Golden Rules of Retort Processing

Ready To Eat, Shelf Stable, Retort Sterilized Foods are completely cooked food packed in airtight containers, which could be preserved at room temperature for a long period of time without the necessity of freezing, cooling and drying.

In order to produce high quality safe Retort Food, it is very important to optimize the retort processing. The product should be sterilized properly to make sure that it is safe for consumption. At the same time, it should not be over cooked or over processed. Because over sterilization kills the taste and food appeal of the product, which in turn make it as a Junk Food..

The person who wish to start Retort Processing should follow the below mentioned Golden Rules to become a successful processor

It is to be noted that all type of food can not be processed in the retort. Only those food which can withstand high temperature ( above 100 deg C) could be processed in the retort. Normally the target temperature of retort processing in 121 deg C. But any temperature above 100 deg C could be considered as sterilisation temperature ( under certain conditions).
The target food / recipe should have a medium to transfer the heat. The heat needs to be penetrated all over the surface and to the interior of the food to make it sterile completely .

Products like sausages etc could be processed in vacuum packed containers. Here the heat penetration will be directly to the products, which eliminates the requirement of additional medium for the heat transfer.

So it is important to select the target food properly and make sure that the product is retortable, before the start of the project.

After selecting the target food, the next step is select the suitable containers for packing the food. The main criteria involved in selecting the containers is its capacity to withstand high temperature and pressure during the processing. Normally the temperature applied is about 121 deg C and pressure is about 2 to 3 bars. So the container with the closure should withstand such high processing conditions.Different types of containers are available for retort processing. Mainly the containers used are Cans, Pouches, Plastc Trays, cups, bottles, glass bottles etc. Retortable cartons are also introduced recently.
The profile of the cans make the processing easy considering the rigidness of the material. But at the same time, the heat penetration becomes slower and it takes more time for the products located at the middle to get proper heat penetration.

Pouches have flat surfaces, which makes the heat penetration faster resulting the production of better products. But because of the flexible nature of the material, utmost care is required to set up the pressure profile properly to avoid damages during processing.

Plastic Trays needs separate films for top sealing. The sealing of two different materials make it more difficult to set the proper over pressure parameters.

The selection of suitable containers is also important while planning for the retort food project.

After selecting the product and packing material, next step is to select the suitable retort for the processing.

Different types of retorts are available in the market, namely Steam Retort, Steam Air Retort, Water Immersion Retort, water cascading retort, water shower retort, water spray retort, rotary retort, shaking retort, tilting retort etc.

Each type of retorts are developed for processing certain types of food in certain types of containers. The processor should be very careful in selecting the suitable retort based on the selected food and products.For example, dairy products should be processed only in rotary retort or shaking retort or oscillation retort. Canned products can be processed in steam retort where as flexible containers can not be processed in steam retort. Retorts with over pressure control is much essential for the production of products in flexible containers. Stem Air retort is considered as general retort for processing flexible containers

Plastic trays and cups gives better performance in water spry retorts than steam air retorts. Plastic bottles should be processed in water cascading retorts to get the best out of it.

Shaking and Rotating technology adds value to the performance of retort. These features reduces the process time by 30 to 50% than the static mode of operation. This improves the quality and also production capacity.

The retort should be selected based on the type of products and type of containers. Anyway the aim of the processor should be to achieve the sterilization within shortest possible time.

After installing the suitable retort which was selected based on the type of products and containers, the next step is to develop the retort processing technology.

The retort processing technology should be developed based on the type of products, type of container and type of retort.

The following points should be considered while developing the technology :

The maximum temperature which the products / receipe could withstand before it loses its food qualities. This is defined as Holding Temperature.

The maximum time which the products could withstand at the holding temperature . This is defined as holding time

The required over pressure profile required for each step of the processing including the come up time, holding time and cooling time. Proper pressure profile should be defined

In case the processor selected the rotary or shaking retort, then he should also find out the suitable speed of rotation or shaking to get the best heat penetration effect.

There are equipment available in the market, which helps the processor to study in detail about the cooking and sterilization effects of the products at higher temperature, behaviour of the containers and products during the processing, estimate the cooking damage occurring on the products during the processing, to study the differential pressure occurring on the containers during processing etc. The processor should make use of such equipment to study the behaviour of the products and containers during the processing and estimate the required temperature, time and differential pressure required to set up the processing parameters.

Overall the processing technology should be developed to optimize the processing parameters. The aim of the processor should be to sterilize the food within shortest time without compromising the quality and safety of the products. The container safety also should be taken care .

This is much required to produce high quality retort food.

The success of the retort processing is the proper implementation of the processing technology. There is no fixed processing technology for any specific product. But there are good guidelines available for the development of the technology. The processor should make use of such guidelines and then develop own processing technology.The processing technology should be developed based on the type of products, type of containers, type of retorts, availability of the supporting machinery, available utilities etc.
For example, if the processor has high speed filling and sealing machine, then he should have proper control of the initial temperature of the products. Other wise, there will be huge variations in the initial temperature resulting non-uniformity of the products.

The low capacity boiler provides less stem flow resulting slow come up time and lengthy processing time.

The availability of the cooling water systems also imparts the processing parameters.

The quality f automatic control system of the retort also plays a major role in setting the parameters. Low profile retorts may not have proper control to set some of the critical parameters like step by step come up time and cooling time setting etc.

So the retort technology should be developed based on many different critical factors involved in the processing .

Proper study of the heat penetration data is most essential while setting the parameters.

The success of the retort processing depends much on the development and implementation of the proper processing technology.


Once the processing technology is implemented, the next step is to validate the retort and process.

Validation of the Retort is to confirm that the retort works fine within its specific conditions and make sure that the products processed in each and every corner of the retort get proper uniform sterilization effect.

The validation of the process is to conform that the implemented technology is adequate to conform the sterility of each and every parts of the products processed are safe even in the adverse conditions.

Temperature Distribution Study, Heat Distribution Study, Heat Penetration Study, partial and full load test etc are the main tests to be performed as part of Validation Study.


It is important to make proper documentation of the validation reports and also daily process details. Daily reports should be checked against the validation data and if any deviations are found, then remedies should be taken immediately.
The details of the utilities like boiler, compressor, cooling water, stem flow, process parameters etc to be documented and regularly check against the actual values.

The food appeal of the finished products should be checked and documented against its fresh equivalence. The color, texture, taste, aroma etc needs to be documented.

Before sending the finished products to the market, it is important to do the microbiological analysis of the sample products from every batch.

The sample products collected from the cold spots of the retort should be kept in the incubator for about 14 days and then analyze it to check for the growth of any kind of bacteria. The products should be sent to the market only after the safety approval from the microbiological lab.

The processor could produce high quality retort food which even resembles with its fresh equivalence in terms of color, taste, texture, nutritional content etc if he strictly follows the above mentioned points.

If compromised on any of the mentioned points, then there could be the possibility of the production of retort food which would be far inferior to its fresh equivalence. There could be significant damages to the flavor, texture, color and nutritional content of the retort food.