Before discussing the difference between pasteurized and unpasteurized milk in detail, let us first look at the meaning of the word pasteurized. Milk is the primary food source for infants, and it can be defined as a white liquid formed by the mammary glands of mammals. Milk consists of all major nutrients such as carbohydrate, protein, fat, minerals and vitamins. As a result of rich nutrient content, it is highly susceptible to microbial spoilage. Thus, raw milk is often pasteurized in order to destroy their pathogenic microbial load. This pasteurized milk is also known as long life milk. The key difference between Pasteurized milk and unpasteurized milk is that pasteurized milk can be stored for a longer period of time under refrigerated conditions whereas unpasteurized milk cannot be kept for an extended period of time. In other words, pasteurized milk has longer shelf life compared to unpasteurized milk. Although this is the key difference between pasteurized and unpasteurized milk, the nutritional and organoleptic properties may also differ between them. Therefore, it is important to identify the difference between pasteurized and unpasteurized milk in order to select healthier options. In this article, let’s elaborate the difference between pasteurized and unpasteurized milk in terms of their nutrients and sensory parameters.
What is Pasteurized Milk?
Pasteurization is a heating process that destroys harmful bacteria by heating milk to a specific temperature for a set period of time. In other words, pasteurized milk is a form of milk that has been heated to a high temperature in order to destroy any injurious pathogenic micro-organisms (Eg. E. coli, Salmonella and Listeria) which may be present in the raw milk. The pasteurized milk is then packaged into sterile containers under aseptic conditions such as Tetra packaged milk or glass-bottled milk. This process was invented by French scientist Louis Pasteur during the nineteenth century. The target of heat-treated milk is to produce milk safe for human consumption and to improve its shelf life. Thus, heat-treated milk/ pasteurized milk has a longer shelf life (Eg. UHT pasteurized milk can store for about 6 months). Pasteurization is a more popular method of heat treatments used to produce long-life milk. But pasteurized milk should be stored under refrigerated conditions because this heat treatment in not sufficient to destroy the spores of pathogenic microorganisms. This processed pasteurized milk is available in whole, semi-skimmed or skimmed product ranges. However, the heat treatment results in a change of organoleptic properties such as taste and color and also slightly decreases the nutritional quality of the milk.
What is Unpasteurized Milk?
Unpasteurized milk also known as raw milk obtained from cow, sheep, camel, buffalo or goat that has not been further processed (pasteurized). This fresh and unpasteurized milk can have hazardous microorganisms and their spores such as Salmonella, E. coli, and Listeria, are accountable for causing several foodborne diseases. Thus, unpasteurized milk is highly susceptible to microbial spoilage because milk is rich in many nutrients which are essential for microbial growth and reproduction. In addition, the bacteria in unpasteurized milk can be mainly unsafe to individuals with declining immune activities, older adults, pregnant women, and infants. Laws and regulation of the marketable packaged raw milk differ across the world. In some countries, selling unpasteurized milk is completely/partially banned. Though, unpasteurized milk is manufactured under good hygienic practices and risk management programs it has not been exposed to any temperature related processing (Eg. heat treatment) that change the sensory or nutritional quality or any characteristics of the milk. Furthermore, unpasteurized milk product is a dairy produce that has not been provided any kind of pathogenic microorganism elimination step. Therefore, unpasteurized milk has a very limited shelf-life (not more than 24 hours) compared to heat treated milk or pasteurized milk.
What is the difference between Pasteurized and Unpasteurized Milk?
Definition of Pasteurized and Unpasteurized Milk
Pasteurized Milk: Pasteurized milk is a form of milk that has been heated to a high temperature in order to destroy any injurious pathogenic micro-organisms.
Unpasteurized Milk: Unpasteurized milk is the raw milk obtained from cow, sheep, camel, buffalo or goat that has not been further processed.
Properties of Pasteurized and Unpasteurized Milk
Shelf-life
Unpasteurized Milk: Its shelf-life is shorter than pasteurized milk or has very limited shelf-life.
Pasteurized Milk: Pasteurized milk has a longer shelf life. (For example, UHT pasteurized milk keeps for approximately 6-month shelf life under refrigeration condition)
Fortification
Unpasteurized Milk: This is not fortified with nutrients.
Pasteurized Milk: This is often fortified with minerals and vitamins to compensate for the loss of nutrients during the pasteurization process.
Processing Steps
Unpasteurized Milk: This is usually consumed after homogenization.
Pasteurized Milk: Various processing steps are involved during milk pasteurization.
