Cheese Vat

Overview

A cheese making vat is the vessel where liquid milk becomes solid curd. The operator fills it with pasteurized milk, brings the batch to a coagulation temperature near 31 °C, adds starter culture and rennet, and lets the milk set into a soft gel. The vat then cuts that gel into uniform cubes, stirs the cubes while heating the batch further to expel whey, and finally drains the whey and discharges the curd. One machine carries the milk through the entire make cycle, which is why the vat combines heating, cutting, stirring, draining, and cleaning in a single welded body. The horizontal double-O shape, two overlapping cylinders joined along their length, gives the cutting and stirring tools a clean sweep with no dead corners where curd can stall.

The wetted vessel is built from 316L stainless steel for resistance to lactic acid and to the caustic and acid cleaning chemicals used between batches. Interior surfaces are polished to a 320 grit finish so that no crevice harbors bacteria, a requirement under 3-A and EHEDG hygienic design rules. The whole assembly rides on a Support Frame tall enough to clear a whey line and a curd drain table beneath the discharge.

Vessel and double-O body

The Vat Vessel is the core that holds the milk. A rolled Inner Shell in the double-O profile forms the wetted surface, surrounded by an Outer Shell that encloses the heating water, and the pair is closed at each end by a dished End Wall. A hinged Manway gives access for inspection and manual cleaning of any stubborn deposit. Two Thermowell pockets let probes read milk temperature without piercing the sanitary boundary, and a pH Port mounts the acidity probe at the milk line.

Heating jacket

Indirect heating keeps the milk from scorching, so the vat carries a Heating Jacket Assembly of dimple plate welded to the shell. Hot water at 40 to 50 °C circulates through the Jacket Plate panels, entering at a Water Inlet and leaving at a Water Outlet, with internal baffles spreading the flow evenly across the surface. A Circulation Pump forces the water around the loop, a Steam Injector raises its temperature with plant steam, and a Heating Element gives electric backup where steam is not available. The water temperature stays close to the milk target so the curd never overheats at the wall, which would toughen the protein and trap fat in the whey.

Cutting and stirring

After the milk sets, the Cut and Stir Assembly assembly does the mechanical work of cheesemaking. Two horizontal shafts each carry a Tool Frame strung with a Cutting Knife grid of tensioned stainless wires. Turning slowly in one direction, the wires slice the coagulum into cubes of 5 to 15 mm, the size set by knife spacing and the cheese being made. Reversing the shafts presents a Stir Paddle face that gently agitates the cubes so whey drains from them without shattering the fragile curd. A Shaft Seal keeps the milk sealed where each shaft passes through the end wall, and each shaft journal runs in a Shaft Bearing outside the vessel.

The Drive Assembly turns these tools. A geared Servo Motor drives each shaft through a Gearbox, with a Variable Frequency Drive setting cutting speed near 1 to 6 rpm and stirring speed up to 18 rpm. A Drive Coupling links the gearbox to the shaft, and a Torque Limiter slips before the tools can bend if the curd mats too firmly.

Whey drainage and curd discharge

Once the curd has firmed and reached its cook temperature, whey is drawn off through the Whey Drainage System system. A Strainer Screen holds the curd back while whey passes through a Whey Valve into the collection manifold, and a Flow Meter records the volume removed so the make stays repeatable. The drained curd then leaves through the Curd Discharge Assembly assembly: a Discharge Valve opens the bottom port and a gentle Curd Pump moves the curd to the drain table without crushing it.

Control and cleaning

The Control Panel runs the make as a timed sequence. A Make-Cycle Controller reads the RTD Probe temperatures and the pH Probe, then drives heating, cutting, stirring, and draining steps in turn while the operator watches an LCD Panel. Because the vessel never comes apart between batches, cleaning happens in place through the CIP System, which pumps caustic, then acid, then a rinse through a rotating CIP Spray Ball and an O-Ring Set of food-grade gaskets seals the process lines during the wash. A sloped Cover and Lid Assembly keeps airborne contamination out and routes condensate away from the milk through its gutter.

Variants and use

Open horizontal vats of this kind suit semi-hard and hard cheeses such as cheddar, gouda, and gruyere, where the curd needs firm cutting and a long cook. Smaller artisan makers run 2,000 to 5,000 L vats, while industrial lines use 15,000 to 20,000 L vessels feeding a draining belt. Enclosed cheese tanks exist for cultures that need a sealed headspace, but the double-O open vat dominates because its tool sweep cuts and stirs the whole batch evenly and discharges cleanly to the next stage.