Pasteurization, Principles, Process and Equipment - Assignment Example

Pasteurization, Principles, Process and Equipment Pasteurization, Fundaments of Pasteurization, Methods, Equipments and Application Pasteurization is one of the most significant unit operations among other unit operations in a food processing industry. Food processing industry is becoming one of the growing industries throughout the world. The major role of the pasteurization is seen in the milk packaging industries, juice manufacturing and packaging industries, oil refining and packaging industries and other similar industries. It is common fact that milk is good after pasteurization or treatment of heat. However, refrigeration also enhances the shelf life of the food product without spoiling it. Pasteurization involves only heating or both heating and refrigerating the food product. Pasteurization is named after the unforgettable contribution of a scientist ‘Louis Pasteur’ in the field of food chemistry. The discovered pasteurization plays a vital role in enhancing the shelf life of the food products and beverages. It is common fact that treating food products with temperature reduces the amount of bacteria in the food and thus prevents food from spoiling. Warming up the food in ovens and stoves also kills bacteria. Cooking also kills bacteria present in the food. However, if the food is kept at room temperature for longer time, it gets rotten due to the regeneration and formation of bacteria that remained in the food after treating it with the temperature. The heat treatment is unable to kill such type of bacteria that are capable of living at higher temperature. Such type of bacteria has protective walls that let them to remain alive at higher temperature. The fundamental principle behind the pasteurization is make utilization of the temperature to control the growth of microbes in the food product. Most of the packaged and tinned food and bottles beverages make utilization of pasteurization to increase the shelf life of the product and to remain the product fresher for longer periods (Bermúdez-Aguirre, et al, 2009). Increasing the temperature of the product is the good idea to get rid of some microbes that are killed with the treatment of heat but with the increase of the temperature some microbes still remained in the food product that are resistant to heat. The heat resistant microbes are also known as the thermoduric bacteria There is no other method to kill the heat resistant microbes, researcher realized that it is difficult to kill the heat resistant bacteria but the growth of the heat resistant bacteria can be limited through refrigeration. Thus, pasteurization is the process that involves both increasing the temperature of the food product and then reducing the temperature of the food product to make it free from spoilage (White, 2010). The concept of pasteurization first associated with the wine industry. Before the pasteurization wine fermentation was considered a purely chemical process but Louis Pasteur described the process as the biochemical process, in which the microorganisms like yeast are responsible for converting the sugar in the fruit juice to alcohol. Due to fermentation a rod shaped microbe known as Mycoderma aceti formed in the wine that made its taste sour and bitter. Louis Pasteur proposed a method of pasteurization to deal with the problem of the change in taste of the wine. The process was then adopted by the milk industry to make the raw milk free from the bacteria and other microbes. The first pasteurization process used to tat the milk was Low temperature, Long time (LTLT) process. The process was specially designed to kill the tuberculosis microbe and it is also referred as Batch pasteurization. The process was developed in around 1800s. However, the process was really slow and thus not feasible for industrial use. The first commercially utilized process of milk pasteurization was High Temperature, Short Time (HTST) process. It is relatively fast process. After the utilization of this process, the development in the sector increased and more laws regarding the pasteurization evolved for the food processing industries. The above processes come in the thermization process (White, 2010). The thermization process is unable to kill all the microbes and bacteria in the food product. The processes are used where; the food product alters its properties with the immense increase in the temperature. High temperature short time takes about 15 seconds to reduce the amount of bacteria in the food product. A well designed HTST process can reduce up to 90% of the non heat resistant bacteria (Latour, 1993). Ultra High Temperature (UHT) pasteurization process is a high temperature thermal process and it is used fro such food product that show similar properties with the increase in the temperature or shoe similar properties when cooled. Food grade Oil is processes through UHT process. UHT can never be used for milk because, high temperature treatment of milk alters the properties of the milk; it may smell burnt or cooked. Thus, HTST is considered good for the pasteurization of milk (White, 2010). Methods of Pasteurization Batch Pasteurization In Batch Pasteurization, the temperature of the food product particularly milk is increased to 154.4 degrees on the Fahrenheit scale or 63 degrees on the Celsius scale. The temperature is maintained for 30 minutes and the product is constantly stirred to ensure that each particle of the product is heated evenly. After 30 minutes the product is cooled to about 4 degrees on the Celsius scale or 39 degrees on the Fahrenheit scale. The method is not suitable for large industries; it can be used at home or at small scale. While, producing the product using the batch pasteurization