Working Principle of Water Bath Continuous Canned Jam Tunnel Pasteurizer

Microbial Pasteurization TheoryPasteurization relies on low-temperature moist heat to inactivate pathogenic bacteria, mold, yeast and endogenous pectin enzymes inside fruit jam. Continuous hot water heat conduction destroys microbial protein structure under 78–92℃ without high-temperature damage to jam flavor, fruit texture and color, inhibiting fermentation, delamination and jar bulging, realizing long shelf life at room temperature.

Overall Mechanical Operation PrincipleThe whole machine is a closed insulated SUS304 stainless steel tunnel with four independent temperature zones. Sealed tin cans or glass jars filled with jam are transported continuously by variable-speed stainless steel chain conveyor, passing through preheating zone, constant temperature pasteurization holding zone, pre-cooling zone and final cooling zone sequentially. Each zone adopts independent circulating hot water heating system with steam/electric heat exchange and PLC constant temperature control.Two heat transfer types: full immersion water bath (cans fully submerged in hot water, uniform heating for large tin cans) and water spray bath (top & bottom nozzles spray hot water, less water consumption for small glass jars). Heat transfers through can wall to jam core to reach required pasteurization temperature and accurate holding time, then gradient cooling to avoid glass crack or tin can deformation, fully automatic continuous production matching jam filling line.

Four-Stage Technological Flow(1) Preheating Zone: 40–60℃, 1–5 minGradually heat cans with mild warm water to eliminate thermal shock, prevent glass breakage and lid bulging caused by sudden high temperature. Waste heat recovery between preheating zone and final cooling zone saves steam consumption.(2) Core Pasteurization Holding Zone: 78–92℃, 12–30 minSteam/electric heating coil maintains stable water temperature with ±0.5℃ precision sensor. Large flow circulating pump ensures full hot water coverage of every can. Conveyor speed decides holding time to reach required PU value, kill spoilage microbes and deactivate pectinase.(3) Gradient Pre-cooling Zone: 60℃ down to 35℃, 3–6 minSlowly release residual heat to balance internal and external pressure of cans, avoid crack and deformation from direct cold water impact.(4) Final Cooling Zone: Cool cans below 30℃ with normal temperature cold water, stop continuous thermal damage to jam color & taste, ready for labeling and packing.

Auxiliary System Coordination