Understanding Pasteurization: Benefits, Limitations, and the Innovative Alternative Methods

What is Pasteurization? 

Pasteurization is a heat-treatment process that destroys pathogenic microorganisms in food and beverages to ensure safety and extend the shelf life of the product. Unlike sterilization, pasteurization operates at temperatures below the boiling point of water (60-80°C, a few minutes), meaning it cannot eliminate all microorganisms, especially bacterial spores. Instead, pasteurization targets the inactivation of vegetative forms of bacteria and enzymes that contribute to spoilage. Pasteurization is often combined with preservation methods such as packaging in anaerobic conditions, acidification, or chemical inhibition (with chemical preservatives such as bacteriocin or essential oils) to ensure effectiveness. (1)

History & Objectives of Pasteurization

The technique of heating wine for preservation has been known in China since AD 1117 and was recorded in Japan in the Tamonin-nikki diary, written by several monks between 1478 and 1618. However, it was named after Louis Pasteur, who demonstrated in the 1860s that heating wine and beer to specific temperatures could prevent spoilage. The method was later adapted for milk and other beverages to ensure safety and extend shelf life (2). Milk is an ideal growth medium for various pathogens, including those responsible for tuberculosis, diphtheria, scarlet fever, brucellosis, Q-fever, and foodborne illnesses such as Salmonella, E. coli, and Listeria. Before the adoption of pasteurization, raw milk was the cause of numerous fatalities. For instance, between 1912 and 1937, approximately 65,000 deaths in England and Wales were attributed to tuberculosis from consuming untreated milk. Following the widespread implementation of pasteurization, there was a significant decline in milk-related illnesses. According to the Centers for Disease Control, between 1998 and 2011, 79% of dairy-related disease outbreaks were associated with consuming raw milk or cheese. Pasteurization is a process applied to a product to prevent public health risks associated with pathogenic microorganisms. Understanding the pathogens that are or could potentially be present in any given product is crucial to effectively achieving the public health goal of pasteurization for that product. It is also necessary to know the thermal characteristics of these organisms. Moreover, pasteurization aims to extend the product’s shelf life and improve its stability and quality. (3)

How Pasteurization Works

Pasteurization’s fundamental principle is that heat effectively eliminates most heat-resistant pathogenic microorganisms (like Mycobacterium tuberculosis and Coxiella burnetii) and deactivates specific proteins, including enzymes contributing to food spoilage and reducing its quality. The time and temperature are determined to eliminate Mycobacterium tuberculosis and other pathogens present in food, eradicating food spoilage microorganisms, and thereby extending the product’s shelf life. Moreover, undetectable levels of the enzyme alkaline phosphatase ensure that milk is safe for human consumption and is used as an indicator of complete pasteurization. 

Different pasteurization methods are employed depending on the product’s characteristics by using an equivalent combination of temperature and time to achieve food safety. After processing, the food product is stored under refrigeration (≤ 6  °C), which can range between 5-6 days in the case of ‘’fresh’’ milk or even weeks depending on the microbial quality of raw milk, the intensity of thermal treatment, type of packaging and supply chain. For liquids, pasteurization typically involves flowing through a pipeline. Heat is applied directly or through steam/hot water in a designated section, followed by a cooling phase. Precise control over temperature and duration during these stages is crucial. Solid foods are pasteurized post-packaged into containers. Glass containers require careful heating with hot water to prevent glass breakage. Alternatively, steam or hot water is applied to plastic and metal containers.

Types of Pasteurization

Pasteurization is primarily conducted through three main methods:

Low-temperature long time (LTLT)

Initially used for fruit juices, LTLT involves batch heating at 63–65°C for an extended period (~30 min). It has drawbacks due to significant quality changes (e.g. vitamin reduction) and is impractical for large-scale production. It has largely been replaced by more efficient methods like high-temperature short-time treatment (HTST).

