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    Food processing techniques and preservation principles

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    What are the differences between (a) Pasteurization, (b) Commercial sterilization, and (c) Ultrahigh temperature processing (UHT). The discussion should be based on the processing method involved and preservation principles behind each method. In addition, what will be the shelf-life expectancy for food products treated by each one of these methods?
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    It is a process of destroying microorganisms that could cause disease. This is usually done by applying heat to a food. Pasteurization is the process of heating liquids, especially milk, for the purpose of destroying viruses and harmful microorganisms such as bacteria, protozoa, molds, and yeasts. The process was devised by a French chemist and microbiologist Louis Pasteur. The process is not intended to kill all pathogenic microorganisms present in the food or liquid. Instead, it aims achieving a "logarithmic reduction" in the number of viable organisms, reducing their number so they are unlikely to cause disease. It is based on the assumption that pasteurized product is refrigerated and consumed before its expiration date.

    Food Safety Implication: Through the process of Pasteurization, a liquid or food is heat processed to kill pathogenic bacteria, rendering food safe for consumption. Pasteurization helps to reduce the transmission of diseases, such as typhoid fever, tuberculosis, scarlet fever, polio, and dysentery. Foods can become contaminated even after they have been pasteurized. Thus, all pasteurized foods have to be refrigerated. If temperature is abused (e.g., if milk or eggs are not kept refrigerated), pasteurized foods can also become contaminated.

    The process of Pasteurization: Foods are heat-processed to kill pathogenic bacteria. Foods can also be pasteurized using gamma irradiation. Such treatments do not make the foods radioactive. The pasteurization process is based on the certain pre-determined time and temperature relationship as follows:
    - High-Temperature-Short-Time Treatment (HTST) - Using higher heat for less time to kill pathogenic bacteria. For example, milk is pasteurized at 161° F (72° C) for 15 seconds.
    - Low-Temperature-Long-Time Treatment (LTLT) - Using lower heat for a longer time to kill pathogenic bacteria. For example, milk is pasteurized at 145° F (63° C) for 30 minutes.
    The times and temperatures depend on the type of food and the final result to be attained, such as retaining a food's nutrients, color, texture, and flavor along with using adequately high temperature for a sufficient amount of time to kill pathogenic bacteria. Some of the processes used to pasteurize food stuffs include:
    Flash Pasteurization - It involves a high temperature, short-time treatment in which products such as juices, are heated for 3 to 15 seconds to a temperature that destroys harmful micro-organisms. After heating, the product is cooled and packaged. Most drink boxes and pouches use this pasteurization method as it allows extended unrefrigerated storage while providing a safe product.
    Steam Pasteurization - It involves heating to control or reduce harmful microorganisms present in beef. The process involves passing freshly-slaughtered beef carcasses which have already been inspected, washed, and trimmed, through a chamber that exposes the beef to pressurized steam for approximately 6 to 8 seconds. The steam raises the surface temperature of the carcasses to 190° to 200° F (88° to 93° C). The carcasses are then cooled with a cold-water spray. This process has proven to be successful in reducing pathogenic bacteria, such as E. coli O157:H7, Salmonella, and Listeria, without the use of any chemicals. It is used to pasteurize nearly 50% of U.S. beef.
    Irradiation Pasteurization - This process is meant to subject foods, such as poultry, red meat, spices, fruits and vegetables to small amounts of gamma rays. It effectively controls vegetative bacteria and parasitic foodborne pathogens and increases the storage time of foods. Pasteurizing eggs are also useful as it reduces the risk of contamination from pathogenic bacteria, such as Salmonella, which can cause severe illness and even death.

    Pasteurization of milk: It improves the quality of milk and milk products, thus providing a longer shelf life by destroying undesirable enzymes and spoilage bacteria. For instance, milk is heated to 145° F (63° C) for at least 30 minutes or at least 161° F (72° C) for 15 seconds. Sometimes higher temperatures are applied for a shorter period of time. ...

    Solution Summary

    The solution explains the differences between various food processing techniques such as pasteurization, commercial sterilization, and ultrahigh temperature processing, along with their respective preservation principles, and shelf-life expectancies.