Pasteurization is a method of heat processing food items in a hermetically closed container at a temperature less than 100°C. The main purpose of pasteurization for preserved food items is the deactivation of enzymes, limiting the life function or partially destroying living microorganisms that can cause food spoilage, and can pose a threat to human health. Pasteurization destroys moulds, yeasts, non-sporogenic microorganisms and vegetative cells of sporogenic bacteria.

During pasteurization, it is very important to properly set the heating regime for the preserved product, in order to properly conserve good product quality. The pasteurization process achieves temporary stability of a product with a limited shelf-life. The heat processing regime during the procedure itself depends on several factors, the most important of which is the pH value of the product.

Products made of fruit, tomatoes and marinated fruits have a pH of less than 4.5. In these products, pasteurization near 100°C is required in order to completely destroy the microflora due to the high acidity of the medium. Pasteurization destroys those microorganisms capable of growth in hermetically closed containers. Since some products are heat-sensitive, their heating should be limited, taking into account the temperature necessary to destroy yeasts. The bacteria that survive this procedure are not able to reproduce in the acidic medium of the product, while the growth of yeast is hindered due to the elimination of oxygen from the container. The temperature must be high enough to deactivate the enzymes that cause spoilage of product quality during the storage period.

With regard to the minimum time and temperature necessary to preserve products, this varies depending on the acidity, heat conductivity and internal contamination of the product. In considering the pasteurization process as a function of time and temperature, it can be divided into two methods. If properly executed, both methods are successful in conserving the natural and fresh aroma of the product. An older method, called extended shelf-life (ESL) pasteurization, treats the product at a relative low temperature over a longer time period, while the newer method, called flash pasteurization or high-temperature short-time (HTST) pasteurization, treats the products at a sufficiently high temperature to achieve pasteurization results in a shorter time period.

In ESL pasteurization, the containers are filled with the cold medium, or with the medium heated to a temperature that is near the pasteurization temperature. The container is then sealed hermetically and exposed to the effects of the pasteurization temperature in a water bath. After the container and its contents are kept at the specified temperature (until the pasteurization procedure is completed), this is followed by rapid cooling. In flash pasteurization, the medium is treated with steam or a steam-heated water bath in order to heat it to the desired temperature.

Once that temperature is achieved, the hot media can be partially cooled prior to filling, or filled directly into the containers, which are then hermetically sealed after filling, thereby pasteurizing the hot medium by sealing. This is followed by rapid cooling of the medium with water. The total time period during which the medium is heated ranges from 1 to 3 minutes. The temperatures used typically range from 77 to 88°C, depending on the product being processed.

Preserved products that are pasteurized include fruit juices and tomato juice, and other products that are treated with the addition of saline or acidity liquids, such as pickles, pickled peppers, mixed salads, beetroot salad, chilli peppers, ajvar relish, green olives and beer. In terms of fruit juices, these can be divided into pulpy juices (cloudy apple juice, peach juice and strawberry juice), opaque juices (orange juice, pineapple juice) and clear juices (clear apple juice, sour cherry juice, raspberry juice, pomegranate juice).

Tunnel Pasteurizer

The universal continuous tunnel pasteurizer is a device for the permanent stabilization of foodstuff items using the pasteurization process. It is used for the processing and preserving of fruits and vegetables in the appropriate solutions, and also for beverages and other products of the food industry. This processing procedure ensures that no important elements or aroma is lost from the food, ensuring its extended shelf life and guaranteeing a high quality of the product itself.

How it works

Using the entrance transporter, the packaging is distributed at the entrance of the tunnel, such that it reaches the main transport line along the entire width of the line and the tunnel. As it passes through the tunnel, the packaging comes into contact with steam or water. The contents of the packaging are heated to the pasteurization temperature, kept at that temperature for the required amount of time, and then cooled. The length of the heating zone, cooling zone and pasteurization zone, and the speed and length of the main transport line are adapted to suit the needs of the capacity and technological regime of production. The option of changing the temperatures in the temperature zones and the speed of the main transport line allow for easy adaptability of the tunnel pasteurizer to the required technological production regimes.

Characteristics of the construction and operation

The construction characteristics of the tunnel enable a wide selection of technological regimes, and therefore the tunnel can serve as both a pasteurizer and a refrigerator. In the heat treatment procedure, steam and fine water spray are used. The steam is regulated as it enters the steam chamber via the automatic regulation valve, in order to maintain the necessary pasteurization temperature. Water is reused multiple times as the basin and pump system return the water to the nozzles, where it is then sprayed into the heating or cooling chambers. No steam is able to escape the tunnel pasteurizer into the work environment, due to the sealing system and ventilation vents at the entrance side of the tunnel.

Water circulation pumps are protected with a dual oversized filter that can be cleaned during normal operations. At the exit from the tunnel, air flow blows the remaining drops of water off the package lid. The continuous transport of packaging in the tunnel is achieved using various transport track lines (depending on the technological requirements) of varying speed, which is made possible with frequent regulation or variation (very important for the beer brewing industry). The ability to change the speed of line movement also enables alterations to the technological regime.

The standard construction of the sections used to build the tunnel pasteurizer enables simple machine transport and assembly, and enables precise design and selection of capacities, easy replacement of parts and simple expansions of machine capacity through the installation of new sections as needed.

Technical data and dimensions of the device

We deliver the tunnel pasteurizer with an operational tunnel length from 8 to 21 metres.
The maximum length of the entire plant is 2600 mm longer than the operational tunnel length.
Operational tunnel width: 2000 - 7000 mm
Maximum plant width: 8400 mm
Tunnel height: 1700 mm ( 1 story ) ; 2450 mm ( 2 story )
Maximum plant height: 2450 mm
Passage time through tunnel is set for all pasteurisers in the range.: 20 - 120 min
Maximum permitted height of packaging: 310 mm

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