High temperature/short time (HTST)

Known as “Flash Pasteurization,” HTST is a continuous process that heats milk to 72-75 °C (~161°F) for 15–20 seconds, effectively eliminating heat-resistant pathogens like C. burnetii from raw milk. This process utilizes heat exchangers such as plate-and-frame or shell-and-tube types to minimize quality changes compared to batch heating. HTST is widely used for pasteurizing beverages such as orange juice at 90–95°C for 15–30 seconds and apple juice at 77–88°C for 25–30 seconds. 

Ultraheat treated (UHT) or ultrahigh-temperature method

This technique is most commonly used for milk or cream. Milk is rapidly heated to 135°C (275°F)  for at least 1 second, enhancing its quality and shelf life through reduction of residual bacteria and their spores. It is often labeled as “UHT” or “ultra-pasteurized.” Sterile packaging is required to maintain product sterility, adding complexity to the process. 

Commonly Pasteurized Products

• Milk and dairy products
• Juices (e.g., orange juice, apple juice)
• Beer and cider
• Wine
• Bottled water
• Canned foods (e.g., soups, fruit and vegetable pulps)
• Noncarbonated beverages (e.g., coffee, flavored water, tea, or herbal infusions)
• Eggs
• Vinegar 
• Plant-based milk

Advantages of Pasteurization

Below can be found some of the benefits of pasteurization:

1. Pasteurization effectively kills pathogenic organisms present in beverages.
2. Extends shelf life significantly; some juices can remain viable for up to a year. 
3. Inactivates enzymes like phosphatase and lipase in milk, which can degrade its quality. 
4. Modifies product characteristics; for example, milk pasteurization for yogurt production alters protein structure, facilitating thicker and more stable yogurt.
5. Pasteurization helps prevent diseases such as diphtheria, tuberculosis, scarlet fever, and brucellosis by eliminating harmful bacteria. (4)
6. UHT minimizes chemical, physical and organoleptic changes in milk, which can also be stored without refrigeration for months allowing for transportation to remote areas. 

Limitations & Challenges of Pasteurization

1. Strict monitoring is required throughout the pasteurization process.
2. Heat-resistant microorganisms may survive even after pasteurization.
3. Refrigeration is necessary to maintain the shelf life of some pasteurized products.
4. Pasteurization (HTST and UHT) can sometimes impart a ‘’cooked’’ taste to milk.
5. The texture and flavor of the product may be impacted. 
6. The HTST pasteurization method can lead to a significant loss of nutrients and thermosensitive vitamins like vitamin C, B1, Β6, Β9, and B12 in milk.
7. Not all products are suitable for pasteurization.
8. Some nutrients and enzymes are lost during pasteurization, which may make raw milk preferable to pasteurized milk. (4)
9. Heating of milk gives rise to insolubilization of calcium phosphate, which leads to fouling of processing surfaces.
10. Loss of aroma compounds and tissue softening 

Despite its effectiveness in reducing pathogens, thermal treatments like pasteurization present significant drawbacks concerning foods’ nutritional and sensory qualities. The process can lead to the breakdown of essential vitamins and nutrients, altering the texture, taste, and aroma of delicate products such as fruit juices and dairy items. These considerations underscore the need for a balanced approach in optimizing pasteurization processes to mitigate these effects while ensuring food safety. (5). In this context, many researchers focus on alternative techniques to face the challenges of thermal treatments and meet the consumer demand for minimally processed, healthier and sustainably produced food. 

Examples of Alternative Non-Thermal Processes

Emerging non-thermal food preservation technologies, including High Hydrostatic Pressure Processing (HPP), Pulsed Electric Field (PEF), Ultrasound (US), and Non-Thermal Plasma (NTP), are innovative technologies that can offer consumers safe, clean-label foods. These technologies allow nutritional and sensory attributes to remain intact while products retain their quality and freshness.

