Equipment for Heat Treatment and Smoking of Sausage Products

Sausages, structured sausage products, and lard pass through a smoking and roasting process before heat treatment — work carried out with equipment for smoking, roasting, and cooking, including autoclaves, universal chambers, and ripening chambers for raw-smoked sausages. Smoking is the treatment of meat products with smoke-curing substances obtained in the form of smoke from the incomplete combustion of wood. The changes that occur in a product during smoking are caused not only by the smoke-curing substances but also by the temperature regime and the duration of treatment. Meat products are smoked under several regimes: 18–20 °C (cold smoking); 35–50 °C (hot smoking); and 72–120 °C (baking in smoke).

The wood species used to generate smoke are oak, beech, birch, poplar, alder, and aspen. Coniferous species are not recommended because of their resin content, and birch may be used only with the bark removed. Besides treatment with smoke, smoking can also be performed by applying a thin layer of smoke-curing liquid to the surface of the meat products — a liquid obtained from the products of incomplete wood combustion or from a mixture of synthetic components.

Smoking of sausage products relies extensively on thermal units, automatic smokers, universal thermal chambers, and smoking cabinets. In thermal units and automatic smokers, heat treatment is carried out while the product moves continuously; in universal thermal chambers, the stationary product is processed in sequence according to the technology (roasting, cooking, smoking, cooling, and drying).

What are thermal units and how do they move product?

Thermal units are designed for the continuous heat treatment of meat products. They are mechanized assemblies — several devices combined into one — with external smoke generators, regulated delivery of a smoke-and-air mixture, mechanized movement of the product, remote monitoring, and automatic regulation of process parameters.

By their method of moving product, thermal units may be chain-type or frame-type; by the character of movement inside the unit, pass-through or dead-end; and by the trajectory of movement, single-line, ring, or carousel. Thermal chambers can be single- or multi-chamber, stationary or non-stationary. The processing equipment is fitted with smoke generators, air conditioners, air heaters (calorifiers), fans, and systems for monitoring and regulating the process.

What types of smoking equipment are used?

Two types of smoking equipment are used: smoking ovens or smoking chambers, and the smoke generators in which the smoke itself is produced. The K7–FKV–U cooking vessel (fig. 1) is intended for cooking sausages, hams, liver, piece meat products, by-products, and meat and bone broths. The vessel is used in the shops of meat-packing plants as well as in low-capacity meat-processing enterprises. Figure 1 — General view of the K7–FKV–U cooking vessel: 1 – tank; 2 – jacket; 3 – hot-water supply valve; 4 – cold-water supply valve; 5 – lid; 6 – removable walls; 7 – thermal insulation; 8 – oil-filling pipe; 9 – oil-draining pipe; 10 – broth drain tap; 11 – hand-wheel/screw mechanism; 12 – slotted groove; 13 – steam-supply pipe; 14 – condensate-discharge pipe.

The K7–FVK–U vessel has a rectangular tank (1) with a jacket (2) filled with oil. Heating elements are installed in the jacket space for the K7–FKV–U250E and K7–FKV–U500E vessels, and a steam heat exchanger for the K7–FKV–U500P vessel. Into the vessel tank (1) one or two baskets are placed by means of an electric hoist, depending on the type or size of the vessel. The baskets are used for loading, cooking, and unloading the meat products.

When cooking hams or sausage products, the baskets are removed and replaced with frames that have grooves for shelves, on which the hams or other meat products are hung. The vessel has a lid (5) with a hand-wheel/screw mechanism (11) for opening and closing it. The outer surfaces of the vessel jacket are thermally insulated (7), and the outer surface is clad with removable walls (6).

On the rear wall of the vessel there is a slotted groove for venting water vapour when the exhaust fan is running while the lid is open and a basket or frame is being unloaded. Two valves are fitted to the vessel — for hot-water supply (3) and cold-water supply (4) — along with a tap for draining the broth.

The steam version of the vessel has flanged pipes for steam supply (13) and condensate discharge (14). The vessel jacket has pipes for filling oil (8) and draining oil (9), as well as sockets for installing thermal bulbs and TGP thermometers. The vessel's operating mode is maintained automatically. The product is cooked by applying voltage to the electric heating elements (in the electric version) or by supplying steam to the steam heat exchanger (in the steam version), which heats the oil in the jacket.

As the oil in the jacket heats up, the water in the working volume of the vessel is warmed. The oil jacket provides the maximum heat-exchange area and even heating of the working volume, and it also allows the energy of the heated oil to be used for cooking while the electric (steam) heating elements are switched off. The working temperature of the oil must not exceed 130 °C.

To maintain the set cooking temperature, part of the electric heating elements is automatically switched on or off, or steam is supplied to the steam heat exchanger in cycles. Modern equipment exists that allows several heat-treatment operations to be combined: settling, roasting, and cooking. Such equipment includes universal thermal chambers, which can be of batch or continuous action.

Universal batch-action thermal chamber

A universal batch-action thermal chamber (fig. 2) consists of three main elements: the chamber for heat treatment, an air conditioner, and a control panel. The product is loaded into the chamber along an overhead track through double-leaf doors. In the upper part of the chamber there is an air conditioner with a calorifier and fan, together with a system of air distributors.

