Validation

The Hydrostatic Retort is a continuous agitating retort. Generally the hydrostatic retort can be thought of as a still steam retort, operated at a constant temperature through which the containers are conveyed by a continuous carrier chain, at a constant rate designed to provide the correct process time. There can be a small amount of product agitation as the convey chain changes direction in the hydrostatic tower, these changes of direction of the conveyer are referred to as “passes”.

These vertical retort systems are manufactured by only a few companies worldwide. They are very large and normally extend several stories into the air. Also smaller horizontal versions  of a hydrostatic retort are available.

Containers are loaded into the horizontal carrier on the continuous chain and conveyed up to the inlet leg of the sterilizer. The inlet leg is a water filled tower that the product travels down whilst being preheated and pressurized. At the bottom of the inlet leg the conveyor passes into the steam dome where sterilization takes place. The product then exits the cooker via another hydrostatic leg that starts the cooling and depressurization process. The conveyor chain then carries the containers back to near the loading station where the processed product is unloaded from the continuous carrier.

The water usage is lower than that of conventional retorts. Unfortunately, hydrostatic retorts have a high capital cost and require very high production volumes which need long cook times.

For validation of temperature and pressure measurements, only TrackSense wireless data loggers ideally mounted inside the cans can be used. For some hydrostatic retorts and hydrolock retorts some can rotation can take place. Typically most products will be sterilized about 121.1˚C, but depending on products and tower height the temperatures can be higher or lower.

Typical products in cans, trays, bottles and pouches processed in Hydrostatic Retorts:

• Pet foods
• Soups
• Vegetables
• Fruits
• Canned specialty products

Internationally Recognized Guidelines

Before doing any measurements, it is a good idea to use equipment which is complying to:

• ISO 9001 Certification
• FDA 21 CFR 113 Thermally Processed Low-Acid Foods
• 21 CFR part 11 Electronic Signatures
• CE & UL Approvals
• cGMP or GAMP5
• ISO/IEC 12207 Software life cycle processes
• IFTPS Guidelines
• Guidelines issued by local authorities

Recommended Test Equipment

The calibrated system should be equipped with sufficient channels, to accurately monitor and record temperature and  pressure – within the process delivery system.
Use TrackSense wireless data loggers of sufficient accuracy and in sufficient quantity, to adequately monitor the process water and product temperatures within the retort.
The data loggers should record the temperatures and pressure at sufficient intervals, not to exceed one minute, throughout the test.
Equipment and procedures for pressure processing in steam in hydrostatic retorts are covered by US legislation 21CFR 113.40(f) of the lacf regulations.
Check the accuracy of the sensors against a reference instrument (ETI). Any single sensor should be within 0.3°C of the reference.
The maximum deviation between any  of the  sensors should not be more than 0.6°C.

• Initial temperature should be recorded
• Depending on size and conveyor speed 6-20 temperature loggers are recommended
• Temperature Loggers must be spread over the whole width of the carriers
• At least one Pressure logger is recommended
• A sampling time of 1-15 seconds
• The TrackSense wireless loggers should be introduced into the carriers with intervals giving a representative mapping of the retort
• The “cold spot” detected is in the geometric center for conduction heating cans.
• Bring the retort up to the same temperature and pressure as designed for the actual processing parameters before any testing commences.