Thermization process

Thermal processing plays a crucial role in ensuring the safety and quality of various food products, particularly in the dairy industry. Among the different techniques employed, pasteurization and sterilization are the two primary temperature categories used. However, there is another technique called thermization, or thermalization, which offers an alternative approach with distinct advantages.

Thermization is a heat treatment method that falls under the category of sub-pasteurization. In this process, milk is subjected to temperatures ranging from 62 to 65 °C for a duration of 10 to 20 seconds, followed by cooling. The objective of thermization is to maintain the properties of raw milk as closely as possible while significantly reducing the presence of bacteria, especially psychrotrophic flora.

Compared to pasteurization, thermization is considered a milder treatment. It is commonly employed to stabilize the quality of milk during extended storage periods or prior to cheesemaking. By applying thermization, the number of spoilage bacteria present in the milk is markedly reduced, thereby extending its shelf life. The advantage of this method lies in its ability to achieve significant bacterial reduction while minimizing collateral heat damage to the milk components. Furthermore, thermization does not result in any noticeable changes to the flavor of the milk, ensuring that its original taste and characteristics are preserved.

Typically, thermization is carried out at temperatures ranging from 62 to 68 °C for a duration of 15 seconds. This temperature range and time combination has been widely adopted within the industry, demonstrating its efficacy and reliability in achieving the desired outcomes.

In conclusion, thermal processing techniques such as pasteurization and sterilization are well-known methods for ensuring food safety. However, thermization provides an alternative approach that offers several advantages, including minimal alteration to the properties and flavor of milk while effectively reducing bacterial presence. By employing thermization at specific temperature and time parameters, the dairy industry can achieve the desired stabilization of milk quality for prolonged storage or in preparation for cheesemaking.
Thermization process

Hermetically sealed container

The preservation of food safety and quality in packaged foods depends on hermetically sealed packages.

The term hermetic refers to a container that is sealed completely against the ingress of gases and vapors. The package can be considered as an air or liquid tight container.

Such a container, as long as it remains intact, will also impervious to bacteria, yeasts, molds and dirt from dust and other sources.

The most common hermetic containers are rigid metal cans and glass bottles, although faulty closures can make them non-hermetic. Canned food can be defend as thermally processed shelf-stable foods in hermetically sealed containers, regardless of the type of container (metal, plastic, paper, etc) or how the thermal process was delivered.

The quality of the seal can readily be ascertained by coating the ampoule with a leak-detection compound or detergent solution, then pacing it in a bell jar of vacuum desiccators and evacuating. Any leaks present will result in an easily seen stream of bubbles.
Hermetically sealed container

Factors Affecting Time of Thermal Process

Factors Affecting Time of Thermal Process
The thermal process time necessary for preservation of a chosen food depends on the rate of heat penetrating into a food.

Since every part of the food in a container or can must receive the same adequate heat treatment to prevent its spoilage, the process time work depended on the part which receives heat most slowly.

The food part near the center of the container usually receives heat most slowly. Heat penetration in food is mainly due to conduction as well as convection, which may operate simultaneously or successively.

Conduction occurs in solid particles of foods and is slow while heat transfer by convection occurs in liquids.

Some foods such as sugar syrup, thick soup and tomato juice undergo changes in their consistency during heating.

A variety of factors influence the time required for thermal processing for food. These include:

1. The material of the container – glass having a slower rate compared to that of a metal.
   


2. The size and shape of the container – smaller and slim cylindrical cans attain the desired temperature faster
   


3. Initial temperature of the food - a higher initial temperature provides the lethal range for the microorganisms for a longer time and its average temperature during heating is higher than the food in the can with a lower initial temperature. A higher temperature is necessary for foods which heat slowly, e.g. meat, pumpkin etc.
   


4. Retort temperature a higher retort temperature heats the food rapidly.
   


5. Consistency of the food – nature, sizes and shapes pieces decide the rate of heat penetration.
   
   The pieces of food may retain the identity as in peas, plums, beets, asparagus and whole grain corn with smaller pieces requiring less time.
   
   Pieces may become mushy or change into a viscous mass as in the case of pumpkin, sweet potatoes, squash and cream-style corn, which get heated slowly as conduction is the main mechanism of heat transfer.
   
   Pieces may form layers as in the case of spinach and asparagus. In addition, the consistency of the foods depends on the different types of sauce starch salt or sugar that may be present.
   
   For example tomato sauce on baked beans slows down heat penetration more compared to plain sauce. Starch concentrations up to 6% decreases heat penetration, but at higher concentration, has no additional effect.
   
   Sodium chloride does not influence heat penetration, as its concentration is usually low. On the other hand increasing of sugar decreases heat penetration. However, this effect is counteracted by the decrease in viscosity of sugar solutions with increasing temperature.
   


6. Rotation and agitation of the container during heat processing hasten heat penetration, particularly if the food is a fluid, but may cause undesirable physical damage to some solid foods.

Cooling of the canned foods also is influenced by the same factors as the heating process. Rapid, artificial cooling is usually adopted to effect a greater control on the cooling rate, because slow cooling may cause overcooking of the food and also allow the growth of thermophilic organisms.
Factors Affecting Time of Thermal Process