How does a universal thermal chamber work?

The heat-treatment process passes through several successive stages. The temperature needed to dry the surface of the sausages (100–108 °C) is obtained from the calorifier. Air heated in the calorifier is delivered into the chamber by the fan, with the smoke duct closed, from both sides through conical blowing nozzles at a speed of 2 m/s and a relative humidity of 10–20%.

The air is removed through openings in the ceiling inside the chamber. For cooking, low-pressure live steam (about 200 kPa) is used, supplied into the chamber through a perforated pipe. Steam condensate collects in the lower part of the chamber and is discharged through a drain pipe.

The smoking process can also be carried out in this same chamber. During smoke treatment, the throttle valve in the smoke duct opens and smoke from the smoke generator is delivered into the chamber by the fan. Figure 2 — Universal thermal chamber: a) front view; b) cross-section; 1 – window; 2 – gas duct; 3 – electric motor; 4 – V-belt; 5 – condensate pipe; 6 – latch; 7 – door; 8 – door handle; 9 – rod; 10 – wall; 11 – nozzles; 12 – drive; 13 – live-steam pipe; 14 – fan; 15 – chimney; 16 – fresh-air pipe; 17 – exhaust-air pipe; 18 – calorifier; 19 – overhead-track beam; 20 – suction pipe; 21 – lamp.

What are smoke generators and which types exist?

Smoke generators are designed to produce the smoke-and-air mixture used in the roasting and smoking of meat products. Smoke generators can be local or centralized, and of batch or continuous action. Local smoke generators serve one or several chambers operating at the same time, while centralized generators serve several chambers operating at different times and under different regimes.

Smoke generators are divided into the following groups:

1. self-heating, through the combustion of wood or sawdust particles;
2. with gas heating;
3. with electric heating;
4. friction-type;
5. smoke generators operating in a stream of hot air or superheated steam.

The D9–FD2G smoke generator (fig. 3), with self-sustaining smouldering of wood, consists of a hopper for wood sawdust, a feeding device, a furnace, a fan, and a smoke cleaner. Moistened sawdust is loaded into the hopper and from there fed into the smouldering zone. The moisture in the sawdust prevents a flame from forming as it burns. The moisture evaporated during smoke formation is removed from the furnace.

The fan first delivers air for the smouldering fire into the air distributor. From there the air is led through a blade agitator into the smouldering zone. The sawdust is ignited by an electric igniter, and with the help of an agitator the fire spreads through the sawdust. Smoke from the generator is led off through a smoke pipe into the chamber. Figure 3 — D9–FD2G smoke generator: 1 – agitator; 2 – wood sawdust; 3 – smoke pipe; 4 – hopper for wood sawdust; 5 – feeding auger; 6 – drive; 7 – fan; 8 – air distributor.

How is smoke cleaned before reaching the product?

When it leaves the generator, the smoke contains impurities (ash, soot, tar, sawdust residues, and so on) that are separated from the smoke to prevent them from settling on the walls of the smoke ducts or on the surface of the product. Cleaners of various designs are used to deposit these particles. Some use a cyclone, in which centrifugal force separates the particles from the smoke.

In others, the smoke is passed through a column packed with porcelain rings, on whose surface the suspended particles settle. The simplest in design is the gravity cleaner, in which cleaning takes place as the smoke circulates along a winding path. Suspended particles, meeting baffles along the way, strike them and settle out.

Equipment set for a low-capacity sausage shop

The K7–FKC–0.5 equipment set for a low-capacity shop with an output of 0.5 t per shift is intended for the production of sausage products and smoked goods. The set is used at low-capacity meat-processing enterprises and in sausage shops. Figure 4 — Equipment set for a low-capacity sausage shop with an output of 0.5 t per shift, K7–FKC–0.5: 1 – meat-boning table model K7–FKC–0.5/1–1, for dividing the carcass into cuts, boning them, and trimming the meat; 2 – meat grinder K7–FVP–82, for mincing meat; 3 – table for accumulating lard; 4 – lard cutter K7–FGShM, for dicing lard into cubes; 5 – brine injector model K7–FShR, for injecting brine into the depth of the meat for smoked goods; 6 – rack model K7–FKC–0.5/2–2, for stacking containers of cured meat during brine curing and meat ripening; 7 – vat model K7–FCK/5–1; 8 – container for soaking smoked pork K7–FKC–0.5/5–1; 9 – meat mixer K7–FM–150, for preparing sausage filling; 10 – unit for fine mincing of meat model K7–FTN, for finely mincing the meat; 11 – table for tying sausages and smoked pork model K7–FCK–0.5/3–1, for tying sausage products and smoked goods before hanging them on shelves and loading them into trolleys or frames; 12 – vacuum stuffer K7–FShV–3, for filling sausage casings with the filling; 13 – thermal chamber K7–FTU, for the heat treatment and smoking of sausage products and cured meats; 14 – vat for soaking casings K7–FKC–0.5/5–1; 15 – vat for washing equipment K7–FKC–0.5/5–1 (3 units); 16 – cooking vessel K7–FKV–250, for cooking cured meats during the production of cooked-smoked goods.