will increase the total cost of the product as the product takes a large amount of energy. Some companies produce milk by utilizing the similar method. Some people suggest that the batch pasteurization has no or little affect on the taste and nutritious value of the milk; while some companies claim that it is impractical to produce milk utilizing this method due to lower efficiency of the product and higher marketing flaws (White, 2010). High Temperature Short Time (HTST) The method is also called flash pasteurization, in which the temperature of the food product particularly milk is decreased to 4 degrees on the Celsius scale or 39.3 degrees on the Fahrenheit scale. The cold food product or milk is then heated to 57 to 68 degrees on the Celsius scale. Steel plates are utilized to warm up the food product as steel produce no harm to the food product. During that time the milk remains in constant speed (Chiodini & Hermon-Taylor 1993). The food product is not allowed to remains in any chamber for longer time, as it is pumped constant out of the heating chamber. The food product (or milk) is then passed to a section that has more temperature as the previous section. Stainless steel heat exchangers increase the temperature of the food product to 72 degrees on the Celsius scale or 162 degrees on the Fahrenheit scale. The constant moving liquid food product or milk remains in this chamber for 15 seconds. A heat recover system, pumps the pasteurized food product (milk) to a regenerative chamber that extracts the heat from the hot liquid food product (milk) through heat exchange mechanism. The pasteurized liquid food product (milk) cools down by attaining the temperature of the incoming cold liquid food product (milk). The temperature of the pasteurized milk reduces to 32 degrees on the Celsius scale or 89.7 degrees on the Fahrenheit scale. In the last section, Heat exchanging mechanism reduces the temperature the liquid food product to 4 degrees on the Celsius scale of 32 degrees on the Fahrenheit scale. This method is widely utilized in milk industry but newer methods like Ultra high temperature (UHT) pasteurization is becoming famous due to increasing the shelf life of the food product (White, 2010). The other method of HTST Pasteurization is to heat up the liquid food product to 80 degrees on the Celsius scale or 175 degrees on the Fahrenheit scale for 25 seconds. The reaming process remains the same (Chiodini & Hermon-Taylor 1993). Higher Heat Shorter Time (HHST) Pasteurization Higher Heat Shorter Time (HHST) pasteurization heats up food product for the least possible time. It uses different times and different temperature for different food products. Food product is heated at 89ºC or 191ºF for one second. Food products are heated at 90ºC or 194ºF for 0.5 seconds. Food products are heated at 94ºC or 201ºF for 0.1 seconds (Kristen, 2013). Food products are heated at 96ºC or 204ºF for 0.05 seconds. Food products are heated at 100ºC or 212ºF for 0.01 seconds. These different times and temperature are used for different food products and it is ensured tat all the microbes in the food product are killed at these temperatures and time durations (Organicvalley.coop, 2013). Most of the bottled and canned food production and processing industries use this type of pasteurization. Bottled beverages and tinned containers are heated up from outside the container and steam is not introduced inside the contained. Ultra High Temperature (UHT) Pasteurization UHT pasteurization is also named as Ultra pasteurization. In UHT pasteurization, a constantly flowing liquid food product is heated to 138 to 150 degrees on the Celsius scale or 280 to 302 degrees on the Fahrenheit scale only for one or two seconds. Stainless steel heat exchanges and pipes are utilized to increase the temperature of the liquid food product. On the other hand, a constant flow is maintained to prevent the food product from damaging. Majority of the milk processing industries are utilizing the UHT pasteurization to increase the shelf life of the product. UHT treatment kills all the spores in the liquid food product but it consumes the most energy all pasteurization processes (Douglas Jr, at al, 1981). Basic type of Heat exchange equipment The temperature of the liquid food product is increased by utilizing the heat exchangers. Heating systems are of two basic types direct heating systems and indirect heating systems. Direct heating system utilize stem to increase the temperature o the liquid food product. Direct heating methods are utilized in UHT Pasteurization. Direct heating methods are characterized as injection direct heating method and infusion direct heating method. Injection Direct heating method In injection direct heating method utilizes an enclosed heating mechanism, in which the steam is kept in the enclosed heat exchangers for some time and injection system makes the way out of the of the enclosed heat exchangers. Steam remains in direct contact with the liquid food product. Pressure is maintained in the heat exchangers. Below is the graphical representation of the injection heating mechanism. Infusion Direct Heating System In infusion direct heating mechanism, steam is diverted to the enclosed heat exchanger and an outlet makes its way out of the enclosed heat exchanger. Steam remains in direct contact with the liquid food product. Steam and liquid food product may not have any separation. Below is the graphical representation of the heat exchange mechanism (Coulter, 1957). Indirect Heating mechanism In indirect heating mechanism, steam is not in direct contact with the liquid food product but separated by metallic heat exchangers. Indirect heat exchanges are widely utilized due to many practical advantages as compared to the direct heating