In cyclic mode, Agitator operates for 2 min after every 13 mins or the cycle programmed by the manufacturer.

Avoid excessive agitation that may introduce air into the milk, leading to undesirable oxidation or foaming. Use gentle agitation to maintain milk homogeneity without compromising quality The recommended speed of the agitator is 25-30 RPM.

Regular Maintenance

Regular maintenance of the milk cooling system is crucial to ensure optimal performance and prevent breakdowns. Follow scheduled routine inspections to check for leaks, worn-out gaskets, and damaged components. Clean & sanitize the milk contact parts as well as the premises regularly. Verify and cross-check the accuracy of the Temperature sensor controls to maintain precise temperature control.

Adhering to SOPs

Always follow the Standard Operating Procedure (SOP) provided by the milk processor when it comes to the operation and cleaning of milk cooling equipment.

Implementing these best practices helps in maintaining the quality of milk. Keeping the whole milk collection premises clean, dust free and maintaining a good environment is essential.

Advances in Milk Cooling Technology

The cooling Industry is dynamic and constantly evolving, with new technologies, regulations, and best practices emerging regularly. With the advancements in technology, dairy farmers now have access to innovative solutions that improve efficiency, reduce energy consumption, and ensure optimal milk preservation. In this blog, we will explore some of the latest advances in milk cooling technology and their benefits for the dairy industry.

Cost-Effective Village-Level Milk Collection

Traditionally, the dairy industry relied on Bulk Milk Coolers (BMC) for Village Level Milk Collection Centers (VLCC). However, the high fixed cost per liter of milk made it impractical for Milk Processors to invest in a collection center for low milk volumes. Additionally, setting up a VLCC posed challenges related to power connection, water supply for cleaning, and wastewater management.

Fortunately, the development of Can Coolers has provided a solution. Milk processors can now reach all villages along their collection routes without disrupting the regular can collection pattern. This cost-effective alternative has opened new opportunities for efficient milk collection at the village level.

Thermal Storage System

The power supply condition in most of the villages is not reliable. Low voltage and frequent power outages make it more difficult for the operation of Buk Milk Coolers. Diesel Generator sets are commonly used as backup power sources. This increases the operational and overall maintenance costs. Handling diesel in remote villages and preventing the theft of diesel is another concern.

The development of the Thermal Storage System has provided a solution. These systems store cold energy using Phase Changing Material (PCM). The cold energy produced in a refrigeration system when grid power is available is stored in the PCM. This cold energy is then used for various cooling applications even in the absence of Grid power thus eliminating the use of a Diesel Generator Set. A nominal amount of electric energy required during milk chilling is tapped from a small DC Battery bank.

Integration with solar power enhances efficiency, allowing the system to run on solar energy during the day and store cold energy for non-solar periods. Thermal storage systems revolutionize milk cooling in villages, offering reliability, sustainability, and cost-effectiveness.

Automated Temperature Control

Modern milk cooling technology incorporates automated temperature control systems that continuously monitor and regulate the temperature within the storage tanks. These systems enable accurate temperature management, preventing milk spoilage and maximizing energy efficiency.

Heat Recovery

Development of Heat Recovery System capture, and reuse waste heat generated during the cooling process. The heat rejected to the atmosphere through the condenser is recovered to generate hot water required for cleaning the cooling tank and other equipment. This makes the equipment energy efficient, reduces operational costs, and minimizes environmental impact.

Data Monitoring and Analysis

Data-driven decision-making has become integral to modern farming practices, and milk-cooling technology is no exception. Advanced systems now offer real-time monitoring and data analysis capabilities, providing farmers with valuable insights into milk quality, cooling performance, and energy consumption. By leveraging this information, farmers can make informed decisions, optimize their milk cooling processes, and ensure compliance with quality standards.

Remote Monitoring and Control

Efficient dairy management often requires constant monitoring and control, even when farmers are away from the farm. Remote monitoring and control features in modern milk-cooling technology allow farmers to access and manage their milk-cooling systems through mobile applications or web interfaces. This enables them to monitor milk temperatures, receive alerts for deviations, and adjust settings remotely, ensuring round-the-clock oversight and timely intervention, if necessary.

Advances in milk cooling technology have transformed the dairy industry, enhancing the quality, efficiency, and sustainability of milk production. Data monitoring & analysis have made the service and maintenance of the equipment more effective. Equipment manufacturers are constantly working on making the equipment more energy-efficient and reliable operation by utilizing modern-day remote monitoring and controls.

Conclusion

In conclusion, understanding the basics of milk cooling technology is crucial for ensuring the quality, safety, and longevity of milk. We have explored the key points that highlight the significance of proper milk cooling practices. Implementation of advanced temperature control systems and storage techniques, that can prevent spoilage, maintain freshness, and optimize energy efficiency.

It is essential for readers to prioritize milk cooling practices and stay updated with the latest advancements in this field. By embracing new technologies and techniques milk processors can enhance milk quality and reduce the risk of bacterial growth.

Proper milk cooling plays a critical role in preserving milk’s nutritional value and extending its shelf life. Let us all commit to implementing best practices and embracing advancements in milk cooling technology to ensure the highest standards of milk quality and safety. Together, we can foster a sustainable dairy industry that delivers fresh and healthy milk to consumers.