Heat Treatment Equipment for Canned Meat: Autoclaves and Sterilizers
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Heat treatment of meat and meat products is the brief or prolonged application of thermal energy to them, either through direct contact or through a separating partition. This page describes the equipment needed for the heat treatment of canned meat. 
What is sterilisation of canned meat?
Sterilisation is the heat treatment of products that have been packed and sealed in airtight containers at a temperature above 100 °C, resulting in the inactivation of enzymes and the destruction of microflora. It is the key process that makes canned meat shelf-stable and safe for storage. The equipment used to carry it out falls into two broad groups defined by how product moves through the machine.
What equipment is used to sterilise canned meat?
Canned meat is sterilised in two categories of apparatus, distinguished by whether they operate in batches or continuously:
- batch (periodic) machines — vertical and horizontal autoclaves;
- continuous machines — hydrostatic, linear and rotary sterilisers.
In the meat industry, batch autoclaves together with linear and hydrostatic continuous sterilisers are the types that have found practical use. Within batch autoclaves, two methods of sterilising cans with live saturated steam are applied: without water and counter-pressure, and in water with counter-pressure.
When is water and counter-pressure required?
The choice between the two batch methods depends on container size and material. Cans in glass jars of up to 500 cm³ are sterilised with live steam without water and without counter-pressure. When the volume exceeds 500 cm³, and for products in metal containers, sterilisation is carried out in water with counter-pressure to prevent deformation of the lid and the bottom of the container.
How does the B6-KAV-2 autoclave work?
The B6-KAV-2 autoclave (Fig. 1) is designed to sterilise hermetically sealed cans of product at temperatures above 100 °C. The B6-KAV-2 is a vertical batch-type apparatus. It consists of a body (3), a lid (4), baskets (10), a fitting (9) for connecting the PRP-2 program controller, and the valves and connections for the lines that supply steam, water and air and that drain condensate.
The welded body of the autoclave is made up of cylindrical shell sections 6 mm thick and a bottom 8 mm thick. Mounted on the body are a pressure gauge (8), a thermometer (7) and the sensors of the PRP-2 program controller. In the lower part of the body sit a steam sparger (11) and a drain pipe with a cup.
The flanges of the lid and the body are pressed together by a quick-action clamp (2), which comprises fifteen sector grippers fixed to a spring-steel ring, together with a system of levers for tightening and releasing the belt clamp. 
On the lid there are fittings for the safety valve (5) and the plug-and-bleed cock (6). The lid is fitted with a balancing device (1) that makes it easier to open and close. Baskets filled with cans are stacked one above another inside the autoclave, after which the lid is closed. The vessel is filled with water and steam is fed in through the sparger.
An air compressor creates and maintains constant pressure in the system. Once the sterilisation time has elapsed, the steam and hot water are gradually displaced from the apparatus by the cold water that flows in. After cooling, the baskets of cans are unloaded from the apparatus.
What types of continuous sterilisers exist?
Continuous sterilisers are divided into rotary, horizontal, conveyor and hydrostatic types. The first two are used rarely. Hydrostatic continuous sterilisers apply the principle of balancing the pressure in the sterilisation chamber by means of hydraulic locks. These machines are tower-type units of considerable height, yet they occupy a relatively small floor area in the production hall. Several types of hydrostatic steriliser are used: the "Stork" with counter-pressure, and the pneumo-hydrostatic "Hunister" and A9-FSA.
How does the "Hunister" continuous steriliser operate?
The "Hunister" continuous steriliser of the OHS type is designed to sterilise finished product in glass or metal cans in a continuous flow. The main assemblies of the OHS-1 steriliser are: a loading conveyor that feeds product into the steriliser from two sides; a device for loading filled cans into carriers; the can carriers and the chains that transport the carriers through the steriliser; the housings; the devices for unloading cans from the carriers; and the conveyor that moves the canned product as it is discharged from the steriliser.
Cans loaded into the carriers by the loading device are directed into the steriliser and pass through six preliminary baths arranged in series, each 4 m high. The upper level of the water columns is regulated automatically by means of receiver towers, and the pressure is regulated individually in each bath. From the heating zone the cans move into the sterilisation zone, which is filled with a steam-water mixture at a pressure of 240 kPa.
Temperature in the "Hunister" is controlled by an electro-pneumatic system. On leaving the sterilisation zone, the carriers with their cans enter a bath where cooling begins. In the lower part of this bath the pressure reaches 380 kPa, the maximum found anywhere in the apparatus. After leaving this bath, the carriers with cans pass into a cooling zone made up of six baths, which are likewise connected to the receiver towers.
Seven pumps move water through the steriliser in the direction opposite to the travel of the cans, ensuring counter-current cooling. After the cans exit the steriliser, they are unloaded from the carriers.