mechanisms. Indirect heat exchangers are of two basic types. Plate Heat Exchangers In plate heat exchange system, alternate plates circulate liquid food product and cooling or heating liquid. Both the liquids exchange heat but none of the liquid remains in contact with other. Metallic plates have lines of small diameter to flow both the liquids. These systems are mostly utilized in cooling systems; while steam can replace the cooling liquid to increase the temperature of the liquid food product. Tubular heat exchangers Tubular heat exchanges are the simplest type of heat exchangers. A tube that contains the flowing liquid food product is kept inside another tube. The outer tube is fed with the steam, hot liquid or cool liquid which exchanges temperature with the inner tube. The medium that is entered into the tubular heat exchanger is constantly taken out by a pumping mechanism. Pasteurization is a significant unit operation of a food processing industry. The other basic unit operations of a food processing industry are homogenization, chilling and packaging. However, homogenization is associated with the milk processing (Organicvalley.coop, 2013). A common food processing industry utilizes different unit operation that commonly depends on the type of the food that is to be processed, type of the processing system and type of the available resources. Food processing is not uncommon. Cooking food at home can be food processing. However, the price of the processed depends on various aspects like the energy use to process the food, maintenance cost of the processing plant and labour cost. Newer processing system produce food is huge mass consuming less energy and thus the price of the processed food is reduced. Pasteurization is widely utilized in most of the food processing industries. Milk industry will not even exist without pasteurization. The three method of pasteurization have been adopted by the milk industry in different situations that are UHT pasteurization, Batch or Vat pasteurization and HTST pasteurization. While the HHST pasteurization methods are widely utilized in the canned food processing industries. While, bottles beverages also utilize the HHST pasteurization in which there s not need to increase the temperature of the food product before packaging or bottling, it can be easily done after bottling or canning. Pasteurization is widely utilized in juice extraction, manufacturing ad packaging industries to make the juice free from the harmful microbes. Moreover, the UHT pasteurization is widely utilized in food grade oil manufacturing and packaging (Kristen, 2013). UHT pasteurization is also utilized widely in milk processing industries to make the milk free from the harmful microbes. However, some people have the view that treating milk in such manner would reduce its nutritious value but the milk processors claim that only a small fraction of the vitamins lost during UHT pasteurization (Kristen, 2013). The loss of the vitamins remains equal if milk is boiled at home. The UHT pasteurization has little impact on the nutritious value of the oil and is considered good for the food grade oil manufacturing and packaging industry (Chiodini & Hermon-Taylor 1993). Pasteurization is the only method that can make the food products free from the harmful microbes. In pasteurization, the first step is to increase the temperature of the food to kill the microbes that are unable to resist high temperatures. However, decreasing the temperature of the food product also remains it fresh fro longer periods. Decreasing the temperature limit the growth of the microbes that remained in the food after increasing its temperature. Industrial revolution in food processing revealed some methods of the pasteurization that are not only fast but also energy efficient. Pasteurization has four commonly known methods. Batch pasteurization or low temperature long time (LTLT), High Temperature Short Time (HTST) pasteurization, High Heat Short Time (HHST) pasteurization and Ultra High Temperature (UHT) pasteurization are the commonly used pasteurization methods. All the pasteurization methods are suitable for different food processing industries. UHT is widely used to make milk free from any contamination. While in some countries pasteurization is also utilized to make water free from any contamination. References Latour, B. (1993). The pasteurization of France. Harvard University Press. Chiodini, R. J., & Hermon-Taylor, J. (1993). The thermal resistance of Mycobacterium paratuberculosis in raw milk under conditions simulating pasteurization. Journal of Veterinary Diagnostic Investigation, 5(4), 629-631. Coulter, W. H. (1957). U.S. Patent No. 2,799,216. Washington, DC: U.S. Patent and Trademark Office. Bermúdez-Aguirre, D., Mawson, R., Versteeg, K. And Barbosa-Cánovas, G. V. (2009), Composition Properties, Physicochemical Characteristics And Shelf Life Of Whole Milk After Thermal And Thermo-Sonication Treatments. Journal of Food Quality, 32: 283–302. doi: 10.1111/j.1745-4557.2009.00250.x Douglas Jr, F. W., Greenberg, R., Farrell Jr, H. M., & Edmondson, L. F. (1981). Effects of ultra-high-temperature pasteurization on milk proteins. Journal of agricultural and food chemistry, 29(1), 11-15. Kristen, M. (2013). Just Say No To UHT Milk | Food Renegade. [online] Retrieved from: http://www.foodrenegade.com/just-say-no-to-uht-milk/ [Accessed: 29 May 2013]. Organicvalley.coop (2013). Organic Valley - Pasteurization. [online] Retrieved from: http://www.organicvalley.coop/products/milk/pasteurization/ [Accessed: 29 May 2013]. White, C. (2010). HowStuffWorks "How Does Pasteurization Kill Bacteria?". [online] Retrieved from: http://science.howstuffworks.com/life/cellular-microscopic/pasteurization2.htm [Accessed: 29 May 2013]. Read More