Pulsed Electric Field

Pulsed Electric Field (PEF) is a technique that applies high-voltage electrical pulses to biological materials (e.g plants, animals, and microorganisms). PEF effectively inactivates microorganisms in liquid and semi-liquid food products while preserving the quality characteristics. Important heat-sensitive nutrients like vitamins are usually minimally impacted. Moreover, the technology is commercially used and regulated as a pasteurization alternative for fruit juices. Food safety and shelf life extension are achieved through inactivation of foodborne pathogens and spoilage microorganisms as discussed in “Exploring Pulsed Electric Field (PEF) Microbial Inactivation for Food Processing” while  industrial application and current optimization efforts can be found in “Harnessing pulsed power to enhance food safety and quality: Risks and benefits of pulsed electric field (PEF) technology”. 

Ultrasound

Ultrasound (US) is an alternative method with antimicrobial potential. It has mainly been utilized for diagnostic purposes and texture enhancement of solid foods. However, the current industrial applications in fresh produce and liquid foods are limited, despite its potential to preserve functional food components compared to conventional heat treatments. To ensure food safety, current research focuses on understanding the microorganism-related factors influencing US efficacy (as discussed in The Impact of Strain Variability on the Inactivation Efficacy of Ultrasound Technology). This information can help increase scalability and optimization in food products, often in combination with other methods, such as gentle heating and elevated pressure treatments. Manothermosonication is one of the most promising combinations, and it is particularly effective for decontaminating food products like liquid eggs as discussed here. 

Non-thermal plasma

Non-thermal plasma (NTP) is an innovative method for sanitizing surfaces and it can be applied to fresh and ready-to-eat products, herbs and spices, grains and nuts. These products are sensitive to heat treatment and/or added to already treated food products. The process is very fast and can be conducted at room temperature, making NTP more cost-efficient than thermal treatments. The products treated with NTP are minimally processed and can maintain their high nutritional value and quality characteristics. Understanding its efficacy against pathogens and spoilage organisms is crucial for advancing NTP technology and promoting its acceptance in the market for production of safe and high-quality foods. Latest research addressing these challenges can be found in “Non-thermal plasma (NTP) for the improvement of food safety and quality”.

High Pressure Processing

High Pressure Processing (HPP), also known as high hydrostatic pressure processing (HHP) or cold pasteurization, is a mild food preservation technology that uses very high hydrostatic pressures (KPa) instead of heat to inactivate microorganisms. This process can provide a wide range of applications but more importantly ensure food safety while maintaining the nutrients and quality characteristics (flavor, texture). HPP has already been used at an industrial level and many food manufacturers use it as an alternative to conventional thermal treatment, especially for products like fruit juices. The efficacy is generally assessed by conducting studies that follow the reduction of relevant microorganisms from a food safety and spoilage perspective, for which further information can be found here. Moreover, combination of HPP with other control measures (pH, temperature, packaging techniques, natural preservatives) can contribute to reduction of production costs, one of the main HPP challenges as discussed here.

A Data-Driven Approach

A significant factor to consider is consumer acceptance. Investigating consumers’ perceptions while developing new products and technologies, such as non-thermal methods for inactivating microorganisms, is essential. A data-driven approach is a key factor for maximizing the potential of these new technologies. Collecting data from current research can help evaluate these new methods against traditional thermal treatments and understand consumer behavior, facilitating the introduction of products treated with these methods into the market as explained in “Understanding Consumer Perception in Food Product Development: Key to Market Success”.

References

1. Food Safety Management: A Practical Guide for the Food Industry. (2023). Netherlands: Elsevier Science.
2. Hornsey, I. S. (2007). A History of Beer and Brewing. United Kingdom: Royal Society of Chemistry.
3. Preservatives and Preservation Approaches in Beverages: Volume 15: The Science of Beverages. (2019). Netherlands: Elsevier Science.
4. Deeth, H. (2017). Optimum thermal processing for extended shelf-life (ESL) milk. Foods, 6(11), 102.
5. Bhadekar, R., & Bhola, J. (2019). Nonconventional preservation techniques: Current trends and future prospects. In Preservatives and preservation approaches in beverages (pp. 115-147). Academic Press.

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