Classification Based on Heat Treatment
Unpasteurized Milk: Heat treatment is not used.
Pasteurized Milk: Milk can be pasteurized to three different stages. They are ultra-high temp (UHT), high-temperature short-time (HTST) and low-temp long-time (LTLT).
UHT milk is heated to a temperature higher than 275°F for more than two seconds and packaged in aseptic tetra pack containers. HTST milk is heated to 162°F for at least 15 seconds. This is the most common technique of pasteurization used in the large-scale commercial dairy industry. LTLT milk is heated to 145°F for at least 30 minutes. This is the most common technique of pasteurization used in the home or in small dairies.
Phosphatase Content
Unpasteurized Milk: This contains phosphatase which is essential for the absorption of calcium.
Pasteurized Milk: Phosphatase content is destroyed during the pasteurization process.
Lipase Content
Unpasteurized Milk: Unpasteurized milk contains lipase which is essential for the digestion of fat.
Pasteurized Milk: Lipase content is destroyed during pasteurization process.
Immunoglobulin Content
Unpasteurized Milk: Unpasteurized milk contains immunoglobulin which protects the body from infectious diseases.
Pasteurized Milk: Immunoglobulin content is destroyed during the pasteurization process.
Lactase Producing Bacteria
Unpasteurized Milk: Unpasteurized milk contains lactase producing bacteria which helps digestion of lactose.
Pasteurized Milk: Lactase producing bacteria is destroyed during the pasteurization process.
Probiotic Bacteria
Unpasteurized Milk: Unpasteurized milk contains probiotic bacteria which help to strengthen the immune system.
Pasteurized Milk: Probiotic bacteria are destroyed during the pasteurization process.
Protein Content
Unpasteurized Milk: Protein content is not denatured in unpasteurized milk.
Pasteurized Milk: Protein content is denatured during pasteurization process.
Vitamin and Mineral Content
Unpasteurized Milk: Vitamin and mineral content is 100% available in unpasteurized milk.
Pasteurized Milk: Vitamin A, D, and B-12 are diminished. Calcium can be altered, and iodine can be destroyed by heat.
Organoleptic Properties
Unpasteurized Milk: Organoleptic properties do not change in this process.
Pasteurized Milk: Organoleptic properties can change (change in color and/or flavor) during pasteurization process (Eg. Cooked flavor can observe in pasteurized milk products)
Available Forms
Unpasteurized Milk: Unpasteurized milk is only available only liquid form.
Pasteurized Milk: The different long-life milk tends to vary according to the way they are produced and their fat content. UHT milk is available in whole, semi-skimmed and skimmed varieties
Availability of Microorganisms
Unpasteurized Milk: Unpasteurized milk can have pathogenic bacteria such as Salmonella, E. coli, and Listeria, and their spores which are responsible for causing numerous foodborne illnesses.
Pasteurized Milk: Pasteurized milk do not contain pathogenic bacteria but contain spores of pathogenic bacteria. Therefore, if the product is exposed to the microbial growth desirable environment conditions milk can be contaminated with pathogenic bacteria originated from spores of pathogenic bacteria.
Foodborne Illnesses
Unpasteurized Milk: Unpasteurized milk is responsible for causing numerous foodborne illnesses.
Pasteurized Milk: Pasteurized milk is not (or rarely) responsible for causing numerous foodborne illnesses.
Consumption Statistics
Unpasteurized Milk: In most countries, raw milk represents only a very small fraction of total milk consumption.
Pasteurized Milk: In most countries, pasteurized milk represents a very large fraction of total milk consumption.
Recommendation
Unpasteurized Milk: Many health agencies in the world strongly recommend that the community do not consume raw milk or raw milk products.
Pasteurized Milk: Many health agencies of the world recommend that the community can consume pasteurized milk products.
In conclusion, people believe that raw milk is a safe healthier alternative because pasteurized milk usually undergoes various heat treatments which result in the destruction of some organoleptic and nutritional quality parameters of milk. Although, from a nutritional standpoint, raw milk is the best, yet pasteurized milk is safe for human consumption. Thus, pasteurized milk can be recommended for daily consumption.
References
Wilson, G. S. (1943). The Pasteurization of Milk. British Medical Journal, 1(4286): 261–2.
Feskanich, D., Willett, W. C., Stampfer, M. J. and Colditz, G. A. (1997). Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. American Journal of Public Health, 87(6): 992–997.
Image Courtesy:
“A2 brand milk” by BlackCab – Self-taken. (CC BY-SA 3.0) via Common