Pasteurization is a process of treating foods, especially fluids, in order to reduce the potential microbial growth. This is a method commonly used to preserve foods for a longer period of time. In this process food is heated to a high temperature for a specified period of time duration and cooled immediately. Although sterilization is a process similar to pasteurization, the former method actually kills the bacteria present in the foods whereas latter only reduces the growth of the microbes to produce disease-free food.
History of Pasteurization Food Preservation Method
Pasteurization as a food preservation method has been known since 1117 in China.The Chinese used to pasteurize wine by heating it to a specified temperature and then cooling it. In 1568, this preservation technique was documented in a Japanese diary ‘Tamonin-nikki’ as well. However, the term ’pasteurization’ was not prevalent in China and Japan in those years, they used to know the process as ‘heating’ until the introduction of pasteurization food preservation method by Louis Pasteur, a French Chemist, after whom the method has been named. He, along with Claude Bernard, a French physiologist, completed the first experimentation of food preservation by heating in April 1862. The process was first developed to heat and prevent beer and wine from turning sour.
Later on this process became largely associated with milk and the idea to pasteurize milk was first suggested in 1886 by Franz von Soxhlet, a German agricultural chemist.
Process of Pasteurizing Foods
Earlier, pasteurization was done for wine to remove or inactivate the organisms by heating the wine at a specified temperature for a desired level of time. The heating temperature was usually below the boiling point. This process preserved the wine largely by not allowing it to turn sour very soon.
After the suggestion of pasteurizing milk, the process has been the best method to increase the shelf-life of milk and it is largely applied to preserve milk and milk products. In this process the milk is heated in a way that all its particles are heated through to a specific temperature so that there is no scope of milk contamination during the process.
There are two types of methods that are applied to milk for pasteurizing it. Here are the methods discussed below:
- High temperature/Short time – In brief, this method is called HTST method. In this method the milk is heated through a temperature of 71.7 °C (161 °F) for at least 15–20 seconds. It is either placed in milk pipes, heated through hot water from outside, or two metal plates are used to force the milk container in between to heat it. The resulting milk has a cooked taste and a creamy color. This type of treated milk is labeled as ‘pasteurized’.
- Ultra-heat Treated - In this UHT or ultra-high temperature method the milk is heated and held at a temperature of 135 °C (275 °F) for minimum one second. This heating treatment improves the milk’s quality and increases its shelf life as well. ‘UHT’ or ‘Ultra pasteurized’ is the label usually given to the milk treated by this method.
Advantages and Disadvantages of Pasteurization Food Preservation Method
Although pasteurization is being done throughout the world since the invention of this method, the effectiveness of the method is under scrutiny from past few years. This method, like other food preservation methods, has advantages and disadvantages that are discussed below:
- The flavor and the texture of the milk have improvised after pasteurizing it.
- The method kills the pathogens or bacteria present in the raw milk and makes is safe to consume without any health risk.
- UHT method is the best to apply, as it has less of an adverse effect on milk’s nutritional value and taste.
- This method may prevent many diseases such as diphtheria, tuberculosis, scarlet fever and brucellosis by killing some of the most harmful bacteria.
- Milk pasteurized with HTST method is believed to lose 1/3rd of the thiamine present in the milk and half of vitamin B12.
- The discovery of heat resistant pathogens has increased the risk of the presence of bacteria even after pasteurizing the food.
- Due to loss of certain enzymes in food during pasteurization, few people consider raw milk a better option to pasteurized milk.
Foods Commonly Pasteurized Other than Milk
Milk is a food product that is pasteurized worldwide, but few other foods are commonly pasteurized in certain parts of the world. Here is the list:
- Canned foods – these foods include meats, vegetables and fruits that are generally heated in the can or container itself to kill the micro-organisms.
- Juices – most of the tetra-pack and bottled juices are pasteurized first before filling in the packs and bottles.
- Low-alcoholic beverages – Like juices, these beverages are also heated and cooled before filling in bottles.
- Water – The bottled water is usually pasteurized and in places where polluted water is available, the pasteurization becomes quite necessary.